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