[PATCH 7/8] perf probe: Support SDT markers having reference counter (semaphore)

[Ravi Bangoria]

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@xxxxxxxxxxxxxxxxxx>
---
 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