Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | [PATCH v2 2/2] perf machine: Include data symbols in the kernel map | Date | Mon, 24 Jul 2023 17:19:29 -0700 |
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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@kernel.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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