From: Jiri Olsa <jolsa@kernel.org>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org, Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
Quentin Monnet <qmo@kernel.org>, Tao Chen <chen.dylane@linux.dev>,
STAR Labs SG <info@starlabs.sg>
Subject: [PATCH bpf-next 6/9] bpf: Factor callchain_store function from __bpf_get_stack
Date: Mon, 20 Jul 2026 10:53:48 +0200 [thread overview]
Message-ID: <20260720085351.655075-7-jolsa@kernel.org> (raw)
In-Reply-To: <20260720085351.655075-1-jolsa@kernel.org>
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 <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 a64b14ffd1e8..b990643f25cd 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -747,6 +747,29 @@ 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 size,
+ 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)
@@ -759,7 +782,6 @@ 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)))
@@ -804,21 +826,10 @@ 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, size, 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();
--
2.54.0
next prev parent reply other threads:[~2026-07-20 8:54 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-20 8:53 [PATCH bpf-next 0/9] bpf: Disable preemption in stack map code Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 1/9] bpf: Factor stackid_init function from __bpf_get_stackid Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 2/9] bpf: Factor stackid_fastpath " Jiri Olsa
2026-07-20 9:09 ` sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 3/9] bpf: Factor stackid_new_bucket " Jiri Olsa
2026-07-20 9:01 ` sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 4/9] bpf: Use stack id functions instead of __bpf_get_stackid Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 5/9] bpf: Disable preemption in bpf_get_stackid Jiri Olsa
2026-07-20 9:04 ` sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` Jiri Olsa [this message]
2026-07-20 9:07 ` [PATCH bpf-next 6/9] bpf: Factor callchain_store function from __bpf_get_stack sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 7/9] bpf: Factor callchain_finalize " Jiri Olsa
2026-07-20 9:08 ` sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 8/9] bpf: Remove trace_in argument " Jiri Olsa
2026-07-20 9:09 ` sashiko-bot
2026-07-20 20:31 ` Jiri Olsa
2026-07-20 8:53 ` [PATCH bpf-next 9/9] bpf: Disable preemption in __bpf_get_stack Jiri Olsa
2026-07-20 9:18 ` sashiko-bot
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