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