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Fri, 09 Aug 2019 06:25:29 -0700 (PDT) From: Arnaldo Carvalho de Melo X-Google-Original-From: Arnaldo Carvalho de Melo Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 8885440340; Fri, 9 Aug 2019 10:25:22 -0300 (-03) Date: Fri, 9 Aug 2019 10:25:22 -0300 To: Leo Yan Cc: Alexander Shishkin , Jiri Olsa , Namhyung Kim , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH] perf trace: Fix segmentation fault when access syscall info Message-ID: <20190809132522.GB20899@kernel.org> References: <20190809104752.27338-1-leo.yan@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190809104752.27338-1-leo.yan@linaro.org> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.12.0 (2019-05-25) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Fri, Aug 09, 2019 at 06:47:52PM +0800, Leo Yan escreveu: > 'perf trace' reports the segmentation fault as below on Arm64: > > # perf trace -e string -e augmented_raw_syscalls.c > LLVM: dumping tools/perf/examples/bpf/augmented_raw_syscalls.o > perf: Segmentation fault > Obtained 12 stack frames. > perf(sighandler_dump_stack+0x47) [0xaaaaac96ac87] > linux-vdso.so.1(+0x5b7) [0xffffadbeb5b7] > /lib/aarch64-linux-gnu/libc.so.6(strlen+0x10) [0xfffface7d5d0] > /lib/aarch64-linux-gnu/libc.so.6(_IO_vfprintf+0x1ac7) [0xfffface49f97] > /lib/aarch64-linux-gnu/libc.so.6(__vsnprintf_chk+0xc7) [0xffffacedfbe7] > perf(scnprintf+0x97) [0xaaaaac9ca3ff] > perf(+0x997bb) [0xaaaaac8e37bb] > perf(cmd_trace+0x28e7) [0xaaaaac8ec09f] > perf(+0xd4a13) [0xaaaaac91ea13] > perf(main+0x62f) [0xaaaaac8a147f] > /lib/aarch64-linux-gnu/libc.so.6(__libc_start_main+0xe3) [0xfffface22d23] > perf(+0x57723) [0xaaaaac8a1723] > Segmentation fault > > This issue is introduced by commit 30a910d7d3e0 ("perf trace: > Preallocate the syscall table"), it allocates trace->syscalls.table[] > array and the element count is 'trace->sctbl->syscalls.nr_entries'; > but on Arm64, the system call number is not continuously used; e.g. the > syscall maximum id is 436 but the real entries is only 281. So the > table is allocated with 'nr_entries' as the element count, but it > accesses the table with the syscall id, which might be out of the bound > of the array and cause the segmentation fault. > > This patch allocates trace->syscalls.table[] with the element count is > 'trace->sctbl->syscalls.max_id + 1', this allows any id to access the > table without out of the bound. Thanks a lot! My bad, that is why we have that max_id there, I forgot about it and since I tested so far only on x86_64... applied to perf/core, since it is only on: [acme@quaco perf]$ git tag --contains 30a910d7d3e0 perf-core-for-mingo-5.4-20190729 [acme@quaco perf]$ - Arnaldo > Fixes: 30a910d7d3e0 ("perf trace: Preallocate the syscall table") > Signed-off-by: Leo Yan > --- > tools/perf/builtin-trace.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c > index 75eb3811e942..d553d06a9aeb 100644 > --- a/tools/perf/builtin-trace.c > +++ b/tools/perf/builtin-trace.c > @@ -1492,7 +1492,7 @@ static int trace__read_syscall_info(struct trace *trace, int id) > const char *name = syscalltbl__name(trace->sctbl, id); > > if (trace->syscalls.table == NULL) { > - trace->syscalls.table = calloc(trace->sctbl->syscalls.nr_entries, sizeof(*sc)); > + trace->syscalls.table = calloc(trace->sctbl->syscalls.max_id + 1, sizeof(*sc)); > if (trace->syscalls.table == NULL) > return -ENOMEM; > } > -- > 2.17.1 -- - Arnaldo