From 33d0f96ffd7394ffb208bb366be312d12dfd24a4 Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Wed, 19 Aug 2020 10:08:16 -0400 Subject: lib/string.c: Use freestanding environment 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, 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. Signed-off-by: Arvind Sankar Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888 Signed-off-by: Linus Torvalds --- lib/Makefile | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'lib/Makefile') 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. -- cgit