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

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Message-ID: <5be21a93-8a28-0214-59f0-21b56b0946a2@redhat.com>
Date:   Wed, 10 Aug 2022 19:59:07 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Florian Weimer <fweimer@...hat.com>, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, maz@...nel.org,
        oliver upton <oliver.upton@...ux.dev>,
        andrew jones <andrew.jones@...ux.dev>, seanjc@...gle.com,
        yihyu@...hat.com, shan gavin <shan.gavin@...il.com>
Subject: Re: [PATCH 1/2] KVM: selftests: Make rseq compatible with glibc-2.35

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