Re: [PATCH net-next v3 1/2] bpf: add support for sys_enter_* and sys_exit_* tracepoints
flat view
From: Alexei Starovoitov <hidden>
Date: 2017-08-04 02:09:01
On 8/3/17 6:29 AM, Yonghong Song wrote:
quoted hunk ↗ jump to hunk
@@ -578,8 +596,9 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id) if (!sys_data) return; + prog = READ_ONCE(sys_data->enter_event->prog); head = this_cpu_ptr(sys_data->enter_event->perf_events); - if (hlist_empty(head)) + if (!prog && hlist_empty(head)) return; /* get the size after alignment with the u32 buffer size field */@@ -594,6 +613,13 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id) rec->nr = syscall_nr; syscall_get_arguments(current, regs, 0, sys_data->nb_args, (unsigned long *)&rec->args); + + if ((prog && !perf_call_bpf_enter(prog, regs, sys_data, rec)) || + hlist_empty(head)) { + perf_swevent_put_recursion_context(rctx); + return; + }
hmm. if I read the patch correctly that makes it different from kprobe/uprobe/tracepoints+bpf behavior. Why make it different and force user space to perf_event_open() on every cpu? In other cases it's the job of the bpf program to filter by cpu if necessary and that is well understood by bcc scripts.