Re: [PATCH 1/1] perf tool: fix handling NULL al->maps returned from thread__find_map

Namhyung Kim
2024-07-09T05:01:19Z

Hello,

On Mon, Jul 8, 2024 at 4:23 PM Casey Chen <cachen@purestorage.com> wrote:
>
> With 0dd5041c9a0e ("perf addr_location: Add init/exit/copy functions"),
> thread__find_map() would return with al->maps or al->map being NULL
> when cpumode is 3 (macro PERF_RECORD_MISC_HYPERVISOR),
> later deferencing on it would crash.
>
> Fix callers of thread__find_map() or thread__find_symbol() to handle
> this.

It looks like you drop the callchain if it doesn't find a map/symbol.
Can we keep the entries with raw hex numbers instead?

Thanks,
Namhyung

> ---
> tools/perf/arch/powerpc/util/skip-callchain-idx.c | 10 ++++++----
> tools/perf/util/machine.c | 5 +++++
> tools/perf/util/unwind-libdw.c | 6 ++++--
> 3 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/arch/powerpc/util/skip-callchain-idx.c b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
> index 5f3edb3004d8..25b0804df4c4 100644
> --- a/tools/perf/arch/powerpc/util/skip-callchain-idx.c
> +++ b/tools/perf/arch/powerpc/util/skip-callchain-idx.c
> @@ -255,13 +255,14 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain)
>
> thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
>
> - if (al.map)
> - dso = map__dso(al.map);
> + if (!al.map)
> + goto out;
> +
> + dso = map__dso(al.map);
>
> if (!dso) {
> pr_debug("%" PRIx64 " dso is NULL\n", ip);
> - addr_location__exit(&al);
> - return skip_slot;
> + goto out;
> }
>
> rc = check_return_addr(dso, map__start(al.map), ip);
> @@ -282,6 +283,7 @@ int arch_skip_callchain_idx(struct thread *thread, struct ip_callchain *chain)
> skip_slot = 3;
> }
>
> +out:
> addr_location__exit(&al);
> return skip_slot;
> }
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 8477edefc299..fa4037d7f3d4 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -2098,7 +2098,12 @@ static int add_callchain_ip(struct thread *thread,
> }
> goto out;
> }
> +
> thread__find_symbol(thread, *cpumode, ip, &al);
> + if (!al.maps || !al.map) {
> + err = 1;
> + goto out;
> + }
> }
>
> if (al.sym != NULL) {
> diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
> index b38d322734b4..fb038ef55be2 100644
> --- a/tools/perf/util/unwind-libdw.c
> +++ b/tools/perf/util/unwind-libdw.c
> @@ -53,8 +53,10 @@ static int __report_module(struct addr_location *al, u64 ip,
> */
> thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
>
> - if (al->map)
> - dso = map__dso(al->map);
> + if (!al->map)
> + return -1;
> +
> + dso = map__dso(al->map);
>
> if (!dso)
> return 0;
> --
> 2.45.2
>
>