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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	linux-kernel@vger.kernel.org, Jiri Olsa <jolsa@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Namhyung Kim <namhyung@kernel.org>
Subject: [PATCH perf/core v2 1/4] perf-probe: Fix to show correct locations for events on modules
Date: Wed, 11 Jan 2017 14:59:38 +0900	[thread overview]
Message-ID: <148411436777.9978.1440275861947194930.stgit@devbox> (raw)
In-Reply-To: <148411429514.9978.10060675441541429175.stgit@devbox>

Fix to show correct locations for events on modules by relocating
given address instead of retrying after failure.

This happens when the module text size is enough big, bigger than
sh_addr, because original code retries withgiven address + sh_addr
if it failed to find CU DIE at the given address. Any address
smaller than sh_addr always fails and it retries with correct
address, but the address which bigger than sh_addr will get a CU
DIE which is on given address (not adjusted by sh_addr).

In my environment(x86-64), the sh_addr of ".text" section is
0x10030. Since i915 is a huge kernel module, we can see this
issue as below.

  $ grep "[Tt] .*\[i915\]" /proc/kallsyms | sort | head -n1
  ffffffffc0270000 t i915_switcheroo_can_switch	[i915]

ffffffffc0270000 + 0x10030 = ffffffffc0280030, so we'll check
symbols cross this boundary.

  $ grep "[Tt] .*\[i915\]" /proc/kallsyms | grep -B1 ^ffffffffc028\
  | head -n 2
  ffffffffc027ff80 t haswell_init_clock_gating	[i915]
  ffffffffc0280110 t valleyview_init_clock_gating	[i915]

So setup probes on both function and see what happen.

  $ sudo ./perf probe -m i915 -a haswell_init_clock_gating \
        -a valleyview_init_clock_gating
  Added new events:
    probe:haswell_init_clock_gating (on haswell_init_clock_gating in i915)
    probe:valleyview_init_clock_gating (on valleyview_init_clock_gating in i915)

  You can now use it in all perf tools, such as:

  	perf record -e probe:valleyview_init_clock_gating -aR sleep 1

  $ sudo ./perf probe -l
    probe:haswell_init_clock_gating (on haswell_init_clock_gating@gpu/drm/i915/intel_pm.c in i915)
    probe:valleyview_init_clock_gating (on i915_vga_set_decode:4@gpu/drm/i915/i915_drv.c in i915)

As you can see, haswell_init_clock_gating is correctly shown,
but valleyview_init_clock_gating is not.

With this patch, both events are shown correctly.

  $ sudo ./perf probe -l
    probe:haswell_init_clock_gating (on haswell_init_clock_gating@gpu/drm/i915/intel_pm.c in i915)
    probe:valleyview_init_clock_gating (on valleyview_init_clock_gating@gpu/drm/i915/intel_pm.c in i915)

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
  Changes in v2:
    - Rewrite patch description with precise instructions.
---
 tools/perf/util/probe-finder.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index df4debe..0278fe1 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1543,16 +1543,12 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
 	Dwarf_Addr _addr = 0, baseaddr = 0;
 	const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp;
 	int baseline = 0, lineno = 0, ret = 0;
-	bool reloc = false;
 
-retry:
+	/* We always need to relocate the address for aranges */
+	if (debuginfo__get_text_offset(dbg, &baseaddr) == 0)
+		addr += baseaddr;
 	/* Find cu die */
 	if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {
-		if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) {
-			addr += baseaddr;
-			reloc = true;
-			goto retry;
-		}
 		pr_warning("Failed to find debug information for address %lx\n",
 			   addr);
 		ret = -EINVAL;

  reply	other threads:[~2017-01-11  6:00 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-11  5:58 [PATCH perf/core v2 0/4] perf-probe: Fix and improve module probe events Masami Hiramatsu
2017-01-11  5:59 ` Masami Hiramatsu [this message]
2017-01-16 18:32   ` [PATCH perf/core v2 1/4] perf-probe: Fix to show correct locations for events on modules Arnaldo Carvalho de Melo
2017-01-18  9:22   ` [tip:perf/urgent] perf probe: " tip-bot for Masami Hiramatsu
2017-01-11  6:00 ` [PATCH perf/core v2 2/4] perf-probe: Add error checks to offline probe post-processing Masami Hiramatsu
2017-01-18  9:22   ` [tip:perf/urgent] perf probe: " tip-bot for Masami Hiramatsu
2017-01-11  6:01 ` [PATCH perf/core v2 3/4] perf-probe: Fix to probe on gcc generated functions in modules Masami Hiramatsu
2017-01-18  9:23   ` [tip:perf/urgent] perf probe: " tip-bot for Masami Hiramatsu
2017-01-11  6:03 ` [PATCH perf/core v2 4/4] perf-probe: Find probe events without target module Masami Hiramatsu
2017-01-16 18:44   ` Arnaldo Carvalho de Melo
2017-01-16 22:21     ` Masami Hiramatsu
2017-01-16  8:08 ` [PATCH perf/core v2 0/4] perf-probe: Fix and improve module probe events Masami Hiramatsu

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