From c8b567c8a96a35acff746b1eef6f859e2a9fc195 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 23 Sep 2019 11:07:29 -0300 Subject: [PATCH] perf record: Move restricted maps check to after a possible fallback to not collect kernel samples Before: [acme@quaco ~]$ perf record -b -e cycles date WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted, check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid. Samples in kernel functions may not be resolved if a suitable vmlinux file is not found in the buildid cache or in the vmlinux path. Samples in kernel modules won't be resolved at all. If some relocation was applied (e.g. kexec) symbols may be misresolved even with a suitable vmlinux or kallsyms file. Mon 23 Sep 2019 11:00:59 AM -03 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.005 MB perf.data (14 samples) ] [acme@quaco ~]$ But we did a fallback and exclude_kernel was set, so no need for resolving kernel symbols: $ perf evlist -v cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: ANY $ After: [acme@quaco ~]$ perf record -b -e cycles date Mon 23 Sep 2019 11:07:18 AM -03 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.007 MB perf.data (16 samples) ] [acme@quaco ~]$ perf evlist -v cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1, exclude_hv: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: ANY [acme@quaco ~]$ No needless warning is emitted. Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Cc: Stephane Eranian Link: https://lkml.kernel.org/n/tip-5yqnr8xcqwhr15xktj2097ac@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 3f66a49a997f..1e1f97139f16 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -788,6 +788,17 @@ try_again: pos->supported = true; } + if (symbol_conf.kptr_restrict && !perf_evlist__exclude_kernel(evlist)) { + pr_warning( +"WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,\n" +"check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n" +"Samples in kernel functions may not be resolved if a suitable vmlinux\n" +"file is not found in the buildid cache or in the vmlinux path.\n\n" +"Samples in kernel modules won't be resolved at all.\n\n" +"If some relocation was applied (e.g. kexec) symbols may be misresolved\n" +"even with a suitable vmlinux or kallsyms file.\n\n"); + } + if (perf_evlist__apply_filters(evlist, &pos)) { pr_err("failed to set filter \"%s\" on event %s with %d (%s)\n", pos->filter, perf_evsel__name(pos), errno, @@ -2364,16 +2375,6 @@ int cmd_record(int argc, const char **argv) err = -ENOMEM; - if (symbol_conf.kptr_restrict && !perf_evlist__exclude_kernel(rec->evlist)) - pr_warning( -"WARNING: Kernel address maps (/proc/{kallsyms,modules}) are restricted,\n" -"check /proc/sys/kernel/kptr_restrict and /proc/sys/kernel/perf_event_paranoid.\n\n" -"Samples in kernel functions may not be resolved if a suitable vmlinux\n" -"file is not found in the buildid cache or in the vmlinux path.\n\n" -"Samples in kernel modules won't be resolved at all.\n\n" -"If some relocation was applied (e.g. kexec) symbols may be misresolved\n" -"even with a suitable vmlinux or kallsyms file.\n\n"); - if (rec->no_buildid_cache || rec->no_buildid) { disable_buildid_cache(); } else if (rec->switch_output.enabled) {