* [PATCH v1] perf maps: Ensure kmap is set up for all inserts
@ 2025-09-14 18:18 Ian Rogers
2025-09-15 15:00 ` Ian Rogers
0 siblings, 1 reply; 3+ messages in thread
From: Ian Rogers @ 2025-09-14 18:18 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Liang, Kan, Chun-Tse Shao,
Christophe Leroy, linux-perf-users, linux-kernel
__maps__fixup_overlap_and_insert may split or directly insert a map,
when doing this the map may need to have a kmap set up for the sake of
the kmaps. The missing kmap set up fails the check_invariants test in
maps, later "Internal error" reports from map__kmap and ultimately
causes segfaults.
Similar fixes were added in commit e0e4e0b8b7fa ("perf maps: Add
missing map__set_kmap_maps() when replacing a kernel map") and commit
25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel
maps") but they missed cases. To try to reduce the risk of this,
update the kmap directly following any manual insert. This identified
another problem in maps__copy_from.
Fixes: e0e4e0b8b7fa ("perf maps: Add missing map__set_kmap_maps() when replacing a kernel map")
Fixes: 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel maps")
Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/maps.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index 85b2a93a59ac..779f6230130a 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -477,6 +477,7 @@ static int __maps__insert(struct maps *maps, struct map *new)
}
/* Insert the value at the end. */
maps_by_address[nr_maps] = map__get(new);
+ map__set_kmap_maps(new, maps);
if (maps_by_name)
maps_by_name[nr_maps] = map__get(new);
@@ -502,8 +503,6 @@ static int __maps__insert(struct maps *maps, struct map *new)
if (map__end(new) < map__start(new))
RC_CHK_ACCESS(maps)->ends_broken = true;
- map__set_kmap_maps(new, maps);
-
return 0;
}
@@ -891,6 +890,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
if (before) {
map__put(maps_by_address[i]);
maps_by_address[i] = before;
+ map__set_kmap_maps(before, maps);
if (maps_by_name) {
map__put(maps_by_name[ni]);
@@ -918,6 +918,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
*/
map__put(maps_by_address[i]);
maps_by_address[i] = map__get(new);
+ map__set_kmap_maps(new, maps);
if (maps_by_name) {
map__put(maps_by_name[ni]);
@@ -942,14 +943,13 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
*/
map__put(maps_by_address[i]);
maps_by_address[i] = map__get(new);
+ map__set_kmap_maps(new, maps);
if (maps_by_name) {
map__put(maps_by_name[ni]);
maps_by_name[ni] = map__get(new);
}
- map__set_kmap_maps(new, maps);
-
check_invariants(maps);
return err;
}
@@ -1019,6 +1019,7 @@ int maps__copy_from(struct maps *dest, struct maps *parent)
err = unwind__prepare_access(dest, new, NULL);
if (!err) {
dest_maps_by_address[i] = new;
+ map__set_kmap_maps(new, dest);
if (dest_maps_by_name)
dest_maps_by_name[i] = map__get(new);
RC_CHK_ACCESS(dest)->nr_maps = i + 1;
--
2.51.0.384.g4c02a37b29-goog
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH v1] perf maps: Ensure kmap is set up for all inserts
2025-09-14 18:18 [PATCH v1] perf maps: Ensure kmap is set up for all inserts Ian Rogers
@ 2025-09-15 15:00 ` Ian Rogers
2025-09-15 17:03 ` Namhyung Kim
0 siblings, 1 reply; 3+ messages in thread
From: Ian Rogers @ 2025-09-15 15:00 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Namhyung Kim, Mark Rutland, Alexander Shishkin, Jiri Olsa,
Ian Rogers, Adrian Hunter, Liang, Kan, Chun-Tse Shao,
Christophe Leroy, linux-perf-users, linux-kernel
On Sun, Sep 14, 2025 at 11:18 AM Ian Rogers <irogers@google.com> wrote:
>
> __maps__fixup_overlap_and_insert may split or directly insert a map,
> when doing this the map may need to have a kmap set up for the sake of
> the kmaps. The missing kmap set up fails the check_invariants test in
> maps, later "Internal error" reports from map__kmap and ultimately
> causes segfaults.
>
> Similar fixes were added in commit e0e4e0b8b7fa ("perf maps: Add
> missing map__set_kmap_maps() when replacing a kernel map") and commit
> 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel
> maps") but they missed cases. To try to reduce the risk of this,
> update the kmap directly following any manual insert. This identified
> another problem in maps__copy_from.
>
> Fixes: e0e4e0b8b7fa ("perf maps: Add missing map__set_kmap_maps() when replacing a kernel map")
> Fixes: 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel maps")
> Signed-off-by: Ian Rogers <irogers@google.com>
This may be worth picking up for v6.17. It was a fairly regular source
of crashes on basic commands like `perf record` for me on certain
kernels. `perf record` by default is processing the whole perf.data
file and if there were overlapping maps, from BPF symbol events
typically, the broken kmap would trigger assertion failures and seg
faults.
Thanks,
Ian
> ---
> tools/perf/util/maps.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
> index 85b2a93a59ac..779f6230130a 100644
> --- a/tools/perf/util/maps.c
> +++ b/tools/perf/util/maps.c
> @@ -477,6 +477,7 @@ static int __maps__insert(struct maps *maps, struct map *new)
> }
> /* Insert the value at the end. */
> maps_by_address[nr_maps] = map__get(new);
> + map__set_kmap_maps(new, maps);
> if (maps_by_name)
> maps_by_name[nr_maps] = map__get(new);
>
> @@ -502,8 +503,6 @@ static int __maps__insert(struct maps *maps, struct map *new)
> if (map__end(new) < map__start(new))
> RC_CHK_ACCESS(maps)->ends_broken = true;
>
> - map__set_kmap_maps(new, maps);
> -
> return 0;
> }
>
> @@ -891,6 +890,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> if (before) {
> map__put(maps_by_address[i]);
> maps_by_address[i] = before;
> + map__set_kmap_maps(before, maps);
>
> if (maps_by_name) {
> map__put(maps_by_name[ni]);
> @@ -918,6 +918,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> */
> map__put(maps_by_address[i]);
> maps_by_address[i] = map__get(new);
> + map__set_kmap_maps(new, maps);
>
> if (maps_by_name) {
> map__put(maps_by_name[ni]);
> @@ -942,14 +943,13 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> */
> map__put(maps_by_address[i]);
> maps_by_address[i] = map__get(new);
> + map__set_kmap_maps(new, maps);
>
> if (maps_by_name) {
> map__put(maps_by_name[ni]);
> maps_by_name[ni] = map__get(new);
> }
>
> - map__set_kmap_maps(new, maps);
> -
> check_invariants(maps);
> return err;
> }
> @@ -1019,6 +1019,7 @@ int maps__copy_from(struct maps *dest, struct maps *parent)
> err = unwind__prepare_access(dest, new, NULL);
> if (!err) {
> dest_maps_by_address[i] = new;
> + map__set_kmap_maps(new, dest);
> if (dest_maps_by_name)
> dest_maps_by_name[i] = map__get(new);
> RC_CHK_ACCESS(dest)->nr_maps = i + 1;
> --
> 2.51.0.384.g4c02a37b29-goog
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH v1] perf maps: Ensure kmap is set up for all inserts
2025-09-15 15:00 ` Ian Rogers
@ 2025-09-15 17:03 ` Namhyung Kim
0 siblings, 0 replies; 3+ messages in thread
From: Namhyung Kim @ 2025-09-15 17:03 UTC (permalink / raw)
To: Ian Rogers
Cc: Peter Zijlstra, Ingo Molnar, Arnaldo Carvalho de Melo,
Mark Rutland, Alexander Shishkin, Jiri Olsa, Adrian Hunter,
Liang, Kan, Chun-Tse Shao, Christophe Leroy, linux-perf-users,
linux-kernel
Hi Ian,
On Mon, Sep 15, 2025 at 08:00:53AM -0700, Ian Rogers wrote:
> On Sun, Sep 14, 2025 at 11:18 AM Ian Rogers <irogers@google.com> wrote:
> >
> > __maps__fixup_overlap_and_insert may split or directly insert a map,
> > when doing this the map may need to have a kmap set up for the sake of
> > the kmaps. The missing kmap set up fails the check_invariants test in
> > maps, later "Internal error" reports from map__kmap and ultimately
> > causes segfaults.
> >
> > Similar fixes were added in commit e0e4e0b8b7fa ("perf maps: Add
> > missing map__set_kmap_maps() when replacing a kernel map") and commit
> > 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel
> > maps") but they missed cases. To try to reduce the risk of this,
> > update the kmap directly following any manual insert. This identified
> > another problem in maps__copy_from.
> >
> > Fixes: e0e4e0b8b7fa ("perf maps: Add missing map__set_kmap_maps() when replacing a kernel map")
> > Fixes: 25d9c0301d36 ("perf maps: Set the kmaps for newly created/added kernel maps")
> > Signed-off-by: Ian Rogers <irogers@google.com>
>
> This may be worth picking up for v6.17. It was a fairly regular source
> of crashes on basic commands like `perf record` for me on certain
> kernels. `perf record` by default is processing the whole perf.data
> file and if there were overlapping maps, from BPF symbol events
> typically, the broken kmap would trigger assertion failures and seg
> faults.
Sounds good, will queue it to perf-tools.
Thanks,
Namhyung
> > ---
> > tools/perf/util/maps.c | 9 +++++----
> > 1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
> > index 85b2a93a59ac..779f6230130a 100644
> > --- a/tools/perf/util/maps.c
> > +++ b/tools/perf/util/maps.c
> > @@ -477,6 +477,7 @@ static int __maps__insert(struct maps *maps, struct map *new)
> > }
> > /* Insert the value at the end. */
> > maps_by_address[nr_maps] = map__get(new);
> > + map__set_kmap_maps(new, maps);
> > if (maps_by_name)
> > maps_by_name[nr_maps] = map__get(new);
> >
> > @@ -502,8 +503,6 @@ static int __maps__insert(struct maps *maps, struct map *new)
> > if (map__end(new) < map__start(new))
> > RC_CHK_ACCESS(maps)->ends_broken = true;
> >
> > - map__set_kmap_maps(new, maps);
> > -
> > return 0;
> > }
> >
> > @@ -891,6 +890,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> > if (before) {
> > map__put(maps_by_address[i]);
> > maps_by_address[i] = before;
> > + map__set_kmap_maps(before, maps);
> >
> > if (maps_by_name) {
> > map__put(maps_by_name[ni]);
> > @@ -918,6 +918,7 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> > */
> > map__put(maps_by_address[i]);
> > maps_by_address[i] = map__get(new);
> > + map__set_kmap_maps(new, maps);
> >
> > if (maps_by_name) {
> > map__put(maps_by_name[ni]);
> > @@ -942,14 +943,13 @@ static int __maps__fixup_overlap_and_insert(struct maps *maps, struct map *new)
> > */
> > map__put(maps_by_address[i]);
> > maps_by_address[i] = map__get(new);
> > + map__set_kmap_maps(new, maps);
> >
> > if (maps_by_name) {
> > map__put(maps_by_name[ni]);
> > maps_by_name[ni] = map__get(new);
> > }
> >
> > - map__set_kmap_maps(new, maps);
> > -
> > check_invariants(maps);
> > return err;
> > }
> > @@ -1019,6 +1019,7 @@ int maps__copy_from(struct maps *dest, struct maps *parent)
> > err = unwind__prepare_access(dest, new, NULL);
> > if (!err) {
> > dest_maps_by_address[i] = new;
> > + map__set_kmap_maps(new, dest);
> > if (dest_maps_by_name)
> > dest_maps_by_name[i] = map__get(new);
> > RC_CHK_ACCESS(dest)->nr_maps = i + 1;
> > --
> > 2.51.0.384.g4c02a37b29-goog
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-09-14 18:18 [PATCH v1] perf maps: Ensure kmap is set up for all inserts Ian Rogers
2025-09-15 15:00 ` Ian Rogers
2025-09-15 17:03 ` Namhyung Kim
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