objtool: Add tool to perform compile-time stack metadata validation

This adds a host tool named objtool which has a "check" subcommand which
analyzes .o files to ensure the validity of stack metadata.  It enforces
a set of rules on asm code and C inline assembly code so that stack
traces can be reliable.

For each function, it recursively follows all possible code paths and
validates the correct frame pointer state at each instruction.

It also follows code paths involving kernel special sections, like
.altinstructions, __jump_table, and __ex_table, which can add
alternative execution paths to a given instruction (or set of
instructions).  Similarly, it knows how to follow switch statements, for
which gcc sometimes uses jump tables.

Here are some of the benefits of validating stack metadata:

a) More reliable stack traces for frame pointer enabled kernels

   Frame pointers are used for debugging purposes.  They allow runtime
   code and debug tools to be able to walk the stack to determine the
   chain of function call sites that led to the currently executing
   code.

   For some architectures, frame pointers are enabled by
   CONFIG_FRAME_POINTER.  For some other architectures they may be
   required by the ABI (sometimes referred to as "backchain pointers").

   For C code, gcc automatically generates instructions for setting up
   frame pointers when the -fno-omit-frame-pointer option is used.

   But for asm code, the frame setup instructions have to be written by
   hand, which most people don't do.  So the end result is that
   CONFIG_FRAME_POINTER is honored for C code but not for most asm code.

   For stack traces based on frame pointers to be reliable, all
   functions which call other functions must first create a stack frame
   and update the frame pointer.  If a first function doesn't properly
   create a stack frame before calling a second function, the *caller*
   of the first function will be skipped on the stack trace.

   For example, consider the following example backtrace with frame
   pointers enabled:

     [<ffffffff81812584>] dump_stack+0x4b/0x63
     [<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
     [<ffffffff8127f568>] seq_read+0x108/0x3e0
     [<ffffffff812cce62>] proc_reg_read+0x42/0x70
     [<ffffffff81256197>] __vfs_read+0x37/0x100
     [<ffffffff81256b16>] vfs_read+0x86/0x130
     [<ffffffff81257898>] SyS_read+0x58/0xd0
     [<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76

   It correctly shows that the caller of cmdline_proc_show() is
   seq_read().

   If we remove the frame pointer logic from cmdline_proc_show() by
   replacing the frame pointer related instructions with nops, here's
   what it looks like instead:

     [<ffffffff81812584>] dump_stack+0x4b/0x63
     [<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
     [<ffffffff812cce62>] proc_reg_read+0x42/0x70
     [<ffffffff81256197>] __vfs_read+0x37/0x100
     [<ffffffff81256b16>] vfs_read+0x86/0x130
     [<ffffffff81257898>] SyS_read+0x58/0xd0
     [<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76

   Notice that cmdline_proc_show()'s caller, seq_read(), has been
   skipped.  Instead the stack trace seems to show that
   cmdline_proc_show() was called by proc_reg_read().

   The benefit of "objtool check" here is that because it ensures that
   *all* functions honor CONFIG_FRAME_POINTER, no functions will ever[*]
   be skipped on a stack trace.

   [*] unless an interrupt or exception has occurred at the very
       beginning of a function before the stack frame has been created,
       or at the very end of the function after the stack frame has been
       destroyed.  This is an inherent limitation of frame pointers.

b) 100% reliable stack traces for DWARF enabled kernels

   This is not yet implemented.  For more details about what is planned,
   see tools/objtool/Documentation/stack-validation.txt.

c) Higher live patching compatibility rate

   This is not yet implemented.  For more details about what is planned,
   see tools/objtool/Documentation/stack-validation.txt.

To achieve the validation, "objtool check" enforces the following rules:

1. Each callable function must be annotated as such with the ELF
   function type.  In asm code, this is typically done using the
   ENTRY/ENDPROC macros.  If objtool finds a return instruction
   outside of a function, it flags an error since that usually indicates
   callable code which should be annotated accordingly.

   This rule is needed so that objtool can properly identify each
   callable function in order to analyze its stack metadata.

2. Conversely, each section of code which is *not* callable should *not*
   be annotated as an ELF function.  The ENDPROC macro shouldn't be used
   in this case.

   This rule is needed so that objtool can ignore non-callable code.
   Such code doesn't have to follow any of the other rules.

3. Each callable function which calls another function must have the
   correct frame pointer logic, if required by CONFIG_FRAME_POINTER or
   the architecture's back chain rules.  This can by done in asm code
   with the FRAME_BEGIN/FRAME_END macros.

   This rule ensures that frame pointer based stack traces will work as
   designed.  If function A doesn't create a stack frame before calling
   function B, the _caller_ of function A will be skipped on the stack
   trace.

4. Dynamic jumps and jumps to undefined symbols are only allowed if:

   a) the jump is part of a switch statement; or

   b) the jump matches sibling call semantics and the frame pointer has
      the same value it had on function entry.

   This rule is needed so that objtool can reliably analyze all of a
   function's code paths.  If a function jumps to code in another file,
   and it's not a sibling call, objtool has no way to follow the jump
   because it only analyzes a single file at a time.

5. A callable function may not execute kernel entry/exit instructions.
   The only code which needs such instructions is kernel entry code,
   which shouldn't be be in callable functions anyway.

   This rule is just a sanity check to ensure that callable functions
   return normally.

It currently only supports x86_64.  I tried to make the code generic so
that support for other architectures can hopefully be plugged in
relatively easily.

On my Lenovo laptop with a i7-4810MQ 4-core/8-thread CPU, building the
kernel with objtool checking every .o file adds about three seconds of
total build time.  It hasn't been optimized for performance yet, so
there are probably some opportunities for better build performance.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/f3efb173de43bd067b060de73f856567c0fa1174.1456719558.git.jpoimboe@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

MAINTAINERS

@@ -7778,6 +7778,11 @@ L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
 S:	Maintained
 F:	sound/soc/codecs/tfa9879*
 
+OBJTOOL
+M:	Josh Poimboeuf <jpoimboe@redhat.com>
+S:	Supported
+F:	tools/objtool/
+
 OMAP SUPPORT
 M:	Tony Lindgren <tony@atomide.com>
 L:	linux-omap@vger.kernel.org

tools/Makefile

@@ -20,6 +20,7 @@ help:
 	@echo '  perf                   - Linux performance measurement and analysis tool'
 	@echo '  selftests              - various kernel selftests'
 	@echo '  spi                    - spi tools'
+	@echo '  objtool                - an ELF object analysis tool'
 	@echo '  tmon                   - thermal monitoring and tuning tool'
 	@echo '  turbostat              - Intel CPU idle stats and freq reporting tool'
 	@echo '  usb                    - USB testing tools'
@@ -53,7 +54,7 @@ acpi: FORCE
 cpupower: FORCE
 	$(call descend,power/$@)
 
-cgroup firewire hv guest spi usb virtio vm net iio: FORCE
+cgroup firewire hv guest spi usb virtio vm net iio objtool: FORCE
 	$(call descend,$@)
 
 liblockdep: FORCE
@@ -85,7 +86,7 @@ freefall: FORCE
 all: acpi cgroup cpupower hv firewire lguest \
 		perf selftests turbostat usb \
 		virtio vm net x86_energy_perf_policy \
-		tmon freefall
+		tmon freefall objtool
 
 acpi_install:
 	$(call descend,power/$(@:_install=),install)
@@ -93,7 +94,7 @@ acpi_install:
 cpupower_install:
 	$(call descend,power/$(@:_install=),install)
 
-cgroup_install firewire_install hv_install lguest_install perf_install usb_install virtio_install vm_install net_install:
+cgroup_install firewire_install hv_install lguest_install perf_install usb_install virtio_install vm_install net_install objtool_install:
 	$(call descend,$(@:_install=),install)
 
 selftests_install:
@@ -111,7 +112,7 @@ freefall_install:
 install: acpi_install cgroup_install cpupower_install hv_install firewire_install lguest_install \
 		perf_install selftests_install turbostat_install usb_install \
 		virtio_install vm_install net_install x86_energy_perf_policy_install \
-		tmon_install freefall_install
+		tmon_install freefall_install objtool_install
 
 acpi_clean:
 	$(call descend,power/acpi,clean)
@@ -119,7 +120,7 @@ acpi_clean:
 cpupower_clean:
 	$(call descend,power/cpupower,clean)
 
-cgroup_clean hv_clean firewire_clean lguest_clean spi_clean usb_clean virtio_clean vm_clean net_clean iio_clean:
+cgroup_clean hv_clean firewire_clean lguest_clean spi_clean usb_clean virtio_clean vm_clean net_clean iio_clean objtool_clean:
 	$(call descend,$(@:_clean=),clean)
 
 liblockdep_clean:
@@ -155,6 +156,7 @@ build_clean:
 clean: acpi_clean cgroup_clean cpupower_clean hv_clean firewire_clean lguest_clean \
 		perf_clean selftests_clean turbostat_clean spi_clean usb_clean virtio_clean \
 		vm_clean net_clean iio_clean x86_energy_perf_policy_clean tmon_clean \
-		freefall_clean build_clean libbpf_clean libsubcmd_clean liblockdep_clean
+		freefall_clean build_clean libbpf_clean libsubcmd_clean liblockdep_clean \
+		objtool_clean
 
 .PHONY: FORCE

tools/objtool/.gitignore

+arch/x86/insn/inat-tables.c
+objtool

tools/objtool/Build

+objtool-y += arch/$(ARCH)/
+objtool-y += builtin-check.o
+objtool-y += elf.o
+objtool-y += special.o
+objtool-y += objtool.o
+
+objtool-y += libstring.o
+
+CFLAGS += -I$(srctree)/tools/lib
+
+$(OUTPUT)libstring.o: ../lib/string.c FORCE
+	$(call rule_mkdir)
+	$(call if_changed_dep,cc_o_c)

tools/objtool/Documentation/stack-validation.txt

+Compile-time stack metadata validation
+======================================
+
+
+Overview
+--------
+
+The kernel CONFIG_STACK_VALIDATION option enables a host tool named
+objtool which runs at compile time.  It has a "check" subcommand which
+analyzes every .o file and ensures the validity of its stack metadata.
+It enforces a set of rules on asm code and C inline assembly code so
+that stack traces can be reliable.
+
+Currently it only checks frame pointer usage, but there are plans to add
+CFI validation for C files and CFI generation for asm files.
+
+For each function, it recursively follows all possible code paths and
+validates the correct frame pointer state at each instruction.
+
+It also follows code paths involving special sections, like
+.altinstructions, __jump_table, and __ex_table, which can add
+alternative execution paths to a given instruction (or set of
+instructions).  Similarly, it knows how to follow switch statements, for
+which gcc sometimes uses jump tables.
+
+
+Why do we need stack metadata validation?
+-----------------------------------------
+
+Here are some of the benefits of validating stack metadata:
+
+a) More reliable stack traces for frame pointer enabled kernels
+
+   Frame pointers are used for debugging purposes.  They allow runtime
+   code and debug tools to be able to walk the stack to determine the
+   chain of function call sites that led to the currently executing
+   code.
+
+   For some architectures, frame pointers are enabled by
+   CONFIG_FRAME_POINTER.  For some other architectures they may be
+   required by the ABI (sometimes referred to as "backchain pointers").
+
+   For C code, gcc automatically generates instructions for setting up
+   frame pointers when the -fno-omit-frame-pointer option is used.
+
+   But for asm code, the frame setup instructions have to be written by
+   hand, which most people don't do.  So the end result is that
+   CONFIG_FRAME_POINTER is honored for C code but not for most asm code.
+
+   For stack traces based on frame pointers to be reliable, all
+   functions which call other functions must first create a stack frame
+   and update the frame pointer.  If a first function doesn't properly
+   create a stack frame before calling a second function, the *caller*
+   of the first function will be skipped on the stack trace.
+
+   For example, consider the following example backtrace with frame
+   pointers enabled:
+
+     [<ffffffff81812584>] dump_stack+0x4b/0x63
+     [<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
+     [<ffffffff8127f568>] seq_read+0x108/0x3e0
+     [<ffffffff812cce62>] proc_reg_read+0x42/0x70
+     [<ffffffff81256197>] __vfs_read+0x37/0x100
+     [<ffffffff81256b16>] vfs_read+0x86/0x130
+     [<ffffffff81257898>] SyS_read+0x58/0xd0
+     [<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76
+
+   It correctly shows that the caller of cmdline_proc_show() is
+   seq_read().
+
+   If we remove the frame pointer logic from cmdline_proc_show() by
+   replacing the frame pointer related instructions with nops, here's
+   what it looks like instead:
+
+     [<ffffffff81812584>] dump_stack+0x4b/0x63
+     [<ffffffff812d6dc2>] cmdline_proc_show+0x12/0x30
+     [<ffffffff812cce62>] proc_reg_read+0x42/0x70
+     [<ffffffff81256197>] __vfs_read+0x37/0x100
+     [<ffffffff81256b16>] vfs_read+0x86/0x130
+     [<ffffffff81257898>] SyS_read+0x58/0xd0
+     [<ffffffff8181c1f2>] entry_SYSCALL_64_fastpath+0x12/0x76
+
+   Notice that cmdline_proc_show()'s caller, seq_read(), has been
+   skipped.  Instead the stack trace seems to show that
+   cmdline_proc_show() was called by proc_reg_read().
+
+   The benefit of objtool here is that because it ensures that *all*
+   functions honor CONFIG_FRAME_POINTER, no functions will ever[*] be
+   skipped on a stack trace.
+
+   [*] unless an interrupt or exception has occurred at the very
+       beginning of a function before the stack frame has been created,
+       or at the very end of the function after the stack frame has been
+       destroyed.  This is an inherent limitation of frame pointers.
+
+b) 100% reliable stack traces for DWARF enabled kernels
+
+   (NOTE: This is not yet implemented)
+
+   As an alternative to frame pointers, DWARF Call Frame Information
+   (CFI) metadata can be used to walk the stack.  Unlike frame pointers,
+   CFI metadata is out of band.  So it doesn't affect runtime
+   performance and it can be reliable even when interrupts or exceptions
+   are involved.
+
+   For C code, gcc automatically generates DWARF CFI metadata.  But for
+   asm code, generating CFI is a tedious manual approach which requires
+   manually placed .cfi assembler macros to be scattered throughout the
+   code.  It's clumsy and very easy to get wrong, and it makes the real
+   code harder to read.
+
+   Stacktool will improve this situation in several ways.  For code
+   which already has CFI annotations, it will validate them.  For code
+   which doesn't have CFI annotations, it will generate them.  So an
+   architecture can opt to strip out all the manual .cfi annotations
+   from their asm code and have objtool generate them instead.
+
+   We might also add a runtime stack validation debug option where we
+   periodically walk the stack from schedule() and/or an NMI to ensure
+   that the stack metadata is sane and that we reach the bottom of the
+   stack.
+
+   So the benefit of objtool here will be that external tooling should
+   always show perfect stack traces.  And the same will be true for
+   kernel warning/oops traces if the architecture has a runtime DWARF
+   unwinder.
+
+c) Higher live patching compatibility rate
+
+   (NOTE: This is not yet implemented)
+
+   Currently with CONFIG_LIVEPATCH there's a basic live patching
+   framework which is safe for roughly 85-90% of "security" fixes.  But
+   patches can't have complex features like function dependency or
+   prototype changes, or data structure changes.
+
+   There's a strong need to support patches which have the more complex
+   features so that the patch compatibility rate for security fixes can
+   eventually approach something resembling 100%.  To achieve that, a
+   "consistency model" is needed, which allows tasks to be safely
+   transitioned from an unpatched state to a patched state.
+
+   One of the key requirements of the currently proposed livepatch
+   consistency model [*] is that it needs to walk the stack of each
+   sleeping task to determine if it can be transitioned to the patched
+   state.  If objtool can ensure that stack traces are reliable, this
+   consistency model can be used and the live patching compatibility
+   rate can be improved significantly.
+
+   [*] https://lkml.kernel.org/r/cover.1423499826.git.jpoimboe@redhat.com
+
+
+Rules
+-----
+
+To achieve the validation, objtool enforces the following rules:
+
+1. Each callable function must be annotated as such with the ELF
+   function type.  In asm code, this is typically done using the
+   ENTRY/ENDPROC macros.  If objtool finds a return instruction
+   outside of a function, it flags an error since that usually indicates
+   callable code which should be annotated accordingly.
+
+   This rule is needed so that objtool can properly identify each
+   callable function in order to analyze its stack metadata.
+
+2. Conversely, each section of code which is *not* callable should *not*
+   be annotated as an ELF function.  The ENDPROC macro shouldn't be used
+   in this case.
+
+   This rule is needed so that objtool can ignore non-callable code.
+   Such code doesn't have to follow any of the other rules.
+
+3. Each callable function which calls another function must have the
+   correct frame pointer logic, if required by CONFIG_FRAME_POINTER or
+   the architecture's back chain rules.  This can by done in asm code
+   with the FRAME_BEGIN/FRAME_END macros.
+
+   This rule ensures that frame pointer based stack traces will work as
+   designed.  If function A doesn't create a stack frame before calling
+   function B, the _caller_ of function A will be skipped on the stack
+   trace.
+
+4. Dynamic jumps and jumps to undefined symbols are only allowed if:
+
+   a) the jump is part of a switch statement; or
+
+   b) the jump matches sibling call semantics and the frame pointer has
+      the same value it had on function entry.
+
+   This rule is needed so that objtool can reliably analyze all of a
+   function's code paths.  If a function jumps to code in another file,
+   and it's not a sibling call, objtool has no way to follow the jump
+   because it only analyzes a single file at a time.
+
+5. A callable function may not execute kernel entry/exit instructions.
+   The only code which needs such instructions is kernel entry code,
+   which shouldn't be be in callable functions anyway.
+
+   This rule is just a sanity check to ensure that callable functions
+   return normally.
+
+
+Errors in .S files
+------------------
+
+If you're getting an error in a compiled .S file which you don't
+understand, first make sure that the affected code follows the above
+rules.
+
+Here are some examples of common warnings reported by objtool, what
+they mean, and suggestions for how to fix them.
+
+
+1. asm_file.o: warning: objtool: func()+0x128: call without frame pointer save/setup
+
+   The func() function made a function call without first saving and/or
+   updating the frame pointer.
+
+   If func() is indeed a callable function, add proper frame pointer
+   logic using the FRAME_BEGIN and FRAME_END macros.  Otherwise, remove
+   its ELF function annotation by changing ENDPROC to END.
+
+   If you're getting this error in a .c file, see the "Errors in .c
+   files" section.
+
+
+2. asm_file.o: warning: objtool: .text+0x53: return instruction outside of a callable function
+
+   A return instruction was detected, but objtool couldn't find a way
+   for a callable function to reach the instruction.
+
+   If the return instruction is inside (or reachable from) a callable
+   function, the function needs to be annotated with the ENTRY/ENDPROC
+   macros.
+
+   If you _really_ need a return instruction outside of a function, and
+   are 100% sure that it won't affect stack traces, you can tell
+   objtool to ignore it.  See the "Adding exceptions" section below.
+
+
+3. asm_file.o: warning: objtool: func()+0x9: function has unreachable instruction
+
+   The instruction lives inside of a callable function, but there's no
+   possible control flow path from the beginning of the function to the
+   instruction.
+
+   If the instruction is actually needed, and it's actually in a
+   callable function, ensure that its function is properly annotated
+   with ENTRY/ENDPROC.
+
+   If it's not actually in a callable function (e.g. kernel entry code),
+   change ENDPROC to END.
+
+
+4. asm_file.o: warning: objtool: func(): can't find starting instruction
+   or
+   asm_file.o: warning: objtool: func()+0x11dd: can't decode instruction
+
+   Did you put data in a text section?  If so, that can confuse
+   objtool's instruction decoder.  Move the data to a more appropriate
+   section like .data or .rodata.
+
+
+5. asm_file.o: warning: objtool: func()+0x6: kernel entry/exit from callable instruction
+
+   This is a kernel entry/exit instruction like sysenter or sysret.
+   Such instructions aren't allowed in a callable function, and are most
+   likely part of the kernel entry code.
+
+   If the instruction isn't actually in a callable function, change
+   ENDPROC to END.
+
+
+6. asm_file.o: warning: objtool: func()+0x26: sibling call from callable instruction with changed frame pointer
+
+   This is a dynamic jump or a jump to an undefined symbol.  Stacktool
+   assumed it's a sibling call and detected that the frame pointer
+   wasn't first restored to its original state.
+
+   If it's not really a sibling call, you may need to move the
+   destination code to the local file.
+
+   If the instruction is not actually in a callable function (e.g.
+   kernel entry code), change ENDPROC to END.
+
+
+7. asm_file: warning: objtool: func()+0x5c: frame pointer state mismatch
+
+   The instruction's frame pointer state is inconsistent, depending on
+   which execution path was taken to reach the instruction.
+
+   Make sure the function pushes and sets up the frame pointer (for
+   x86_64, this means rbp) at the beginning of the function and pops it
+   at the end of the function.  Also make sure that no other code in the
+   function touches the frame pointer.
+
+
+Errors in .c files
+------------------
+
+If you're getting an objtool error in a compiled .c file, chances are
+the file uses an asm() statement which has a "call" instruction.  An
+asm() statement with a call instruction must declare the use of the
+stack pointer in its output operand.  For example, on x86_64:
+
+   register void *__sp asm("rsp");
+   asm volatile("call func" : "+r" (__sp));
+
+Otherwise the stack frame may not get created before the call.
+
+Another possible cause for errors in C code is if the Makefile removes
+-fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options.
+
+Also see the above section for .S file errors for more information what
+the individual error messages mean.
+
+If the error doesn't seem to make sense, it could be a bug in objtool.
+Feel free to ask the objtool maintainer for help.
+
+
+Adding exceptions
+-----------------
+
+If you _really_ need objtool to ignore something, and are 100% sure
+that it won't affect kernel stack traces, you can tell objtool to
+ignore it:
+
+- To skip validation of a function, use the STACK_FRAME_NON_STANDARD
+  macro.
+
+- To skip validation of a file, add
+
+    OBJECT_FILES_NON_STANDARD_filename.o := n
+
+  to the Makefile.
+
+- To skip validation of a directory, add
+
+    OBJECT_FILES_NON_STANDARD := y
+
+  to the Makefile.

tools/objtool/Makefile

+include ../scripts/Makefile.include
+
+ifndef ($(ARCH))
+ARCH ?= $(shell uname -m)
+ifeq ($(ARCH),x86_64)
+ARCH := x86
+endif
+endif
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(shell pwd)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+SUBCMD_SRCDIR	= $(srctree)/tools/lib/subcmd/
+LIBSUBCMD	= $(if $(OUTPUT),$(OUTPUT),$(SUBCMD_SRCDIR))libsubcmd.a
+
+OBJTOOL    := $(OUTPUT)objtool
+OBJTOOL_IN := $(OBJTOOL)-in.o
+
+all: $(OBJTOOL)
+
+INCLUDES := -I$(srctree)/tools/include
+CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -fomit-frame-pointer -O2 $(INCLUDES)
+LDFLAGS  += -lelf $(LIBSUBCMD)
+
+AWK = awk
+export srctree OUTPUT CFLAGS ARCH AWK
+include $(srctree)/tools/build/Makefile.include
+
+$(OBJTOOL_IN): fixdep FORCE
+	@$(MAKE) $(build)=objtool
+
+$(OBJTOOL): $(LIBSUBCMD) $(OBJTOOL_IN)
+	@(test -d ../../kernel -a -d ../../tools -a -d ../objtool && (( \
+	diff -I'^#include' arch/x86/insn/insn.c ../../arch/x86/lib/insn.c >/dev/null && \
+	diff -I'^#include' arch/x86/insn/inat.c ../../arch/x86/lib/inat.c >/dev/null && \
+	diff arch/x86/insn/x86-opcode-map.txt ../../arch/x86/lib/x86-opcode-map.txt >/dev/null && \
+	diff arch/x86/insn/gen-insn-attr-x86.awk ../../arch/x86/tools/gen-insn-attr-x86.awk >/dev/null && \
+	diff -I'^#include' arch/x86/insn/insn.h ../../arch/x86/include/asm/insn.h >/dev/null && \
+	diff -I'^#include' arch/x86/insn/inat.h ../../arch/x86/include/asm/inat.h >/dev/null && \
+	diff -I'^#include' arch/x86/insn/inat_types.h ../../arch/x86/include/asm/inat_types.h >/dev/null) \
+	|| echo "Warning: objtool: x86 instruction decoder differs from kernel" >&2 )) || true
+	$(QUIET_LINK)$(CC) $(OBJTOOL_IN) $(LDFLAGS) -o $@
+
+
+$(LIBSUBCMD): fixdep FORCE
+	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR)
+
+$(LIBSUBCMD)-clean:
+	$(Q)$(MAKE) -C $(SUBCMD_SRCDIR) clean > /dev/null
+
+clean: $(LIBSUBCMD)-clean
+	$(call QUIET_CLEAN, objtool) $(RM) $(OBJTOOL)
+	$(Q)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
+	$(Q)$(RM) $(OUTPUT)arch/x86/insn/inat-tables.c $(OUTPUT)fixdep
+
+FORCE:
+
+.PHONY: clean FORCE

tools/objtool/arch.h

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _ARCH_H
+#define _ARCH_H
+
+#include <stdbool.h>
+#include "elf.h"
+
+#define INSN_FP_SAVE		1
+#define INSN_FP_SETUP		2
+#define INSN_FP_RESTORE		3
+#define INSN_JUMP_CONDITIONAL	4
+#define INSN_JUMP_UNCONDITIONAL	5
+#define INSN_JUMP_DYNAMIC	6
+#define INSN_CALL		7
+#define INSN_CALL_DYNAMIC	8
+#define INSN_RETURN		9
+#define INSN_CONTEXT_SWITCH	10
+#define INSN_BUG		11
+#define INSN_NOP		12
+#define INSN_OTHER		13
+#define INSN_LAST		INSN_OTHER
+
+int arch_decode_instruction(struct elf *elf, struct section *sec,
+			    unsigned long offset, unsigned int maxlen,
+			    unsigned int *len, unsigned char *type,
+			    unsigned long *displacement);
+
+#endif /* _ARCH_H */

tools/objtool/arch/x86/Build

+objtool-y += decode.o
+
+inat_tables_script = arch/x86/insn/gen-insn-attr-x86.awk
+inat_tables_maps = arch/x86/insn/x86-opcode-map.txt
+
+$(OUTPUT)arch/x86/insn/inat-tables.c: $(inat_tables_script) $(inat_tables_maps)
+	$(call rule_mkdir)
+	$(Q)$(call echo-cmd,gen)$(AWK) -f $(inat_tables_script) $(inat_tables_maps) > $@
+
+$(OUTPUT)arch/x86/decode.o: $(OUTPUT)arch/x86/insn/inat-tables.c
+
+CFLAGS_decode.o += -I$(OUTPUT)arch/x86/insn

tools/objtool/arch/x86/decode.c

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define unlikely(cond) (cond)
+#include "insn/insn.h"
+#include "insn/inat.c"
+#include "insn/insn.c"
+
+#include "../../elf.h"
+#include "../../arch.h"
+#include "../../warn.h"
+
+static int is_x86_64(struct elf *elf)
+{
+	switch (elf->ehdr.e_machine) {
+	case EM_X86_64:
+		return 1;
+	case EM_386:
+		return 0;
+	default:
+		WARN("unexpected ELF machine type %d", elf->ehdr.e_machine);
+		return -1;
+	}
+}
+
+int arch_decode_instruction(struct elf *elf, struct section *sec,
+			    unsigned long offset, unsigned int maxlen,
+			    unsigned int *len, unsigned char *type,
+			    unsigned long *immediate)
+{
+	struct insn insn;
+	int x86_64;
+	unsigned char op1, op2, ext;
+
+	x86_64 = is_x86_64(elf);
+	if (x86_64 == -1)
+		return -1;
+
+	insn_init(&insn, (void *)(sec->data + offset), maxlen, x86_64);
+	insn_get_length(&insn);
+	insn_get_opcode(&insn);
+	insn_get_modrm(&insn);
+	insn_get_immediate(&insn);
+
+	if (!insn_complete(&insn)) {
+		WARN_FUNC("can't decode instruction", sec, offset);
+		return -1;
+	}
+
+	*len = insn.length;
+	*type = INSN_OTHER;
+
+	if (insn.vex_prefix.nbytes)
+		return 0;
+
+	op1 = insn.opcode.bytes[0];
+	op2 = insn.opcode.bytes[1];
+
+	switch (op1) {
+	case 0x55:
+		if (!insn.rex_prefix.nbytes)
+			/* push rbp */
+			*type = INSN_FP_SAVE;
+		break;
+
+	case 0x5d:
+		if (!insn.rex_prefix.nbytes)
+			/* pop rbp */
+			*type = INSN_FP_RESTORE;
+		break;
+
+	case 0x70 ... 0x7f:
+		*type = INSN_JUMP_CONDITIONAL;
+		break;
+
+	case 0x89:
+		if (insn.rex_prefix.nbytes == 1 &&
+		    insn.rex_prefix.bytes[0] == 0x48 &&
+		    insn.modrm.nbytes && insn.modrm.bytes[0] == 0xe5)
+			/* mov rsp, rbp */
+			*type = INSN_FP_SETUP;
+		break;
+
+	case 0x90:
+		*type = INSN_NOP;
+		break;
+
+	case 0x0f:
+		if (op2 >= 0x80 && op2 <= 0x8f)
+			*type = INSN_JUMP_CONDITIONAL;
+		else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
+			 op2 == 0x35)
+			/* sysenter, sysret */
+			*type = INSN_CONTEXT_SWITCH;
+		else if (op2 == 0x0b || op2 == 0xb9)
+			/* ud2 */
+			*type = INSN_BUG;
+		else if (op2 == 0x0d || op2 == 0x1f)
+			/* nopl/nopw */
+			*type = INSN_NOP;
+		else if (op2 == 0x01 && insn.modrm.nbytes &&
+			 (insn.modrm.bytes[0] == 0xc2 ||
+			  insn.modrm.bytes[0] == 0xd8))
+			/* vmlaunch, vmrun */
+			*type = INSN_CONTEXT_SWITCH;
+
+		break;
+
+	case 0xc9: /* leave */
+		*type = INSN_FP_RESTORE;
+		break;
+
+	case 0xe3: /* jecxz/jrcxz */
+		*type = INSN_JUMP_CONDITIONAL;
+		break;
+
+	case 0xe9:
+	case 0xeb:
+		*type = INSN_JUMP_UNCONDITIONAL;
+		break;
+
+	case 0xc2:
+	case 0xc3:
+		*type = INSN_RETURN;
+		break;
+
+	case 0xc5: /* iret */
+	case 0xca: /* retf */
+	case 0xcb: /* retf */
+		*type = INSN_CONTEXT_SWITCH;
+		break;
+
+	case 0xe8:
+		*type = INSN_CALL;
+		break;
+
+	case 0xff:
+		ext = X86_MODRM_REG(insn.modrm.bytes[0]);
+		if (ext == 2 || ext == 3)
+			*type = INSN_CALL_DYNAMIC;
+		else if (ext == 4)
+			*type = INSN_JUMP_DYNAMIC;
+		else if (ext == 5) /*jmpf */
+			*type = INSN_CONTEXT_SWITCH;
+
+		break;
+
+	default:
+		break;
+	}
+
+	*immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
+
+	return 0;
+}

tools/objtool/arch/x86/insn/gen-insn-attr-x86.awk

+#!/bin/awk -f
+# gen-insn-attr-x86.awk: Instruction attribute table generator
+# Written by Masami Hiramatsu <mhiramat@redhat.com>
+#
+# Usage: awk -f gen-insn-attr-x86.awk x86-opcode-map.txt > inat-tables.c
+
+# Awk implementation sanity check
+function check_awk_implement() {
+	if (sprintf("%x", 0) != "0")
+		return "Your awk has a printf-format problem."
+	return ""
+}
+
+# Clear working vars
+function clear_vars() {
+	delete table
+	delete lptable2
+	delete lptable1
+	delete lptable3
+	eid = -1 # escape id
+	gid = -1 # group id
+	aid = -1 # AVX id
+	tname = ""
+}
+
+BEGIN {
+	# Implementation error checking
+	awkchecked = check_awk_implement()
+	if (awkchecked != "") {
+		print "Error: " awkchecked > "/dev/stderr"
+		print "Please try to use gawk." > "/dev/stderr"
+		exit 1
+	}
+
+	# Setup generating tables
+	print "/* x86 opcode map generated from x86-opcode-map.txt */"
+	print "/* Do not change this code. */\n"
+	ggid = 1
+	geid = 1
+	gaid = 0
+	delete etable
+	delete gtable
+	delete atable
+
+	opnd_expr = "^[A-Za-z/]"
+	ext_expr = "^\\("
+	sep_expr = "^\\|$"
+	group_expr = "^Grp[0-9A-Za-z]+"
+
+	imm_expr = "^[IJAOL][a-z]"
+	imm_flag["Ib"] = "INAT_MAKE_IMM(INAT_IMM_BYTE)"
+	imm_flag["Jb"] = "INAT_MAKE_IMM(INAT_IMM_BYTE)"
+	imm_flag["Iw"] = "INAT_MAKE_IMM(INAT_IMM_WORD)"
+	imm_flag["Id"] = "INAT_MAKE_IMM(INAT_IMM_DWORD)"
+	imm_flag["Iq"] = "INAT_MAKE_IMM(INAT_IMM_QWORD)"
+	imm_flag["Ap"] = "INAT_MAKE_IMM(INAT_IMM_PTR)"
+	imm_flag["Iz"] = "INAT_MAKE_IMM(INAT_IMM_VWORD32)"
+	imm_flag["Jz"] = "INAT_MAKE_IMM(INAT_IMM_VWORD32)"
+	imm_flag["Iv"] = "INAT_MAKE_IMM(INAT_IMM_VWORD)"
+	imm_flag["Ob"] = "INAT_MOFFSET"
+	imm_flag["Ov"] = "INAT_MOFFSET"
+	imm_flag["Lx"] = "INAT_MAKE_IMM(INAT_IMM_BYTE)"
+
+	modrm_expr = "^([CDEGMNPQRSUVW/][a-z]+|NTA|T[012])"
+	force64_expr = "\\([df]64\\)"
+	rex_expr = "^REX(\\.[XRWB]+)*"
+	fpu_expr = "^ESC" # TODO
+
+	lprefix1_expr = "\\((66|!F3)\\)"
+	lprefix2_expr = "\\(F3\\)"
+	lprefix3_expr = "\\((F2|!F3|66\\&F2)\\)"
+	lprefix_expr = "\\((66|F2|F3)\\)"
+	max_lprefix = 4
+
+	# All opcodes starting with lower-case 'v' or with (v1) superscript
+	# accepts VEX prefix
+	vexok_opcode_expr = "^v.*"
+	vexok_expr = "\\(v1\\)"
+	# All opcodes with (v) superscript supports *only* VEX prefix
+	vexonly_expr = "\\(v\\)"
+
+	prefix_expr = "\\(Prefix\\)"
+	prefix_num["Operand-Size"] = "INAT_PFX_OPNDSZ"
+	prefix_num["REPNE"] = "INAT_PFX_REPNE"
+	prefix_num["REP/REPE"] = "INAT_PFX_REPE"
+	prefix_num["XACQUIRE"] = "INAT_PFX_REPNE"
+	prefix_num["XRELEASE"] = "INAT_PFX_REPE"
+	prefix_num["LOCK"] = "INAT_PFX_LOCK"
+	prefix_num["SEG=CS"] = "INAT_PFX_CS"
+	prefix_num["SEG=DS"] = "INAT_PFX_DS"
+	prefix_num["SEG=ES"] = "INAT_PFX_ES"
+	prefix_num["SEG=FS"] = "INAT_PFX_FS"
+	prefix_num["SEG=GS"] = "INAT_PFX_GS"
+	prefix_num["SEG=SS"] = "INAT_PFX_SS"
+	prefix_num["Address-Size"] = "INAT_PFX_ADDRSZ"
+	prefix_num["VEX+1byte"] = "INAT_PFX_VEX2"
+	prefix_num["VEX+2byte"] = "INAT_PFX_VEX3"
+
+	clear_vars()
+}
+
+function semantic_error(msg) {
+	print "Semantic error at " NR ": " msg > "/dev/stderr"
+	exit 1
+}
+
+function debug(msg) {
+	print "DEBUG: " msg
+}
+
+function array_size(arr,   i,c) {
+	c = 0
+	for (i in arr)
+		c++
+	return c
+}
+
+/^Table:/ {
+	print "/* " $0 " */"
+	if (tname != "")
+		semantic_error("Hit Table: before EndTable:.");
+}
+
+/^Referrer:/ {
+	if (NF != 1) {
+		# escape opcode table
+		ref = ""
+		for (i = 2; i <= NF; i++)
+			ref = ref $i
+		eid = escape[ref]
+		tname = sprintf("inat_escape_table_%d", eid)
+	}
+}
+
+/^AVXcode:/ {
+	if (NF != 1) {
+		# AVX/escape opcode table
+		aid = $2
+		if (gaid <= aid)
+			gaid = aid + 1
+		if (tname == "")	# AVX only opcode table
+			tname = sprintf("inat_avx_table_%d", $2)
+	}
+	if (aid == -1 && eid == -1)	# primary opcode table
+		tname = "inat_primary_table"
+}
+
+/^GrpTable:/ {
+	print "/* " $0 " */"
+	if (!($2 in group))
+		semantic_error("No group: " $2 )
+	gid = group[$2]
+	tname = "inat_group_table_" gid
+}
+
+function print_table(tbl,name,fmt,n)
+{
+	print "const insn_attr_t " name " = {"
+	for (i = 0; i < n; i++) {
+		id = sprintf(fmt, i)
+		if (tbl[id])
+			print "	[" id "] = " tbl[id] ","
+	}
+	print "};"
+}
+
+/^EndTable/ {
+	if (gid != -1) {
+		# print group tables
+		if (array_size(table) != 0) {
+			print_table(table, tname "[INAT_GROUP_TABLE_SIZE]",
+				    "0x%x", 8)
+			gtable[gid,0] = tname
+		}
+		if (array_size(lptable1) != 0) {
+			print_table(lptable1, tname "_1[INAT_GROUP_TABLE_SIZE]",
+				    "0x%x", 8)
+			gtable[gid,1] = tname "_1"
+		}
+		if (array_size(lptable2) != 0) {
+			print_table(lptable2, tname "_2[INAT_GROUP_TABLE_SIZE]",
+				    "0x%x", 8)
+			gtable[gid,2] = tname "_2"
+		}
+		if (array_size(lptable3) != 0) {
+			print_table(lptable3, tname "_3[INAT_GROUP_TABLE_SIZE]",
+				    "0x%x", 8)
+			gtable[gid,3] = tname "_3"
+		}
+	} else {
+		# print primary/escaped tables
+		if (array_size(table) != 0) {
+			print_table(table, tname "[INAT_OPCODE_TABLE_SIZE]",
+				    "0x%02x", 256)
+			etable[eid,0] = tname
+			if (aid >= 0)
+				atable[aid,0] = tname
+		}
+		if (array_size(lptable1) != 0) {
+			print_table(lptable1,tname "_1[INAT_OPCODE_TABLE_SIZE]",
+				    "0x%02x", 256)
+			etable[eid,1] = tname "_1"
+			if (aid >= 0)
+				atable[aid,1] = tname "_1"
+		}
+		if (array_size(lptable2) != 0) {
+			print_table(lptable2,tname "_2[INAT_OPCODE_TABLE_SIZE]",
+				    "0x%02x", 256)
+			etable[eid,2] = tname "_2"
+			if (aid >= 0)
+				atable[aid,2] = tname "_2"
+		}
+		if (array_size(lptable3) != 0) {
+			print_table(lptable3,tname "_3[INAT_OPCODE_TABLE_SIZE]",
+				    "0x%02x", 256)
+			etable[eid,3] = tname "_3"
+			if (aid >= 0)
+				atable[aid,3] = tname "_3"
+		}
+	}
+	print ""
+	clear_vars()
+}
+
+function add_flags(old,new) {
+	if (old && new)
+		return old " | " new
+	else if (old)
+		return old
+	else
+		return new
+}
+
+# convert operands to flags.
+function convert_operands(count,opnd,       i,j,imm,mod)
+{
+	imm = null
+	mod = null
+	for (j = 1; j <= count; j++) {
+		i = opnd[j]
+		if (match(i, imm_expr) == 1) {
+			if (!imm_flag[i])
+				semantic_error("Unknown imm opnd: " i)
+			if (imm) {
+				if (i != "Ib")
+					semantic_error("Second IMM error")
+				imm = add_flags(imm, "INAT_SCNDIMM")
+			} else
+				imm = imm_flag[i]
+		} else if (match(i, modrm_expr))
+			mod = "INAT_MODRM"
+	}
+	return add_flags(imm, mod)
+}
+
+/^[0-9a-f]+\:/ {
+	if (NR == 1)
+		next
+	# get index
+	idx = "0x" substr($1, 1, index($1,":") - 1)
+	if (idx in table)
+		semantic_error("Redefine " idx " in " tname)
+
+	# check if escaped opcode
+	if ("escape" == $2) {
+		if ($3 != "#")
+			semantic_error("No escaped name")
+		ref = ""
+		for (i = 4; i <= NF; i++)
+			ref = ref $i
+		if (ref in escape)
+			semantic_error("Redefine escape (" ref ")")
+		escape[ref] = geid
+		geid++
+		table[idx] = "INAT_MAKE_ESCAPE(" escape[ref] ")"
+		next
+	}
+
+	variant = null
+	# converts
+	i = 2
+	while (i <= NF) {
+		opcode = $(i++)
+		delete opnds
+		ext = null
+		flags = null
+		opnd = null
+		# parse one opcode
+		if (match($i, opnd_expr)) {
+			opnd = $i
+			count = split($(i++), opnds, ",")
+			flags = convert_operands(count, opnds)
+		}
+		if (match($i, ext_expr))
+			ext = $(i++)
+		if (match($i, sep_expr))
+			i++
+		else if (i < NF)
+			semantic_error($i " is not a separator")
+
+		# check if group opcode
+		if (match(opcode, group_expr)) {
+			if (!(opcode in group)) {
+				group[opcode] = ggid
+				ggid++
+			}
+			flags = add_flags(flags, "INAT_MAKE_GROUP(" group[opcode] ")")
+		}
+		# check force(or default) 64bit
+		if (match(ext, force64_expr))
+			flags = add_flags(flags, "INAT_FORCE64")
+
+		# check REX prefix
+		if (match(opcode, rex_expr))
+			flags = add_flags(flags, "INAT_MAKE_PREFIX(INAT_PFX_REX)")
+
+		# check coprocessor escape : TODO
+		if (match(opcode, fpu_expr))
+			flags = add_flags(flags, "INAT_MODRM")
+
+		# check VEX codes
+		if (match(ext, vexonly_expr))
+			flags = add_flags(flags, "INAT_VEXOK | INAT_VEXONLY")
+		else if (match(ext, vexok_expr) || match(opcode, vexok_opcode_expr))
+			flags = add_flags(flags, "INAT_VEXOK")
+
+		# check prefixes
+		if (match(ext, prefix_expr)) {
+			if (!prefix_num[opcode])
+				semantic_error("Unknown prefix: " opcode)
+			flags = add_flags(flags, "INAT_MAKE_PREFIX(" prefix_num[opcode] ")")
+		}
+		if (length(flags) == 0)
+			continue
+		# check if last prefix
+		if (match(ext, lprefix1_expr)) {
+			lptable1[idx] = add_flags(lptable1[idx],flags)
+			variant = "INAT_VARIANT"
+		}
+		if (match(ext, lprefix2_expr)) {
+			lptable2[idx] = add_flags(lptable2[idx],flags)
+			variant = "INAT_VARIANT"
+		}
+		if (match(ext, lprefix3_expr)) {
+			lptable3[idx] = add_flags(lptable3[idx],flags)
+			variant = "INAT_VARIANT"
+		}
+		if (!match(ext, lprefix_expr)){
+			table[idx] = add_flags(table[idx],flags)
+		}
+	}
+	if (variant)
+		table[idx] = add_flags(table[idx],variant)
+}
+
+END {
+	if (awkchecked != "")
+		exit 1
+	# print escape opcode map's array
+	print "/* Escape opcode map array */"
+	print "const insn_attr_t * const inat_escape_tables[INAT_ESC_MAX + 1]" \
+	      "[INAT_LSTPFX_MAX + 1] = {"
+	for (i = 0; i < geid; i++)
+		for (j = 0; j < max_lprefix; j++)
+			if (etable[i,j])
+				print "	["i"]["j"] = "etable[i,j]","
+	print "};\n"
+	# print group opcode map's array
+	print "/* Group opcode map array */"
+	print "const insn_attr_t * const inat_group_tables[INAT_GRP_MAX + 1]"\
+	      "[INAT_LSTPFX_MAX + 1] = {"
+	for (i = 0; i < ggid; i++)
+		for (j = 0; j < max_lprefix; j++)
+			if (gtable[i,j])
+				print "	["i"]["j"] = "gtable[i,j]","
+	print "};\n"
+	# print AVX opcode map's array
+	print "/* AVX opcode map array */"
+	print "const insn_attr_t * const inat_avx_tables[X86_VEX_M_MAX + 1]"\
+	      "[INAT_LSTPFX_MAX + 1] = {"
+	for (i = 0; i < gaid; i++)
+		for (j = 0; j < max_lprefix; j++)
+			if (atable[i,j])
+				print "	["i"]["j"] = "atable[i,j]","
+	print "};"
+}
+

tools/objtool/arch/x86/insn/inat.c

+/*
+ * x86 instruction attribute tables
+ *
+ * Written by Masami Hiramatsu <mhiramat@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+#include "insn.h"
+
+/* Attribute tables are generated from opcode map */
+#include "inat-tables.c"
+
+/* Attribute search APIs */
+insn_attr_t inat_get_opcode_attribute(insn_byte_t opcode)
+{
+	return inat_primary_table[opcode];
+}
+
+int inat_get_last_prefix_id(insn_byte_t last_pfx)
+{
+	insn_attr_t lpfx_attr;
+
+	lpfx_attr = inat_get_opcode_attribute(last_pfx);
+	return inat_last_prefix_id(lpfx_attr);
+}
+
+insn_attr_t inat_get_escape_attribute(insn_byte_t opcode, int lpfx_id,
+				      insn_attr_t esc_attr)
+{
+	const insn_attr_t *table;
+	int n;
+
+	n = inat_escape_id(esc_attr);
+
+	table = inat_escape_tables[n][0];
+	if (!table)
+		return 0;
+	if (inat_has_variant(table[opcode]) && lpfx_id) {
+		table = inat_escape_tables[n][lpfx_id];
+		if (!table)
+			return 0;
+	}
+	return table[opcode];
+}
+
+insn_attr_t inat_get_group_attribute(insn_byte_t modrm, int lpfx_id,
+				     insn_attr_t grp_attr)
+{
+	const insn_attr_t *table;
+	int n;
+
+	n = inat_group_id(grp_attr);
+
+	table = inat_group_tables[n][0];
+	if (!table)
+		return inat_group_common_attribute(grp_attr);
+	if (inat_has_variant(table[X86_MODRM_REG(modrm)]) && lpfx_id) {
+		table = inat_group_tables[n][lpfx_id];
+		if (!table)
+			return inat_group_common_attribute(grp_attr);
+	}
+	return table[X86_MODRM_REG(modrm)] |
+	       inat_group_common_attribute(grp_attr);
+}
+
+insn_attr_t inat_get_avx_attribute(insn_byte_t opcode, insn_byte_t vex_m,
+				   insn_byte_t vex_p)
+{
+	const insn_attr_t *table;
+	if (vex_m > X86_VEX_M_MAX || vex_p > INAT_LSTPFX_MAX)
+		return 0;
+	/* At first, this checks the master table */
+	table = inat_avx_tables[vex_m][0];
+	if (!table)
+		return 0;
+	if (!inat_is_group(table[opcode]) && vex_p) {
+		/* If this is not a group, get attribute directly */
+		table = inat_avx_tables[vex_m][vex_p];
+		if (!table)
+			return 0;
+	}
+	return table[opcode];
+}
+

tools/objtool/arch/x86/insn/inat.h

+#ifndef _ASM_X86_INAT_H
+#define _ASM_X86_INAT_H
+/*
+ * x86 instruction attributes
+ *
+ * Written by Masami Hiramatsu <mhiramat@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+#include "inat_types.h"
+
+/*
+ * Internal bits. Don't use bitmasks directly, because these bits are
+ * unstable. You should use checking functions.
+ */
+
+#define INAT_OPCODE_TABLE_SIZE 256
+#define INAT_GROUP_TABLE_SIZE 8
+
+/* Legacy last prefixes */
+#define INAT_PFX_OPNDSZ	1	/* 0x66 */ /* LPFX1 */
+#define INAT_PFX_REPE	2	/* 0xF3 */ /* LPFX2 */
+#define INAT_PFX_REPNE	3	/* 0xF2 */ /* LPFX3 */
+/* Other Legacy prefixes */
+#define INAT_PFX_LOCK	4	/* 0xF0 */
+#define INAT_PFX_CS	5	/* 0x2E */
+#define INAT_PFX_DS	6	/* 0x3E */
+#define INAT_PFX_ES	7	/* 0x26 */
+#define INAT_PFX_FS	8	/* 0x64 */
+#define INAT_PFX_GS	9	/* 0x65 */
+#define INAT_PFX_SS	10	/* 0x36 */
+#define INAT_PFX_ADDRSZ	11	/* 0x67 */
+/* x86-64 REX prefix */
+#define INAT_PFX_REX	12	/* 0x4X */
+/* AVX VEX prefixes */
+#define INAT_PFX_VEX2	13	/* 2-bytes VEX prefix */
+#define INAT_PFX_VEX3	14	/* 3-bytes VEX prefix */
+
+#define INAT_LSTPFX_MAX	3
+#define INAT_LGCPFX_MAX	11
+
+/* Immediate size */
+#define INAT_IMM_BYTE		1
+#define INAT_IMM_WORD		2
+#define INAT_IMM_DWORD		3
+#define INAT_IMM_QWORD		4
+#define INAT_IMM_PTR		5
+#define INAT_IMM_VWORD32	6
+#define INAT_IMM_VWORD		7
+
+/* Legacy prefix */
+#define INAT_PFX_OFFS	0
+#define INAT_PFX_BITS	4
+#define INAT_PFX_MAX    ((1 << INAT_PFX_BITS) - 1)
+#define INAT_PFX_MASK	(INAT_PFX_MAX << INAT_PFX_OFFS)
+/* Escape opcodes */
+#define INAT_ESC_OFFS	(INAT_PFX_OFFS + INAT_PFX_BITS)
+#define INAT_ESC_BITS	2
+#define INAT_ESC_MAX	((1 << INAT_ESC_BITS) - 1)
+#define INAT_ESC_MASK	(INAT_ESC_MAX << INAT_ESC_OFFS)
+/* Group opcodes (1-16) */
+#define INAT_GRP_OFFS	(INAT_ESC_OFFS + INAT_ESC_BITS)
+#define INAT_GRP_BITS	5
+#define INAT_GRP_MAX	((1 << INAT_GRP_BITS) - 1)
+#define INAT_GRP_MASK	(INAT_GRP_MAX << INAT_GRP_OFFS)
+/* Immediates */
+#define INAT_IMM_OFFS	(INAT_GRP_OFFS + INAT_GRP_BITS)
+#define INAT_IMM_BITS	3
+#define INAT_IMM_MASK	(((1 << INAT_IMM_BITS) - 1) << INAT_IMM_OFFS)
+/* Flags */
+#define INAT_FLAG_OFFS	(INAT_IMM_OFFS + INAT_IMM_BITS)
+#define INAT_MODRM	(1 << (INAT_FLAG_OFFS))
+#define INAT_FORCE64	(1 << (INAT_FLAG_OFFS + 1))
+#define INAT_SCNDIMM	(1 << (INAT_FLAG_OFFS + 2))
+#define INAT_MOFFSET	(1 << (INAT_FLAG_OFFS + 3))
+#define INAT_VARIANT	(1 << (INAT_FLAG_OFFS + 4))
+#define INAT_VEXOK	(1 << (INAT_FLAG_OFFS + 5))
+#define INAT_VEXONLY	(1 << (INAT_FLAG_OFFS + 6))
+/* Attribute making macros for attribute tables */
+#define INAT_MAKE_PREFIX(pfx)	(pfx << INAT_PFX_OFFS)
+#define INAT_MAKE_ESCAPE(esc)	(esc << INAT_ESC_OFFS)
+#define INAT_MAKE_GROUP(grp)	((grp << INAT_GRP_OFFS) | INAT_MODRM)
+#define INAT_MAKE_IMM(imm)	(imm << INAT_IMM_OFFS)
+
+/* Attribute search APIs */
+extern insn_attr_t inat_get_opcode_attribute(insn_byte_t opcode);
+extern int inat_get_last_prefix_id(insn_byte_t last_pfx);
+extern insn_attr_t inat_get_escape_attribute(insn_byte_t opcode,
+					     int lpfx_id,
+					     insn_attr_t esc_attr);
+extern insn_attr_t inat_get_group_attribute(insn_byte_t modrm,
+					    int lpfx_id,
+					    insn_attr_t esc_attr);
+extern insn_attr_t inat_get_avx_attribute(insn_byte_t opcode,
+					  insn_byte_t vex_m,
+					  insn_byte_t vex_pp);
+
+/* Attribute checking functions */
+static inline int inat_is_legacy_prefix(insn_attr_t attr)
+{
+	attr &= INAT_PFX_MASK;
+	return attr && attr <= INAT_LGCPFX_MAX;
+}
+
+static inline int inat_is_address_size_prefix(insn_attr_t attr)
+{
+	return (attr & INAT_PFX_MASK) == INAT_PFX_ADDRSZ;
+}
+
+static inline int inat_is_operand_size_prefix(insn_attr_t attr)
+{
+	return (attr & INAT_PFX_MASK) == INAT_PFX_OPNDSZ;
+}
+
+static inline int inat_is_rex_prefix(insn_attr_t attr)
+{
+	return (attr & INAT_PFX_MASK) == INAT_PFX_REX;
+}
+
+static inline int inat_last_prefix_id(insn_attr_t attr)
+{
+	if ((attr & INAT_PFX_MASK) > INAT_LSTPFX_MAX)
+		return 0;
+	else
+		return attr & INAT_PFX_MASK;
+}
+
+static inline int inat_is_vex_prefix(insn_attr_t attr)
+{
+	attr &= INAT_PFX_MASK;
+	return attr == INAT_PFX_VEX2 || attr == INAT_PFX_VEX3;
+}
+
+static inline int inat_is_vex3_prefix(insn_attr_t attr)
+{
+	return (attr & INAT_PFX_MASK) == INAT_PFX_VEX3;
+}
+
+static inline int inat_is_escape(insn_attr_t attr)
+{
+	return attr & INAT_ESC_MASK;
+}
+
+static inline int inat_escape_id(insn_attr_t attr)
+{
+	return (attr & INAT_ESC_MASK) >> INAT_ESC_OFFS;
+}
+
+static inline int inat_is_group(insn_attr_t attr)
+{
+	return attr & INAT_GRP_MASK;
+}
+
+static inline int inat_group_id(insn_attr_t attr)
+{
+	return (attr & INAT_GRP_MASK) >> INAT_GRP_OFFS;
+}
+
+static inline int inat_group_common_attribute(insn_attr_t attr)
+{
+	return attr & ~INAT_GRP_MASK;
+}
+
+static inline int inat_has_immediate(insn_attr_t attr)
+{
+	return attr & INAT_IMM_MASK;
+}
+
+static inline int inat_immediate_size(insn_attr_t attr)
+{
+	return (attr & INAT_IMM_MASK) >> INAT_IMM_OFFS;
+}
+
+static inline int inat_has_modrm(insn_attr_t attr)
+{
+	return attr & INAT_MODRM;
+}
+
+static inline int inat_is_force64(insn_attr_t attr)
+{
+	return attr & INAT_FORCE64;
+}
+
+static inline int inat_has_second_immediate(insn_attr_t attr)
+{
+	return attr & INAT_SCNDIMM;
+}
+
+static inline int inat_has_moffset(insn_attr_t attr)
+{
+	return attr & INAT_MOFFSET;
+}
+
+static inline int inat_has_variant(insn_attr_t attr)
+{
+	return attr & INAT_VARIANT;
+}
+
+static inline int inat_accept_vex(insn_attr_t attr)
+{
+	return attr & INAT_VEXOK;
+}
+
+static inline int inat_must_vex(insn_attr_t attr)
+{
+	return attr & INAT_VEXONLY;
+}
+#endif

tools/objtool/arch/x86/insn/inat_types.h

+#ifndef _ASM_X86_INAT_TYPES_H
+#define _ASM_X86_INAT_TYPES_H
+/*
+ * x86 instruction attributes
+ *
+ * Written by Masami Hiramatsu <mhiramat@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ */
+
+/* Instruction attributes */
+typedef unsigned int insn_attr_t;
+typedef unsigned char insn_byte_t;
+typedef signed int insn_value_t;
+
+#endif

tools/objtool/arch/x86/insn/insn.c

+/*
+ * x86 instruction analysis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004, 2009
+ */
+
+#ifdef __KERNEL__
+#include <linux/string.h>
+#else
+#include <string.h>
+#endif
+#include "inat.h"
+#include "insn.h"
+
+/* Verify next sizeof(t) bytes can be on the same instruction */
+#define validate_next(t, insn, n)	\
+	((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
+
+#define __get_next(t, insn)	\
+	({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
+
+#define __peek_nbyte_next(t, insn, n)	\
+	({ t r = *(t*)((insn)->next_byte + n); r; })
+
+#define get_next(t, insn)	\
+	({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
+
+#define peek_nbyte_next(t, insn, n)	\
+	({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); })
+
+#define peek_next(t, insn)	peek_nbyte_next(t, insn, 0)
+
+/**
+ * insn_init() - initialize struct insn
+ * @insn:	&struct insn to be initialized
+ * @kaddr:	address (in kernel memory) of instruction (or copy thereof)
+ * @x86_64:	!0 for 64-bit kernel or 64-bit app
+ */
+void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64)
+{
+	/*
+	 * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid
+	 * even if the input buffer is long enough to hold them.
+	 */
+	if (buf_len > MAX_INSN_SIZE)
+		buf_len = MAX_INSN_SIZE;
+
+	memset(insn, 0, sizeof(*insn));
+	insn->kaddr = kaddr;
+	insn->end_kaddr = kaddr + buf_len;
+	insn->next_byte = kaddr;
+	insn->x86_64 = x86_64 ? 1 : 0;
+	insn->opnd_bytes = 4;
+	if (x86_64)
+		insn->addr_bytes = 8;
+	else
+		insn->addr_bytes = 4;
+}
+
+/**
+ * insn_get_prefixes - scan x86 instruction prefix bytes
+ * @insn:	&struct insn containing instruction
+ *
+ * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
+ * to point to the (first) opcode.  No effect if @insn->prefixes.got
+ * is already set.
+ */
+void insn_get_prefixes(struct insn *insn)
+{
+	struct insn_field *prefixes = &insn->prefixes;
+	insn_attr_t attr;
+	insn_byte_t b, lb;
+	int i, nb;
+
+	if (prefixes->got)
+		return;
+
+	nb = 0;
+	lb = 0;
+	b = peek_next(insn_byte_t, insn);
+	attr = inat_get_opcode_attribute(b);
+	while (inat_is_legacy_prefix(attr)) {
+		/* Skip if same prefix */
+		for (i = 0; i < nb; i++)
+			if (prefixes->bytes[i] == b)
+				goto found;
+		if (nb == 4)
+			/* Invalid instruction */
+			break;
+		prefixes->bytes[nb++] = b;
+		if (inat_is_address_size_prefix(attr)) {
+			/* address size switches 2/4 or 4/8 */
+			if (insn->x86_64)
+				insn->addr_bytes ^= 12;
+			else
+				insn->addr_bytes ^= 6;
+		} else if (inat_is_operand_size_prefix(attr)) {
+			/* oprand size switches 2/4 */
+			insn->opnd_bytes ^= 6;
+		}
+found:
+		prefixes->nbytes++;
+		insn->next_byte++;
+		lb = b;
+		b = peek_next(insn_byte_t, insn);
+		attr = inat_get_opcode_attribute(b);
+	}
+	/* Set the last prefix */
+	if (lb && lb != insn->prefixes.bytes[3]) {
+		if (unlikely(insn->prefixes.bytes[3])) {
+			/* Swap the last prefix */
+			b = insn->prefixes.bytes[3];
+			for (i = 0; i < nb; i++)
+				if (prefixes->bytes[i] == lb)
+					prefixes->bytes[i] = b;
+		}
+		insn->prefixes.bytes[3] = lb;
+	}
+
+	/* Decode REX prefix */
+	if (insn->x86_64) {
+		b = peek_next(insn_byte_t, insn);
+		attr = inat_get_opcode_attribute(b);
+		if (inat_is_rex_prefix(attr)) {
+			insn->rex_prefix.value = b;
+			insn->rex_prefix.nbytes = 1;
+			insn->next_byte++;
+			if (X86_REX_W(b))
+				/* REX.W overrides opnd_size */
+				insn->opnd_bytes = 8;
+		}
+	}
+	insn->rex_prefix.got = 1;
+
+	/* Decode VEX prefix */
+	b = peek_next(insn_byte_t, insn);
+	attr = inat_get_opcode_attribute(b);
+	if (inat_is_vex_prefix(attr)) {
+		insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
+		if (!insn->x86_64) {
+			/*
+			 * In 32-bits mode, if the [7:6] bits (mod bits of
+			 * ModRM) on the second byte are not 11b, it is
+			 * LDS or LES.
+			 */
+			if (X86_MODRM_MOD(b2) != 3)
+				goto vex_end;
+		}
+		insn->vex_prefix.bytes[0] = b;
+		insn->vex_prefix.bytes[1] = b2;
+		if (inat_is_vex3_prefix(attr)) {
+			b2 = peek_nbyte_next(insn_byte_t, insn, 2);
+			insn->vex_prefix.bytes[2] = b2;
+			insn->vex_prefix.nbytes = 3;
+			insn->next_byte += 3;
+			if (insn->x86_64 && X86_VEX_W(b2))
+				/* VEX.W overrides opnd_size */
+				insn->opnd_bytes = 8;
+		} else {
+			/*
+			 * For VEX2, fake VEX3-like byte#2.
+			 * Makes it easier to decode vex.W, vex.vvvv,
+			 * vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
+			 */
+			insn->vex_prefix.bytes[2] = b2 & 0x7f;
+			insn->vex_prefix.nbytes = 2;
+			insn->next_byte += 2;
+		}
+	}
+vex_end:
+	insn->vex_prefix.got = 1;
+
+	prefixes->got = 1;
+
+err_out:
+	return;
+}
+
+/**
+ * insn_get_opcode - collect opcode(s)
+ * @insn:	&struct insn containing instruction
+ *
+ * Populates @insn->opcode, updates @insn->next_byte to point past the
+ * opcode byte(s), and set @insn->attr (except for groups).
+ * If necessary, first collects any preceding (prefix) bytes.
+ * Sets @insn->opcode.value = opcode1.  No effect if @insn->opcode.got
+ * is already 1.
+ */
+void insn_get_opcode(struct insn *insn)
+{
+	struct insn_field *opcode = &insn->opcode;
+	insn_byte_t op;
+	int pfx_id;
+	if (opcode->got)
+		return;
+	if (!insn->prefixes.got)
+		insn_get_prefixes(insn);
+
+	/* Get first opcode */
+	op = get_next(insn_byte_t, insn);
+	opcode->bytes[0] = op;
+	opcode->nbytes = 1;
+
+	/* Check if there is VEX prefix or not */
+	if (insn_is_avx(insn)) {
+		insn_byte_t m, p;
+		m = insn_vex_m_bits(insn);
+		p = insn_vex_p_bits(insn);
+		insn->attr = inat_get_avx_attribute(op, m, p);
+		if (!inat_accept_vex(insn->attr) && !inat_is_group(insn->attr))
+			insn->attr = 0;	/* This instruction is bad */
+		goto end;	/* VEX has only 1 byte for opcode */
+	}
+
+	insn->attr = inat_get_opcode_attribute(op);
+	while (inat_is_escape(insn->attr)) {
+		/* Get escaped opcode */
+		op = get_next(insn_byte_t, insn);
+		opcode->bytes[opcode->nbytes++] = op;
+		pfx_id = insn_last_prefix_id(insn);
+		insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
+	}
+	if (inat_must_vex(insn->attr))
+		insn->attr = 0;	/* This instruction is bad */
+end:
+	opcode->got = 1;
+
+err_out:
+	return;
+}
+
+/**
+ * insn_get_modrm - collect ModRM byte, if any
+ * @insn:	&struct insn containing instruction
+ *
+ * Populates @insn->modrm and updates @insn->next_byte to point past the
+ * ModRM byte, if any.  If necessary, first collects the preceding bytes
+ * (prefixes and opcode(s)).  No effect if @insn->modrm.got is already 1.
+ */
+void insn_get_modrm(struct insn *insn)
+{
+	struct insn_field *modrm = &insn->modrm;
+	insn_byte_t pfx_id, mod;
+	if (modrm->got)
+		return;
+	if (!insn->opcode.got)
+		insn_get_opcode(insn);
+
+	if (inat_has_modrm(insn->attr)) {
+		mod = get_next(insn_byte_t, insn);
+		modrm->value = mod;
+		modrm->nbytes = 1;
+		if (inat_is_group(insn->attr)) {
+			pfx_id = insn_last_prefix_id(insn);
+			insn->attr = inat_get_group_attribute(mod, pfx_id,
+							      insn->attr);
+			if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
+				insn->attr = 0;	/* This is bad */
+		}
+	}
+
+	if (insn->x86_64 && inat_is_force64(insn->attr))
+		insn->opnd_bytes = 8;
+	modrm->got = 1;
+
+err_out:
+	return;
+}
+
+
+/**
+ * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
+ * @insn:	&struct insn containing instruction
+ *
+ * If necessary, first collects the instruction up to and including the
+ * ModRM byte.  No effect if @insn->x86_64 is 0.
+ */
+int insn_rip_relative(struct insn *insn)
+{
+	struct insn_field *modrm = &insn->modrm;
+
+	if (!insn->x86_64)
+		return 0;
+	if (!modrm->got)
+		insn_get_modrm(insn);
+	/*
+	 * For rip-relative instructions, the mod field (top 2 bits)
+	 * is zero and the r/m field (bottom 3 bits) is 0x5.
+	 */
+	return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
+}
+
+/**
+ * insn_get_sib() - Get the SIB byte of instruction
+ * @insn:	&struct insn containing instruction
+ *
+ * If necessary, first collects the instruction up to and including the
+ * ModRM byte.
+ */
+void insn_get_sib(struct insn *insn)
+{
+	insn_byte_t modrm;
+
+	if (insn->sib.got)
+		return;
+	if (!insn->modrm.got)
+		insn_get_modrm(insn);
+	if (insn->modrm.nbytes) {
+		modrm = (insn_byte_t)insn->modrm.value;
+		if (insn->addr_bytes != 2 &&
+		    X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
+			insn->sib.value = get_next(insn_byte_t, insn);
+			insn->sib.nbytes = 1;
+		}
+	}
+	insn->sib.got = 1;
+
+err_out:
+	return;
+}
+
+
+/**
+ * insn_get_displacement() - Get the displacement of instruction
+ * @insn:	&struct insn containing instruction
+ *
+ * If necessary, first collects the instruction up to and including the
+ * SIB byte.
+ * Displacement value is sign-expanded.
+ */
+void insn_get_displacement(struct insn *insn)
+{
+	insn_byte_t mod, rm, base;
+
+	if (insn->displacement.got)
+		return;
+	if (!insn->sib.got)
+		insn_get_sib(insn);
+	if (insn->modrm.nbytes) {
+		/*
+		 * Interpreting the modrm byte:
+		 * mod = 00 - no displacement fields (exceptions below)
+		 * mod = 01 - 1-byte displacement field
+		 * mod = 10 - displacement field is 4 bytes, or 2 bytes if
+		 * 	address size = 2 (0x67 prefix in 32-bit mode)
+		 * mod = 11 - no memory operand
+		 *
+		 * If address size = 2...
+		 * mod = 00, r/m = 110 - displacement field is 2 bytes
+		 *
+		 * If address size != 2...
+		 * mod != 11, r/m = 100 - SIB byte exists
+		 * mod = 00, SIB base = 101 - displacement field is 4 bytes
+		 * mod = 00, r/m = 101 - rip-relative addressing, displacement
+		 * 	field is 4 bytes
+		 */
+		mod = X86_MODRM_MOD(insn->modrm.value);
+		rm = X86_MODRM_RM(insn->modrm.value);
+		base = X86_SIB_BASE(insn->sib.value);
+		if (mod == 3)
+			goto out;
+		if (mod == 1) {
+			insn->displacement.value = get_next(char, insn);
+			insn->displacement.nbytes = 1;
+		} else if (insn->addr_bytes == 2) {
+			if ((mod == 0 && rm == 6) || mod == 2) {
+				insn->displacement.value =
+					 get_next(short, insn);
+				insn->displacement.nbytes = 2;
+			}
+		} else {
+			if ((mod == 0 && rm == 5) || mod == 2 ||
+			    (mod == 0 && base == 5)) {
+				insn->displacement.value = get_next(int, insn);
+				insn->displacement.nbytes = 4;
+			}
+		}
+	}
+out:
+	insn->displacement.got = 1;
+
+err_out:
+	return;
+}
+
+/* Decode moffset16/32/64. Return 0 if failed */
+static int __get_moffset(struct insn *insn)
+{
+	switch (insn->addr_bytes) {
+	case 2:
+		insn->moffset1.value = get_next(short, insn);
+		insn->moffset1.nbytes = 2;
+		break;
+	case 4:
+		insn->moffset1.value = get_next(int, insn);
+		insn->moffset1.nbytes = 4;
+		break;
+	case 8:
+		insn->moffset1.value = get_next(int, insn);
+		insn->moffset1.nbytes = 4;
+		insn->moffset2.value = get_next(int, insn);
+		insn->moffset2.nbytes = 4;
+		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
+	}
+	insn->moffset1.got = insn->moffset2.got = 1;
+
+	return 1;
+
+err_out:
+	return 0;
+}
+
+/* Decode imm v32(Iz). Return 0 if failed */
+static int __get_immv32(struct insn *insn)
+{
+	switch (insn->opnd_bytes) {
+	case 2:
+		insn->immediate.value = get_next(short, insn);
+		insn->immediate.nbytes = 2;
+		break;
+	case 4:
+	case 8:
+		insn->immediate.value = get_next(int, insn);
+		insn->immediate.nbytes = 4;
+		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
+	}
+
+	return 1;
+
+err_out:
+	return 0;
+}
+
+/* Decode imm v64(Iv/Ov), Return 0 if failed */
+static int __get_immv(struct insn *insn)
+{
+	switch (insn->opnd_bytes) {
+	case 2:
+		insn->immediate1.value = get_next(short, insn);
+		insn->immediate1.nbytes = 2;
+		break;
+	case 4:
+		insn->immediate1.value = get_next(int, insn);
+		insn->immediate1.nbytes = 4;
+		break;
+	case 8:
+		insn->immediate1.value = get_next(int, insn);
+		insn->immediate1.nbytes = 4;
+		insn->immediate2.value = get_next(int, insn);
+		insn->immediate2.nbytes = 4;
+		break;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
+	}
+	insn->immediate1.got = insn->immediate2.got = 1;
+
+	return 1;
+err_out:
+	return 0;
+}
+
+/* Decode ptr16:16/32(Ap) */
+static int __get_immptr(struct insn *insn)
+{
+	switch (insn->opnd_bytes) {
+	case 2:
+		insn->immediate1.value = get_next(short, insn);
+		insn->immediate1.nbytes = 2;
+		break;
+	case 4:
+		insn->immediate1.value = get_next(int, insn);
+		insn->immediate1.nbytes = 4;
+		break;
+	case 8:
+		/* ptr16:64 is not exist (no segment) */
+		return 0;
+	default:	/* opnd_bytes must be modified manually */
+		goto err_out;
+	}
+	insn->immediate2.value = get_next(unsigned short, insn);
+	insn->immediate2.nbytes = 2;
+	insn->immediate1.got = insn->immediate2.got = 1;
+
+	return 1;
+err_out:
+	return 0;
+}
+
+/**
+ * insn_get_immediate() - Get the immediates of instruction
+ * @insn:	&struct insn containing instruction
+ *
+ * If necessary, first collects the instruction up to and including the
+ * displacement bytes.
+ * Basically, most of immediates are sign-expanded. Unsigned-value can be
+ * get by bit masking with ((1 << (nbytes * 8)) - 1)
+ */
+void insn_get_immediate(struct insn *insn)
+{
+	if (insn->immediate.got)
+		return;
+	if (!insn->displacement.got)
+		insn_get_displacement(insn);
+
+	if (inat_has_moffset(insn->attr)) {
+		if (!__get_moffset(insn))
+			goto err_out;
+		goto done;
+	}
+
+	if (!inat_has_immediate(insn->attr))
+		/* no immediates */
+		goto done;
+
+	switch (inat_immediate_size(insn->attr)) {
+	case INAT_IMM_BYTE:
+		insn->immediate.value = get_next(char, insn);
+		insn->immediate.nbytes = 1;
+		break;
+	case INAT_IMM_WORD:
+		insn->immediate.value = get_next(short, insn);
+		insn->immediate.nbytes = 2;
+		break;
+	case INAT_IMM_DWORD:
+		insn->immediate.value = get_next(int, insn);
+		insn->immediate.nbytes = 4;
+		break;
+	case INAT_IMM_QWORD:
+		insn->immediate1.value = get_next(int, insn);
+		insn->immediate1.nbytes = 4;
+		insn->immediate2.value = get_next(int, insn);
+		insn->immediate2.nbytes = 4;
+		break;
+	case INAT_IMM_PTR:
+		if (!__get_immptr(insn))
+			goto err_out;
+		break;
+	case INAT_IMM_VWORD32:
+		if (!__get_immv32(insn))
+			goto err_out;
+		break;
+	case INAT_IMM_VWORD:
+		if (!__get_immv(insn))
+			goto err_out;
+		break;
+	default:
+		/* Here, insn must have an immediate, but failed */
+		goto err_out;
+	}
+	if (inat_has_second_immediate(insn->attr)) {
+		insn->immediate2.value = get_next(char, insn);
+		insn->immediate2.nbytes = 1;
+	}
+done:
+	insn->immediate.got = 1;
+
+err_out:
+	return;
+}
+
+/**
+ * insn_get_length() - Get the length of instruction
+ * @insn:	&struct insn containing instruction
+ *
+ * If necessary, first collects the instruction up to and including the
+ * immediates bytes.
+ */
+void insn_get_length(struct insn *insn)
+{
+	if (insn->length)
+		return;
+	if (!insn->immediate.got)
+		insn_get_immediate(insn);
+	insn->length = (unsigned char)((unsigned long)insn->next_byte
+				     - (unsigned long)insn->kaddr);
+}

tools/objtool/arch/x86/insn/insn.h

+#ifndef _ASM_X86_INSN_H
+#define _ASM_X86_INSN_H
+/*
+ * x86 instruction analysis
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2009
+ */
+
+/* insn_attr_t is defined in inat.h */
+#include "inat.h"
+
+struct insn_field {
+	union {
+		insn_value_t value;
+		insn_byte_t bytes[4];
+	};
+	/* !0 if we've run insn_get_xxx() for this field */
+	unsigned char got;
+	unsigned char nbytes;
+};
+
+struct insn {
+	struct insn_field prefixes;	/*
+					 * Prefixes
+					 * prefixes.bytes[3]: last prefix
+					 */
+	struct insn_field rex_prefix;	/* REX prefix */
+	struct insn_field vex_prefix;	/* VEX prefix */
+	struct insn_field opcode;	/*
+					 * opcode.bytes[0]: opcode1
+					 * opcode.bytes[1]: opcode2
+					 * opcode.bytes[2]: opcode3
+					 */
+	struct insn_field modrm;
+	struct insn_field sib;
+	struct insn_field displacement;
+	union {
+		struct insn_field immediate;
+		struct insn_field moffset1;	/* for 64bit MOV */
+		struct insn_field immediate1;	/* for 64bit imm or off16/32 */
+	};
+	union {
+		struct insn_field moffset2;	/* for 64bit MOV */
+		struct insn_field immediate2;	/* for 64bit imm or seg16 */
+	};
+
+	insn_attr_t attr;
+	unsigned char opnd_bytes;
+	unsigned char addr_bytes;
+	unsigned char length;
+	unsigned char x86_64;
+
+	const insn_byte_t *kaddr;	/* kernel address of insn to analyze */
+	const insn_byte_t *end_kaddr;	/* kernel address of last insn in buffer */
+	const insn_byte_t *next_byte;
+};
+
+#define MAX_INSN_SIZE	15
+
+#define X86_MODRM_MOD(modrm) (((modrm) & 0xc0) >> 6)
+#define X86_MODRM_REG(modrm) (((modrm) & 0x38) >> 3)
+#define X86_MODRM_RM(modrm) ((modrm) & 0x07)
+
+#define X86_SIB_SCALE(sib) (((sib) & 0xc0) >> 6)
+#define X86_SIB_INDEX(sib) (((sib) & 0x38) >> 3)
+#define X86_SIB_BASE(sib) ((sib) & 0x07)
+
+#define X86_REX_W(rex) ((rex) & 8)
+#define X86_REX_R(rex) ((rex) & 4)
+#define X86_REX_X(rex) ((rex) & 2)
+#define X86_REX_B(rex) ((rex) & 1)
+
+/* VEX bit flags  */
+#define X86_VEX_W(vex)	((vex) & 0x80)	/* VEX3 Byte2 */
+#define X86_VEX_R(vex)	((vex) & 0x80)	/* VEX2/3 Byte1 */
+#define X86_VEX_X(vex)	((vex) & 0x40)	/* VEX3 Byte1 */
+#define X86_VEX_B(vex)	((vex) & 0x20)	/* VEX3 Byte1 */
+#define X86_VEX_L(vex)	((vex) & 0x04)	/* VEX3 Byte2, VEX2 Byte1 */
+/* VEX bit fields */
+#define X86_VEX3_M(vex)	((vex) & 0x1f)		/* VEX3 Byte1 */
+#define X86_VEX2_M	1			/* VEX2.M always 1 */
+#define X86_VEX_V(vex)	(((vex) & 0x78) >> 3)	/* VEX3 Byte2, VEX2 Byte1 */
+#define X86_VEX_P(vex)	((vex) & 0x03)		/* VEX3 Byte2, VEX2 Byte1 */
+#define X86_VEX_M_MAX	0x1f			/* VEX3.M Maximum value */
+
+extern void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64);
+extern void insn_get_prefixes(struct insn *insn);
+extern void insn_get_opcode(struct insn *insn);
+extern void insn_get_modrm(struct insn *insn);
+extern void insn_get_sib(struct insn *insn);
+extern void insn_get_displacement(struct insn *insn);
+extern void insn_get_immediate(struct insn *insn);
+extern void insn_get_length(struct insn *insn);
+
+/* Attribute will be determined after getting ModRM (for opcode groups) */
+static inline void insn_get_attribute(struct insn *insn)
+{
+	insn_get_modrm(insn);
+}
+
+/* Instruction uses RIP-relative addressing */
+extern int insn_rip_relative(struct insn *insn);
+
+/* Init insn for kernel text */
+static inline void kernel_insn_init(struct insn *insn,
+				    const void *kaddr, int buf_len)
+{
+#ifdef CONFIG_X86_64
+	insn_init(insn, kaddr, buf_len, 1);
+#else /* CONFIG_X86_32 */
+	insn_init(insn, kaddr, buf_len, 0);
+#endif
+}
+
+static inline int insn_is_avx(struct insn *insn)
+{
+	if (!insn->prefixes.got)
+		insn_get_prefixes(insn);
+	return (insn->vex_prefix.value != 0);
+}
+
+/* Ensure this instruction is decoded completely */
+static inline int insn_complete(struct insn *insn)
+{
+	return insn->opcode.got && insn->modrm.got && insn->sib.got &&
+		insn->displacement.got && insn->immediate.got;
+}
+
+static inline insn_byte_t insn_vex_m_bits(struct insn *insn)
+{
+	if (insn->vex_prefix.nbytes == 2)	/* 2 bytes VEX */
+		return X86_VEX2_M;
+	else
+		return X86_VEX3_M(insn->vex_prefix.bytes[1]);
+}
+
+static inline insn_byte_t insn_vex_p_bits(struct insn *insn)
+{
+	if (insn->vex_prefix.nbytes == 2)	/* 2 bytes VEX */
+		return X86_VEX_P(insn->vex_prefix.bytes[1]);
+	else
+		return X86_VEX_P(insn->vex_prefix.bytes[2]);
+}
+
+/* Get the last prefix id from last prefix or VEX prefix */
+static inline int insn_last_prefix_id(struct insn *insn)
+{
+	if (insn_is_avx(insn))
+		return insn_vex_p_bits(insn);	/* VEX_p is a SIMD prefix id */
+
+	if (insn->prefixes.bytes[3])
+		return inat_get_last_prefix_id(insn->prefixes.bytes[3]);
+
+	return 0;
+}
+
+/* Offset of each field from kaddr */
+static inline int insn_offset_rex_prefix(struct insn *insn)
+{
+	return insn->prefixes.nbytes;
+}
+static inline int insn_offset_vex_prefix(struct insn *insn)
+{
+	return insn_offset_rex_prefix(insn) + insn->rex_prefix.nbytes;
+}
+static inline int insn_offset_opcode(struct insn *insn)
+{
+	return insn_offset_vex_prefix(insn) + insn->vex_prefix.nbytes;
+}
+static inline int insn_offset_modrm(struct insn *insn)
+{
+	return insn_offset_opcode(insn) + insn->opcode.nbytes;
+}
+static inline int insn_offset_sib(struct insn *insn)
+{
+	return insn_offset_modrm(insn) + insn->modrm.nbytes;
+}
+static inline int insn_offset_displacement(struct insn *insn)
+{
+	return insn_offset_sib(insn) + insn->sib.nbytes;
+}
+static inline int insn_offset_immediate(struct insn *insn)
+{
+	return insn_offset_displacement(insn) + insn->displacement.nbytes;
+}
+
+#endif /* _ASM_X86_INSN_H */

tools/objtool/builtin.h

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef _BUILTIN_H
+#define _BUILTIN_H
+
+extern int cmd_check(int argc, const char **argv);
+
+#endif /* _BUILTIN_H */

tools/objtool/elf.c

+/*
+ * elf.c - ELF access library
+ *
+ * Adapted from kpatch (https://github.com/dynup/kpatch):
+ * Copyright (C) 2013-2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "elf.h"
+#include "warn.h"
+
+struct section *find_section_by_name(struct elf *elf, const char *name)
+{
+	struct section *sec;
+
+	list_for_each_entry(sec, &elf->sections, list)
+		if (!strcmp(sec->name, name))
+			return sec;
+
+	return NULL;
+}
+
+static struct section *find_section_by_index(struct elf *elf,
+					     unsigned int idx)
+{
+	struct section *sec;
+
+	list_for_each_entry(sec, &elf->sections, list)
+		if (sec->idx == idx)
+			return sec;
+
+	return NULL;
+}
+
+static struct symbol *find_symbol_by_index(struct elf *elf, unsigned int idx)
+{
+	struct section *sec;
+	struct symbol *sym;
+
+	list_for_each_entry(sec, &elf->sections, list)
+		list_for_each_entry(sym, &sec->symbols, list)
+			if (sym->idx == idx)
+				return sym;
+
+	return NULL;
+}
+
+struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
+{
+	struct symbol *sym;
+
+	list_for_each_entry(sym, &sec->symbols, list)
+		if (sym->type != STT_SECTION &&
+		    sym->offset == offset)
+			return sym;
+
+	return NULL;
+}
+
+struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
+				     unsigned int len)
+{
+	struct rela *rela;
+
+	if (!sec->rela)
+		return NULL;
+
+	list_for_each_entry(rela, &sec->rela->relas, list)
+		if (rela->offset >= offset && rela->offset < offset + len)
+			return rela;
+
+	return NULL;
+}
+
+struct rela *find_rela_by_dest(struct section *sec, unsigned long offset)
+{
+	return find_rela_by_dest_range(sec, offset, 1);
+}
+
+struct symbol *find_containing_func(struct section *sec, unsigned long offset)
+{
+	struct symbol *func;
+
+	list_for_each_entry(func, &sec->symbols, list)
+		if (func->type == STT_FUNC && offset >= func->offset &&
+		    offset < func->offset + func->len)
+			return func;
+
+	return NULL;
+}
+
+static int read_sections(struct elf *elf)
+{
+	Elf_Scn *s = NULL;
+	struct section *sec;
+	size_t shstrndx, sections_nr;
+	int i;
+
+	if (elf_getshdrnum(elf->elf, &sections_nr)) {
+		perror("elf_getshdrnum");
+		return -1;
+	}
+
+	if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
+		perror("elf_getshdrstrndx");
+		return -1;
+	}
+
+	for (i = 0; i < sections_nr; i++) {
+		sec = malloc(sizeof(*sec));
+		if (!sec) {
+			perror("malloc");
+			return -1;
+		}
+		memset(sec, 0, sizeof(*sec));
+
+		INIT_LIST_HEAD(&sec->symbols);
+		INIT_LIST_HEAD(&sec->relas);
+
+		list_add_tail(&sec->list, &elf->sections);
+
+		s = elf_getscn(elf->elf, i);
+		if (!s) {
+			perror("elf_getscn");
+			return -1;
+		}
+
+		sec->idx = elf_ndxscn(s);
+
+		if (!gelf_getshdr(s, &sec->sh)) {
+			perror("gelf_getshdr");
+			return -1;
+		}
+
+		sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
+		if (!sec->name) {
+			perror("elf_strptr");
+			return -1;
+		}
+
+		sec->elf_data = elf_getdata(s, NULL);
+		if (!sec->elf_data) {
+			perror("elf_getdata");
+			return -1;
+		}
+
+		if (sec->elf_data->d_off != 0 ||
+		    sec->elf_data->d_size != sec->sh.sh_size) {
+			WARN("unexpected data attributes for %s", sec->name);
+			return -1;
+		}
+
+		sec->data = (unsigned long)sec->elf_data->d_buf;
+		sec->len = sec->elf_data->d_size;
+	}
+
+	/* sanity check, one more call to elf_nextscn() should return NULL */
+	if (elf_nextscn(elf->elf, s)) {
+		WARN("section entry mismatch");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int read_symbols(struct elf *elf)
+{
+	struct section *symtab;
+	struct symbol *sym;
+	struct list_head *entry, *tmp;
+	int symbols_nr, i;
+
+	symtab = find_section_by_name(elf, ".symtab");
+	if (!symtab) {
+		WARN("missing symbol table");
+		return -1;
+	}
+
+	symbols_nr = symtab->sh.sh_size / symtab->sh.sh_entsize;
+
+	for (i = 0; i < symbols_nr; i++) {
+		sym = malloc(sizeof(*sym));
+		if (!sym) {
+			perror("malloc");
+			return -1;
+		}
+		memset(sym, 0, sizeof(*sym));
+
+		sym->idx = i;
+
+		if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
+			perror("gelf_getsym");
+			goto err;
+		}
+
+		sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
+				       sym->sym.st_name);
+		if (!sym->name) {
+			perror("elf_strptr");
+			goto err;
+		}
+
+		sym->type = GELF_ST_TYPE(sym->sym.st_info);
+		sym->bind = GELF_ST_BIND(sym->sym.st_info);
+
+		if (sym->sym.st_shndx > SHN_UNDEF &&
+		    sym->sym.st_shndx < SHN_LORESERVE) {
+			sym->sec = find_section_by_index(elf,
+							 sym->sym.st_shndx);
+			if (!sym->sec) {
+				WARN("couldn't find section for symbol %s",
+				     sym->name);
+				goto err;
+			}
+			if (sym->type == STT_SECTION) {
+				sym->name = sym->sec->name;
+				sym->sec->sym = sym;
+			}
+		} else
+			sym->sec = find_section_by_index(elf, 0);
+
+		sym->offset = sym->sym.st_value;
+		sym->len = sym->sym.st_size;
+
+		/* sorted insert into a per-section list */
+		entry = &sym->sec->symbols;
+		list_for_each_prev(tmp, &sym->sec->symbols) {
+			struct symbol *s;
+
+			s = list_entry(tmp, struct symbol, list);
+
+			if (sym->offset > s->offset) {
+				entry = tmp;
+				break;
+			}
+
+			if (sym->offset == s->offset && sym->len >= s->len) {
+				entry = tmp;
+				break;
+			}
+		}
+		list_add(&sym->list, entry);
+	}
+
+	return 0;
+
+err:
+	free(sym);
+	return -1;
+}
+
+static int read_relas(struct elf *elf)
+{
+	struct section *sec;
+	struct rela *rela;
+	int i;
+	unsigned int symndx;
+
+	list_for_each_entry(sec, &elf->sections, list) {
+		if (sec->sh.sh_type != SHT_RELA)
+			continue;
+
+		sec->base = find_section_by_name(elf, sec->name + 5);
+		if (!sec->base) {
+			WARN("can't find base section for rela section %s",
+			     sec->name);
+			return -1;
+		}
+
+		sec->base->rela = sec;
+
+		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
+			rela = malloc(sizeof(*rela));
+			if (!rela) {
+				perror("malloc");
+				return -1;
+			}
+			memset(rela, 0, sizeof(*rela));
+
+			list_add_tail(&rela->list, &sec->relas);
+
+			if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
+				perror("gelf_getrela");
+				return -1;
+			}
+
+			rela->type = GELF_R_TYPE(rela->rela.r_info);
+			rela->addend = rela->rela.r_addend;
+			rela->offset = rela->rela.r_offset;
+			symndx = GELF_R_SYM(rela->rela.r_info);
+			rela->sym = find_symbol_by_index(elf, symndx);
+			if (!rela->sym) {
+				WARN("can't find rela entry symbol %d for %s",
+				     symndx, sec->name);
+				return -1;
+			}
+		}
+	}
+
+	return 0;
+}
+
+struct elf *elf_open(const char *name)
+{
+	struct elf *elf;
+
+	elf_version(EV_CURRENT);
+
+	elf = malloc(sizeof(*elf));
+	if (!elf) {
+		perror("malloc");
+		return NULL;
+	}
+	memset(elf, 0, sizeof(*elf));
+
+	INIT_LIST_HEAD(&elf->sections);
+
+	elf->name = strdup(name);
+	if (!elf->name) {
+		perror("strdup");
+		goto err;
+	}
+
+	elf->fd = open(name, O_RDONLY);
+	if (elf->fd == -1) {
+		perror("open");
+		goto err;
+	}
+
+	elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
+	if (!elf->elf) {
+		perror("elf_begin");
+		goto err;
+	}
+
+	if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
+		perror("gelf_getehdr");
+		goto err;
+	}
+
+	if (read_sections(elf))
+		goto err;
+
+	if (read_symbols(elf))
+		goto err;
+
+	if (read_relas(elf))
+		goto err;
+
+	return elf;
+
+err:
+	elf_close(elf);
+	return NULL;
+}
+
+void elf_close(struct elf *elf)
+{
+	struct section *sec, *tmpsec;
+	struct symbol *sym, *tmpsym;
+	struct rela *rela, *tmprela;
+
+	list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
+		list_for_each_entry_safe(sym, tmpsym, &sec->symbols, list) {
+			list_del(&sym->list);
+			free(sym);
+		}
+		list_for_each_entry_safe(rela, tmprela, &sec->relas, list) {
+			list_del(&rela->list);
+			free(rela);
+		}
+		list_del(&sec->list);
+		free(sec);
+	}
+	if (elf->name)
+		free(elf->name);
+	if (elf->fd > 0)
+		close(elf->fd);
+	if (elf->elf)
+		elf_end(elf->elf);
+	free(elf);
+}

tools/objtool/elf.h

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _OBJTOOL_ELF_H
+#define _OBJTOOL_ELF_H
+
+#include <stdio.h>
+#include <gelf.h>
+#include <linux/list.h>
+
+struct section {
+	struct list_head list;
+	GElf_Shdr sh;
+	struct list_head symbols;
+	struct list_head relas;
+	struct section *base, *rela;
+	struct symbol *sym;
+	Elf_Data *elf_data;
+	char *name;
+	int idx;
+	unsigned long data;
+	unsigned int len;
+};
+
+struct symbol {
+	struct list_head list;
+	GElf_Sym sym;
+	struct section *sec;
+	char *name;
+	int idx;
+	unsigned char bind, type;
+	unsigned long offset;
+	unsigned int len;
+};
+
+struct rela {
+	struct list_head list;
+	GElf_Rela rela;
+	struct symbol *sym;
+	unsigned int type;
+	int offset;
+	int addend;
+};
+
+struct elf {
+	Elf *elf;
+	GElf_Ehdr ehdr;
+	int fd;
+	char *name;
+	struct list_head sections;
+};
+
+
+struct elf *elf_open(const char *name);
+struct section *find_section_by_name(struct elf *elf, const char *name);
+struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
+struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
+struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
+				     unsigned int len);
+struct symbol *find_containing_func(struct section *sec, unsigned long offset);
+void elf_close(struct elf *elf);
+
+
+
+#endif /* _OBJTOOL_ELF_H */

tools/objtool/objtool.c

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * objtool:
+ *
+ * The 'check' subcmd analyzes every .o file and ensures the validity of its
+ * stack trace metadata.  It enforces a set of rules on asm code and C inline
+ * assembly code so that stack traces can be reliable.
+ *
+ * For more information, see tools/objtool/Documentation/stack-validation.txt.
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <subcmd/exec-cmd.h>
+#include <subcmd/pager.h>
+
+#include "builtin.h"
+
+#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
+
+struct cmd_struct {
+	const char *name;
+	int (*fn)(int, const char **);
+	const char *help;
+};
+
+static const char objtool_usage_string[] =
+	"objtool [OPTIONS] COMMAND [ARGS]";
+
+static struct cmd_struct objtool_cmds[] = {
+	{"check",	cmd_check,	"Perform stack metadata validation on an object file" },
+};
+
+bool help;
+
+static void cmd_usage(void)
+{
+	unsigned int i, longest = 0;
+
+	printf("\n usage: %s\n\n", objtool_usage_string);
+
+	for (i = 0; i < ARRAY_SIZE(objtool_cmds); i++) {
+		if (longest < strlen(objtool_cmds[i].name))
+			longest = strlen(objtool_cmds[i].name);
+	}
+
+	puts(" Commands:");
+	for (i = 0; i < ARRAY_SIZE(objtool_cmds); i++) {
+		printf("   %-*s   ", longest, objtool_cmds[i].name);
+		puts(objtool_cmds[i].help);
+	}
+
+	printf("\n");
+
+	exit(1);
+}
+
+static void handle_options(int *argc, const char ***argv)
+{
+	while (*argc > 0) {
+		const char *cmd = (*argv)[0];
+
+		if (cmd[0] != '-')
+			break;
+
+		if (!strcmp(cmd, "--help") || !strcmp(cmd, "-h")) {
+			help = true;
+			break;
+		} else {
+			fprintf(stderr, "Unknown option: %s\n", cmd);
+			fprintf(stderr, "\n Usage: %s\n",
+				objtool_usage_string);
+			exit(1);
+		}
+
+		(*argv)++;
+		(*argc)--;
+	}
+}
+
+static void handle_internal_command(int argc, const char **argv)
+{
+	const char *cmd = argv[0];
+	unsigned int i, ret;
+
+	for (i = 0; i < ARRAY_SIZE(objtool_cmds); i++) {
+		struct cmd_struct *p = objtool_cmds+i;
+
+		if (strcmp(p->name, cmd))
+			continue;
+
+		ret = p->fn(argc, argv);
+
+		exit(ret);
+	}
+
+	cmd_usage();
+}
+
+int main(int argc, const char **argv)
+{
+	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
+
+	/* libsubcmd init */
+	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
+	pager_init(UNUSED);
+
+	argv++;
+	argc--;
+	handle_options(&argc, &argv);
+
+	if (!argc || help)
+		cmd_usage();
+
+	handle_internal_command(argc, argv);
+
+	return 0;
+}

tools/objtool/special.h

+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _SPECIAL_H
+#define _SPECIAL_H
+
+#include <stdbool.h>
+#include "elf.h"
+
+struct special_alt {
+	struct list_head list;
+
+	bool group;
+	bool skip_orig;
+	bool jump_or_nop;
+
+	struct section *orig_sec;
+	unsigned long orig_off;
+
+	struct section *new_sec;
+	unsigned long new_off;
+
+	unsigned int orig_len, new_len; /* group only */
+};
+
+int special_get_alts(struct elf *elf, struct list_head *alts);
+
+#endif /* _SPECIAL_H */