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Message-ID: <CAP-5=fU6xad0EGzQ=gJy6eUJtYrgV2FKSu=JcndeWVTKZE_RrA@mail.gmail.com>
Date: Thu, 13 Nov 2025 09:03:42 -0800
From: Ian Rogers <irogers@...gle.com>
To: Guilherme Amadio <amadio@...too.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>,
Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] perf libbfd: Ensure libbfd is initialized prior to use
On Tue, Nov 11, 2025 at 11:43 PM Ian Rogers <irogers@...gle.com> wrote:
>
> Multiple threads may be creating and destroying BFD objects in
> situations like `perf top`. Without appropriate initialization crashes
> may occur during libbfd's cache management. BFD's locks require
> recursive mutexes, add support for these.
>
> Reported-by: Guilherme Amadio <amadio@...too.org>
> Closes: https://lore.kernel.org/lkml/aQt66zhfxSA80xwt@gentoo.org/
> Fixes: 95931d9a594d ("perf libbfd: Move libbfd functionality to its own file")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
I'm hoping adding the missing initialization is just obviously
correct, Guilherme if you could provide a Tested-by it would be great.
Thanks,
Ian
> ---
> v2: Remove unneeded unistd.h include.
> ---
> tools/perf/util/libbfd.c | 38 ++++++++++++++++++++++++++++++++++++++
> tools/perf/util/mutex.c | 14 ++++++++++----
> tools/perf/util/mutex.h | 2 ++
> 3 files changed, 50 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/libbfd.c b/tools/perf/util/libbfd.c
> index 01147fbf73b3..6434c2dccd4a 100644
> --- a/tools/perf/util/libbfd.c
> +++ b/tools/perf/util/libbfd.c
> @@ -38,6 +38,39 @@ struct a2l_data {
> asymbol **syms;
> };
>
> +static bool perf_bfd_lock(void *bfd_mutex)
> +{
> + mutex_lock(bfd_mutex);
> + return true;
> +}
> +
> +static bool perf_bfd_unlock(void *bfd_mutex)
> +{
> + mutex_unlock(bfd_mutex);
> + return true;
> +}
> +
> +static void perf_bfd_init(void)
> +{
> + static struct mutex bfd_mutex;
> +
> + mutex_init_recursive(&bfd_mutex);
> +
> + if (bfd_init() != BFD_INIT_MAGIC) {
> + pr_err("Error initializing libbfd\n");
> + return;
> + }
> + if (!bfd_thread_init(perf_bfd_lock, perf_bfd_unlock, &bfd_mutex))
> + pr_err("Error initializing libbfd threading\n");
> +}
> +
> +static void ensure_bfd_init(void)
> +{
> + static pthread_once_t bfd_init_once = PTHREAD_ONCE_INIT;
> +
> + pthread_once(&bfd_init_once, perf_bfd_init);
> +}
> +
> static int bfd_error(const char *string)
> {
> const char *errmsg;
> @@ -132,6 +165,7 @@ static struct a2l_data *addr2line_init(const char *path)
> bfd *abfd;
> struct a2l_data *a2l = NULL;
>
> + ensure_bfd_init();
> abfd = bfd_openr(path, NULL);
> if (abfd == NULL)
> return NULL;
> @@ -288,6 +322,7 @@ int dso__load_bfd_symbols(struct dso *dso, const char *debugfile)
> bfd *abfd;
> u64 start, len;
>
> + ensure_bfd_init();
> abfd = bfd_openr(debugfile, NULL);
> if (!abfd)
> return -1;
> @@ -393,6 +428,7 @@ int libbfd__read_build_id(const char *filename, struct build_id *bid, bool block
> if (fd < 0)
> return -1;
>
> + ensure_bfd_init();
> abfd = bfd_fdopenr(filename, /*target=*/NULL, fd);
> if (!abfd)
> return -1;
> @@ -421,6 +457,7 @@ int libbfd_filename__read_debuglink(const char *filename, char *debuglink,
> asection *section;
> bfd *abfd;
>
> + ensure_bfd_init();
> abfd = bfd_openr(filename, NULL);
> if (!abfd)
> return -1;
> @@ -480,6 +517,7 @@ int symbol__disassemble_bpf_libbfd(struct symbol *sym __maybe_unused,
> memset(tpath, 0, sizeof(tpath));
> perf_exe(tpath, sizeof(tpath));
>
> + ensure_bfd_init();
> bfdf = bfd_openr(tpath, NULL);
> if (bfdf == NULL)
> abort();
> diff --git a/tools/perf/util/mutex.c b/tools/perf/util/mutex.c
> index bca7f0717f35..7aa1f3f55a7d 100644
> --- a/tools/perf/util/mutex.c
> +++ b/tools/perf/util/mutex.c
> @@ -17,7 +17,7 @@ static void check_err(const char *fn, int err)
>
> #define CHECK_ERR(err) check_err(__func__, err)
>
> -static void __mutex_init(struct mutex *mtx, bool pshared)
> +static void __mutex_init(struct mutex *mtx, bool pshared, bool recursive)
> {
> pthread_mutexattr_t attr;
>
> @@ -27,21 +27,27 @@ static void __mutex_init(struct mutex *mtx, bool pshared)
> /* In normal builds enable error checking, such as recursive usage. */
> CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK));
> #endif
> + if (recursive)
> + CHECK_ERR(pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE));
> if (pshared)
> CHECK_ERR(pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
> -
> CHECK_ERR(pthread_mutex_init(&mtx->lock, &attr));
> CHECK_ERR(pthread_mutexattr_destroy(&attr));
> }
>
> void mutex_init(struct mutex *mtx)
> {
> - __mutex_init(mtx, /*pshared=*/false);
> + __mutex_init(mtx, /*pshared=*/false, /*recursive=*/false);
> }
>
> void mutex_init_pshared(struct mutex *mtx)
> {
> - __mutex_init(mtx, /*pshared=*/true);
> + __mutex_init(mtx, /*pshared=*/true, /*recursive=*/false);
> +}
> +
> +void mutex_init_recursive(struct mutex *mtx)
> +{
> + __mutex_init(mtx, /*pshared=*/false, /*recursive=*/true);
> }
>
> void mutex_destroy(struct mutex *mtx)
> diff --git a/tools/perf/util/mutex.h b/tools/perf/util/mutex.h
> index 38458f00846f..70232d8d094f 100644
> --- a/tools/perf/util/mutex.h
> +++ b/tools/perf/util/mutex.h
> @@ -104,6 +104,8 @@ void mutex_init(struct mutex *mtx);
> * process-private attribute.
> */
> void mutex_init_pshared(struct mutex *mtx);
> +/* Initializes a mutex that may be recursively held on the same thread. */
> +void mutex_init_recursive(struct mutex *mtx);
> void mutex_destroy(struct mutex *mtx);
>
> void mutex_lock(struct mutex *mtx) EXCLUSIVE_LOCK_FUNCTION(*mtx);
> --
> 2.51.2.1041.gc1ab5b90ca-goog
>
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