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Subject[PATCH V2 52/52] perf tools: Add support for 32-bit compatibility VDSOs
Date
'perf record' post-processes the event stream  to create
a list of build-ids for object files for which sample
events have been recorded. That results in those object
files being recorded in the build-id cache.

In the case of VDSO, perf tools reads it from memory
and copies it into a temporary file, which as decribed
above, gets added to the build-id cache.

Then when the perf.data file is processed by other
tools, the build-id of VDSO is listed in the perf.data
file and the VDSO can be read from the build-id cache.
In that case the name of the map, the short name of the
DSO, and the entry in the build-id cache are all
"[vdso]".

However, in the 64-bit case, there also can be 32-bit
compatibility VDSOs.

A previous patch added programs "perf-read-vdso32" and
"perf read-vdsox32". This patch uses those programs to
read the correct VDSO for a thread and create a
temporary file just as for the 64-bit VDSO. The map
name and the entry in the build-id cache are still
"[vdso]" but the DSO short name becomes "[vdso32]"
and "[vdsox32]" respectively.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---


V2:
Fix copy-and-paste errors spotted by Namhyung (Thank you!)


tools/perf/util/vdso.c | 170 ++++++++++++++++++++++++++++++++++++++++++++++++-
tools/perf/util/vdso.h | 4 +-
2 files changed, 172 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/vdso.c b/tools/perf/util/vdso.c
index adca693..25381cf 100644
--- a/tools/perf/util/vdso.c
+++ b/tools/perf/util/vdso.c
@@ -12,6 +12,7 @@
#include "util.h"
#include "symbol.h"
#include "machine.h"
+#include "thread.h"
#include "linux/string.h"
#include "debug.h"

@@ -22,10 +23,15 @@ struct vdso_file {
bool error;
char temp_file_name[sizeof(VDSO__TEMP_FILE_NAME)];
const char *dso_name;
+ const char *read_prog;
};

struct vdso_info {
struct vdso_file vdso;
+#if BITS_PER_LONG == 64
+ struct vdso_file vdso32;
+ struct vdso_file vdsox32;
+#endif
};

static struct vdso_info *vdso_info__new(void)
@@ -35,6 +41,18 @@ static struct vdso_info *vdso_info__new(void)
.temp_file_name = VDSO__TEMP_FILE_NAME,
.dso_name = DSO__NAME_VDSO,
},
+#if BITS_PER_LONG == 64
+ .vdso32 = {
+ .temp_file_name = VDSO__TEMP_FILE_NAME,
+ .dso_name = DSO__NAME_VDSO32,
+ .read_prog = "perf-read-vdso32",
+ },
+ .vdsox32 = {
+ .temp_file_name = VDSO__TEMP_FILE_NAME,
+ .dso_name = DSO__NAME_VDSOX32,
+ .read_prog = "perf-read-vdsox32",
+ },
+#endif
};

return memdup(&vdso_info_init, sizeof(vdso_info_init));
@@ -117,6 +135,12 @@ void vdso__exit(struct machine *machine)

if (vdso_info->vdso.found)
unlink(vdso_info->vdso.temp_file_name);
+#if BITS_PER_LONG == 64
+ if (vdso_info->vdso32.found)
+ unlink(vdso_info->vdso32.temp_file_name);
+ if (vdso_info->vdsox32.found)
+ unlink(vdso_info->vdsox32.temp_file_name);
+#endif

zfree(&machine->vdso_info);
}
@@ -135,6 +159,143 @@ static struct dso *vdso__new(struct machine *machine, const char *short_name,
return dso;
}

+#if BITS_PER_LONG == 64
+
+static enum dso_type machine__thread_dso_type(struct machine *machine,
+ struct thread *thread)
+{
+ enum dso_type dso_type = DSO__TYPE_UNKNOWN;
+ struct map *map;
+ struct dso *dso;
+
+ map = map_groups__first(thread->mg, MAP__FUNCTION);
+ for (; map ; map = map_groups__next(map)) {
+ dso = map->dso;
+ if (!dso || dso->long_name[0] != '/')
+ continue;
+ dso_type = dso__type(dso, machine);
+ if (dso_type != DSO__TYPE_UNKNOWN)
+ break;
+ }
+
+ return dso_type;
+}
+
+static int vdso__do_copy_compat(FILE *f, int fd)
+{
+ char buf[4096];
+ size_t count;
+
+ while (1) {
+ count = fread(buf, 1, sizeof(buf), f);
+ if (ferror(f))
+ return -errno;
+ if (feof(f))
+ break;
+ if (count && writen(fd, buf, count) != (ssize_t)count)
+ return -errno;
+ }
+
+ return 0;
+}
+
+static int vdso__copy_compat(const char *prog, int fd)
+{
+ FILE *f;
+ int err;
+
+ f = popen(prog, "r");
+ if (!f)
+ return -errno;
+
+ err = vdso__do_copy_compat(f, fd);
+
+ if (pclose(f) == -1)
+ return -errno;
+
+ return err;
+}
+
+static int vdso__create_compat_file(const char *prog, char *temp_name)
+{
+ int fd, err;
+
+ fd = mkstemp(temp_name);
+ if (fd < 0)
+ return -errno;
+
+ err = vdso__copy_compat(prog, fd);
+
+ if (close(fd) == -1)
+ return -errno;
+
+ return err;
+}
+
+static const char *vdso__get_compat_file(struct vdso_file *vdso_file)
+{
+ int err;
+
+ if (vdso_file->found)
+ return vdso_file->temp_file_name;
+
+ if (vdso_file->error)
+ return NULL;
+
+ err = vdso__create_compat_file(vdso_file->read_prog,
+ vdso_file->temp_file_name);
+ if (err) {
+ pr_err("%s failed, error %d\n", vdso_file->read_prog, err);
+ vdso_file->error = true;
+ return NULL;
+ }
+
+ vdso_file->found = true;
+
+ return vdso_file->temp_file_name;
+}
+
+static struct dso *vdso__findnew_compat(struct machine *machine,
+ struct vdso_file *vdso_file)
+{
+ const char *file_name;
+ struct dso *dso;
+
+ dso = dsos__find(&machine->user_dsos, vdso_file->dso_name, true);
+ if (dso)
+ return dso;
+
+ file_name = vdso__get_compat_file(vdso_file);
+ if (!file_name)
+ return NULL;
+
+ return vdso__new(machine, vdso_file->dso_name, file_name);
+}
+
+static int vdso__dso_findnew_compat(struct machine *machine,
+ struct thread *thread,
+ struct vdso_info *vdso_info,
+ struct dso **dso)
+{
+ enum dso_type dso_type;
+
+ dso_type = machine__thread_dso_type(machine, thread);
+ switch (dso_type) {
+ case DSO__TYPE_32BIT:
+ *dso = vdso__findnew_compat(machine, &vdso_info->vdso32);
+ return 1;
+ case DSO__TYPE_X32BIT:
+ *dso = vdso__findnew_compat(machine, &vdso_info->vdsox32);
+ return 1;
+ case DSO__TYPE_UNKNOWN:
+ case DSO__TYPE_64BIT:
+ default:
+ return 0;
+ }
+}
+
+#endif
+
struct dso *vdso__dso_findnew(struct machine *machine,
struct thread *thread __maybe_unused)
{
@@ -148,6 +309,11 @@ struct dso *vdso__dso_findnew(struct machine *machine,
if (!vdso_info)
return NULL;

+#if BITS_PER_LONG == 64
+ if (vdso__dso_findnew_compat(machine, thread, vdso_info, &dso))
+ return dso;
+#endif
+
dso = dsos__find(&machine->user_dsos, DSO__NAME_VDSO, true);
if (!dso) {
char *file;
@@ -164,5 +330,7 @@ struct dso *vdso__dso_findnew(struct machine *machine,

bool dso__is_vdso(struct dso *dso)
{
- return !strcmp(dso->short_name, DSO__NAME_VDSO);
+ return !strcmp(dso->short_name, DSO__NAME_VDSO) ||
+ !strcmp(dso->short_name, DSO__NAME_VDSO32) ||
+ !strcmp(dso->short_name, DSO__NAME_VDSOX32);
}
diff --git a/tools/perf/util/vdso.h b/tools/perf/util/vdso.h
index af9d692..d97da16 100644
--- a/tools/perf/util/vdso.h
+++ b/tools/perf/util/vdso.h
@@ -7,7 +7,9 @@

#define VDSO__MAP_NAME "[vdso]"

-#define DSO__NAME_VDSO "[vdso]"
+#define DSO__NAME_VDSO "[vdso]"
+#define DSO__NAME_VDSO32 "[vdso32]"
+#define DSO__NAME_VDSOX32 "[vdsox32]"

static inline bool is_vdso_map(const char *filename)
{
--
1.8.3.2


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