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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id 13-20020a62190d000000b0052d4ffac466sm1487969pfz.188.2022.08.04.16.41.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Aug 2022 16:41:51 -0700 (PDT) Date: Thu, 4 Aug 2022 23:41:47 +0000 From: Sean Christopherson To: Andrew Jones Cc: Jinrong Liang , Paolo Bonzini , Wanpeng Li , Jim Mattson , Vitaly Kuznetsov , Joerg Roedel , Jinrong Liang , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests: kvm: Fix a compile error in selftests/kvm/rseq_test.c Message-ID: References: <20220802071240.84626-1-cloudliang@tencent.com> <20220802150830.rgzeg47enbpsucbr@kamzik> <20220803142637.3y5fj2cwyvbrwect@kamzik> <20220803172627.kccwzda6eshx3vol@kamzik> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220803172627.kccwzda6eshx3vol@kamzik> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Aug 03, 2022, Andrew Jones wrote: > On Wed, Aug 03, 2022 at 04:10:53PM +0000, Sean Christopherson wrote: > > On Wed, Aug 03, 2022, Andrew Jones wrote: > > > On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote: > > > > My ldd version is (GNU libc) 2.28, and I get a compilation error in this case. > > > > But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine. > > > > This shows that compilation errors may occur in different GNU libc environments. > > > > Would it be more appropriate to use syscall for better compatibility? > > > > > > OK, it's a pity, but no big deal to use syscall(). > > > > Ya, https://man7.org/linux/man-pages/man2/gettid.2.html says: > > > > The gettid() system call first appeared on Linux in kernel 2.4.11. Library > > support was added in glibc 2.30. > > > > But there are already two other instances of syscall(SYS_gettid) in KVM selftests, > > tools/testing/selftests/kvm/lib/assert.c even adds a _gettid() wrapper. > > Ha! And I found four more in selftests... > > testing/selftests/powerpc/include/utils.h > testing/selftests/proc/proc.h > testing/selftests/rseq/param_test.c > testing/selftests/sched/cs_prctl_test.c > > and even more in tools... Ha, and tools/testing/selftests/sched/cs_prctl_test.c even has the GLIBC crud. #if __GLIBC_PREREQ(2, 30) == 0 #include static pid_t gettid(void) { return syscall(SYS_gettid); } #endif > > So rather than having to remember (or discover) to use syscall(SYS_gettid), I wonder > > if it's possible to conditionally define gettid()? E.g. check for GLIBC version? > > Or do > > > > #define gettid() syscall(SYS_gettid) > > > > so that it's always available and simply overrides the library's gettid() if it's > > provided? > > Sounds good to me. Now the question is where to put it? kvm_util.h, > test_util.h, or maybe we should create a new header just for stuff > like this? tools/include/uapi/linux/syscall.h? Kind of dirty, but not thaaaat dirty.