From 77b004f4c5c3c90b20ad61c5fa2ba7d494c1dba1 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 12 Sep 2024 15:42:08 -0700 Subject: [PATCH] perf symbol: Do not fixup end address of labels When it loads symbols from an ELF file, it loads label symbols which is 0 size. Sometimes it has the same address with other symbols and might shadow the original symbols because it fixes up the size of the symbol. For example, in my system __do_softirq is shadowed and only accepts the __softirqentry_text_start instead. But it should accept __do_softirq. $ readelf -sW vmlinux | grep -e __do_softirq -e __softirqentry_text_start 105089: ffffffff82000000 814 FUNC GLOBAL DEFAULT 1 __do_softirq 111954: ffffffff82000000 0 NOTYPE GLOBAL DEFAULT 1 __softirqentry_text_start $ perf annotate --stdio __do_softirq Error: The perf.data data has no samples! $ perf annotate --stdio __softirqentry_text_start | head Percent | Source code & Disassembly of vmlinux for cycles (26 samples, percent: local period) --------------------------------------------------------------------------------------------------- : 0 0xffffffff82000000 <__softirqentry_text_start>: 0.00 : ffffffff82000000: nopl (%rax,%rax) 30.77 : ffffffff82000005: pushq %rbp 3.85 : ffffffff82000006: movq %rsp, %rbp 0.00 : ffffffff82000009: pushq %r15 3.85 : ffffffff8200000b: pushq %r14 3.85 : ffffffff8200000d: pushq %r13 0.00 : ffffffff8200000f: pushq %r12 We can ignore NOTYPE symbols in the symbols__fixup_end() so that it can pick the __do_softirq() in choose_best_symbol(). This should be fine since most symbols have either STT_FUNC or STT_OBJECT. Link: https://lore.kernel.org/r/20240912224208.3360116-1-namhyung@kernel.org Signed-off-by: Namhyung Kim --- tools/perf/util/symbol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index a18927d792afc..d9ecef526645b 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -257,7 +257,7 @@ void symbols__fixup_end(struct rb_root_cached *symbols, bool is_kallsyms) * like in: * ffffffffc1937000 T hdmi_driver_init [snd_hda_codec_hdmi] */ - if (prev->end == prev->start) { + if (prev->end == prev->start && prev->type != STT_NOTYPE) { const char *prev_mod; const char *curr_mod;