On Wed, Mar 13, 2019 at 12:43:14PM -0700, Sean Christopherson wrote:
> Since 4.8.3, gcc has enabled -fstack-protector by default. This is
> problematic for the KVM selftests as they do not configure fs or gs
> segments (the stack canary is pulled from fs:0x28). With the default
> behavior, gcc will insert a stack canary on any function that creates
> buffers of 8 bytes or more. As a result, ucall() will hit a triple
> fault shutdown due to reading a bad fs segment when inserting its
> stack canary, i.e. every test fails with an unexpected SHUTDOWN.
>
> Fixes: 14c47b7530e2d ("kvm: selftests: introduce ucall")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> tools/testing/selftests/kvm/Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 3c1f4bdf9000..596c0864d0df 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -29,7 +29,7 @@ LIBKVM += $(LIBKVM_$(UNAME_M))
> INSTALL_HDR_PATH = $(top_srcdir)/usr
> LINUX_HDR_PATH = $(INSTALL_HDR_PATH)/include/
> LINUX_TOOL_INCLUDE = $(top_srcdir)/tools/include
> -CFLAGS += -O2 -g -std=gnu99 -I$(LINUX_TOOL_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude -I$(<D) -Iinclude/$(UNAME_M) -I..
> +CFLAGS += -O2 -g -std=gnu99 -fno-stack-protector -I$(LINUX_TOOL_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude -I$(<D) -Iinclude/$(UNAME_M) -I..
> LDFLAGS += -pthread
>
> # After inclusion, $(OUTPUT) is defined and
Please ignore this patch, I figured out why the TLS wasn't in the elf
headers, which is a separate fix of its own. With the TLS in hand a
better fix is to actually set fs.
