From 98b5c2c65c2951772a8fc661f50d675e450e8bce Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Wed, 6 Apr 2016 18:43:25 -0700 Subject: perf, bpf: allow bpf programs attach to tracepoints introduce BPF_PROG_TYPE_TRACEPOINT program type and allow it to be attached to the perf tracepoint handler, which will copy the arguments into the per-cpu buffer and pass it to the bpf program as its first argument. The layout of the fields can be discovered by doing 'cat /sys/kernel/debug/tracing/events/sched/sched_switch/format' prior to the compilation of the program with exception that first 8 bytes are reserved and not accessible to the program. This area is used to store the pointer to 'struct pt_regs' which some of the bpf helpers will use: +---------+ | 8 bytes | hidden 'struct pt_regs *' (inaccessible to bpf program) +---------+ | N bytes | static tracepoint fields defined in tracepoint/format (bpf readonly) +---------+ | dynamic | __dynamic_array bytes of tracepoint (inaccessible to bpf yet) +---------+ Not that all of the fields are already dumped to user space via perf ring buffer and broken application access it directly without consulting tracepoint/format. Same rule applies here: static tracepoint fields should only be accessed in a format defined in tracepoint/format. The order of fields and field sizes are not an ABI. Signed-off-by: Alexei Starovoitov Acked-by: Peter Zijlstra (Intel) Signed-off-by: David S. Miller --- include/trace/perf.h | 10 +++++++++- include/uapi/linux/bpf.h | 1 + 2 files changed, 10 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/trace/perf.h b/include/trace/perf.h index 77cd9043b7e4..a182306eefd7 100644 --- a/include/trace/perf.h +++ b/include/trace/perf.h @@ -34,6 +34,7 @@ perf_trace_##call(void *__data, proto) \ struct trace_event_call *event_call = __data; \ struct trace_event_data_offsets_##call __maybe_unused __data_offsets;\ struct trace_event_raw_##call *entry; \ + struct bpf_prog *prog = event_call->prog; \ struct pt_regs *__regs; \ u64 __count = 1; \ struct task_struct *__task = NULL; \ @@ -45,7 +46,7 @@ perf_trace_##call(void *__data, proto) \ __data_size = trace_event_get_offsets_##call(&__data_offsets, args); \ \ head = this_cpu_ptr(event_call->perf_events); \ - if (__builtin_constant_p(!__task) && !__task && \ + if (!prog && __builtin_constant_p(!__task) && !__task && \ hlist_empty(head)) \ return; \ \ @@ -63,6 +64,13 @@ perf_trace_##call(void *__data, proto) \ \ { assign; } \ \ + if (prog) { \ + *(struct pt_regs **)entry = __regs; \ + if (!trace_call_bpf(prog, entry) || hlist_empty(head)) { \ + perf_swevent_put_recursion_context(rctx); \ + return; \ + } \ + } \ perf_trace_buf_submit(entry, __entry_size, rctx, \ event_call->event.type, __count, __regs, \ head, __task); \ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 23917bb47bf3..70eda5aeb304 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -92,6 +92,7 @@ enum bpf_prog_type { BPF_PROG_TYPE_KPROBE, BPF_PROG_TYPE_SCHED_CLS, BPF_PROG_TYPE_SCHED_ACT, + BPF_PROG_TYPE_TRACEPOINT, }; #define BPF_PSEUDO_MAP_FD 1 -- cgit v1.2.3