Messages in this thread Patch in this message | | | From | Arvind Sankar <> | Subject | [PATCH v2] lib/string.c: Use freestanding environment | Date | Wed, 19 Aug 2020 10:08:16 -0400 |
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gcc can transform the loop in a naive implementation of memset/memcpy etc into a call to the function itself. This optimization is enabled by -ftree-loop-distribute-patterns.
This has been the case for a while (see eg [0]), but gcc-10.x enables this option at -O2 rather than -O3 as in previous versions.
Add -ffreestanding, which implicitly disables this optimization with gcc. It is unclear whether clang performs such optimizations, but hopefully it will also not do so in a freestanding environment.
[0] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu> --- lib/Makefile | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/lib/Makefile b/lib/Makefile index e290fc5707ea..a4a4c6864f51 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -15,11 +15,16 @@ KCOV_INSTRUMENT_debugobjects.o := n KCOV_INSTRUMENT_dynamic_debug.o := n KCOV_INSTRUMENT_fault-inject.o := n +# string.o implements standard library functions like memset/memcpy etc. +# Use -ffreestanding to ensure that the compiler does not try to "optimize" +# them into calls to themselves. +CFLAGS_string.o := -ffreestanding + # Early boot use of cmdline, don't instrument it ifdef CONFIG_AMD_MEM_ENCRYPT KASAN_SANITIZE_string.o := n -CFLAGS_string.o := -fno-stack-protector +CFLAGS_string.o += -fno-stack-protector endif # Used by KCSAN while enabled, avoid recursion. -- 2.26.2
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