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  1. 23 6月, 2016 1 次提交
  3. 25 5月, 2016 1 次提交
  5. 26 4月, 2016 1 次提交
  7. 29 2月, 2016 1 次提交
    • J
      objtool: Add tool to perform compile-time stack metadata validation · 442f04c3
      由 Josh Poimboeuf 提交于 
      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>
      442f04c3
  9. 09 2月, 2016 1 次提交
    • L
      tools/gpio: create GPIO tools · 6d591c46
      由 Linus Walleij 提交于 
      This creates GPIO tools under tools/gpio/* and adds a single
example program to list the GPIOs on a system. When proper
devices are created it provides this minimal output:

Cc: Johan Hovold <johan@kernel.org>
Cc: Michael Welling <mwelling@ieee.org>
Cc: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
      6d591c46
  11. 12 1月, 2016 1 次提交
  13. 11 1月, 2016 1 次提交
  15. 23 11月, 2015 1 次提交
  17. 19 11月, 2015 1 次提交
  19. 13 11月, 2015 1 次提交
  21. 12 11月, 2015 1 次提交
  23. 09 6月, 2015 1 次提交
  25. 29 4月, 2015 2 次提交
  27. 09 4月, 2015 1 次提交
  29. 09 5月, 2014 1 次提交
  31. 16 2月, 2014 1 次提交
  33. 16 1月, 2014 1 次提交
  35. 17 12月, 2013 1 次提交
    • B
      tools/: Convert to new topic libraries · 553873e1
      由 Borislav Petkov 提交于 
      Move debugfs.* to api/fs/. We have a common tools/lib/api/ place where
the Makefile lives and then we place the headers in subdirs.

For example, all the fs-related stuff goes to tools/lib/api/fs/ from
which we get libapikfs.a (acme got almost the naming he wanted :-)) and
we link it into the tools which need it - in this case perf and
tools/vm/page-types.

acme:

"Looking at the implementation, I think some tools can even link
directly to the .o files, avoiding the .a file altogether.

But that is just an optimization/finer granularity tools/lib/
cherrypicking that toolers can make use of."

Fixup documentation cleaning target while at it.
Signed-off-by: NBorislav Petkov <bp@suse.de>
Acked-by: NIngo Molnar <mingo@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Stanislav Fomichev <stfomichev@yandex-team.ru>
Cc: Stephane Eranian <eranian@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1386605664-24041-2-git-send-email-bp@alien8.deSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      553873e1
  37. 07 11月, 2013 1 次提交
    • J
      tools/thermal: Introduce tmon, a tool for thermal subsystem · 94f69966
      由 Jacob Pan 提交于 
      Increasingly, Linux is running on thermally constrained devices. The simple
thermal relationship between processor and fan has become past for modern
computers.

As hardware vendors cope with the thermal constraints on their products,
more sensors are added, new cooling capabilities are introduced. The
complexity of the thermal relationship can grow exponentially among cooling
devices, zones, sensors, and trip points. They can also change dynamically.

To expose such relationship to the userspace, Linux generic thermal layer
introduced sysfs entry at /sys/class/thermal with a matrix of symbolic
links, trip point bindings, and device instances. To traverse such
matrix by hand is not a trivial task. Testing is also difficult in that
thermal conditions are often exception cases that hard to reach in
normal operations.

TMON is conceived as a tool to help visualize, tune, and test the
complex thermal subsystem.
Signed-off-by: NJacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: NZhang Rui <rui.zhang@intel.com>
      94f69966
  39. 21 3月, 2013 1 次提交
    • D
      filter: add minimal BPF JIT image disassembler · e306e2c1
      由 Daniel Borkmann 提交于 
      This is a minimal stand-alone user space helper, that allows for debugging or
verification of emitted BPF JIT images. This is in particular useful for
emitted opcode debugging, since minor bugs in the JIT compiler can be fatal.
The disassembler is architecture generic and uses libopcodes and libbfd.

How to get to the disassembly, example:

  1) `echo 2 > /proc/sys/net/core/bpf_jit_enable`
  2) Load a BPF filter (e.g. `tcpdump -p -n -s 0 -i eth1 host 192.168.20.0/24`)
  3) Run e.g. `bpf_jit_disasm -o` to disassemble the most recent JIT code output

`bpf_jit_disasm -o` will display the related opcodes to a particular instruction
as well. Example for x86_64:

$ ./bpf_jit_disasm
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
   1:	mov    %rsp,%rbp
   4:	sub    $0x60,%rsp
   8:	mov    %rbx,-0x8(%rbp)
   c:	mov    0x68(%rdi),%r9d
  10:	sub    0x6c(%rdi),%r9d
  14:	mov    0xe0(%rdi),%r8
  1b:	mov    $0xc,%esi
  20:	callq  0xffffffffe0d01b71
  25:	cmp    $0x86dd,%eax
  2a:	jne    0x000000000000003d
  2c:	mov    $0x14,%esi
  31:	callq  0xffffffffe0d01b8d
  36:	cmp    $0x6,%eax
[...]
  5c:	leaveq
  5d:	retq

$ ./bpf_jit_disasm -o
94 bytes emitted from JIT compiler (pass:3, flen:9)
ffffffffa0356000 + <x>:
   0:	push   %rbp
	55
   1:	mov    %rsp,%rbp
	48 89 e5
   4:	sub    $0x60,%rsp
	48 83 ec 60
   8:	mov    %rbx,-0x8(%rbp)
	48 89 5d f8
   c:	mov    0x68(%rdi),%r9d
	44 8b 4f 68
  10:	sub    0x6c(%rdi),%r9d
	44 2b 4f 6c
[...]
  5c:	leaveq
	c9
  5d:	retq
	c3
Signed-off-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      e306e2c1
  41. 16 3月, 2013 1 次提交
  43. 30 1月, 2013 1 次提交
  45. 08 1月, 2013 1 次提交
  47. 20 11月, 2012 1 次提交
  49. 15 11月, 2012 1 次提交
  51. 12 4月, 2012 3 次提交