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[45.79.221.244]) by smtp.gmail.com with ESMTPSA id d45sm3752547qtc.70.2019.09.02.07.15.17 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 02 Sep 2019 07:15:28 -0700 (PDT) Date: Mon, 2 Sep 2019 22:15:11 +0800 From: Leo Yan To: Adrian Hunter Subject: Re: [PATCH v5] perf machine: arm/arm64: Improve completeness for kernel address space Message-ID: <20190902141511.GF4931@leoy-ThinkPad-X240s> References: <20190815082521.16885-1-leo.yan@linaro.org> <20190815113242.GA28881@leoy-ThinkPad-X240s> <20190816014541.GA17960@leoy-ThinkPad-X240s> <363577f1-097e-eddd-a6ca-b23f644dd8ce@intel.com> <20190826125105.GA3288@leoy-ThinkPad-X240s> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190826125105.GA3288@leoy-ThinkPad-X240s> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190902_071531_551499_F51A98DC X-CRM114-Status: GOOD ( 30.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Song Liu , Mathieu Poirier , Daniel Borkmann , Suzuki Poulouse , Alexander Shishkin , netdev@vger.kernel.org, coresight@lists.linaro.org, Alexei Starovoitov , Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Peter Zijlstra , Yonghong Song , Namhyung Kim , bpf@vger.kernel.org, Jiri Olsa , Martin KaFai Lau , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Adrian, On Mon, Aug 26, 2019 at 08:51:05PM +0800, Leo Yan wrote: > Hi Adrian, > > On Fri, Aug 16, 2019 at 04:00:02PM +0300, Adrian Hunter wrote: > > On 16/08/19 4:45 AM, Leo Yan wrote: > > > Hi Adrian, > > > > > > On Thu, Aug 15, 2019 at 02:45:57PM +0300, Adrian Hunter wrote: > > > > > > [...] > > > > > >>>> How come you cannot use kallsyms to get the information? > > >>> > > >>> Thanks for pointing out this. Sorry I skipped your comment "I don't > > >>> know how you intend to calculate ARM_PRE_START_SIZE" when you reviewed > > >>> the patch v3, I should use that chance to elaborate the detailed idea > > >>> and so can get more feedback/guidance before procceed. > > >>> > > >>> Actually, I have considered to use kallsyms when worked on the previous > > >>> patch set. > > >>> > > >>> As mentioned in patch set v4's cover letter, I tried to implement > > >>> machine__create_extra_kernel_maps() for arm/arm64, the purpose is to > > >>> parse kallsyms so can find more kernel maps and thus also can fixup > > >>> the kernel start address. But I found the 'perf script' tool directly > > >>> calls machine__get_kernel_start() instead of running into the flow for > > >>> machine__create_extra_kernel_maps(); > > >> > > >> Doesn't it just need to loop through each kernel map to find the lowest > > >> start address? > > > > > > Based on your suggestion, I worked out below change and verified it > > > can work well on arm64 for fixing up start address; please let me know > > > if the change works for you? > > > > How does that work if take a perf.data file to a machine with a different > > architecture? > > Sorry I delayed so long to respond to your question; I didn't have > confidence to give out very reasonale answer and this is the main reason > for delaying. Could you take chance to review my below replying? I'd like to get your confirmation before I send out offical patch. Thanks, Leo Yan > > For your question for taking a perf.data file to a machine with a > different architecture, we can firstly use command 'perf buildid-list' > to print out the buildid for kallsyms, based on the dumped buildid we > can find out the location for the saved kallsyms file; then we can use > option '--kallsyms' to specify the offline kallsyms file and use the > offline kallsyms to fixup kernel start address. The detailed commands > are listed as below: > > root@debian:~# perf buildid-list > 7b36dfca8317ef74974ebd7ee5ec0a8b35c97640 [kernel.kallsyms] > 56b84aa88a1bcfe222a97a53698b92723a3977ca /usr/lib/systemd/systemd > 0956b952e9cd673d48ff2cfeb1a9dbd0c853e686 /usr/lib/aarch64-linux-gnu/libm-2.28.so > [...] > > root@debian:~# perf script --kallsyms ~/.debug/\[kernel.kallsyms\]/7b36dfca8317ef74974ebd7ee5ec0a8b35c97640/kallsyms > > The amended patch is as below, please review and always welcome > any suggestions or comments! > > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > index 5734460fc89e..593f05cc453f 100644 > --- a/tools/perf/util/machine.c > +++ b/tools/perf/util/machine.c > @@ -2672,9 +2672,26 @@ int machine__nr_cpus_avail(struct machine *machine) > return machine ? perf_env__nr_cpus_avail(machine->env) : 0; > } > > +static int machine__fixup_kernel_start(void *arg, > + const char *name __maybe_unused, > + char type, > + u64 start) > +{ > + struct machine *machine = arg; > + > + type = toupper(type); > + > + /* Fixup for text, weak, data and bss sections. */ > + if (type == 'T' || type == 'W' || type == 'D' || type == 'B') > + machine->kernel_start = min(machine->kernel_start, start); > + > + return 0; > +} > + > int machine__get_kernel_start(struct machine *machine) > { > struct map *map = machine__kernel_map(machine); > + char filename[PATH_MAX]; > int err = 0; > > /* > @@ -2696,6 +2713,22 @@ int machine__get_kernel_start(struct machine *machine) > if (!err && !machine__is(machine, "x86_64")) > machine->kernel_start = map->start; > } > + > + if (symbol_conf.kallsyms_name != NULL) { > + strncpy(filename, symbol_conf.kallsyms_name, PATH_MAX); > + } else { > + machine__get_kallsyms_filename(machine, filename, PATH_MAX); > + > + if (symbol__restricted_filename(filename, "/proc/kallsyms")) > + goto out; > + } > + > + if (kallsyms__parse(filename, machine, machine__fixup_kernel_start)) > + pr_warning("Fail to fixup kernel start address. skipping...\n"); > + > +out: > return err; > } > > > Thanks, > Leo Yan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel