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Subject[PATCH 7/8] perf probe: Support SDT markers having reference counter (semaphore)
Date
With this, perf buildid-cache will save SDT markers with reference
counter in probe cache. Perf probe will be able to probe markers
having reference counter. Ex,

# readelf -n /tmp/tick | grep -A1 loop2
Name: loop2
... Semaphore: 0x0000000010020036

# ./perf buildid-cache --add /tmp/tick
# ./perf probe sdt_tick:loop2
# ./perf stat -e sdt_tick:loop2 /tmp/tick
hi: 0
hi: 1
hi: 2
^C
Performance counter stats for '/tmp/tick':
3 sdt_tick:loop2
2.561851452 seconds time elapsed

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
---
tools/perf/util/probe-event.c | 21 +++++++++++++++++----
tools/perf/util/probe-event.h | 1 +
tools/perf/util/probe-file.c | 22 +++++++++++++++++++---
tools/perf/util/symbol-elf.c | 10 ++++++++++
tools/perf/util/symbol.h | 1 +
5 files changed, 48 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index e1dbc98..2cbe68a 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1832,6 +1832,12 @@ int parse_probe_trace_command(const char *cmd, struct probe_trace_event *tev)
tp->offset = strtoul(fmt2_str, NULL, 10);
}

+ if (tev->uprobes) {
+ fmt2_str = strchr(p, '(');
+ if (fmt2_str)
+ tp->ref_ctr_offset = strtoul(fmt2_str + 1, NULL, 0);
+ }
+
tev->nargs = argc - 2;
tev->args = zalloc(sizeof(struct probe_trace_arg) * tev->nargs);
if (tev->args == NULL) {
@@ -2054,15 +2060,22 @@ char *synthesize_probe_trace_command(struct probe_trace_event *tev)
}

/* Use the tp->address for uprobes */
- if (tev->uprobes)
- err = strbuf_addf(&buf, "%s:0x%lx", tp->module, tp->address);
- else if (!strncmp(tp->symbol, "0x", 2))
+ if (tev->uprobes) {
+ if (tp->ref_ctr_offset)
+ err = strbuf_addf(&buf, "%s:0x%lx(0x%lx)", tp->module,
+ tp->address, tp->ref_ctr_offset);
+ else
+ err = strbuf_addf(&buf, "%s:0x%lx", tp->module,
+ tp->address);
+ } else if (!strncmp(tp->symbol, "0x", 2)) {
/* Absolute address. See try_to_find_absolute_address() */
err = strbuf_addf(&buf, "%s%s0x%lx", tp->module ?: "",
tp->module ? ":" : "", tp->address);
- else
+ } else {
err = strbuf_addf(&buf, "%s%s%s+%lu", tp->module ?: "",
tp->module ? ":" : "", tp->symbol, tp->offset);
+ }
+
if (err)
goto error;

diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 45b14f0..15a98c3 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -27,6 +27,7 @@ struct probe_trace_point {
char *symbol; /* Base symbol */
char *module; /* Module name */
unsigned long offset; /* Offset from symbol */
+ unsigned long ref_ctr_offset; /* SDT reference counter offset */
unsigned long address; /* Actual address of the trace point */
bool retprobe; /* Return probe flag */
};
diff --git a/tools/perf/util/probe-file.c b/tools/perf/util/probe-file.c
index 4ae1123..08ba3a6 100644
--- a/tools/perf/util/probe-file.c
+++ b/tools/perf/util/probe-file.c
@@ -701,6 +701,12 @@ static unsigned long long sdt_note__get_addr(struct sdt_note *note)
: (unsigned long long)note->addr.a64[0];
}

+static unsigned long long sdt_note__get_ref_ctr_offset(struct sdt_note *note)
+{
+ return note->bit32 ? (unsigned long long)note->addr.a32[2]
+ : (unsigned long long)note->addr.a64[2];
+}
+
static const char * const type_to_suffix[] = {
":s64", "", "", "", ":s32", "", ":s16", ":s8",
"", ":u8", ":u16", "", ":u32", "", "", "", ":u64"
@@ -776,14 +782,24 @@ static char *synthesize_sdt_probe_command(struct sdt_note *note,
{
struct strbuf buf;
char *ret = NULL, **args;
- int i, args_count;
+ int i, args_count, err;
+ unsigned long long ref_ctr_offset;

if (strbuf_init(&buf, 32) < 0)
return NULL;

- if (strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
+ ref_ctr_offset = sdt_note__get_ref_ctr_offset(note);
+
+ if (ref_ctr_offset)
+ err = strbuf_addf(&buf, "p:%s/%s %s:0x%llx(0x%llx)",
sdtgrp, note->name, pathname,
- sdt_note__get_addr(note)) < 0)
+ sdt_note__get_addr(note), ref_ctr_offset);
+ else
+ err = strbuf_addf(&buf, "p:%s/%s %s:0x%llx",
+ sdtgrp, note->name, pathname,
+ sdt_note__get_addr(note));
+
+ if (err < 0)
goto error;

if (!note->args)
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 2de7705..76c7b54 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1928,6 +1928,16 @@ static int populate_sdt_note(Elf **elf, const char *data, size_t len,
}
}

+ /* Adjust reference counter offset */
+ if (elf_section_by_name(*elf, &ehdr, &shdr, SDT_PROBES_SCN, NULL)) {
+ if (shdr.sh_offset) {
+ if (tmp->bit32)
+ tmp->addr.a32[2] -= (shdr.sh_addr - shdr.sh_offset);
+ else
+ tmp->addr.a64[2] -= (shdr.sh_addr - shdr.sh_offset);
+ }
+ }
+
list_add_tail(&tmp->note_list, sdt_notes);
return 0;

diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index 70c16741..ad0c4f2 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -384,6 +384,7 @@ struct sdt_note {
int cleanup_sdt_note_list(struct list_head *sdt_notes);
int sdt_notes__get_count(struct list_head *start);

+#define SDT_PROBES_SCN ".probes"
#define SDT_BASE_SCN ".stapsdt.base"
#define SDT_NOTE_SCN ".note.stapsdt"
#define SDT_NOTE_TYPE 3
--
1.8.3.1
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