From 15b837759a97237d647962f9943afe0d55af615a Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:38 +0200 Subject: [PATCH 01/12] bpf: Factor stackid_init function from __bpf_get_stackid The new stackid_init function stores all the necessary bits for stackid trace and it will be used by other functions in following changes. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-2-jolsa@kernel.org --- kernel/bpf/stackmap.c | 95 +++++++++++++++++++++++++++---------------- 1 file changed, 59 insertions(+), 36 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 463f94ba1cc4..19f9ea605a3e 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -504,33 +504,54 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) #endif } -static long __bpf_get_stackid(struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) +struct stackid { + struct stack_map_bucket *bucket; + u64 *ips; + u32 nr; + u32 len; + u32 hash; + u32 id; +}; + +static int stackid_init(struct stackid *stackid, struct bpf_map *map, + struct perf_callchain_entry *trace, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); - struct stack_map_bucket *bucket, *new_bucket, *old_bucket; - u32 hash, id, trace_nr, trace_len, i, max_depth; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; - bool user = flags & BPF_F_USER_STACK; - u64 *ips; - bool hash_matches; + u32 max_depth; if (trace->nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); - trace_nr = min_t(u32, trace->nr - skip, max_depth - skip); - trace_len = trace_nr * sizeof(u64); - ips = trace->ip + skip; - hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); - id = hash & (smap->n_buckets - 1); - bucket = READ_ONCE(smap->buckets[id]); + stackid->nr = min_t(u32, trace->nr - skip, max_depth - skip); + stackid->len = stackid->nr * sizeof(u64); + stackid->ips = trace->ip + skip; + stackid->hash = jhash2((u32 *)stackid->ips, stackid->len / sizeof(u32), 0); + stackid->id = stackid->hash & (smap->n_buckets - 1); + stackid->bucket = READ_ONCE(smap->buckets[stackid->id]); + return 0; +} - hash_matches = bucket && bucket->hash == hash; +static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, + struct perf_callchain_entry *trace, u64 flags) +{ + struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); + struct stack_map_bucket *new_bucket, *old_bucket; + bool user = flags & BPF_F_USER_STACK; + bool hash_matches; + u32 trace_len, i; + int err; + + err = stackid_init(stackid, map, trace, flags); + if (err) + return err; + + hash_matches = stackid->bucket && stackid->bucket->hash == stackid->hash; /* fast cmp */ if (hash_matches && flags & BPF_F_FAST_STACK_CMP) - return id; + return stackid->id; if (stack_map_use_build_id(map)) { struct bpf_stack_build_id *id_offs; @@ -540,42 +561,42 @@ static long __bpf_get_stackid(struct bpf_map *map, pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; - new_bucket->nr = trace_nr; + new_bucket->nr = stackid->nr; id_offs = (struct bpf_stack_build_id *)new_bucket->data; - for (i = 0; i < trace_nr; i++) - id_offs[i].ip = ips[i]; - stack_map_get_build_id_offset(id_offs, trace_nr, user, false /* !may_fault */); - trace_len = trace_nr * sizeof(struct bpf_stack_build_id); - if (hash_matches && bucket->nr == trace_nr && - memcmp(bucket->data, new_bucket->data, trace_len) == 0) { + for (i = 0; i < stackid->nr; i++) + id_offs[i].ip = stackid->ips[i]; + stack_map_get_build_id_offset(id_offs, stackid->nr, user, false /* !may_fault */); + trace_len = stackid->nr * sizeof(struct bpf_stack_build_id); + if (hash_matches && stackid->bucket->nr == stackid->nr && + memcmp(stackid->bucket->data, new_bucket->data, trace_len) == 0) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); - return id; + return stackid->id; } - if (bucket && !(flags & BPF_F_REUSE_STACKID)) { + if (stackid->bucket && !(flags & BPF_F_REUSE_STACKID)) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return -EEXIST; } } else { - if (hash_matches && bucket->nr == trace_nr && - memcmp(bucket->data, ips, trace_len) == 0) - return id; - if (bucket && !(flags & BPF_F_REUSE_STACKID)) + if (hash_matches && stackid->bucket->nr == stackid->nr && + memcmp(stackid->bucket->data, stackid->ips, stackid->len) == 0) + return stackid->id; + if (stackid->bucket && !(flags & BPF_F_REUSE_STACKID)) return -EEXIST; new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) return -ENOMEM; - memcpy(new_bucket->data, ips, trace_len); + memcpy(new_bucket->data, stackid->ips, stackid->len); } - new_bucket->hash = hash; - new_bucket->nr = trace_nr; + new_bucket->hash = stackid->hash; + new_bucket->nr = stackid->nr; - old_bucket = xchg(&smap->buckets[id], new_bucket); + old_bucket = xchg(&smap->buckets[stackid->id], new_bucket); if (old_bucket) pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); - return id; + return stackid->id; } BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, @@ -584,6 +605,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, u32 elem_size = stack_map_data_size(map); bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; + struct stackid stackid; bool kernel = !user; u32 max_depth; @@ -599,7 +621,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, /* couldn't fetch the stack trace */ return -EFAULT; - return __bpf_get_stackid(map, trace, flags); + return __bpf_get_stackid(&stackid, map, trace, flags); } const struct bpf_func_proto bpf_get_stackid_proto = { @@ -628,6 +650,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, { struct perf_event *event = ctx->event; struct perf_callchain_entry *trace; + struct stackid stackid; bool kernel, user; __u64 nr_kernel; int ret; @@ -653,7 +676,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, if (kernel) { trace->nr = nr_kernel; - ret = __bpf_get_stackid(map, trace, flags); + ret = __bpf_get_stackid(&stackid, map, trace, flags); } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK; @@ -662,7 +685,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT; flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; - ret = __bpf_get_stackid(map, trace, flags); + ret = __bpf_get_stackid(&stackid, map, trace, flags); } /* restore nr */ From 0ca56befcffec3a6c9d1842eae06c74e1cf41f11 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:39 +0200 Subject: [PATCH 02/12] bpf: Factor stackid_fastpath function from __bpf_get_stackid The new stackid_fastpath does the fast stack hash and trace check, that does not need new bucket allocation. It covers both just-ip and buildid code paths. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-3-jolsa@kernel.org --- kernel/bpf/stackmap.c | 43 ++++++++++++++++++++++++++++--------------- 1 file changed, 28 insertions(+), 15 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 19f9ea605a3e..27210b5d16fc 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -511,6 +511,7 @@ struct stackid { u32 len; u32 hash; u32 id; + bool hash_matches; }; static int stackid_init(struct stackid *stackid, struct bpf_map *map, @@ -531,28 +532,46 @@ static int stackid_init(struct stackid *stackid, struct bpf_map *map, stackid->hash = jhash2((u32 *)stackid->ips, stackid->len / sizeof(u32), 0); stackid->id = stackid->hash & (smap->n_buckets - 1); stackid->bucket = READ_ONCE(smap->buckets[stackid->id]); + stackid->hash_matches = stackid->bucket && stackid->bucket->hash == stackid->hash; return 0; } +static int stackid_fastpath(struct stackid *stackid, struct bpf_map *map, + struct perf_callchain_entry *trace, u64 flags) +{ + int err; + + err = stackid_init(stackid, map, trace, flags); + if (err) + return err; + + /* fast cmp */ + if (stackid->hash_matches && flags & BPF_F_FAST_STACK_CMP) + return stackid->id; + + if (stack_map_use_build_id(map)) + return -ENOENT; + if (stackid->hash_matches && stackid->bucket->nr == stackid->nr && + memcmp(stackid->bucket->data, stackid->ips, stackid->len) == 0) + return stackid->id; + if (stackid->bucket && !(flags & BPF_F_REUSE_STACKID)) + return -EEXIST; + return -ENOENT; +} + static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, struct perf_callchain_entry *trace, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct stack_map_bucket *new_bucket, *old_bucket; bool user = flags & BPF_F_USER_STACK; - bool hash_matches; u32 trace_len, i; int err; - err = stackid_init(stackid, map, trace, flags); - if (err) + err = stackid_fastpath(stackid, map, trace, flags); + if (err != -ENOENT) return err; - hash_matches = stackid->bucket && stackid->bucket->hash == stackid->hash; - /* fast cmp */ - if (hash_matches && flags & BPF_F_FAST_STACK_CMP) - return stackid->id; - if (stack_map_use_build_id(map)) { struct bpf_stack_build_id *id_offs; @@ -567,7 +586,7 @@ static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, id_offs[i].ip = stackid->ips[i]; stack_map_get_build_id_offset(id_offs, stackid->nr, user, false /* !may_fault */); trace_len = stackid->nr * sizeof(struct bpf_stack_build_id); - if (hash_matches && stackid->bucket->nr == stackid->nr && + if (stackid->hash_matches && stackid->bucket->nr == stackid->nr && memcmp(stackid->bucket->data, new_bucket->data, trace_len) == 0) { pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return stackid->id; @@ -577,12 +596,6 @@ static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, return -EEXIST; } } else { - if (hash_matches && stackid->bucket->nr == stackid->nr && - memcmp(stackid->bucket->data, stackid->ips, stackid->len) == 0) - return stackid->id; - if (stackid->bucket && !(flags & BPF_F_REUSE_STACKID)) - return -EEXIST; - new_bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); if (unlikely(!new_bucket)) From bb4e6f4e1b68fe60c04ca04c564c6624e837dbf4 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:40 +0200 Subject: [PATCH 03/12] bpf: Factor stackid_new_bucket from __bpf_get_stackid The new stackid_new_bucket allocates the new bucket and initializes it with the trace data. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-4-jolsa@kernel.org --- kernel/bpf/stackmap.c | 48 +++++++++++++++++++++++++++---------------- 1 file changed, 30 insertions(+), 18 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 27210b5d16fc..d930d9754d7d 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -559,31 +559,52 @@ static int stackid_fastpath(struct stackid *stackid, struct bpf_map *map, return -ENOENT; } +static struct stack_map_bucket * +stackid_new_bucket(struct stackid *stackid, struct bpf_map *map) +{ + struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); + struct bpf_stack_build_id *id_offs; + struct stack_map_bucket *bucket; + u32 i; + + bucket = (struct stack_map_bucket *) pcpu_freelist_pop(&smap->freelist); + if (unlikely(!bucket)) + return NULL; + + if (stack_map_use_build_id(map)) { + id_offs = (struct bpf_stack_build_id *)bucket->data; + for (i = 0; i < stackid->nr; i++) + id_offs[i].ip = stackid->ips[i]; + } else { + memcpy(bucket->data, stackid->ips, stackid->len); + } + + bucket->hash = stackid->hash; + bucket->nr = stackid->nr; + return bucket; +} + static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, struct perf_callchain_entry *trace, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct stack_map_bucket *new_bucket, *old_bucket; bool user = flags & BPF_F_USER_STACK; - u32 trace_len, i; + u32 trace_len; int err; err = stackid_fastpath(stackid, map, trace, flags); if (err != -ENOENT) return err; + new_bucket = stackid_new_bucket(stackid, map); + if (!new_bucket) + return -ENOMEM; + if (stack_map_use_build_id(map)) { struct bpf_stack_build_id *id_offs; - /* for build_id+offset, pop a bucket before slow cmp */ - new_bucket = (struct stack_map_bucket *) - pcpu_freelist_pop(&smap->freelist); - if (unlikely(!new_bucket)) - return -ENOMEM; - new_bucket->nr = stackid->nr; id_offs = (struct bpf_stack_build_id *)new_bucket->data; - for (i = 0; i < stackid->nr; i++) - id_offs[i].ip = stackid->ips[i]; stack_map_get_build_id_offset(id_offs, stackid->nr, user, false /* !may_fault */); trace_len = stackid->nr * sizeof(struct bpf_stack_build_id); if (stackid->hash_matches && stackid->bucket->nr == stackid->nr && @@ -595,17 +616,8 @@ static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, pcpu_freelist_push(&smap->freelist, &new_bucket->fnode); return -EEXIST; } - } else { - new_bucket = (struct stack_map_bucket *) - pcpu_freelist_pop(&smap->freelist); - if (unlikely(!new_bucket)) - return -ENOMEM; - memcpy(new_bucket->data, stackid->ips, stackid->len); } - new_bucket->hash = stackid->hash; - new_bucket->nr = stackid->nr; - old_bucket = xchg(&smap->buckets[stackid->id], new_bucket); if (old_bucket) pcpu_freelist_push(&smap->freelist, &old_bucket->fnode); From 09b3fd6caa0b57f8a39254ee5db3af30bdd53c18 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:41 +0200 Subject: [PATCH 04/12] bpf: Use stack id functions instead of __bpf_get_stackid Replacing __bpf_get_stackid calls with sequence of following functions: stackid_fastpath stackid_new_bucket stackid_install This makes code more structured and allows us to easily disable preemption only in bpf_get_stackid in following changes. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-5-jolsa@kernel.org --- kernel/bpf/stackmap.c | 43 +++++++++++++++++++++++++++---------------- 1 file changed, 27 insertions(+), 16 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index d930d9754d7d..3ee0034daf52 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -584,22 +584,13 @@ stackid_new_bucket(struct stackid *stackid, struct bpf_map *map) return bucket; } -static long __bpf_get_stackid(struct stackid *stackid, struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) +static long stackid_install(struct stackid *stackid, struct bpf_map *map, + struct stack_map_bucket *new_bucket, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); - struct stack_map_bucket *new_bucket, *old_bucket; bool user = flags & BPF_F_USER_STACK; + struct stack_map_bucket *old_bucket; u32 trace_len; - int err; - - err = stackid_fastpath(stackid, map, trace, flags); - if (err != -ENOENT) - return err; - - new_bucket = stackid_new_bucket(stackid, map); - if (!new_bucket) - return -ENOMEM; if (stack_map_use_build_id(map)) { struct bpf_stack_build_id *id_offs; @@ -629,10 +620,12 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, { u32 elem_size = stack_map_data_size(map); bool user = flags & BPF_F_USER_STACK; + struct stack_map_bucket *new_bucket; struct perf_callchain_entry *trace; struct stackid stackid; bool kernel = !user; u32 max_depth; + int err; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) @@ -646,7 +639,15 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, /* couldn't fetch the stack trace */ return -EFAULT; - return __bpf_get_stackid(&stackid, map, trace, flags); + err = stackid_fastpath(&stackid, map, trace, flags); + if (err != -ENOENT) + return err; + + new_bucket = stackid_new_bucket(&stackid, map); + if (!new_bucket) + return -ENOMEM; + + return stackid_install(&stackid, map, new_bucket, flags); } const struct bpf_func_proto bpf_get_stackid_proto = { @@ -674,6 +675,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, struct bpf_map *, map, u64, flags) { struct perf_event *event = ctx->event; + struct stack_map_bucket *new_bucket; struct perf_callchain_entry *trace; struct stackid stackid; bool kernel, user; @@ -701,7 +703,6 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, if (kernel) { trace->nr = nr_kernel; - ret = __bpf_get_stackid(&stackid, map, trace, flags); } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK; @@ -710,12 +711,22 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT; flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; - ret = __bpf_get_stackid(&stackid, map, trace, flags); } + ret = stackid_fastpath(&stackid, map, trace, flags); + if (ret != -ENOENT) + goto out; + + new_bucket = stackid_new_bucket(&stackid, map); + if (new_bucket) { + trace->nr = nr; + return stackid_install(&stackid, map, new_bucket, flags); + } + ret = -ENOMEM; + +out: /* restore nr */ trace->nr = nr; - return ret; } From 15f1bd8574662f1b7b26aaa2e23ebf4066f0117d Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:42 +0200 Subject: [PATCH 05/12] bpf: Disable preemption in bpf_get_stackid The get_perf_callchain call needs disabled preemption plus we need it disabled as long as we access its returned trace entries buffer. Note the bpf_get_stackid_pe function is executed already with preemption disabled. Fixes: d5a3b1f69186 ("bpf: introduce BPF_MAP_TYPE_STACK_TRACE") Reported-by: Tao Chen Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20260803210149.296496-6-jolsa@kernel.org Closes: https://lore.kernel.org/bpf/20260206090653.1336687-2-chen.dylane@linux.dev/ --- kernel/bpf/stackmap.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 3ee0034daf52..5b18d728f4b8 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -632,20 +632,22 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, return -EINVAL; max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); - trace = get_perf_callchain(regs, kernel, user, max_depth, - false, false, 0); - if (unlikely(!trace)) - /* couldn't fetch the stack trace */ - return -EFAULT; + scoped_guard(preempt) { + trace = get_perf_callchain(regs, kernel, user, max_depth, + false, false, 0); + if (unlikely(!trace)) + /* couldn't fetch the stack trace */ + return -EFAULT; - err = stackid_fastpath(&stackid, map, trace, flags); - if (err != -ENOENT) - return err; + err = stackid_fastpath(&stackid, map, trace, flags); + if (err != -ENOENT) + return err; - new_bucket = stackid_new_bucket(&stackid, map); - if (!new_bucket) - return -ENOMEM; + new_bucket = stackid_new_bucket(&stackid, map); + if (!new_bucket) + return -ENOMEM; + } return stackid_install(&stackid, map, new_bucket, flags); } From cbb99938e7935c9f62c891573a4b09690e5e22de Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:43 +0200 Subject: [PATCH 06/12] bpf: Factor callchain_store function from __bpf_get_stack The new callchain_store function stores trace entries buffer into user supplied buffer. It covers both just-ip and buildid data. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-7-jolsa@kernel.org --- kernel/bpf/stackmap.c | 39 +++++++++++++++++++++++++-------------- 1 file changed, 25 insertions(+), 14 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 5b18d728f4b8..ee9905d67b8e 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -741,6 +741,29 @@ const struct bpf_func_proto bpf_get_stackid_proto_pe = { .arg3_type = ARG_ANYTHING, }; +static u32 callchain_store(struct perf_callchain_entry *trace, void *buf, + u32 elem_size, u64 flags) +{ + bool user_build_id = flags & BPF_F_USER_BUILD_ID; + u32 skip = flags & BPF_F_SKIP_FIELD_MASK; + u32 trace_nr, copy_len; + u64 *ips; + + trace_nr = trace->nr - skip; + copy_len = trace_nr * elem_size; + + ips = trace->ip + skip; + if (user_build_id) { + struct bpf_stack_build_id *id_offs = buf; + + for (u32 i = 0; i < trace_nr; i++) + id_offs[i].ip = ips[i]; + } else { + memcpy(buf, ips, copy_len); + } + return trace_nr; +} + static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, struct perf_callchain_entry *trace_in, void *buf, u32 size, u64 flags, bool may_fault) @@ -753,7 +776,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, struct perf_callchain_entry *trace; bool kernel = !user; int err = -EINVAL; - u64 *ips; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_USER_BUILD_ID))) @@ -798,21 +820,10 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, goto err_fault; } - trace_nr = trace->nr - skip; + trace_nr = callchain_store(trace, buf, elem_size, flags); copy_len = trace_nr * elem_size; - ips = trace->ip + skip; - if (user_build_id) { - struct bpf_stack_build_id *id_offs = buf; - u32 i; - - for (i = 0; i < trace_nr; i++) - id_offs[i].ip = ips[i]; - } else { - memcpy(buf, ips, copy_len); - } - - /* trace/ips should not be dereferenced after this point */ + /* trace should not be dereferenced after this point */ if (may_fault) rcu_read_unlock(); From 014fbe5902dccdaef69114abdcdb15e3dbe55e34 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:44 +0200 Subject: [PATCH 07/12] bpf: Factor callchain_finalize function from __bpf_get_stack The new callchain_finalize function calls the build-id retrieval (if needed) and zeroes the buffer. This makes things easier for preemption fix in following change. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-8-jolsa@kernel.org --- kernel/bpf/stackmap.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index ee9905d67b8e..cdeb6c2e50da 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -764,16 +764,31 @@ static u32 callchain_store(struct perf_callchain_entry *trace, void *buf, return trace_nr; } +static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size, + u64 flags, bool may_fault) +{ + bool user_build_id = flags & BPF_F_USER_BUILD_ID; + bool user = flags & BPF_F_USER_STACK; + u32 copy_len = trace_nr * elem_size; + + if (user_build_id) + stack_map_get_build_id_offset(buf, trace_nr, user, may_fault); + + if (size > copy_len) + memset(buf + copy_len, 0, size - copy_len); + return copy_len; +} + static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, struct perf_callchain_entry *trace_in, void *buf, u32 size, u64 flags, bool may_fault) { - u32 trace_nr, copy_len, elem_size, max_depth; bool user_build_id = flags & BPF_F_USER_BUILD_ID; bool crosstask = task && task != current; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; + u32 trace_nr, elem_size, max_depth; bool kernel = !user; int err = -EINVAL; @@ -821,18 +836,12 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, } trace_nr = callchain_store(trace, buf, elem_size, flags); - copy_len = trace_nr * elem_size; /* trace should not be dereferenced after this point */ if (may_fault) rcu_read_unlock(); - if (user_build_id) - stack_map_get_build_id_offset(buf, trace_nr, user, may_fault); - - if (size > copy_len) - memset(buf + copy_len, 0, size - copy_len); - return copy_len; + return callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault); err_fault: err = -EFAULT; From 58cfc2201d964163fe9c4a703136eb64db799f08 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:45 +0200 Subject: [PATCH 08/12] bpf: Remove trace_in argument from __bpf_get_stack Now with the new callchain_* helper functions we can process trace_in case directly in bpf_get_stack_pe function and remove it from __bpf_get_stack which makes things easier for preemption fix in following change. Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-9-jolsa@kernel.org --- kernel/bpf/stackmap.c | 49 ++++++++++++++++++++++++++++++------------- 1 file changed, 35 insertions(+), 14 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index cdeb6c2e50da..976c4e4c1af6 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -780,7 +780,6 @@ static long callchain_finalize(void *buf, u32 size, u32 trace_nr, u32 elem_size, } static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, - struct perf_callchain_entry *trace_in, void *buf, u32 size, u64 flags, bool may_fault) { bool user_build_id = flags & BPF_F_USER_BUILD_ID; @@ -819,10 +818,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, if (may_fault) rcu_read_lock(); /* need RCU for perf's callchain below */ - if (trace_in) { - trace = trace_in; - trace->nr = min_t(u32, trace->nr, max_depth); - } else if (kernel && task) { + if (kernel && task) { trace = get_callchain_entry_for_task(task, max_depth); } else { trace = get_perf_callchain(regs, kernel, user, max_depth, @@ -853,7 +849,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, BPF_CALL_4(bpf_get_stack, struct pt_regs *, regs, void *, buf, u32, size, u64, flags) { - return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, false /* !may_fault */); + return __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */); } const struct bpf_func_proto bpf_get_stack_proto = { @@ -869,7 +865,7 @@ const struct bpf_func_proto bpf_get_stack_proto = { BPF_CALL_4(bpf_get_stack_sleepable, struct pt_regs *, regs, void *, buf, u32, size, u64, flags) { - return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, true /* may_fault */); + return __bpf_get_stack(regs, NULL, buf, size, flags, true /* may_fault */); } const struct bpf_func_proto bpf_get_stack_sleepable_proto = { @@ -893,7 +889,7 @@ static long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size, regs = task_pt_regs(task); if (regs) - res = __bpf_get_stack(regs, task, NULL, buf, size, flags, may_fault); + res = __bpf_get_stack(regs, task, buf, size, flags, may_fault); put_task_stack(task); return res; @@ -933,6 +929,32 @@ const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = { .arg4_type = ARG_ANYTHING, }; +static int __bpf_get_stack_pe(struct perf_callchain_entry *trace, void *buf, u32 size, + u64 flags) +{ + bool user_build_id = flags & BPF_F_USER_BUILD_ID; + u64 skip = flags & BPF_F_SKIP_FIELD_MASK; + bool user = flags & BPF_F_USER_STACK; + u32 elem_size, max_depth, nr_trace; + bool kernel = !user; + + if (kernel && user_build_id) + return -EINVAL; + + elem_size = user_build_id ? sizeof(struct bpf_stack_build_id) : sizeof(u64); + if (unlikely(size % elem_size)) + return -EINVAL; + + max_depth = stack_map_calculate_max_depth(size, elem_size, flags); + trace->nr = min_t(u32, trace->nr, max_depth); + + if (trace->nr < skip) + return -EFAULT; + + nr_trace = callchain_store(trace, buf, elem_size, flags); + return callchain_finalize(buf, size, nr_trace, elem_size, flags, false /* !may_fault */); +} + BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, void *, buf, u32, size, u64, flags) { @@ -944,7 +966,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, __u64 nr_kernel; if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)) - return __bpf_get_stack(regs, NULL, NULL, buf, size, flags, false /* !may_fault */); + return __bpf_get_stack(regs, NULL, buf, size, flags, false /* !may_fault */); if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_USER_BUILD_ID))) @@ -964,7 +986,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, __u64 nr = trace->nr; trace->nr = nr_kernel; - err = __bpf_get_stack(regs, NULL, trace, buf, size, flags, false /* !may_fault */); + err = __bpf_get_stack_pe(trace, buf, size, flags); /* restore nr */ trace->nr = nr; @@ -974,14 +996,13 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, skip += nr_kernel; if (skip > BPF_F_SKIP_FIELD_MASK) goto clear; - flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; - err = __bpf_get_stack(regs, NULL, trace, buf, size, flags, false /* !may_fault */); + err = __bpf_get_stack_pe(trace, buf, size, flags); } - return err; clear: - memset(buf, 0, size); + if (err < 0) + memset(buf, 0, size); return err; } From f5d242825ca417bb6afe35fde6e8880f97ca43fb Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:46 +0200 Subject: [PATCH 09/12] bpf: Clear buf on error in __bpf_get_task_stack Both bpf_get_task_stack and bpf_get_task_stack_sleepable helpers that use __bpf_get_task_stack have buf defined as ARG_PTR_TO_UNINIT_MEM argument and we should initialize the buf on every return path. Adding missing buf memset for __bpf_get_task_stack fail paths. This provides deterministic buffer contents, which is useful when the buffer is used directly as a map key. Fixes: 06ab134ce8ec ("bpf: Refcount task stack in bpf_get_task_stack") Fixes: b992f01e6615 ("bpf: Guard against accessing NULL pt_regs in bpf_get_task_stack()") Reported-by: Sashiko Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-10-jolsa@kernel.org --- kernel/bpf/stackmap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 976c4e4c1af6..7f728d319a65 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -884,14 +884,17 @@ static long __bpf_get_task_stack(struct task_struct *task, void *buf, u32 size, struct pt_regs *regs; long res = -EINVAL; - if (!try_get_task_stack(task)) + if (!try_get_task_stack(task)) { + memset(buf, 0, size); return -EFAULT; + } regs = task_pt_regs(task); if (regs) res = __bpf_get_stack(regs, task, buf, size, flags, may_fault); + else + memset(buf, 0, size); put_task_stack(task); - return res; } From b1a47b2708d4e95dbd23aee2ec83752190897b3f Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 3 Aug 2026 23:01:47 +0200 Subject: [PATCH 10/12] bpf: Disable preemption in __bpf_get_stack get_perf_callchain() returns a per-CPU perf_callchain_entry buffer and releases its recursion slot via put_callchain_entry() before returning, so nothing keeps the entry reserved while __bpf_get_stack() consumes it below. A preemptible BPF program (e.g. a non-sleepable raw tracepoint program on a PREEMPT kernel, which runs under migrate_disable() but not preempt_disable()) can be scheduled out between obtaining the entry and the copy. Another task scheduled on the same CPU then reuses the same per-CPU buffer and overwrites trace->nr with a larger value. copy_len is then computed from the inflated trace->nr and can exceed the caller's buffer, causing an out-of-bounds write in the memcpy() and in the build_id path. The rcu_read_lock() taken here alone does not prevent this. It is only taken on the may_fault path, and under CONFIG_PREEMPT_RCU it does not disable preemption; it merely keeps perf's callchain buffer array alive (freed via call_rcu()) and does nothing to stop another task from reusing the entry. Disable preemption around obtaining the callchain entry and copying it into the caller's buffer, so the entry cannot be reused underneath us and trace->nr stays bounded by max_depth. Build ID resolution may fault and is therefore deferred until after preemption is re-enabled; by then the instruction pointers have already been copied into buf, so it operates only on that private copy. Note, preempt_disable() also subsumes the buffer-lifetime guarantee the rcu_read_lock() provided, since a preempt-disabled section is an RCU read-side critical section for the callchain buffers' call_rcu() reclaim. Fixes: c195651e565a ("bpf: add bpf_get_stack helper") Reported-by: Tao Chen Reported-by: STAR Labs SG Signed-off-by: Daniel Borkmann Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20260803210149.296496-11-jolsa@kernel.org Closes: https://lore.kernel.org/bpf/20260206090653.1336687-1-chen.dylane@linux.dev/ [ changed Fixes: commit ] --- kernel/bpf/stackmap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 7f728d319a65..121caa90707b 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -815,6 +815,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, max_depth = stack_map_calculate_max_depth(size, elem_size, flags); + preempt_disable(); if (may_fault) rcu_read_lock(); /* need RCU for perf's callchain below */ @@ -828,6 +829,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, if (unlikely(!trace) || trace->nr < skip) { if (may_fault) rcu_read_unlock(); + preempt_enable(); goto err_fault; } @@ -836,6 +838,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, /* trace should not be dereferenced after this point */ if (may_fault) rcu_read_unlock(); + preempt_enable(); return callchain_finalize(buf, size, trace_nr, elem_size, flags, may_fault); From 347c1d722e3ea4ffa2850585f5c76c6e551eac83 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:48 +0200 Subject: [PATCH 11/12] bpf: Avoid changing callchain in bpf_get_stack_pe There's no need to modify the trace object bpf_get_stack_pe, we just need to pass the needed callchain length in separate argument. This way we can have callchain pointers const and remove the trace->nr modification and restoration. Assisted-by: Codex:GPT-5.5 Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-12-jolsa@kernel.org --- kernel/bpf/stackmap.c | 36 +++++++++++++++--------------------- 1 file changed, 15 insertions(+), 21 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 121caa90707b..57a25b56d0ac 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -661,7 +661,7 @@ const struct bpf_func_proto bpf_get_stackid_proto = { .arg3_type = ARG_ANYTHING, }; -static __u64 count_kernel_ip(struct perf_callchain_entry *trace) +static __u64 count_kernel_ip(const struct perf_callchain_entry *trace) { __u64 nr_kernel = 0; @@ -741,15 +741,15 @@ const struct bpf_func_proto bpf_get_stackid_proto_pe = { .arg3_type = ARG_ANYTHING, }; -static u32 callchain_store(struct perf_callchain_entry *trace, void *buf, - u32 elem_size, u64 flags) +static u32 callchain_store(const struct perf_callchain_entry *trace, u32 trace_nr, + void *buf, u32 elem_size, u64 flags) { bool user_build_id = flags & BPF_F_USER_BUILD_ID; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; - u32 trace_nr, copy_len; - u64 *ips; + const u64 *ips; + u32 copy_len; - trace_nr = trace->nr - skip; + trace_nr = trace_nr - skip; copy_len = trace_nr * elem_size; ips = trace->ip + skip; @@ -833,7 +833,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, goto err_fault; } - trace_nr = callchain_store(trace, buf, elem_size, flags); + trace_nr = callchain_store(trace, trace->nr, buf, elem_size, flags); /* trace should not be dereferenced after this point */ if (may_fault) @@ -935,8 +935,8 @@ const struct bpf_func_proto bpf_get_task_stack_sleepable_proto = { .arg4_type = ARG_ANYTHING, }; -static int __bpf_get_stack_pe(struct perf_callchain_entry *trace, void *buf, u32 size, - u64 flags) +static int __bpf_get_stack_pe(const struct perf_callchain_entry *trace, u32 trace_nr, + void *buf, u32 size, u64 flags) { bool user_build_id = flags & BPF_F_USER_BUILD_ID; u64 skip = flags & BPF_F_SKIP_FIELD_MASK; @@ -952,12 +952,12 @@ static int __bpf_get_stack_pe(struct perf_callchain_entry *trace, void *buf, u32 return -EINVAL; max_depth = stack_map_calculate_max_depth(size, elem_size, flags); - trace->nr = min_t(u32, trace->nr, max_depth); + trace_nr = min_t(u32, trace_nr, max_depth); - if (trace->nr < skip) + if (trace_nr < skip) return -EFAULT; - nr_trace = callchain_store(trace, buf, elem_size, flags); + nr_trace = callchain_store(trace, trace_nr, buf, elem_size, flags); return callchain_finalize(buf, size, nr_trace, elem_size, flags, false /* !may_fault */); } @@ -965,8 +965,8 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, void *, buf, u32, size, u64, flags) { struct pt_regs *regs = (struct pt_regs *)(ctx->regs); + const struct perf_callchain_entry *trace; struct perf_event *event = ctx->event; - struct perf_callchain_entry *trace; bool kernel, user; int err = -EINVAL; __u64 nr_kernel; @@ -989,13 +989,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, nr_kernel = count_kernel_ip(trace); if (kernel) { - __u64 nr = trace->nr; - - trace->nr = nr_kernel; - err = __bpf_get_stack_pe(trace, buf, size, flags); - - /* restore nr */ - trace->nr = nr; + err = __bpf_get_stack_pe(trace, nr_kernel, buf, size, flags); } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK; @@ -1003,7 +997,7 @@ BPF_CALL_4(bpf_get_stack_pe, struct bpf_perf_event_data_kern *, ctx, if (skip > BPF_F_SKIP_FIELD_MASK) goto clear; flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; - err = __bpf_get_stack_pe(trace, buf, size, flags); + err = __bpf_get_stack_pe(trace, trace->nr, buf, size, flags); } clear: From a74594607a0b310c1533e713b9097cc1cbbb85bf Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Mon, 3 Aug 2026 23:01:49 +0200 Subject: [PATCH 12/12] bpf: Avoid changing callchain in bpf_get_stackid_pe There's no need to modify the trace object bpf_get_stackid_pe, we just need to pass the needed callchain length in separate argument. This way we can have callchain pointers const and remove the trace->nr modification and restoration. Assisted-by: Codex:GPT-5.5 Signed-off-by: Jiri Olsa Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20260803210149.296496-13-jolsa@kernel.org --- kernel/bpf/stackmap.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 57a25b56d0ac..8f0f3ff1a869 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -506,7 +506,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) struct stackid { struct stack_map_bucket *bucket; - u64 *ips; + const u64 *ips; u32 nr; u32 len; u32 hash; @@ -515,21 +515,21 @@ struct stackid { }; static int stackid_init(struct stackid *stackid, struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) + const struct perf_callchain_entry *trace, u32 trace_nr, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); u32 skip = flags & BPF_F_SKIP_FIELD_MASK; u32 max_depth; - if (trace->nr <= skip) + if (trace_nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); - stackid->nr = min_t(u32, trace->nr - skip, max_depth - skip); + stackid->nr = min_t(u32, trace_nr - skip, max_depth - skip); stackid->len = stackid->nr * sizeof(u64); stackid->ips = trace->ip + skip; - stackid->hash = jhash2((u32 *)stackid->ips, stackid->len / sizeof(u32), 0); + stackid->hash = jhash2((const u32 *)stackid->ips, stackid->len / sizeof(u32), 0); stackid->id = stackid->hash & (smap->n_buckets - 1); stackid->bucket = READ_ONCE(smap->buckets[stackid->id]); stackid->hash_matches = stackid->bucket && stackid->bucket->hash == stackid->hash; @@ -537,11 +537,12 @@ static int stackid_init(struct stackid *stackid, struct bpf_map *map, } static int stackid_fastpath(struct stackid *stackid, struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) + const struct perf_callchain_entry *trace, u32 trace_nr, + u64 flags) { int err; - err = stackid_init(stackid, map, trace, flags); + err = stackid_init(stackid, map, trace, trace_nr, flags); if (err) return err; @@ -640,7 +641,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, /* couldn't fetch the stack trace */ return -EFAULT; - err = stackid_fastpath(&stackid, map, trace, flags); + err = stackid_fastpath(&stackid, map, trace, trace->nr, flags); if (err != -ENOENT) return err; @@ -676,12 +677,13 @@ static __u64 count_kernel_ip(const struct perf_callchain_entry *trace) BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, struct bpf_map *, map, u64, flags) { + const struct perf_callchain_entry *trace; struct perf_event *event = ctx->event; struct stack_map_bucket *new_bucket; - struct perf_callchain_entry *trace; struct stackid stackid; bool kernel, user; __u64 nr_kernel; + u32 trace_nr; int ret; /* perf_sample_data doesn't have callchain, use bpf_get_stackid */ @@ -701,13 +703,13 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT; nr_kernel = count_kernel_ip(trace); - __u64 nr = trace->nr; /* save original */ if (kernel) { - trace->nr = nr_kernel; + trace_nr = nr_kernel; } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK; + trace_nr = trace->nr; skip += nr_kernel; if (skip > BPF_F_SKIP_FIELD_MASK) return -EFAULT; @@ -715,21 +717,14 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; } - ret = stackid_fastpath(&stackid, map, trace, flags); + ret = stackid_fastpath(&stackid, map, trace, trace_nr, flags); if (ret != -ENOENT) - goto out; + return ret; new_bucket = stackid_new_bucket(&stackid, map); - if (new_bucket) { - trace->nr = nr; + if (new_bucket) return stackid_install(&stackid, map, new_bucket, flags); - } - ret = -ENOMEM; - -out: - /* restore nr */ - trace->nr = nr; - return ret; + return -ENOMEM; } const struct bpf_func_proto bpf_get_stackid_proto_pe = {