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

[Namhyung Kim]

Hello,

On Mon, Jul 8, 2024 at 4:23 PM Casey Chen <cachen@xxxxxxxxxxxxxxx> 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
>
>