From: Nick Desaulniers ndesaulniers@google.com
[ Upstream commit 51da9dfb7f20911ae4e79e9b412a9c2d4c373d4b ]
ELFNOTE_START allows callers to specify flags for .pushsection assembler directives. All callsites but ELF_NOTE use "a" for SHF_ALLOC. For vdso's that explicitly use ELF_NOTE_START and BUILD_SALT, the same section is specified twice after preprocessing, once with "a" flag, once without. Example:
.pushsection .note.Linux, "a", @note ; .pushsection .note.Linux, "", @note ;
While GNU as allows this ordering, it warns for the opposite ordering, making these directives position dependent. We'd prefer not to precisely match this behavior in Clang's integrated assembler. Instead, the non __ASSEMBLY__ definition of ELF_NOTE uses __attribute__((section(".note.Linux"))) which is created with SHF_ALLOC, so let's make the __ASSEMBLY__ definition of ELF_NOTE consistent with C and just always use "a" flag.
This allows Clang to assemble a working mainline (5.6) kernel via: $ make CC=clang AS=clang
Signed-off-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Reviewed-by: Nathan Chancellor natechancellor@gmail.com Reviewed-by: Fangrui Song maskray@google.com Cc: Jeremy Fitzhardinge jeremy@goop.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Vincenzo Frascino vincenzo.frascino@arm.com Link: https://github.com/ClangBuiltLinux/linux/issues/913 Link: http://lkml.kernel.org/r/20200325231250.99205-1-ndesaulniers@google.com Debugged-by: Ilie Halip ilie.halip@gmail.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/elfnote.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h index 278e3ef05336..56c6d9031663 100644 --- a/include/linux/elfnote.h +++ b/include/linux/elfnote.h @@ -53,7 +53,7 @@ .popsection ;
#define ELFNOTE(name, type, desc) \ - ELFNOTE_START(name, type, "") \ + ELFNOTE_START(name, type, "a") \ desc ; \ ELFNOTE_END