If it runs on an old kernel, perf_event_open would fail because of the
new fields sigtrap and sig_data. Just skipping the test could miss an
actual bug in the kernel.
Let's check BTF if it has the perf_event_attr.sigtrap field.
Cc: Marco Elver <[email protected]>
Acked-by: Song Liu <[email protected]>
Signed-off-by: Namhyung Kim <[email protected]>
---
* move #include under #ifdef
* return true when BPF is not supported
* update comment
tools/perf/tests/sigtrap.c | 50 +++++++++++++++++++++++++++++++++++++-
1 file changed, 49 insertions(+), 1 deletion(-)
diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
index e32ece90e164..cdf75eab6a8a 100644
--- a/tools/perf/tests/sigtrap.c
+++ b/tools/perf/tests/sigtrap.c
@@ -54,6 +54,48 @@ static struct perf_event_attr make_event_attr(void)
return attr;
}
+#ifdef HAVE_BPF_SKEL
+#include <bpf/btf.h>
+
+static bool attr_has_sigtrap(void)
+{
+ bool ret = false;
+ struct btf *btf;
+ const struct btf_type *t;
+ const struct btf_member *m;
+ const char *name;
+ int i, id;
+
+ btf = btf__load_vmlinux_btf();
+ if (btf == NULL) {
+ /* should be an old kernel */
+ return false;
+ }
+
+ id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT);
+ if (id < 0)
+ goto out;
+
+ t = btf__type_by_id(btf, id);
+ for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
+ name = btf__name_by_offset(btf, m->name_off);
+ if (!strcmp(name, "sigtrap")) {
+ ret = true;
+ break;
+ }
+ }
+out:
+ btf__free(btf);
+ return ret;
+}
+#else /* !HAVE_BPF_SKEL */
+static bool attr_has_sigtrap(void)
+{
+ /* to maintain current behavior */
+ return true;
+}
+#endif /* HAVE_BPF_SKEL */
+
static void
sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused)
{
@@ -139,7 +181,13 @@ static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __m
fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag());
if (fd < 0) {
- pr_debug("FAILED sys_perf_event_open(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
+ if (attr_has_sigtrap()) {
+ pr_debug("FAILED sys_perf_event_open(): %s\n",
+ str_error_r(errno, sbuf, sizeof(sbuf)));
+ } else {
+ pr_debug("perf_event_attr doesn't have sigtrap\n");
+ ret = TEST_SKIP;
+ }
goto out_restore_sigaction;
}
--
2.37.2.789.g6183377224-goog
On Wed, Sep 7, 2022 at 12:12 AM Namhyung Kim <[email protected]> wrote:
>
> If it runs on an old kernel, perf_event_open would fail because of the
> new fields sigtrap and sig_data. Just skipping the test could miss an
> actual bug in the kernel.
>
> Let's check BTF if it has the perf_event_attr.sigtrap field.
>
> Cc: Marco Elver <[email protected]>
> Acked-by: Song Liu <[email protected]>
> Signed-off-by: Namhyung Kim <[email protected]>
> ---
> * move #include under #ifdef
> * return true when BPF is not supported
> * update comment
>
> tools/perf/tests/sigtrap.c | 50 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
> index e32ece90e164..cdf75eab6a8a 100644
> --- a/tools/perf/tests/sigtrap.c
> +++ b/tools/perf/tests/sigtrap.c
> @@ -54,6 +54,48 @@ static struct perf_event_attr make_event_attr(void)
> return attr;
> }
>
> +#ifdef HAVE_BPF_SKEL
> +#include <bpf/btf.h>
> +
> +static bool attr_has_sigtrap(void)
> +{
> + bool ret = false;
> + struct btf *btf;
> + const struct btf_type *t;
> + const struct btf_member *m;
> + const char *name;
> + int i, id;
> +
> + btf = btf__load_vmlinux_btf();
> + if (btf == NULL) {
> + /* should be an old kernel */
> + return false;
> + }
> +
> + id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT);
> + if (id < 0)
> + goto out;
> +
> + t = btf__type_by_id(btf, id);
> + for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
> + name = btf__name_by_offset(btf, m->name_off);
> + if (!strcmp(name, "sigtrap")) {
> + ret = true;
> + break;
> + }
> + }
> +out:
> + btf__free(btf);
> + return ret;
> +}
> +#else /* !HAVE_BPF_SKEL */
> +static bool attr_has_sigtrap(void)
> +{
> + /* to maintain current behavior */
nit: I don't think this comment will age well and the behavior of the
function is a bit counterintuitive. Perhaps:
/* If we don't have libbpf then guess we're on a newer kernel with
sigtrap support. This will mean the test will fail on older kernels.
*/
> + return true;
> +}
> +#endif /* HAVE_BPF_SKEL */
> +
> static void
> sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused)
> {
> @@ -139,7 +181,13 @@ static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __m
>
> fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag());
> if (fd < 0) {
> - pr_debug("FAILED sys_perf_event_open(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
> + if (attr_has_sigtrap()) {
> + pr_debug("FAILED sys_perf_event_open(): %s\n",
> + str_error_r(errno, sbuf, sizeof(sbuf)));
> + } else {
> + pr_debug("perf_event_attr doesn't have sigtrap\n");
> + ret = TEST_SKIP;
> + }
> goto out_restore_sigaction;
> }
>
> --
> 2.37.2.789.g6183377224-goog
>
Hi Ian,
On Wed, Sep 7, 2022 at 8:48 AM Ian Rogers <[email protected]> wrote:
>
> On Wed, Sep 7, 2022 at 12:12 AM Namhyung Kim <[email protected]> wrote:
> >
> > If it runs on an old kernel, perf_event_open would fail because of the
> > new fields sigtrap and sig_data. Just skipping the test could miss an
> > actual bug in the kernel.
> >
> > Let's check BTF if it has the perf_event_attr.sigtrap field.
> >
> > Cc: Marco Elver <[email protected]>
> > Acked-by: Song Liu <[email protected]>
> > Signed-off-by: Namhyung Kim <[email protected]>
> > ---
> > * move #include under #ifdef
> > * return true when BPF is not supported
> > * update comment
> >
> > tools/perf/tests/sigtrap.c | 50 +++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 49 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c
> > index e32ece90e164..cdf75eab6a8a 100644
> > --- a/tools/perf/tests/sigtrap.c
> > +++ b/tools/perf/tests/sigtrap.c
> > @@ -54,6 +54,48 @@ static struct perf_event_attr make_event_attr(void)
> > return attr;
> > }
> >
> > +#ifdef HAVE_BPF_SKEL
> > +#include <bpf/btf.h>
> > +
> > +static bool attr_has_sigtrap(void)
> > +{
> > + bool ret = false;
> > + struct btf *btf;
> > + const struct btf_type *t;
> > + const struct btf_member *m;
> > + const char *name;
> > + int i, id;
> > +
> > + btf = btf__load_vmlinux_btf();
> > + if (btf == NULL) {
> > + /* should be an old kernel */
> > + return false;
> > + }
> > +
> > + id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT);
> > + if (id < 0)
> > + goto out;
> > +
> > + t = btf__type_by_id(btf, id);
> > + for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
> > + name = btf__name_by_offset(btf, m->name_off);
> > + if (!strcmp(name, "sigtrap")) {
> > + ret = true;
> > + break;
> > + }
> > + }
> > +out:
> > + btf__free(btf);
> > + return ret;
> > +}
> > +#else /* !HAVE_BPF_SKEL */
> > +static bool attr_has_sigtrap(void)
> > +{
> > + /* to maintain current behavior */
>
> nit: I don't think this comment will age well and the behavior of the
> function is a bit counterintuitive. Perhaps:
>
> /* If we don't have libbpf then guess we're on a newer kernel with
> sigtrap support. This will mean the test will fail on older kernels.
> */
Thanks for the clarification, will update!
Namhyung