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Message-ID: <20230725001929.368041-2-namhyung@kernel.org>
Date: Mon, 24 Jul 2023 17:19:29 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>
Cc: Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-perf-users@...r.kernel.org
Subject: [PATCH v2 2/2] perf machine: Include data symbols in the kernel map
When perf record -d is used, it needs data mmaps to symbolize global data.
But it missed to collect kernel data maps so it cannot symbolize them.
Instead of having a separate map, just increase the kernel map size to
include the data section.
Probably we can have a separate kernel map for data, but the current
code assumes a single kernel map. So it'd require more changes in other
places and looks error-prone. I decided not to go that way for now.
Also it seems the kernel module size already includes the data section.
For example, my system has the following.
$ grep -e _stext -e _etext -e _edata /proc/kallsyms
ffffffff99800000 T _stext
ffffffff9a601ac8 T _etext
ffffffff9b446a00 D _edata
Size of the text section is (0x9a601ac8 - 0x99800000 = 0xe01ac8) and
size including data section is (0x9b446a00 - 0x99800000 = 0x1c46a00).
Before:
$ perf record -d true
$ perf report -D | grep MMAP | head -1
0 0 0x460 [0x60]: PERF_RECORD_MMAP -1/0: [0xffffffff99800000(0xe01ac8) @ 0xffffffff99800000]: x [kernel.kallsyms]_text
^^^^^^^^
here
After:
$ perf report -D | grep MMAP | head -1
0 0 0x460 [0x60]: PERF_RECORD_MMAP -1/0: [0xffffffff99800000(0x1c46a00) @ 0xffffffff99800000]: x [kernel.kallsyms]_text
^^^^^^^^^
Instead of just replacing it to _edata, try _edata first and then fall
back to _etext just in case.
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
tools/perf/util/machine.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 4e62843d51b7..11de3ca8d4fa 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1216,7 +1216,9 @@ static int machine__get_running_kernel_start(struct machine *machine,
*start = addr;
- err = kallsyms__get_function_start(filename, "_etext", &addr);
+ err = kallsyms__get_symbol_start(filename, "_edata", &addr);
+ if (err)
+ err = kallsyms__get_function_start(filename, "_etext", &addr);
if (!err)
*end = addr;
--
2.41.0.487.g6d72f3e995-goog
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