From 106dacd86f042968e0bb974490fcb9cd017cd03a Mon Sep 17 00:00:00 2001 From: Mark Santaniello Date: Mon, 19 Jun 2017 09:38:25 -0700 Subject: [PATCH] perf script: Support -F brstackoff,dso The idea here is to make AutoFDO easier in cloud environment with ASLR. It's easiest to show how this is useful by example. I built a small test akin to "while(1) { do_nothing(); }" where the do_nothing function is loaded from a dso: $ cat burncpu.cpp #include int main() { void* handle = dlopen("./dso.so", RTLD_LAZY); if (!handle) return -1; typedef void (*fp)(); fp do_nothing = (fp) dlsym(handle, "do_nothing"); while(1) { do_nothing(); } } $ cat dso.cpp extern "C" void do_nothing() {} $ cat build.sh #!/bin/bash g++ -shared dso.cpp -o dso.so g++ burncpu.cpp -o burncpu -ldl I sampled the execution of this program with perf record -b. Using the existing "brstack,dso", we get absolute addresses that are affected by ASLR, and could be different on different hosts. The address does not uniquely identify a branch/target in the binary: $ perf script -F brstack,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1 0x7f967139b6aa(/tmp/burncpu/dso.so)/0x4006b1(/tmp/burncpu/exe)/P/-/-/0 Using the existing "brstacksym,dso" is a little better, because the symbol plus offset and dso name *does* uniquely identify a branch/target in the binary. Ultimately, however, AutoFDO wants a simple offset into the binary, so we'd have to undo all the work perf did to symbolize in the first place: $ perf script -F brstacksym,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1 do_nothing+0x5(/tmp/burncpu/dso.so)/main+0x44(/tmp/burncpu/exe)/P/-/-/0 With the new "brstackoff,dso" we get what we need: a simple offset into a specific dso/binary that uniquely identifies a branch/target: $ perf script -F brstackoff,dso | sed 's/\/0 /\/0\n/g' | grep burncpu | grep dso.so | head -n 1 0x6aa(/tmp/burncpu/dso.so)/0x4006b1(/tmp/burncpu/exe)/P/-/-/0 Signed-off-by: Mark Santaniello Tested-by: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20170619163825.2012979-2-marksan@fb.com [ Updated documentation about 'brstackoff' using text from above ] Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/Documentation/perf-script.txt | 4 ++- tools/perf/builtin-script.c | 56 +++++++++++++++++++++++++++++--- 2 files changed, 55 insertions(+), 5 deletions(-) diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt index 3eca8c0..e2468ed 100644 --- a/tools/perf/Documentation/perf-script.txt +++ b/tools/perf/Documentation/perf-script.txt @@ -116,7 +116,7 @@ OPTIONS --fields:: Comma separated list of fields to print. Options are: comm, tid, pid, time, cpu, event, trace, ip, sym, dso, addr, symoff, - srcline, period, iregs, brstack, brstacksym, flags, bpf-output, brstackinsn, + srcline, period, iregs, brstack, brstacksym, flags, bpf-output, brstackinsn, brstackoff, callindent, insn, insnlen. Field list can be prepended with the type, trace, sw or hw, to indicate to which event type the field list applies. e.g., -F sw:comm,tid,time,ip,sym and -F trace:time,cpu,trace @@ -211,6 +211,8 @@ OPTIONS is printed. This is the full execution path leading to the sample. This is only supported when the sample was recorded with perf record -b or -j any. + The brstackoff field will print an offset into a specific dso/binary. + -k:: --vmlinux=:: vmlinux pathname diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c index 3c21089..db5261c 100644 --- a/tools/perf/builtin-script.c +++ b/tools/perf/builtin-script.c @@ -85,6 +85,7 @@ enum perf_output_field { PERF_OUTPUT_INSN = 1U << 21, PERF_OUTPUT_INSNLEN = 1U << 22, PERF_OUTPUT_BRSTACKINSN = 1U << 23, + PERF_OUTPUT_BRSTACKOFF = 1U << 24, }; struct output_option { @@ -115,6 +116,7 @@ struct output_option { {.str = "insn", .field = PERF_OUTPUT_INSN}, {.str = "insnlen", .field = PERF_OUTPUT_INSNLEN}, {.str = "brstackinsn", .field = PERF_OUTPUT_BRSTACKINSN}, + {.str = "brstackoff", .field = PERF_OUTPUT_BRSTACKOFF}, }; /* default set to maintain compatibility with current format */ @@ -299,10 +301,9 @@ static int perf_evsel__check_attr(struct perf_evsel *evsel, return -EINVAL; } if (PRINT_FIELD(DSO) && !PRINT_FIELD(IP) && !PRINT_FIELD(ADDR) && - !PRINT_FIELD(BRSTACK) && !PRINT_FIELD(BRSTACKSYM)) { - pr_err("Display of DSO requested but none of sample IP, sample address, " - "brstack\nor brstacksym are selected. Hence, no addresses to " - "convert to DSO.\n"); + !PRINT_FIELD(BRSTACK) && !PRINT_FIELD(BRSTACKSYM) && !PRINT_FIELD(BRSTACKOFF)) { + pr_err("Display of DSO requested but no address to convert. Select\n" + "sample IP, sample address, brstack, brstacksym, or brstackoff.\n"); return -EINVAL; } if (PRINT_FIELD(SRCLINE) && !PRINT_FIELD(IP)) { @@ -606,6 +607,51 @@ static void print_sample_brstacksym(struct perf_sample *sample, } } +static void print_sample_brstackoff(struct perf_sample *sample, + struct thread *thread, + struct perf_event_attr *attr) +{ + struct branch_stack *br = sample->branch_stack; + struct addr_location alf, alt; + u64 i, from, to; + + if (!(br && br->nr)) + return; + + for (i = 0; i < br->nr; i++) { + + memset(&alf, 0, sizeof(alf)); + memset(&alt, 0, sizeof(alt)); + from = br->entries[i].from; + to = br->entries[i].to; + + thread__find_addr_map(thread, sample->cpumode, MAP__FUNCTION, from, &alf); + if (alf.map && !alf.map->dso->adjust_symbols) + from = map__map_ip(alf.map, from); + + thread__find_addr_map(thread, sample->cpumode, MAP__FUNCTION, to, &alt); + if (alt.map && !alt.map->dso->adjust_symbols) + to = map__map_ip(alt.map, to); + + printf("0x%"PRIx64, from); + if (PRINT_FIELD(DSO)) { + printf("("); + map__fprintf_dsoname(alf.map, stdout); + printf(")"); + } + printf("/0x%"PRIx64, to); + if (PRINT_FIELD(DSO)) { + printf("("); + map__fprintf_dsoname(alt.map, stdout); + printf(")"); + } + printf("/%c/%c/%c/%d ", + mispred_str(br->entries + i), + br->entries[i].flags.in_tx ? 'X' : '-', + br->entries[i].flags.abort ? 'A' : '-', + br->entries[i].flags.cycles); + } +} #define MAXBB 16384UL static int grab_bb(u8 *buffer, u64 start, u64 end, @@ -1227,6 +1273,8 @@ static void process_event(struct perf_script *script, print_sample_brstack(sample, thread, attr); else if (PRINT_FIELD(BRSTACKSYM)) print_sample_brstacksym(sample, thread, attr); + else if (PRINT_FIELD(BRSTACKOFF)) + print_sample_brstackoff(sample, thread, attr); if (perf_evsel__is_bpf_output(evsel) && PRINT_FIELD(BPF_OUTPUT)) print_sample_bpf_output(sample); -- 2.7.4