[PATCH v2 1/3] SDT markers listing by perf:

From: Hemant Kumar
Date: Mon Oct 07 2013 - 02:48:14 EST

This patch will enable perf to list all the sdt markers present
in an elf file. The markers are present in the .note.stapsdt section
of the elf. We can traverse through this section and collect the
required info about the markers.
We can use '-S/--markers' with perf to view the SDT notes.

Currently, the sdt notes which have their semaphores enabled, are being
ignored silently. But, they will be supported soon.

I think wrapping this inside #ifdef LIBELF_SUPPORT pair is not required,
because, if NO_LIBELF = 1, then 'probe' command of perf is itself disabled.

Usage:
perf probe --markers -x /lib64/libc.so.6

Output :
%libc:setjmp
%libc:longjmp
%libc:longjmp_target
%libc:lll_futex_wake
%libc:lll_lock_wait_private
%libc:longjmp
%libc:longjmp_target
%libc:lll_futex_wake

Signed-off-by: Hemant Kumar Shaw <hkshaw@xxxxxxxxxxxxxxxxxx>
---
tools/perf/builtin-probe.c | 24 +++++-
tools/perf/util/probe-event.c | 39 +++++++++
tools/perf/util/probe-event.h | 2
tools/perf/util/symbol-elf.c | 176 +++++++++++++++++++++++++++++++++++++++++
tools/perf/util/symbol.h | 18 ++++
5 files changed, 257 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-probe.c b/tools/perf/builtin-probe.c
index e8a66f9..cbd2383 100644
--- a/tools/perf/builtin-probe.c
+++ b/tools/perf/builtin-probe.c
@@ -55,6 +55,7 @@ static struct {
bool show_funcs;
bool mod_events;
bool uprobes;
+ bool sdt;
int nevents;
struct perf_probe_event events[MAX_PROBES];
struct strlist *dellist;
@@ -325,6 +326,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
opt_set_filter),
OPT_CALLBACK('x', "exec", NULL, "executable|path",
"target executable name or path", opt_set_target),
+ OPT_BOOLEAN('S', "markers", &params.sdt, "Show probe-able sdt notes"),
OPT_END()
};
int ret;
@@ -347,7 +349,7 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
params.max_probe_points = MAX_PROBES;

if ((!params.nevents && !params.dellist && !params.list_events &&
- !params.show_lines && !params.show_funcs))
+ !params.show_lines && !params.show_funcs && !params.sdt))
usage_with_options(probe_usage, options);

/*
@@ -355,6 +357,26 @@ int cmd_probe(int argc, const char **argv, const char *prefix __maybe_unused)
*/
symbol_conf.try_vmlinux_path = (symbol_conf.vmlinux_name == NULL);

+ if (params.sdt) {
+ if (params.show_lines) {
+ pr_err("Error: Don't use --markers with --lines.\n");
+ usage_with_options(probe_usage, options);
+ }
+ if (params.show_vars) {
+ pr_err("Error: Don't use --markers with --vars.\n");
+ usage_with_options(probe_usage, options);
+ }
+ if (params.show_funcs) {
+ pr_err("Error: Don't use --markers with --funcs.\n");
+ usage_with_options(probe_usage, options);
+ }
+ ret = show_sdt_notes(params.target);
+ if (ret < 0) {
+ pr_err(" Error : Failed to find SDT markers!"
+ "(%d)\n", ret);
+ }
+ return ret;
+ }
if (params.list_events) {
if (params.mod_events) {
pr_err(" Error: Don't use --list with --add/--del.\n");
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index aa04bf9..4e94092 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1909,6 +1909,20 @@ static int __add_probe_trace_events(struct perf_probe_event *pev,
return ret;
}

+static void cleanup_sdt_note_list(struct list_head *sdt_notes)
+{
+ struct sdt_note *tmp;
+ struct list_head *pos, *s;
+
+ list_for_each_safe(pos, s, sdt_notes) {
+ tmp = list_entry(pos, struct sdt_note, note_list);
+ list_del(pos);
+ free(tmp->name);
+ free(tmp->provider);
+ free(tmp);
+ }
+}
+
static int convert_to_probe_trace_events(struct perf_probe_event *pev,
struct probe_trace_event **tevs,
int max_tevs, const char *target)
@@ -2372,3 +2386,28 @@ out:
free(name);
return ret;
}
+
+static void display_sdt_note_info(struct list_head *start)
+{
+ struct list_head *pos;
+ struct sdt_note *tmp;
+
+ list_for_each(pos, start) {
+ tmp = list_entry(pos, struct sdt_note, note_list);
+ printf("%%%s:%s\n", tmp->provider, tmp->name);
+ }
+}
+
+int show_sdt_notes(const char *target)
+{
+ struct list_head sdt_notes;
+ int ret = -1;
+
+ INIT_LIST_HEAD(&sdt_notes);
+ ret = get_sdt_note_list(&sdt_notes, target);
+ if (!ret) {
+ display_sdt_note_info(&sdt_notes);
+ cleanup_sdt_note_list(&sdt_notes);
+ }
+ return ret;
+}
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index f9f3de8..b8a9347 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -133,7 +133,7 @@ extern int show_available_vars(struct perf_probe_event *pevs, int npevs,
struct strfilter *filter, bool externs);
extern int show_available_funcs(const char *module, struct strfilter *filter,
bool user);
-
+int show_sdt_notes(const char *target);
/* Maximum index number of event-name postfix */
#define MAX_EVENT_INDEX 1024

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 4b12bf8..6b17260 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -846,6 +846,182 @@ out_elf_end:
return err;
}

+/*
+ * Populate the name, type, offset in the SDT note structure and
+ * ignore the argument fields (for now)
+ */
+static struct sdt_note *populate_sdt_note(Elf **elf, const char *data,
+ size_t len, int type)
+{
+ const char *provider, *name;
+ struct sdt_note *note;
+
+ /*
+ * Three addresses need to be obtained :
+ * Marker location, address of base section and semaphore location
+ */
+ union {
+ Elf64_Addr a64[3];
+ Elf32_Addr a32[3];
+ } buf;
+
+ /*
+ * dst and src are required for translation from file to memory
+ * representation
+ */
+ Elf_Data dst = {
+ .d_buf = &buf, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
+ .d_size = gelf_fsize((*elf), ELF_T_ADDR, 3, EV_CURRENT),
+ .d_off = 0, .d_align = 0
+ };
+
+ Elf_Data src = {
+ .d_buf = (void *) data, .d_type = ELF_T_ADDR,
+ .d_version = EV_CURRENT, .d_size = dst.d_size, .d_off = 0,
+ .d_align = 0
+ };
+
+ /* Check the type of each of the notes */
+ if (type != SDT_NOTE_TYPE)
+ goto out_ret;
+
+ note = (struct sdt_note *)zalloc(sizeof(struct sdt_note));
+ if (note == NULL) {
+ pr_err("Memory allocation error\n");
+ goto out_ret;
+ }
+ INIT_LIST_HEAD(&note->note_list);
+
+ if (len < dst.d_size + 3)
+ goto out_free;
+
+ /* Translation from file representation to memory representation */
+ if (gelf_xlatetom(*elf, &dst, &src,
+ elf_getident(*elf, NULL)[EI_DATA]) == NULL)
+ pr_debug("gelf_xlatetom : %s", elf_errmsg(-1));
+
+ /* Populate the fields of sdt_note */
+ provider = data + dst.d_size;
+
+ name = (const char *)memchr(provider, '\0', data + len - provider);
+ if (name++ == NULL)
+ goto out_free;
+ note->provider = strdup(provider);
+ note->name = strdup(name);
+
+ /* Obtain the addresses and ignore notes with semaphores set*/
+ if (gelf_getclass(*elf) == ELFCLASS32) {
+ note->addr.a32[0] = buf.a32[0];
+ note->addr.a32[1] = buf.a32[1];
+ note->addr.a32[2] = buf.a32[2];
+ note->bit32 = true;
+ if (buf.a32[2] != 0)
+ goto out_free;
+ } else {
+ note->addr.a64[0] = buf.a64[0];
+ note->addr.a64[1] = buf.a64[1];
+ note->addr.a64[2] = buf.a64[2];
+ note->bit32 = false;
+ if (buf.a64[2] != 0)
+ goto out_free;
+ }
+ return note;
+
+out_free:
+ free(note);
+out_ret:
+ return NULL;
+}
+
+static struct list_head *construct_sdt_notes_list(Elf *elf)
+{
+ GElf_Ehdr ehdr;
+ Elf_Scn *scn = NULL;
+ Elf_Data *data;
+ GElf_Shdr shdr;
+ size_t shstrndx;
+ size_t next;
+ GElf_Nhdr nhdr;
+ size_t name_off, desc_off, offset;
+ struct sdt_note *tmp = NULL, *note = NULL;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ pr_debug("%s: Can't get elf header.\n", __func__);
+ goto out_err;
+ }
+ if (elf_getshdrstrndx(elf, &shstrndx) != 0) {
+ pr_debug("getshdrstrndx failed\n");
+ goto out_err;
+ }
+
+ /*
+ * Look for section type = SHT_NOTE, flags = no SHF_ALLOC
+ * and name = .note.stapsdt
+ */
+ scn = elf_section_by_name(elf, &ehdr, &shdr, NOTE_SCN, NULL);
+ if (!scn) {
+ printf("SDT markers not present!\n");
+ goto out_err;
+ }
+ if (!(shdr.sh_type == SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC))
+ goto out_err;
+
+ data = elf_getdata(scn, NULL);
+
+ /* Get the SDT notes */
+ for (offset = 0; (next = gelf_getnote(data, offset, &nhdr, &name_off,
+ &desc_off)) > 0; offset = next) {
+ if (nhdr.n_namesz == sizeof(SDT_NOTE_NAME) &&
+ !memcmp(data->d_buf + name_off, SDT_NOTE_NAME,
+ sizeof(SDT_NOTE_NAME))) {
+ tmp = populate_sdt_note(&elf, (const char *)
+ ((long)(data->d_buf) +
+ (long)desc_off),
+ nhdr.n_descsz, nhdr.n_type);
+ if (!note && tmp)
+ note = tmp;
+ else if (tmp)
+ list_add_tail(&tmp->note_list,
+ &(note->note_list));
+ }
+ }
+ if (tmp)
+ return &tmp->note_list;
+out_err:
+ return NULL;
+}
+
+int get_sdt_note_list(struct list_head *head, const char *target)
+{
+ Elf *elf;
+ int fd, ret = -1;
+ struct list_head *tmp = NULL;
+
+ fd = open(target, O_RDONLY);
+ if (fd < 0) {
+ pr_err("Failed to open %s\n", target);
+ goto out_ret;
+ }
+
+ symbol__elf_init();
+ elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+ if (!elf) {
+ pr_err("%s: cannot read %s ELF file.\n", __func__, target);
+ goto out_close;
+ }
+ tmp = construct_sdt_notes_list(elf);
+ if (tmp) {
+ list_add(head, tmp);
+ ret = 0;
+ }
+ elf_end(elf);
+
+out_close:
+ close(fd);
+out_ret:
+ return ret;
+}
+
void symbol__elf_init(void)
{
elf_version(EV_CURRENT);
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 5f720dc..037185c 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -197,6 +197,17 @@ struct symsrc {
#endif
};

+struct sdt_note {
+ char *name;
+ char *provider;
+ bool bit32; /* 32 or 64 bit flag */
+ union {
+ Elf64_Addr a64[3];
+ Elf32_Addr a32[3];
+ } addr;
+ struct list_head note_list;
+};
+
void symsrc__destroy(struct symsrc *ss);
int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
enum dso_binary_type type);
@@ -247,4 +258,11 @@ void symbols__fixup_duplicate(struct rb_root *symbols);
void symbols__fixup_end(struct rb_root *symbols);
void __map_groups__fixup_end(struct map_groups *mg, enum map_type type);

+/* Specific to SDT notes */
+int get_sdt_note_list(struct list_head *head, const char *target);
+
+#define SDT_NOTE_TYPE 3
+#define NOTE_SCN ".note.stapsdt"
+#define SDT_NOTE_NAME "stapsdt"
+
#endif /* __PERF_SYMBOL */

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/