[PATCH v4 05/17] ctype: Work around Clang -mbranch-protection=none bug
From: Kees Cook <hidden>
Date: 2020-06-29 20:48:45
Also in:
linux-arm-kernel, linux-efi, lkml
Subsystem:
library code, the rest · Maintainers:
Andrew Morton, Linus Torvalds
In preparation for building efi/libstub with -mbranch-protection=none (EFI does not support branch protection features[1]), add no-op code to work around a Clang bug that emits an unwanted .note.gnu.property section for object files without code[2]. [1] https://lore.kernel.org/lkml/CAMj1kXHck12juGi=E=P4hWP_8vQhQ+-x3vBMc3TGeRWdQ-XkxQ@mail.gmail.com (local) [2] https://bugs.llvm.org/show_bug.cgi?id=46480 Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Will Deacon <will@kernel.org> Cc: Dave Martin <Dave.Martin@arm.com> Cc: clang-built-linux@googlegroups.com Signed-off-by: Kees Cook <redacted> --- lib/ctype.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/lib/ctype.c b/lib/ctype.c
index c819fe269eb2..21245ed57d90 100644
--- a/lib/ctype.c
+++ b/lib/ctype.c@@ -36,3 +36,13 @@ _L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L,_L, /* 224-239 */ _L,_L,_L,_L,_L,_L,_L,_P,_L,_L,_L,_L,_L,_L,_L,_L}; /* 240-255 */ EXPORT_SYMBOL(_ctype); + +/* + * Clang will generate .note.gnu.property sections for object files + * without code, even in the presence of -mbranch-protection=none. + * To work around this, define an unused static function. + * https://bugs.llvm.org/show_bug.cgi?id=46480 + */ +#ifdef CONFIG_CC_IS_CLANG +void __maybe_unused __clang_needs_code_here(void) { } +#endif
--
2.25.1