Re: [PATCH 4.9 131/172] perf probe: Fix to probe on gcc generated functions in modules

From: Greg Kroah-Hartman
Date: Thu Jul 13 2017 - 09:01:06 EST

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On Wed, Jul 05, 2017 at 01:02:36PM -0700, Krister Johansen wrote:
> Hey Greg,
>
> > 4.9-stable review patch. If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> >
> >
> > [ Upstream commit 613f050d68a8ed3c0b18b9568698908ef7bbc1f7 ]
> >
> > 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@xxxxxxxxxx>
> > Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> > Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Link: http://lkml.kernel.org/r/148411450673.9978.14905987549651656075.stgit@devbox
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> > 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(-)
> >
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -645,18 +645,31 @@ static int add_exec_to_probe_trace_event
> > 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) {
> > @@ -666,6 +679,8 @@ static int add_module_to_probe_trace_eve
> > }
> >
> > free(mod_name);
> > + map__put(map);
> > +
> > return ret;
> > }
> >
> > @@ -722,7 +737,7 @@ arch__post_process_probe_trace_events(st
> > 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;
> >
> > @@ -730,7 +745,8 @@ static int post_process_probe_trace_even
> > 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);
> >
> > @@ -774,30 +790,27 @@ static int try_to_find_probe_trace_event
> > }
> > }
> >
> > - 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");
> > --- a/tools/perf/util/probe-finder.c
> > +++ b/tools/perf/util/probe-finder.c
> > @@ -1501,7 +1501,8 @@ int debuginfo__find_available_vars_at(st
> > }
> >
> > /* 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(st
> > 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 d
> > 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)) {
> > --- a/tools/perf/util/probe-finder.h
> > +++ b/tools/perf/util/probe-finder.h
> > @@ -46,6 +46,9 @@ int debuginfo__find_trace_events(struct
> > 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);
>
> I'm getting the following error when I try to build perf from 4.9.36:
>
> util/probe-event.c: In function âpost_process_module_probe_trace_eventsâ:
> util/probe-event.c:685:3: error: implicit declaration of function âpost_process_probe_trace_pointâ [-Werror=implicit-function-declaration]
> ret = post_process_probe_trace_point(&tevs[i].point,
> ^
> util/probe-event.c:685:3: error: nested extern declaration of âpost_process_probe_trace_pointâ [-Werror=nested-externs]
> cc1: all warnings being treated as errors
>
> At first blush, it looks like we're missing another patch upon which
> this one depends. However, after cherry-picking the fix for
> 3e96dac7c956089d3f23aca98c4dfca57b6aaf8a back to 4.9.36, the build then
> fails with:
>
> util/probe-event.c:549:12: note: declared here
> static int get_text_start_address(const char *exec, unsigned long *address,
> ^
> util/probe-event.c: At top level:
> util/probe-event.c:672:1: error: âpost_process_offline_probe_trace_eventsâ defined but not used [-Werror=unused-function]
> post_process_offline_probe_trace_events(struct probe_trace_event *tevs,
> ^
> cc1: all warnings being treated as errors
>
> It turns out that this has a second dependency,
> 8a937a25a7e3c19d5fb3f9d92f605cf5fda219d8. After fiddling with this a
> little bit more, I realized I need to invert the order to get a clean
> merge of the two fixes. This ordering is good:
>
> 8a937a25a7e3c19d5fb3f9d92f605cf5fda219d8
> 3e96dac7c956089d3f23aca98c4dfca57b6aaf8a
>
> With that I can get a clean build of the perf tree. All of that said,
> I'm not sure whether there are additional patches needed to fully
> leverage the added functionality. Perhaps Arnaldo or Masami can
> comment?

Thanks for these, I've now queued them up.

greg k-h

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