Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

[Gavin Shan]

Hi Paolo,

On 8/10/22 7:14 PM, Paolo Bonzini wrote:
> On 8/9/22 14:21, Mathieu Desnoyers wrote:
> > > For kvm/selftests, there are 3 architectures involved actually. So we
> > > just need consider 4 cases: aarch64, x86, s390 and other. For other
> > > case, we just use __builtin_thread_pointer() to maintain code's
> > > integrity, but it's not called at all.
> > >
> > > I think kvm/selftest is always relying on glibc if I'm correct.
> > All those are handled in the rseq selftests and in librseq. Why duplicate all that logic again?
>
> Yeah, rseq_test should reuse librseq code.  The simplest way,
> if slightly hackish, is to do something like
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 690b499c3471..6c192b0ec304 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -37,6 +37,7 @@ ifeq ($(ARCH),riscv)
>       UNAME_M := riscv
>   endif
>
>   LIBKVM += lib/assert.c
>   LIBKVM += lib/elf.c
>   LIBKVM += lib/guest_modes.c
> @@ -198,7 +199,7 @@ endif
>   CFLAGS += -Wall -Wstrict-prototypes -Wuninitialized -O2 -g -std=gnu99 \
>       -fno-stack-protector -fno-PIE -I$(LINUX_TOOL_INCLUDE) \
>       -I$(LINUX_TOOL_ARCH_INCLUDE) -I$(LINUX_HDR_PATH) -Iinclude \
> -    -I$(<D) -Iinclude/$(UNAME_M) -I.. $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
> +    -I$(<D) -Iinclude/$(UNAME_M) -I.. $(EXTRA_CFLAGS) $(KHDR_INCLUDES) -I../rseq
>
>   no-pie-option := $(call try-run, echo 'int main() { return 0; }' | \
>           $(CC) -Werror -no-pie -x c - -o "$$TMP", -no-pie)
>
>
> and just #include "../rseq/rseq.c" in rseq_test.c.

Thank you. It's really a nice idea. I think it's best way to share
"../rseq/rseq.c". In this way, we needn't to rely on "../rseq/librseq.so",
which is compiled by "../rseq/Makefile".

I will modify the code accordingly in v2 :)

Thanks,
Gavin