From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Jiri Olsa <jolsa@kernel.org>, Andrii Nakryiko <andrii@kernel.org>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18.y 1/5] bpf: Factor stackid_init function from __bpf_get_stackid
Date: Tue, 8 Sep 2026 09:12:05 -0400 [thread overview]
Message-ID: <20260908131209.2236373-1-sashal@kernel.org> (raw)
In-Reply-To: <2026090347-bodacious-studio-93ee@gregkh>
From: Jiri Olsa <jolsa@kernel.org>
[ Upstream commit 15b837759a97237d647962f9943afe0d55af615a ]
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 <jolsa@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260803210149.296496-2-jolsa@kernel.org
Stable-dep-of: 15f1bd857466 ("bpf: Disable preemption in bpf_get_stackid")
Signed-off-by: Sasha Levin <sashal@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 13f4f696a7c04..db64199dbd6fb 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -246,33 +246,54 @@ 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;
@@ -282,42 +303,42 @@ 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,
@@ -326,6 +347,7 @@ 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;
@@ -341,7 +363,7 @@ 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 = {
@@ -370,6 +392,7 @@ 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;
@@ -395,7 +418,7 @@ 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;
@@ -404,7 +427,7 @@ 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 */
--
2.53.0
next prev parent reply other threads:[~2026-09-08 13:12 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-03 13:51 FAILED: patch "[PATCH] bpf: Disable preemption in bpf_get_stackid" failed to apply to 6.18-stable tree gregkh
2026-09-08 13:12 ` Sasha Levin [this message]
2026-09-08 13:12 ` [PATCH 6.18.y 2/5] bpf: Factor stackid_fastpath function from __bpf_get_stackid Sasha Levin
2026-09-08 13:12 ` [PATCH 6.18.y 3/5] bpf: Factor stackid_new_bucket " Sasha Levin
2026-09-08 13:12 ` [PATCH 6.18.y 4/5] bpf: Use stack id functions instead of __bpf_get_stackid Sasha Levin
2026-09-08 13:12 ` [PATCH 6.18.y 5/5] bpf: Disable preemption in bpf_get_stackid Sasha Levin
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