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Subject[PATCH] perf, report: use properly build_id kernel binaries
resending with correct lkml address, sry
jirka

---
If we bring the recorded perf data together with kernel
binary from another machine using:

on server A:
perf archive

on server B:
tar xjvf perf.data.tar.bz2 -C ~/.debug

the build_id kernel dso is not properly recognized during
the "perf report" command on server B.

The reason is, that build_id dsos are added during the session initialization,
while the kernel maps are created during the sample event processing.

The machine__create_kernel_maps functions ends up creating new dso object
for kernel, but it does not check if we already have one added by build_id
processing.


Also the build_id reading ABI quirk added in commit:

- commit b25114817a73bbd2b84ce9dba02ee1ef8989a947
perf build-id: Add quirk to deal with perf.data file format breakage

populates the "struct build_id_event::pid" with 0, which
is later interpreted as DEFAULT_GUEST_KERNEL_ID.

This is not always correct, so it's better to guess the pid
value based on the "struct build_id_event::header::misc" value.


- Tested with data generated on x86 kernel version v2.6.34
and reported back on x86_64 current kernel.
- Not tested for guest kernel case.


Note the problem stays for PERF_RECORD_MMAP events recorded by perf that
does not use proper pid (HOST_KERNEL_ID/DEFAULT_GUEST_KERNEL_ID). They are
misinterpreted within the current perf code. Probably there's not much we
can do about that.


Signed-off-by: Jiri Olsa <jolsa@redhat.com>
---
tools/perf/util/header.c | 11 ++++++++-
tools/perf/util/symbol.c | 57 +++++++++++++++++++++++++--------------------
tools/perf/util/symbol.h | 1 -
3 files changed, 42 insertions(+), 27 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index afb0849..a0d90b1 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -726,7 +726,16 @@ static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
return -1;

bev.header = old_bev.header;
- bev.pid = 0;
+
+ /*
+ * As the pid is the missing value, we need to fill
+ * it properly. The header.misc value give us nice hint.
+ */
+ bev.pid = HOST_KERNEL_ID;
+ if (bev.header.misc == PERF_RECORD_MISC_GUEST_USER ||
+ bev.header.misc == PERF_RECORD_MISC_GUEST_KERNEL)
+ bev.pid = DEFAULT_GUEST_KERNEL_ID;
+
memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
__event_process_build_id(&bev, filename, session);

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index eec1963..c307121 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -2170,27 +2170,22 @@ size_t machines__fprintf_dsos_buildid(struct rb_root *machines,
return ret;
}

-struct dso *dso__new_kernel(const char *name)
+static struct dso*
+dso__kernel_findnew(struct machine *machine, const char *name,
+ const char *short_name, int dso_type)
{
- struct dso *dso = dso__new(name ?: "[kernel.kallsyms]");
-
- if (dso != NULL) {
- dso__set_short_name(dso, "[kernel]");
- dso->kernel = DSO_TYPE_KERNEL;
- }
-
- return dso;
-}
+ /*
+ * The kernel dso could be created by build_id processing.
+ */
+ struct dso *dso = __dsos__findnew(&machine->kernel_dsos, name);

-static struct dso *dso__new_guest_kernel(struct machine *machine,
- const char *name)
-{
- char bf[PATH_MAX];
- struct dso *dso = dso__new(name ?: machine__mmap_name(machine, bf,
- sizeof(bf)));
+ /*
+ * We need to run this in all cases, since during the build_id
+ * processing we had no idea this was the kernel dso.
+ */
if (dso != NULL) {
- dso__set_short_name(dso, "[guest.kernel]");
- dso->kernel = DSO_TYPE_GUEST_KERNEL;
+ dso__set_short_name(dso, short_name);
+ dso->kernel = dso_type;
}

return dso;
@@ -2208,24 +2203,36 @@ void dso__read_running_kernel_build_id(struct dso *dso, struct machine *machine)
dso->has_build_id = true;
}

-static struct dso *machine__create_kernel(struct machine *machine)
+static struct dso *machine__get_kernel(struct machine *machine)
{
const char *vmlinux_name = NULL;
struct dso *kernel;

if (machine__is_host(machine)) {
vmlinux_name = symbol_conf.vmlinux_name;
- kernel = dso__new_kernel(vmlinux_name);
+ if (!vmlinux_name)
+ vmlinux_name = "[kernel.kallsyms]";
+
+ kernel = dso__kernel_findnew(machine, vmlinux_name,
+ "[kernel]",
+ DSO_TYPE_KERNEL);
} else {
+ char bf[PATH_MAX];
+
if (machine__is_default_guest(machine))
vmlinux_name = symbol_conf.default_guest_vmlinux_name;
- kernel = dso__new_guest_kernel(machine, vmlinux_name);
+ if (!vmlinux_name)
+ vmlinux_name = machine__mmap_name(machine, bf,
+ sizeof(bf));
+
+ kernel = dso__kernel_findnew(machine, vmlinux_name,
+ "[guest.kernel]",
+ DSO_TYPE_GUEST_KERNEL);
}

- if (kernel != NULL) {
+ if (kernel != NULL && (!kernel->has_build_id))
dso__read_running_kernel_build_id(kernel, machine);
- dsos__add(&machine->kernel_dsos, kernel);
- }
+
return kernel;
}

@@ -2329,7 +2336,7 @@ void machine__destroy_kernel_maps(struct machine *machine)

int machine__create_kernel_maps(struct machine *machine)
{
- struct dso *kernel = machine__create_kernel(machine);
+ struct dso *kernel = machine__get_kernel(machine);

if (kernel == NULL ||
__machine__create_kernel_maps(machine, kernel) < 0)
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 325ee36..4f377d9 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -155,7 +155,6 @@ struct dso {
};

struct dso *dso__new(const char *name);
-struct dso *dso__new_kernel(const char *name);
void dso__delete(struct dso *dso);

int dso__name_len(const struct dso *dso);
--
1.7.1

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