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bpf: add helper bpf_perf_prog_read_value

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This patch adds helper bpf_perf_prog_read_cvalue for perf event based bpf
programs, to read event counter and enabled/running time.
The enabled/running time is accumulated since the perf event open.

The typical use case for perf event based bpf program is to attach itself
to a single event. In such cases, if it is desirable to get scaling factor
between two bpf invocations, users can can save the time values in a map,
and use the value from the map and the current value to calculate
the scaling factor.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yonghong Song 2017-10-05 09:19:22 -07:00 committed by David S. Miller
parent 020a32d958
commit 4bebdc7a85
2 changed files with 37 additions and 1 deletions
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10
include/uapi/linux/bpf.h
View File

@ -649,6 +649,13 @@ union bpf_attr {
* @buf: buf to fill
* @buf_size: size of the buf
* Return: 0 on success or negative error code
*
* int bpf_perf_prog_read_value(ctx, buf, buf_size)
* read perf prog attached perf event counter and enabled/running time
* @ctx: pointer to ctx
* @buf: buf to fill
* @buf_size: size of the buf
* Return : 0 on success or negative error code
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@ -706,7 +713,8 @@ union bpf_attr {
FN(sk_redirect_map), \
FN(sock_map_update), \
FN(xdp_adjust_meta), \
FN(perf_event_read_value),
FN(perf_event_read_value), \
FN(perf_prog_read_value),
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call

28
kernel/trace/bpf_trace.c
View File

@ -613,6 +613,32 @@ static const struct bpf_func_proto bpf_get_stackid_proto_tp = {
.arg3_type = ARG_ANYTHING,
};
BPF_CALL_3(bpf_perf_prog_read_value_tp, struct bpf_perf_event_data_kern *, ctx,
struct bpf_perf_event_value *, buf, u32, size)
{
int err = -EINVAL;
if (unlikely(size != sizeof(struct bpf_perf_event_value)))
goto clear;
err = perf_event_read_local(ctx->event, &buf->counter, &buf->enabled,
&buf->running);
if (unlikely(err))
goto clear;
return 0;
clear:
memset(buf, 0, size);
return err;
}
static const struct bpf_func_proto bpf_perf_prog_read_value_proto_tp = {
.func = bpf_perf_prog_read_value_tp,
.gpl_only = true,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_PTR_TO_UNINIT_MEM,
.arg3_type = ARG_CONST_SIZE,
};
static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
{
switch (func_id) {
@ -620,6 +646,8 @@ static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
return &bpf_perf_event_output_proto_tp;
case BPF_FUNC_get_stackid:
return &bpf_get_stackid_proto_tp;
case BPF_FUNC_perf_prog_read_value:
return &bpf_perf_prog_read_value_proto_tp;
default:
return tracing_func_proto(func_id);
}