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? > > 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 >