Commit 1ca1cc98 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf: minor cleanups on fd maps and helpers 



Some minor cleanups: i) Remove the unlikely() from fd array map lookups
and let the CPU branch predictor do its job, scenarios where there is not
always a map entry are very well valid. ii) Move the attribute type check
in the bpf_perf_event_read() helper a bit earlier so it's consistent wrt
checks with bpf_perf_event_output() helper as well. iii) remove some
comments that are self-documenting in kprobe_prog_is_valid_access() and
therefore make it consistent to tp_prog_is_valid_access() as well.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ee58b571

kernel/bpf/core.c

+1 −2
Original line number Diff line number Diff line
@@ -719,14 +719,13 @@ select_insn: 


		if (unlikely(index >= array->map.max_entries))

			goto out;



		if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT))

			goto out;



		tail_call_cnt++;



		prog = READ_ONCE(array->ptrs[index]);

		if (unlikely(!prog))

		if (!prog)

			goto out;



		/* ARG1 at this point is guaranteed to point to CTX from

kernel/trace/bpf_trace.c

+6 −12
Original line number Diff line number Diff line
@@ -199,19 +199,19 @@ static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5) 
		return -E2BIG;



	ee = READ_ONCE(array->ptrs[index]);

	if (unlikely(!ee))

	if (!ee)

		return -ENOENT;



	event = ee->event;

	if (unlikely(event->attr.type != PERF_TYPE_HARDWARE &&

		     event->attr.type != PERF_TYPE_RAW))

		return -EINVAL;



	/* make sure event is local and doesn't have pmu::count */

	if (event->oncpu != smp_processor_id() ||

	    event->pmu->count)

		return -EINVAL;



	if (unlikely(event->attr.type != PERF_TYPE_HARDWARE &&

		     event->attr.type != PERF_TYPE_RAW))

		return -EINVAL;



	/*

	 * we don't know if the function is run successfully by the

	 * return value. It can be judged in other places, such as
@@ -251,7 +251,7 @@ static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 flags, u64 r4, u64 size) 
		return -E2BIG;



	ee = READ_ONCE(array->ptrs[index]);

	if (unlikely(!ee))

	if (!ee)

		return -ENOENT;



	event = ee->event;
@@ -354,18 +354,12 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func 
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type,

					enum bpf_reg_type *reg_type)

{

	/* check bounds */

	if (off < 0 || off >= sizeof(struct pt_regs))

		return false;



	/* only read is allowed */

	if (type != BPF_READ)

		return false;



	/* disallow misaligned access */

	if (off % size != 0)

		return false;



	return true;

}

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