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authorAndrii Nakryiko <andrii@kernel.org>2021-08-15 00:05:58 -0700
committerDaniel Borkmann <daniel@iogearbox.net>2021-08-17 00:45:07 +0200
commit82e6b1eee6a8875ef4eacfd60711cce6965c6b04 (patch)
tree61a1865e08aa9917ff436d6603c6ce5f9126d971 /kernel/trace
parentb89fbfbb854c9afc3047e8273cc3a694650b802e (diff)
bpf: Allow to specify user-provided bpf_cookie for BPF perf links
Add ability for users to specify custom u64 value (bpf_cookie) when creating BPF link for perf_event-backed BPF programs (kprobe/uprobe, perf_event, tracepoints). This is useful for cases when the same BPF program is used for attaching and processing invocation of different tracepoints/kprobes/uprobes in a generic fashion, but such that each invocation is distinguished from each other (e.g., BPF program can look up additional information associated with a specific kernel function without having to rely on function IP lookups). This enables new use cases to be implemented simply and efficiently that previously were possible only through code generation (and thus multiple instances of almost identical BPF program) or compilation at runtime (BCC-style) on target hosts (even more expensive resource-wise). For uprobes it is not even possible in some cases to know function IP before hand (e.g., when attaching to shared library without PID filtering, in which case base load address is not known for a library). This is done by storing u64 bpf_cookie in struct bpf_prog_array_item, corresponding to each attached and run BPF program. Given cgroup BPF programs already use two 8-byte pointers for their needs and cgroup BPF programs don't have (yet?) support for bpf_cookie, reuse that space through union of cgroup_storage and new bpf_cookie field. Make it available to kprobe/tracepoint BPF programs through bpf_trace_run_ctx. This is set by BPF_PROG_RUN_ARRAY, used by kprobe/uprobe/tracepoint BPF program execution code, which luckily is now also split from BPF_PROG_RUN_ARRAY_CG. This run context will be utilized by a new BPF helper giving access to this user-provided cookie value from inside a BPF program. Generic perf_event BPF programs will access this value from perf_event itself through passed in BPF program context. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lore.kernel.org/bpf/20210815070609.987780-6-andrii@kernel.org
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/bpf_trace.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 91867b14b222..57879d28f824 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1675,7 +1675,8 @@ static DEFINE_MUTEX(bpf_event_mutex);
#define BPF_TRACE_MAX_PROGS 64
int perf_event_attach_bpf_prog(struct perf_event *event,
- struct bpf_prog *prog)
+ struct bpf_prog *prog,
+ u64 bpf_cookie)
{
struct bpf_prog_array *old_array;
struct bpf_prog_array *new_array;
@@ -1702,12 +1703,13 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
goto unlock;
}
- ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
+ ret = bpf_prog_array_copy(old_array, NULL, prog, bpf_cookie, &new_array);
if (ret < 0)
goto unlock;
/* set the new array to event->tp_event and set event->prog */
event->prog = prog;
+ event->bpf_cookie = bpf_cookie;
rcu_assign_pointer(event->tp_event->prog_array, new_array);
bpf_prog_array_free(old_array);
@@ -1728,7 +1730,7 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
goto unlock;
old_array = bpf_event_rcu_dereference(event->tp_event->prog_array);
- ret = bpf_prog_array_copy(old_array, event->prog, NULL, &new_array);
+ ret = bpf_prog_array_copy(old_array, event->prog, NULL, 0, &new_array);
if (ret == -ENOENT)
goto unlock;
if (ret < 0) {

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