perf probe: Skip end-of-sequence and non statement lines
[ Upstream commit f4d99bdfd124823a81878b44b5e8750b97f73902 ] Skip end-of-sequence and non-statement lines while walking through lines list. The "end-of-sequence" line information means: "the current address is that of the first byte after the end of a sequence of target machine instructions." (DWARF version 4 spec 6.2.2) This actually means out of scope and we can not probe on it. On the other hand, the statement lines (is_stmt) means: "the current instruction is a recommended breakpoint location. A recommended breakpoint location is intended to “represent” a line, a statement and/or a semantically distinct subpart of a statement." (DWARF version 4 spec 6.2.2) So, non-statement line info also should be skipped. These can reduce unneeded probe points and also avoid an error. E.g. without this patch: # perf probe -a "clear_tasks_mm_cpumask:1" Added new events: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_1 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_2 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_3 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_4 (on clear_tasks_mm_cpumask:1) You can now use it in all perf tools, such as: perf record -e probe:clear_tasks_mm_cpumask_4 -aR sleep 1 # This puts 5 probes on one line, but acutally it's not inlined function. This is because there are many non statement instructions at the function prologue. With this patch: # perf probe -a "clear_tasks_mm_cpumask:1" Added new event: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) You can now use it in all perf tools, such as: perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1 # Now perf-probe skips unneeded addresses. Committer testing: Slightly different results, but similar: Before: # uname -a Linux quaco 5.3.8-200.fc30.x86_64 #1 SMP Tue Oct 29 14:46:22 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux # # perf probe -a "clear_tasks_mm_cpumask:1" Added new events: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_1 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_2 (on clear_tasks_mm_cpumask:1) You can now use it in all perf tools, such as: perf record -e probe:clear_tasks_mm_cpumask_2 -aR sleep 1 # After: # perf probe -a "clear_tasks_mm_cpumask:1" Added new event: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) You can now use it in all perf tools, such as: perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1 # perf probe -l probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask@kernel/cpu.c) # Fixes: 4cc9cec636e7 ("perf probe: Introduce lines walker interface") Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: http://lore.kernel.org/lkml/157241936090.32002.12156347518596111660.stgit@devnote2 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -746,6 +746,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
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int decl = 0, inl;
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Dwarf_Die die_mem, *cu_die;
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size_t nlines, i;
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bool flag;
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/* Get the CU die */
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if (dwarf_tag(rt_die) != DW_TAG_compile_unit) {
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@ -776,6 +777,12 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
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"Possible error in debuginfo.\n");
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continue;
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}
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/* Skip end-of-sequence */
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if (dwarf_lineendsequence(line, &flag) != 0 || flag)
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continue;
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/* Skip Non statement line-info */
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if (dwarf_linebeginstatement(line, &flag) != 0 || !flag)
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continue;
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/* Filter lines based on address */
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if (rt_die != cu_die) {
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/*
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