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Date: Wed, 4 Jan 2017 11:48:56 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH perf/core 3/3] perf-probe: Fix to probe on gcc generated
functions in modules
Em Wed, Jan 04, 2017 at 12:31:39PM +0900, Masami Hiramatsu escreveu:
> 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
> -----
Tested this one on a x86-64 fedora25 system, applied all three.
As always, please take a look at the patch when sent to Ingo, I usually
put some committer notes there, in this case I put the test steps I
performed, using e1000e.ko and e1000_flash_cycle_ich8lan.constprop.22
BTW, it would be cool if...
Oops, I retract that, while I was testing what I was went to ask you to
implement, I saw that this last patch broke this use case:
[root@...et ~]# perf probe -m e1000e e1000_xmit_frame
Failed to get ELF symbols for e1000e
Probe point 'e1000_xmit_frame' not found.
Error: Failed to add events.
[root@...et ~]#
If I remove it, I get it back:
[root@...et ~]# perf probe -m e1000e e1000_xmit_frame
Added new event:
probe:e1000_xmit_frame (on e1000_xmit_frame in e1000e)
You can now use it in all perf tools, such as:
perf record -e probe:e1000_xmit_frame -aR sleep 1
[root@...et ~]# perf probe -l
probe:e1000_xmit_frame (on e1000_get_link_up_info_80003es2lan:7@...el/e1000e/80003es2lan.c in e1000e)
[root@...et ~]#
BTW, what I would find cool, besides fixing this new problem, would be that:
perf probe e1000_xmit_frame
worked, as we can get the module name from kallsyms:
[acme@...et linux]$ grep e1000_xmit_frame /proc/kallsyms
ffffffffc046fc10 t e1000_xmit_frame [e1000e]
[acme@...et linux]$
I applied the first two patches, and now I'm preparing a pull req to Ingo,
Thanks!
- Arnaldo
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
> tools/perf/util/probe-event.c | 38 +++++++++++++++++++++++---------------
> tools/perf/util/probe-finder.c | 2 +-
> tools/perf/util/probe-finder.h | 2 ++
> 3 files changed, 26 insertions(+), 16 deletions(-)
>
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 4a57c8a..f75c99a 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -682,15 +682,19 @@ 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;
> int i, ret = 0;
> char *mod_name = NULL;
>
> if (!module)
> return 0;
>
> + debuginfo__get_text_offset(dinfo, &text_offs);
> mod_name = find_module_name(module);
>
> for (i = 0; i < ntevs; i++) {
> @@ -700,9 +704,15 @@ static int add_module_to_probe_trace_events(struct probe_trace_event *tevs,
> ret = -ENOMEM;
> break;
> }
> + /* kernel module needs a special care to adjust addresses */
> + tevs[i].point.address -= (unsigned long)text_offs;
> }
>
> free(mod_name);
> +
> + if (!ret)
> + ret = post_process_offline_probe_trace_events(tevs, ntevs,
> + module);
> return ret;
> }
>
> @@ -760,7 +770,7 @@ 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;
>
> @@ -768,7 +778,8 @@ 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);
>
> @@ -812,30 +823,27 @@ 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 df4debe..6dede24 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -1501,7 +1501,7 @@ 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)
> {
> int n, i;
> Elf32_Word shndx;
> diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
> index f1d8558..1e03bbb 100644
> --- a/tools/perf/util/probe-finder.h
> +++ b/tools/perf/util/probe-finder.h
> @@ -46,6 +46,8 @@ 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);
> +
> /* Find a line range */
> int debuginfo__find_line_range(struct debuginfo *dbg, struct line_range *lr);
>
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