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[50.116.10.16]) by smtp.gmail.com with ESMTPSA id v15sm3255539pfn.69.2019.08.15.18.45.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 15 Aug 2019 18:45:48 -0700 (PDT) Date: Fri, 16 Aug 2019 09:45:41 +0800 From: Leo Yan To: Adrian Hunter Cc: Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, clang-built-linux@googlegroups.com, Mathieu Poirier , Peter Zijlstra , Suzuki Poulouse , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5] perf machine: arm/arm64: Improve completeness for kernel address space Message-ID: <20190816014541.GA17960@leoy-ThinkPad-X240s> References: <20190815082521.16885-1-leo.yan@linaro.org> <20190815113242.GA28881@leoy-ThinkPad-X240s> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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? diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index f6ee7fbad3e4..51d78313dca1 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -2671,9 +2671,26 @@ 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; /* @@ -2687,6 +2704,7 @@ int machine__get_kernel_start(struct machine *machine) machine->kernel_start = 1ULL << 63; if (map) { err = map__load(map); /* * On x86_64, PTI entry trampolines are less than the * start of kernel text, but still above 2^63. So leave @@ -2695,6 +2713,16 @@ int machine__get_kernel_start(struct machine *machine) if (!err && !machine__is(machine, "x86_64")) machine->kernel_start = map->start; } + + 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