linux/scripts/mod
Masahiro Yamada 31cb50b559 kbuild: check static EXPORT_SYMBOL* by script instead of modpost
The 'static' specifier and EXPORT_SYMBOL() are an odd combination.

Commit 15bfc2348d ("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 15bfc2348d.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
2022-06-01 23:07:02 +09:00
..
.gitignore .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
devicetable-offsets.c HID: intel-ish-hid: add support for MODULE_DEVICE_TABLE() 2021-11-09 11:41:46 +01:00
empty.c
file2alias.c modpost: reuse ARRAY_SIZE() macro for section_mismatch() 2022-05-27 16:15:40 +09:00
list.h modpost: import include/linux/list.h 2022-05-08 03:17:00 +09:00
Makefile scripts/mod: disable LTO for empty.c 2021-01-14 08:21:09 -08:00
mk_elfconfig.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
modpost.c kbuild: check static EXPORT_SYMBOL* by script instead of modpost 2022-06-01 23:07:02 +09:00
modpost.h modpost: reuse ARRAY_SIZE() macro for section_mismatch() 2022-05-27 16:15:40 +09:00
sumversion.c modpost: use bool type where appropriate 2022-05-08 03:17:00 +09:00