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authorArvind Sankar <nivedita@alum.mit.edu>2020-08-19 17:08:16 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-19 21:23:45 +0300
commit33d0f96ffd7394ffb208bb366be312d12dfd24a4 (patch)
tree786d9469c3f97b255001d323964ad23b83118728 /lib/Makefile
parent394b19d6cb58ae292c0e1ad6b893fed8ece477ce (diff)
downloadlinux-33d0f96ffd7394ffb208bb366be312d12dfd24a4.tar.xz
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 <nivedita@alum.mit.edu> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/Makefile')
-rw-r--r--lib/Makefile7
1 files changed, 6 insertions, 1 deletions
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.