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
