Messages in this thread | | | Date | Fri, 8 Apr 2022 15:12:15 +0100 | Subject | Re: [PATCH] perf: Don't show unwind error messages when augmenting frame pointer stack | From | John Garry <> |
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On 06/04/2022 15:56, James Clark wrote: > Commit b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf > record --call-graph=fp'") intended to add a 'best effort' Dwarf unwind > that improved the frame pointer stack in most scenarios. It's expected > that the unwind will fail sometimes, but this shouldn't be reported as > an error. It only works when the return address can be determined from > the contents of the link register alone. > > Fix the error shown when the unwinder requires extra registers by adding > a new flag that suppresses error messages. This flag is not set in the > normal --call-graph=dwarf unwind mode so that behavior is not changed. > > Reported-by: John Garry <john.garry@huawei.com> > Fixes: b9f6fbb3b2c2 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'") > Signed-off-by: James Clark <james.clark@arm.com>
Seems ok: Tested-by: John Garry <john.garry@huawei.com>
Thanks!
> --- > tools/perf/tests/dwarf-unwind.c | 2 +- > .../perf/util/arm64-frame-pointer-unwind-support.c | 2 +- > tools/perf/util/machine.c | 2 +- > tools/perf/util/unwind-libdw.c | 10 +++++++--- > tools/perf/util/unwind-libdw.h | 1 + > tools/perf/util/unwind-libunwind-local.c | 10 +++++++--- > tools/perf/util/unwind-libunwind.c | 6 ++++-- > tools/perf/util/unwind.h | 13 ++++++++++--- > 8 files changed, 32 insertions(+), 14 deletions(-) > > diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c > index 2dab2d262060..afdca7f2959f 100644 > --- a/tools/perf/tests/dwarf-unwind.c > +++ b/tools/perf/tests/dwarf-unwind.c > @@ -122,7 +122,7 @@ NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__thread(struct thread *thr > } > > err = unwind__get_entries(unwind_entry, &cnt, thread, > - &sample, MAX_STACK); > + &sample, MAX_STACK, false); > if (err) > pr_debug("unwind failed\n"); > else if (cnt != MAX_STACK) { > diff --git a/tools/perf/util/arm64-frame-pointer-unwind-support.c b/tools/perf/util/arm64-frame-pointer-unwind-support.c > index 2242a885fbd7..4940be4a0569 100644 > --- a/tools/perf/util/arm64-frame-pointer-unwind-support.c > +++ b/tools/perf/util/arm64-frame-pointer-unwind-support.c > @@ -53,7 +53,7 @@ u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thr > sample->user_regs.cache_regs[PERF_REG_ARM64_SP] = 0; > } > > - ret = unwind__get_entries(add_entry, &entries, thread, sample, 2); > + ret = unwind__get_entries(add_entry, &entries, thread, sample, 2, true); > sample->user_regs = old_regs; > > if (ret || entries.length != 2) > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c > index b80048546451..95391236f5f6 100644 > --- a/tools/perf/util/machine.c > +++ b/tools/perf/util/machine.c > @@ -2987,7 +2987,7 @@ static int thread__resolve_callchain_unwind(struct thread *thread, > return 0; > > return unwind__get_entries(unwind_entry, cursor, > - thread, sample, max_stack); > + thread, sample, max_stack, false); > } > > int thread__resolve_callchain(struct thread *thread, > diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c > index a74b517f7497..94aa40f6e348 100644 > --- a/tools/perf/util/unwind-libdw.c > +++ b/tools/perf/util/unwind-libdw.c > @@ -200,7 +200,8 @@ frame_callback(Dwfl_Frame *state, void *arg) > bool isactivation; > > if (!dwfl_frame_pc(state, &pc, NULL)) { > - pr_err("%s", dwfl_errmsg(-1)); > + if (!ui->best_effort) > + pr_err("%s", dwfl_errmsg(-1)); > return DWARF_CB_ABORT; > } > > @@ -208,7 +209,8 @@ frame_callback(Dwfl_Frame *state, void *arg) > report_module(pc, ui); > > if (!dwfl_frame_pc(state, &pc, &isactivation)) { > - pr_err("%s", dwfl_errmsg(-1)); > + if (!ui->best_effort) > + pr_err("%s", dwfl_errmsg(-1)); > return DWARF_CB_ABORT; > } > > @@ -222,7 +224,8 @@ frame_callback(Dwfl_Frame *state, void *arg) > int unwind__get_entries(unwind_entry_cb_t cb, void *arg, > struct thread *thread, > struct perf_sample *data, > - int max_stack) > + int max_stack, > + bool best_effort) > { > struct unwind_info *ui, ui_buf = { > .sample = data, > @@ -231,6 +234,7 @@ int unwind__get_entries(unwind_entry_cb_t cb, void *arg, > .cb = cb, > .arg = arg, > .max_stack = max_stack, > + .best_effort = best_effort > }; > Dwarf_Word ip; > int err = -EINVAL, i; > diff --git a/tools/perf/util/unwind-libdw.h b/tools/perf/util/unwind-libdw.h > index 0cbd2650e280..8c88bc4f2304 100644 > --- a/tools/perf/util/unwind-libdw.h > +++ b/tools/perf/util/unwind-libdw.h > @@ -20,6 +20,7 @@ struct unwind_info { > void *arg; > int max_stack; > int idx; > + bool best_effort; > struct unwind_entry entries[]; > }; > > diff --git a/tools/perf/util/unwind-libunwind-local.c b/tools/perf/util/unwind-libunwind-local.c > index 71a353349181..41e29fc7648a 100644 > --- a/tools/perf/util/unwind-libunwind-local.c > +++ b/tools/perf/util/unwind-libunwind-local.c > @@ -96,6 +96,7 @@ struct unwind_info { > struct perf_sample *sample; > struct machine *machine; > struct thread *thread; > + bool best_effort;
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