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bpf: permit multiple bpf attachments for a single perf event

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This patch enables multiple bpf attachments for a
kprobe/uprobe/tracepoint single trace event.
Each trace_event keeps a list of attached perf events.
When an event happens, all attached bpf programs will
be executed based on the order of attachment.

A global bpf_event_mutex lock is introduced to protect
prog_array attaching and detaching. An alternative will
be introduce a mutex lock in every trace_event_call
structure, but it takes a lot of extra memory.
So a global bpf_event_mutex lock is a good compromise.

The bpf prog detachment involves allocation of memory.
If the allocation fails, a dummy do-nothing program
will replace to-be-detached program in-place.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yonghong Song
2017-10-23 23:53:08 -07:00
zatwierdzone przez David S. Miller
rodzic 0b4c6841fe
commit e87c6bc385
9 zmienionych plików z 255 dodań i 56 usunięć
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26
kernel/events/core.c
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@@ -7954,11 +7954,9 @@ void perf_trace_run_bpf_submit(void *raw_data, int size, int rctx,
struct pt_regs *regs, struct hlist_head *head,
struct task_struct *task)
{
struct bpf_prog *prog = call->prog;
if (prog) {
if (bpf_prog_array_valid(call)) {
*(struct pt_regs **)raw_data = regs;
if (!trace_call_bpf(prog, raw_data) || hlist_empty(head)) {
if (!trace_call_bpf(call, raw_data) || hlist_empty(head)) {
perf_swevent_put_recursion_context(rctx);
return;
}
@@ -8147,13 +8145,11 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
{
bool is_kprobe, is_tracepoint, is_syscall_tp;
struct bpf_prog *prog;
int ret;
if (event->attr.type != PERF_TYPE_TRACEPOINT)
return perf_event_set_bpf_handler(event, prog_fd);
if (event->tp_event->prog)
return -EEXIST;
is_kprobe = event->tp_event->flags & TRACE_EVENT_FL_UKPROBE;
is_tracepoint = event->tp_event->flags & TRACE_EVENT_FL_TRACEPOINT;
is_syscall_tp = is_syscall_trace_event(event->tp_event);
@@ -8181,26 +8177,20 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
return -EACCES;
}
}
event->tp_event->prog = prog;
event->tp_event->bpf_prog_owner = event;
return 0;
ret = perf_event_attach_bpf_prog(event, prog);
if (ret)
bpf_prog_put(prog);
return ret;
}
static void perf_event_free_bpf_prog(struct perf_event *event)
{
struct bpf_prog *prog;
if (event->attr.type != PERF_TYPE_TRACEPOINT) {
perf_event_free_bpf_handler(event);
return;
}
prog = event->tp_event->prog;
if (prog && event->tp_event->bpf_prog_owner == event) {
event->tp_event->prog = NULL;
bpf_prog_put(prog);
}
perf_event_detach_bpf_prog(event);
}
#else