[PATCH perf/core v2 3/4] perf-probe: Fix to probe on gcc generated functions in modules

Masami Hiramatsu
2017-01-11T06:02:54Z

Fix to probe on gcc generated functions on modules. Since
probing on a module is based on its symbol name, it should
be adjusted on actual symbols.

E.g. without this fix, perf probe shows probe definition
on non-exist symbol as below.

$ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -F in_range*
in_range.isra.12
$ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -D in_range
p:probe/in_range nf_nat:in_range+0

With this fix, perf probe correctly shows a probe on
gcc-generated symbol.

$ perf probe -m build-x86_64/net/netfilter/nf_nat.ko -D in_range
p:probe/in_range nf_nat:in_range.isra.12+0

This also fixes same problem on online module as below.

$ perf probe -m i915 -D assert_plane
p:probe/assert_plane i915:assert_plane.constprop.134+0

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
tools/perf/util/probe-event.c | 45 ++++++++++++++++++++++++++--------------
tools/perf/util/probe-finder.c | 7 ++++--
tools/perf/util/probe-finder.h | 3 +++
3 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index aa8a922..6a6f44d 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -698,18 +698,31 @@ static int add_exec_to_probe_trace_events(struct probe_trace_event *tevs,
return ret;
}

-static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
- int ntevs, const char *module)
+static int
+post_process_module_probe_trace_events(struct probe_trace_event *tevs,
+ int ntevs, const char *module,
+ struct debuginfo *dinfo)
{
+ Dwarf_Addr text_offs = 0;
int i, ret = 0;
char *mod_name = NULL;
+ struct map *map;

if (!module)
return 0;

- mod_name = find_module_name(module);
+ map = get_target_map(module, false);
+ if (!map || debuginfo__get_text_offset(dinfo, &text_offs, true) < 0) {
+ pr_warning("Failed to get ELF symbols for %s\n", module);
+ return -EINVAL;
+ }

+ mod_name = find_module_name(module);
for (i = 0; i < ntevs; i++) {
+ ret = post_process_probe_trace_point(&tevs[i].point,
+ map, (unsigned long)text_offs);
+ if (ret < 0)
+ break;
tevs[i].point.module =
strdup(mod_name ? mod_name : module);
if (!tevs[i].point.module) {
@@ -719,6 +732,8 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
}

free(mod_name);
+ map__put(map);
+
return ret;
}

@@ -776,7 +791,7 @@ arch__post_process_probe_trace_events(struct perf_probe_event *pev __maybe_unuse
static int post_process_probe_trace_events(struct perf_probe_event *pev,
struct probe_trace_event *tevs,
int ntevs, const char *module,
- bool uprobe)
+ bool uprobe, struct debuginfo *dinfo)
{
int ret;

@@ -784,7 +799,8 @@ static int post_process_probe_trace_events(struct perf_probe_event *pev,
ret = add_exec_to_probe_trace_events(tevs, ntevs, module);
else if (module)
/* Currently ref_reloc_sym based probe is not for drivers */
- ret = add_module_to_probe_trace_events(tevs, ntevs, module);
+ ret = post_process_module_probe_trace_events(tevs, ntevs,
+ module, dinfo);
else
ret = post_process_kernel_probe_trace_events(tevs, ntevs);

@@ -828,30 +844,27 @@ static int try_to_find_probe_trace_events(struct perf_probe_event *pev,
}
}

- debuginfo__delete(dinfo);
-
if (ntevs > 0) { /* Succeeded to find trace events */
pr_debug("Found %d probe_trace_events.\n", ntevs);
ret = post_process_probe_trace_events(pev, *tevs, ntevs,
- pev->target, pev->uprobes);
+ pev->target, pev->uprobes, dinfo);
if (ret < 0 || ret == ntevs) {
+ pr_debug("Post processing failed or all events are skipped. (%d)\n", ret);
clear_probe_trace_events(*tevs, ntevs);
zfree(tevs);
+ ntevs = 0;
}
- if (ret != ntevs)
- return ret < 0 ? ret : ntevs;
- ntevs = 0;
- /* Fall through */
}

+ debuginfo__delete(dinfo);
+
if (ntevs == 0) { /* No error but failed to find probe point. */
pr_warning("Probe point '%s' not found.\n",
synthesize_perf_probe_point(&pev->point));
return -ENOENT;
- }
- /* Error path : ntevs < 0 */
- pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
- if (ntevs < 0) {
+ } else if (ntevs < 0) {
+ /* Error path : ntevs < 0 */
+ pr_debug("An error occurred in debuginfo analysis (%d).\n", ntevs);
if (ntevs == -EBADF)
pr_warning("Warning: No dwarf info found in the vmlinux - "
"please rebuild kernel with CONFIG_DEBUG_INFO=y.\n");
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 0278fe1..0d9d6e0 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1501,7 +1501,8 @@ int debuginfo__find_available_vars_at(struct debuginfo *dbg,
}

/* For the kernel module, we need a special code to get a DIE */
-static int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs)
+int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs,
+ bool adjust_offset)
{
int n, i;
Elf32_Word shndx;
@@ -1530,6 +1531,8 @@ static int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs)
if (!shdr)
return -ENOENT;
*offs = shdr->sh_addr;
+ if (adjust_offset)
+ *offs -= shdr->sh_offset;
}
}
return 0;
@@ -1545,7 +1548,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
int baseline = 0, lineno = 0, ret = 0;

/* We always need to relocate the address for aranges */
- if (debuginfo__get_text_offset(dbg, &baseaddr) == 0)
+ if (debuginfo__get_text_offset(dbg, &baseaddr, false) == 0)
addr += baseaddr;
/* Find cu die */
if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index f1d8558..2956c51 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -46,6 +46,9 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
struct perf_probe_point *ppt);

+int debuginfo__get_text_offset(struct debuginfo *dbg, Dwarf_Addr *offs,
+ bool adjust_offset);
+
/* Find a line range */
int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr);