[PATCH 09/14] KVM: selftests: Explicitly disable builtins for mem*() overrides

[Sean Christopherson]

Explicitly disable the compiler's builtin memcmp(), memcpy(), and
memset().  Because only lib/string_override.c is built with -ffreestanding,
the compiler reserves the right to do what it wants and can try to link the
non-freestanding code to its own crud.

  /usr/bin/x86_64-linux-gnu-ld: /lib/x86_64-linux-gnu/libc.a(memcmp.o): in function `memcmp_ifunc':
  (.text+0x0): multiple definition of `memcmp'; tools/testing/selftests/kvm/lib/string_override.o:
  tools/testing/selftests/kvm/lib/string_override.c:15: first defined here
  clang: error: linker command failed with exit code 1 (use -v to see invocation)

Fixes: 6b6f71484bf4 ("KVM: selftests: Implement memcmp(), memcpy(), and memset() for guest use")
Reported-by: Aaron Lewis <aaronlewis@xxxxxxxxxx>
Reported-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index a6050dcc381a..6594ed51eeea 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -191,6 +191,7 @@ else
 LINUX_TOOL_ARCH_INCLUDE = $(top_srcdir)/tools/arch/$(ARCH)/include
 endif
 CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
+	-fno-builtin-memcmp -fno-builtin-memcpy -fno-builtin-memset \
 	-fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
 	-I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \
 	-I$(<D) -Iinclude/$(ARCH_DIR) -I ../rseq -I.. $(EXTRA_CFLAGS) \
-- 
2.39.0.rc1.256.g54fd8350bd-goog