Commits ffb1b4a4 ("x86/unwind/orc: Add 'signal' field to ORC
metadata") and fb799447 ("x86,objtool: Split UNWIND_HINT_EMPTY in
two") changed the ORC format. Although ORC is internal to the kernel,
it's the only way for external tools to get reliable kernel stack traces
on x86-64. In particular, the drgn debugger [1] uses ORC for stack
unwinding, and these format changes broke it [2]. As the drgn
maintainer, I don't care how often or how much the kernel changes the
ORC format as long as I have a way to detect the change.

It suffices to store a version identifier in the vmlinux and kernel
module ELF files (to use when parsing ORC sections from ELF), and in
kernel memory (to use when parsing ORC from a core dump+symbol table).
Rather than hard-coding a version number that needs to be manually
bumped, Peterz suggested hashing the definitions from orc_types.h. If
there is a format change that isn't caught by this, the hashing script
can be updated.

This patch adds an .orc_header allocated ELF section containing the
20-byte hash to vmlinux and kernel modules, along with the corresponding
__start_orc_header and __stop_orc_header symbols in vmlinux.

1: https://github.com/osandov/drgn
2: https://github.com/osandov/drgn/issues/303

Fixes: ffb1b4a4 ("x86/unwind/orc: Add 'signal' field to ORC metadata")
Fixes: fb799447 ("x86,objtool: Split UNWIND_HINT_EMPTY in two")
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NJosh Poimboeuf <jpoimboe@kernel.org>
Link: https://lkml.kernel.org/r/aef9c8dc43915b886a8c48509a12ec1b006ca1ca.1686690801.git.osandov@osandov.com

The L0 symbol is generated when build module on LoongArch, ignore it in
modpost and when looking at module symbols, otherwise we can not see the
expected call trace.

Now is_arm_mapping_symbol() is not only for ARM, in order to reflect the
reality, rename is_arm_mapping_symbol() to is_mapping_symbol().

This is related with commit c17a2538 ("mksysmap: Fix the mismatch of
'L0' symbols in System.map").

(1) Simple test case

  [loongson@linux hello]$ cat hello.c
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/printk.h>

  static void test_func(void)
  {
  	  pr_info("This is a test\n");
	  dump_stack();
  }

  static int __init hello_init(void)
  {
	  pr_warn("Hello, world\n");
	  test_func();

	  return 0;
  }

  static void __exit hello_exit(void)
  {
	  pr_warn("Goodbye\n");
  }

  module_init(hello_init);
  module_exit(hello_exit);
  MODULE_LICENSE("GPL");
  [loongson@linux hello]$ cat Makefile
  obj-m:=hello.o

  ccflags-y += -g -Og

  all:
	  make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) modules
  clean:
	  make -C /lib/modules/$(shell uname -r)/build/ M=$(PWD) clean

(2) Test environment

system: LoongArch CLFS 5.5
https://github.com/sunhaiyong1978/CLFS-for-LoongArch/releases/tag/5.0
It needs to update grub to avoid booting error "invalid magic number".

kernel: 6.3-rc1 with loongson3_defconfig + CONFIG_DYNAMIC_FTRACE=y

(3) Test result

Without this patch:

  [root@linux hello]# insmod hello.ko
  [root@linux hello]# dmesg
  ...
  Hello, world
  This is a test
  ...
  Call Trace:
  [<9000000000223728>] show_stack+0x68/0x18c
  [<90000000013374cc>] dump_stack_lvl+0x60/0x88
  [<ffff800002050028>] L0\x01+0x20/0x2c [hello]
  [<ffff800002058028>] L0\x01+0x20/0x30 [hello]
  [<900000000022097c>] do_one_initcall+0x88/0x288
  [<90000000002df890>] do_init_module+0x54/0x200
  [<90000000002e1e18>] __do_sys_finit_module+0xc4/0x114
  [<90000000013382e8>] do_syscall+0x7c/0x94
  [<9000000000221e3c>] handle_syscall+0xbc/0x158

With this patch:

  [root@linux hello]# insmod hello.ko
  [root@linux hello]# dmesg
  ...
  Hello, world
  This is a test
  ...
  Call Trace:
  [<9000000000223728>] show_stack+0x68/0x18c
  [<90000000013374cc>] dump_stack_lvl+0x60/0x88
  [<ffff800002050028>] test_func+0x28/0x34 [hello]
  [<ffff800002058028>] hello_init+0x28/0x38 [hello]
  [<900000000022097c>] do_one_initcall+0x88/0x288
  [<90000000002df890>] do_init_module+0x54/0x200
  [<90000000002e1e18>] __do_sys_finit_module+0xc4/0x114
  [<90000000013382e8>] do_syscall+0x7c/0x94
  [<9000000000221e3c>] handle_syscall+0xbc/0x158
Signed-off-by: NTiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Youling Tang <tangyouling@loongson.cn> # for LoongArch
Signed-off-by: NLuis Chamberlain <mcgrof@kernel.org>

In order to avoid duplicated code, move is_arm_mapping_symbol() to
include/linux/module_symbol.h, then remove is_arm_mapping_symbol()
in the other places.
Signed-off-by: NTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: NLuis Chamberlain <mcgrof@kernel.org>

After commit 2e3a10a1 ("ARM: avoid ARM binutils leaking ELF local
symbols") and commit d6b73266 ("modpost: fix undefined behavior of
is_arm_mapping_symbol()"), many differences of is_arm_mapping_symbol()
exist in kernel/module/kallsyms.c and scripts/mod/modpost.c, just sync
the code to keep consistent.
Signed-off-by: NTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: NLuis Chamberlain <mcgrof@kernel.org>

modpost now reads CRCs from .*.cmd files, parsing them using strtol().
This is inconsistent with its parsing of Module.symvers and with their
definition as *unsigned* 32-bit values.

strtol() clamps values to [LONG_MIN, LONG_MAX], and when building on a
32-bit system this changes all CRCs >= 0x80000000 to be 0x7fffffff.

Change extract_crcs_for_object() to use strtoul() instead.

Cc: stable@vger.kernel.org
Fixes: f292d875 ("modpost: extract symbol versions from *.cmd files")
Signed-off-by: NBen Hutchings <ben@decadent.org.uk>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Commit 6c730bfc ("modpost: handle -ffunction-sections") added
".text.*" to the OTHER_TEXT_SECTIONS macro to fix certain section
mismatch warnings. Unfortunately, this makes it impossible for modpost
to warn about section mismatches with LTO, which implies
'-ffunction-sections', as all functions are put in their own
'.text.<func_name>' sections, which may still reference functions in
sections they are not supposed to, such as __init.

Fix this by moving ".text.*" into TEXT_SECTIONS, so that configurations
with '-ffunction-sections' will see warnings about mismatched sections.

Link: https://lore.kernel.org/Y39kI3MOtVI5BAnV@google.com/Reported-by: NVincent Donnefort <vdonnefort@google.com>
Reviewed-and-tested-by: NAlexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: NSami Tolvanen <samitolvanen@google.com>
Tested-by: NVincent Donnefort <vdonnefort@google.com>
Signed-off-by: NNathan Chancellor <nathan@kernel.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.build replaces the suffix .o with .ko, then
scripts/Makefile.modpost calls the sed command to change .ko back
to the original .o suffix.

Instead of converting the suffixes back-and-forth, store the .o paths
in modules.order, and replace it with .ko in 'make modules_install'.

This avoids the unneeded sed command.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>

Similar to other architectures such as arm64, x86, riscv and so on, use
offsets relative to the exception table entry values rather than their
absolute addresses for both the exception location and the fixup.

However, LoongArch label difference because it will actually produce two
relocations, a pair of R_LARCH_ADD32 and R_LARCH_SUB32. Take simple code
below for example:

$ cat test_ex_table.S
.section .text
1:
        nop
.section __ex_table,"a"
        .balign 4
        .long (1b - .)
.previous

$ loongarch64-unknown-linux-gnu-gcc -c test_ex_table.S
$ loongarch64-unknown-linux-gnu-readelf -Wr test_ex_table.o

Relocation section '.rela__ex_table' at offset 0x100 contains 2 entries:
    Offset            Info             Type         Symbol's Value   Symbol's Name + Addend
0000000000000000 0000000600000032 R_LARCH_ADD32    0000000000000000  .L1^B1 + 0
0000000000000000 0000000500000037 R_LARCH_SUB32    0000000000000000  L0^A + 0

The modpost will complain the R_LARCH_SUB32 relocation, so we need to
patch modpost.c to skip this relocation for .rela__ex_table section.
Signed-off-by: NYouling Tang <tangyouling@loongson.cn>
Signed-off-by: NHuacai Chen <chenhuacai@loongson.cn>

Breaking long printed messages in multiple lines makes it very hard to
look up where they originated from.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Since commit 7b453719 ("kbuild: link symbol CRCs at final link,
removing CONFIG_MODULE_REL_CRCS"), module versioning is broken on
some architectures. Loading a module fails with "disagrees about
version of symbol module_layout".

On such architectures (e.g. ARCH=sparc build with sparc64_defconfig),
modpost shows a warning, like follows:

  WARNING: modpost: EXPORT symbol "_mcount" [vmlinux] version generation failed, symbol will not be versioned.
  Is "_mcount" prototyped in <asm/asm-prototypes.h>?

Previously, it was a harmless warning (CRC check was just skipped),
but now wrong CRCs are used for comparison because invalid CRCs are
just skipped.

  $ sparc64-linux-gnu-nm -n vmlinux
    [snip]
  0000000000c2cea0 r __ksymtab__kstrtol
  0000000000c2ceb8 r __ksymtab__kstrtoul
  0000000000c2ced0 r __ksymtab__local_bh_enable
  0000000000c2cee8 r __ksymtab__mcount
  0000000000c2cf00 r __ksymtab__printk
  0000000000c2cf18 r __ksymtab__raw_read_lock
  0000000000c2cf30 r __ksymtab__raw_read_lock_bh
    [snip]
  0000000000c53b34 D __crc__kstrtol
  0000000000c53b38 D __crc__kstrtoul
  0000000000c53b3c D __crc__local_bh_enable
  0000000000c53b40 D __crc__printk
  0000000000c53b44 D __crc__raw_read_lock
  0000000000c53b48 D __crc__raw_read_lock_bh

Please notice __crc__mcount is missing here.

When the module subsystem looks up a CRC that comes after, it results
in reading out a wrong address. For example, when __crc__printk is
needed, the module subsystem reads 0xc53b44 instead of 0xc53b40.

All CRC entries must be output for correct index accessing. Invalid
CRCs will be unused, but are needed to keep the one-to-one mapping
between __ksymtab_* and __crc_*.

The best is to fix all modpost warnings, but several warnings are still
remaining on less popular architectures.

Fixes: 7b453719 ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS")
Reported-by: Nmatoro <matoro_mailinglist_kernel@matoro.tk>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Tested-by: Nmatoro <matoro_mailinglist_kernel@matoro.tk>

It is not so useful to have symbol whitelists in arrays. With this
over-engineering, the code is difficult to follow.

Let's do it more directly, and collect the relevant code to one place.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

The ->symbol_white_list field is referenced in secref_whitelist(),
only when 'fromsec' is data_sections.

        /* Check for pattern 2 */
        if (match(tosec, init_exit_sections) &&
            match(fromsec, data_sections) &&
            match(fromsym, mismatch->symbol_white_list))
                return 0;

If .fromsec is not data sections, the .symbol_white_list member is
not used by anyone.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

This will be useful to define a NULL-terminated array inside a function
call.

Currently, string arrays passed to match() are defined in separate
places:

    static const char *const init_sections[] = { ALL_INIT_SECTIONS, NULL };
    static const char *const text_sections[] = { ALL_TEXT_SECTIONS, NULL };
    static const char *const optim_symbols[] = { "*.constprop.*", NULL };

            ...

            /* Check for pattern 5 */
            if (match(fromsec, text_sections) &&
                match(tosec, init_sections) &&
                match(fromsym, optim_symbols))
                    return 0;

With the new helper macro, you can list the patterns directly in the
function call, like this:

            /* Check for pattern 5 */
            if (match(fromsec, PATTERNS(ALL_TEXT_SECTIONS)) &&
                match(tosec, PATTERNS(ALL_INIT_SECTIONS)) &&
                match(fromsym, PATTERNS("*.contprop.*")))
                    return 0;
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Each section mismatch results in long warning messages. Too much.

Make each warning fit in one line, and remove a lot of messy code.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

This reverts commit 77ab21ad.

Even after 8 years later, GCC LTO has not been upstreamed. Also, it said
"This is a workaround". If this is needed in the future, it should be
added in a proper way.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Acked-by: NJiri Slaby <jirislaby@kernel.org>

The section name of Rel and Rela starts with ".rel" and ".rela"
respectively (but, I do not know whether this is specification or
convention).

For example, ".rela.text" holds relocation entries applied to the
".text" section.

So, the code chops the ".rel" or ".rela" prefix to get the name of
the section to which the relocation applies.

However, I do not like to skip 4 or 5 bytes blindly because it is
potential memory overrun.

The ELF specification provides a more reliable way to do this.

 - The sh_info field holds extra information, whose interpretation
   depends on the section type

 - If the section type is SHT_REL or SHT_RELA, the sh_info field holds
   the section header index of the section to which the relocation
   applies.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

The section index is always positive, so the argument, secindex, should
be unsigned.

Also, inserted the array range check.

If sym->st_shndx is a special section index (between SHN_LORESERVE and
SHN_HIRESERVE), there is no corresponding section header.

For example, if a symbol specifies an absolute value, sym->st_shndx is
SHN_ABS (=0xfff1).

The current users do not cause the out-of-range access of
info->sechddrs[], but it is better to avoid such a pitfall.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

Use sym_get_data() to replace the long code.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Since commit 269a535c ("modpost: generate vmlinux.symvers and
reuse it for the second modpost"), modpost only parses relocatable
files (ET_REL).
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

This reverts commit 4d10c223.

Commit 37744fee ("sh: remove sh5 support") removed the sh64 support
entirely.

Note:
.cranges was only used for sh64 ever.
Commit 211dc24b8744 ("Remove sh5 and sh64 support") in binutils-gdb
already removed the relevant code.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Taint the kernel with TAINT_TEST whenever a test module loads, by adding
a new "TEST" module property, and setting it for all modules in the
tools/testing directory. This property can also be set manually, for
tests which live outside the tools/testing directory with:
MODULE_INFO(test, "Y");
Reviewed-by: NLuis Chamberlain <mcgrof@kernel.org>
Reviewed-by: NAaron Tomlin <atomlin@redhat.com>
Acked-by: NBrendan Higgins <brendanhiggins@google.com>
Signed-off-by: NDavid Gow <davidgow@google.com>
Signed-off-by: NShuah Khan <skhan@linuxfoundation.org>

Since commit f02e8a65 ("module: Sort exported symbols"),
EXPORT_SYMBOL* is placed in the individual section ___ksymtab(_gpl)+<sym>
(3 leading underscores instead of 2).

Since then, modpost cannot detect the bad combination of EXPORT_SYMBOL
and __init/__exit.

Fix the .fromsec field.

Fixes: f02e8a65 ("module: Sort exported symbols")
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Replace the own implementation for wildcard (glob) matching with
a function call to fnmatch().

Also, change the return type to 'bool'.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

mod->name is set to the ELF filename with the suffix ".o" stripped.

The current code calls strdup() and free() to manipulate the string,
but a simpler approach is to pass new_module() with the name length
subtracted by 2.

Also, check if the passed filename ends with ".o" before stripping it.

The current code blindly chops the suffix:

    tmp[strlen(tmp) - 2] = '\0'

It will cause buffer under-run if strlen(tmp) < 2;
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

The 'static' specifier and EXPORT_SYMBOL() are an odd combination.

Commit 15bfc234 ("modpost: check for static EXPORT_SYMBOL*
functions") tried to detect it, but this check has false negatives.

Here is the sample code.

  Makefile:

    obj-y += foo1.o foo2.o

  foo1.c:

    #include <linux/export.h>
    static void foo(void) {}
    EXPORT_SYMBOL(foo);

  foo2.c:

    void foo(void) {}

foo1.c exports the static symbol 'foo', but modpost cannot catch it
because it is fooled by foo2.c, which has a global symbol with the
same name.

s->is_static is cleared if a global symbol with the same name is found
somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily
belong to the same compilation unit.

This check should be done per compilation unit, but I do not know how
to do it in modpost. modpost runs against vmlinux.o or modules, which
merges multiple objects, then forgets their origin.

modpost cannot parse individual objects because they may not be ELF but
LLVM IR when CONFIG_LTO_CLANG=y.

Add a simple bash script to parse the output from ${NM}. This works for
CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM IR files.

Revert 15bfc234.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.

CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.

This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.

The following figures show how the LTO build currently works, and
how this commit is changing it.

Current build flow
==================

 [1] single-object module

                                      $(LD)
           $(CC)                     +objtool              $(LD)
    foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
                              (LLVM IR)          (ELF)       |    (ELF)
                                                             |
                                                 foo.mod.o --/
                                                 (LLVM IR)

 [2] multi-object module
                                      $(LD)
           $(CC)         $(AR)       +objtool               $(LD)
    foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
                           |  (archive)          (ELF)       |    (ELF)
    foo2.c -----> foo2.o --/                                 |
                 (LLVM IR)                       foo.mod.o --/
                                                 (LLVM IR)

  One confusion is that foo.o in multi-object module is an archive
  despite of its suffix.

New build flow
==============

 [1] single-object module

  Since there is only one object, there is no need to keep the LLVM IR.
  Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
  is disabled, $(LD) is unneeded because $(CC) produces an ELF object.

               $(CC)+$(LD)+objtool              $(LD)
    foo.c ----------------------------> foo.o ---------> foo.ko
                                        (ELF)     |      (ELF)
                                                  |
                                      foo.mod.o --/
                                      (LLVM IR)

 [2] multi-object module

  Previously, $(AR) was used to combine LLVM IR files into an archive,
  but there was no technical reason to do so. Use $(LD) to merge them
  into a single ELF object.

                               $(LD)
             $(CC)            +objtool          $(LD)
    foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
                                 |      (ELF)     |      (ELF)
    foo2.c ---------> foo2.o ----/                |
                     (LLVM IR)        foo.mod.o --/
                                      (LLVM IR)
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Reviewed-by: NSami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: NJosh Poimboeuf <jpoimboe@kernel.org>

if ((addr - sym->st_value) < distance) {
            distance = addr - sym->st_value;
            near = sym;
    } else if ((addr - sym->st_value) == distance) {
            near = sym;
    }

is equivalent to:

    if (addr - sym->st_value <= distance) {
            distance = addr - sym->st_value;
            near = sym;
    }

(The else-if block can overwrite 'distance' with the same value).
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Move ARRAY_SIZE() from file2alias.c to modpost.h to reuse it in
section_mismatch().

Also, move the variable 'check' inside the for-loop.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

check_sec_ref() does not use the first parameter 'mod'.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

The return value of is_arm_mapping_symbol() is unpredictable when "$"
is passed in.

strchr(3) says:
  The strchr() and strrchr() functions return a pointer to the matched
  character or NULL if the character is not found. The terminating null
  byte is considered part of the string, so that if c is specified as
  '\0', these functions return a pointer to the terminator.

When str[1] is '\0', strchr("axtd", str[1]) is not NULL, and str[2] is
referenced (i.e. buffer overrun).

Test code
---------

  char str1[] = "abc";
  char str2[] = "ab";

  strcpy(str1, "$");
  strcpy(str2, "$");

  printf("test1: %d\n", is_arm_mapping_symbol(str1));
  printf("test2: %d\n", is_arm_mapping_symbol(str2));

Result
------

  test1: 0
  test2: 1
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

With the `-z unique-symbol` linker flag or any similar mechanism,
it is possible to trigger the following:

ERROR: modpost: "param_set_uint.0" [vmlinux] is a static EXPORT_SYMBOL

The reason is that for now the condition from remove_dot():

if (m && (s[n + m] == '.' || s[n + m] == 0))

which was designed to test if it's a dot or a '\0' after the suffix
is never satisfied.
This is due to that `s[n + m]` always points to the last digit of a
numeric suffix, not on the symbol next to it (from a custom debug
print added to modpost):

param_set_uint.0, s[n + m] is '0', s[n + m + 1] is '\0'

So it's off-by-one and was like that since 2014.

Fix this for the sake of any potential upcoming features, but don't
bother stable-backporting, as it's well hidden -- apart from that
LD flag, it can be triggered only with GCC LTO which never landed
upstream.

Fixes: fcd38ed0 ("scripts: modpost: fix compilation warning")
Signed-off-by: NAlexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>

include/{linux,asm-generic}/export.h defines a weak symbol, __crc_*
as a placeholder.

Genksyms writes the version CRCs into the linker script, which will be
used for filling the __crc_* symbols. The linker script format depends
on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset
to the reference of CRC.

It is time to get rid of this complexity.

Now that modpost parses text files (.*.cmd) to collect all the CRCs,
it can generate C code that will be linked to the vmlinux or modules.

Generate a new C file, .vmlinux.export.c, which contains the CRCs of
symbols exported by vmlinux. It is compiled and linked to vmlinux in
scripts/link-vmlinux.sh.

Put the CRCs of symbols exported by modules into the existing *.mod.c
files. No additional build step is needed for modules. As before,
*.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal.

No linker magic is used here. The new C implementation works in the
same way, whether CONFIG_RELOCATABLE is enabled or not.
CONFIG_MODULE_REL_CRCS is no longer needed.

Previously, Kbuild invoked additional $(LD) to update the CRCs in
objects, but this step is unneeded too.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Tested-by: NNicolas Schier <nicolas@fjasle.eu>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol
versions into ELF objects. Then, modpost extracts the version CRCs
from them.

The following figures show how it currently works, and how I am trying
to change it.

Current implementation
======================
                                                           |----------|
                 embed CRC      -------------------------->| final    |
       $(CC)       $(LD)       /  |---------|              | link for |
       -----> *.o -------> *.o -->| modpost |              | vmlinux  |
      /              /            |         |-- *.mod.c -->| or       |
     / genksyms     /             |---------|              | module   |
  *.c ------> *.symversions                                |----------|

Genksyms outputs the calculated CRCs in the form of linker script
(*.symversions), which is used by $(LD) to update the object.

If CONFIG_LTO_CLANG=y, the build process is much more complex. Embedding
the CRCs is postponed until the LLVM bitcode is converted into ELF,
creating another intermediate *.prelink.o.

However, this complexity is unneeded. There is no reason why we must
embed version CRCs in objects so early.

There is final link stage for vmlinux (scripts/link-vmlinux.sh) and
modules (scripts/Makefile.modfinal). We can link CRCs at the very last
moment.

New implementation
==================
                                                           |----------|
                   --------------------------------------->| final    |
       $(CC)      /    |---------|                         | link for |
       -----> *.o ---->|         |                         | vmlinux  |
      /                | modpost |--- .vmlinux.export.c -->| or       |
     / genksyms        |         |--- *.mod.c ------------>| module   |
  *.c ------> *.cmd -->|---------|                         |----------|

Pass the symbol versions to modpost as separate text data, which are
available in *.cmd files.

This commit changes modpost to extract CRCs from *.cmd files instead of
from ELF objects.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Reviewed-by: NSami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

find_symbol() returns the first symbol found in the hash table. This
table is global, so it may return a symbol from an unexpected module.

There is a case where we want to search for a symbol with a given name
in a specified module.

Add sym_find_with_module(), which receives the module pointer as the
second argument. It is equivalent to find_module() if NULL is passed
as the module pointer.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)

There were more EXPORT_SYMBOL types in the past. The following commits
removed unused ones.

 - f1c3d73e ("module: remove EXPORT_SYMBOL_GPL_FUTURE")
 - 36794822 ("module: remove EXPORT_UNUSED_SYMBOL*")

There are 3 remaining in enum export, but export_unknown does not make
any sense because we never expect such a situation like "we do not know
how it was exported".

If the symbol name starts with "__ksymtab_", but the section name
does not start with "___ksymtab+" or "___ksymtab_gpl+", it is not an
exported symbol.

It occurs when a variable starting with "__ksymtab_" is directly defined:

   int __ksymtab_foo;

Presumably, there is no practical issue for using such a weird variable
name (but there is no good reason for doing so, either).

Anyway, that is not an exported symbol. Setting export_unknown is not
the right thing to do. Do not call sym_add_exported() in this case.

With pointless export_unknown removed, the export type finally becomes
boolean (either EXPORT_SYMBOL or EXPORT_SYMBOL_GPL).

I renamed the field name to is_gpl_only. EXPORT_SYMBOL_GPL sets it true.
Only GPL-compatible modules can use it.

I removed the orphan comment, "How a symbol is exported", which is
unrelated to sec_mismatch_count. It is about enum export.
See commit bd5cbced ("kbuild: export-type enhancement to modpost.c")
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>

A later commit will add more code to this list_for_each_entry loop.

Before that, move the loop body into a separate helper function.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>

add_intree_flag(), add_retpoline(), and add_staging_flag() are small
enough to be merged into add_header().
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNicolas Schier <nicolas@fjasle.eu>
Tested-by: NNathan Chancellor <nathan@kernel.org>

new_symbol() does two things; allocate a new symbol and register it
to the hash table.

Using a separate function for each is easier to understand.

Replace new_symbol() with hash_add_symbol(). Remove the second parameter
of alloc_symbol().
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

Currently, sym_add_exported() does not allocate a symbol if the same
name symbol already exists in the hash table.

This does not reflect the real use cases. You can let an external
module override the in-tree one. In this case, the external module
will export the same name symbols as the in-tree one. However,
modpost simply ignores those symbols, then Module.symvers for the
external module loses its symbols.

sym_add_exported() should allocate a new symbol.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>

This is currently a warning, but I think modpost should stop building
in this case.

If the same symbol is exported multiple times and we let it keep going,
the sanity check becomes difficult.

Only the legitimate case is that an external module overrides the
corresponding in-tree module to provide a different implementation
with the same interface.

Also, there exists an upstream example that exploits this feature.

  $ make M=tools/testing/nvdimm

... builds tools/testing/nvdimm/libnvdimm.ko. This is a mocked module
that overrides the symbols from drivers/nvdimm/libnvdimm.ko.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>