From bacefe0c7b77b7527a613e053b6d378412a8a779 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Mon, 12 Feb 2024 15:33:22 -0800 Subject: [PATCH] perf tools: Fixup module symbol end address properly I got a strange error on ARM to fail on processing FINISHED_ROUND record. It turned out that it was failing in symbol__alloc_hist() because the symbol size is too big. When a sample is captured on a specific BPF program, it failed. I've added a debug code and found the end address of the symbol is from the next module which is placed far way. ffff800008795778-ffff80000879d6d8: bpf_prog_1bac53b8aac4bc58_netcg_sock [bpf] ffff80000879d6d8-ffff80000ad656b4: bpf_prog_76867454b5944e15_netcg_getsockopt [bpf] ffff80000ad656b4-ffffd69b7af74048: bpf_prog_1d50286d2eb1be85_hn_egress [bpf] <---------- here ffffd69b7af74048-ffffd69b7af74048: $x.5 [sha3_generic] ffffd69b7af74048-ffffd69b7af740b8: crypto_sha3_init [sha3_generic] ffffd69b7af740b8-ffffd69b7af741e0: crypto_sha3_update [sha3_generic] The logic in symbols__fixup_end() just uses curr->start to update the prev->end. But in this case, it won't work as it's too different. I think ARM has a different kernel memory layout for modules and BPF than on x86. Actually there's a logic to handle kernel and module boundary. Let's do the same for symbols between different modules. Signed-off-by: Namhyung Kim Reviewed-by: Leo Yan Cc: Will Deacon Cc: Mike Leach Cc: John Garry Link: https://lore.kernel.org/r/20240212233322.1855161-1-namhyung@kernel.org --- tools/perf/util/symbol.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index 35975189999b..9ebdb8e13c0b 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -248,14 +248,31 @@ void symbols__fixup_end(struct rb_root_cached *symbols, bool is_kallsyms) * segment is very big. Therefore do not fill this gap and do * not assign it to the kernel dso map (kallsyms). * + * Also BPF code can be allocated separately from text segments + * and modules. So the last entry in a module should not fill + * the gap too. + * * In kallsyms, it determines module symbols using '[' character * like in: * ffffffffc1937000 T hdmi_driver_init [snd_hda_codec_hdmi] */ if (prev->end == prev->start) { + const char *prev_mod; + const char *curr_mod; + + if (!is_kallsyms) { + prev->end = curr->start; + continue; + } + + prev_mod = strchr(prev->name, '['); + curr_mod = strchr(curr->name, '['); + /* Last kernel/module symbol mapped to end of page */ - if (is_kallsyms && (!strchr(prev->name, '[') != - !strchr(curr->name, '['))) + if (!prev_mod != !curr_mod) + prev->end = roundup(prev->end + 4096, 4096); + /* Last symbol in the previous module */ + else if (prev_mod && strcmp(prev_mod, curr_mod)) prev->end = roundup(prev->end + 4096, 4096); else prev->end = curr->start;