Commit 0515e599 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: introduce BPF_PROG_TYPE_PERF_EVENT program type 



Introduce BPF_PROG_TYPE_PERF_EVENT programs that can be attached to
HW and SW perf events (PERF_TYPE_HARDWARE and PERF_TYPE_SOFTWARE
correspondingly in uapi/linux/perf_event.h)

The program visible context meta structure is
struct bpf_perf_event_data {
    struct pt_regs regs;
     __u64 sample_period;
};
which is accessible directly from the program:
int bpf_prog(struct bpf_perf_event_data *ctx)
{
  ... ctx->sample_period ...
  ... ctx->regs.ip ...
}

The bpf verifier rewrites the accesses into kernel internal
struct bpf_perf_event_data_kern which allows changing
struct perf_sample_data without affecting bpf programs.
New fields can be added to the end of struct bpf_perf_event_data
in the future.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ea2e7ce5

include/linux/perf_event.h

+5 −0
Original line number Diff line number Diff line
@@ -788,6 +788,11 @@ struct perf_output_handle { 
	int				page;

};



struct bpf_perf_event_data_kern {

	struct pt_regs *regs;

	struct perf_sample_data *data;

};



#ifdef CONFIG_CGROUP_PERF



/*

include/uapi/linux/Kbuild

+1 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ header-y += binfmts.h 
header-y += blkpg.h

header-y += blktrace_api.h

header-y += bpf_common.h

header-y += bpf_perf_event.h

header-y += bpf.h

header-y += bpqether.h

header-y += bsg.h

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ enum bpf_prog_type { 
	BPF_PROG_TYPE_SCHED_ACT,

	BPF_PROG_TYPE_TRACEPOINT,

	BPF_PROG_TYPE_XDP,

	BPF_PROG_TYPE_PERF_EVENT,

};



#define BPF_PSEUDO_MAP_FD	1

include/uapi/linux/bpf_perf_event.h

0 → 100644
+18 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2016 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 */

#ifndef _UAPI__LINUX_BPF_PERF_EVENT_H__

#define _UAPI__LINUX_BPF_PERF_EVENT_H__



#include <linux/types.h>

#include <linux/ptrace.h>



struct bpf_perf_event_data {

	struct pt_regs regs;

	__u64 sample_period;

};



#endif /* _UAPI__LINUX_BPF_PERF_EVENT_H__ */

kernel/trace/bpf_trace.c

+61 −0
Original line number Diff line number Diff line 
/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com

 * Copyright (c) 2016 Facebook

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public
@@ -8,6 +9,7 @@ 
#include <linux/types.h>

#include <linux/slab.h>

#include <linux/bpf.h>

#include <linux/bpf_perf_event.h>

#include <linux/filter.h>

#include <linux/uaccess.h>

#include <linux/ctype.h>
@@ -552,10 +554,69 @@ static struct bpf_prog_type_list tracepoint_tl = { 
	.type	= BPF_PROG_TYPE_TRACEPOINT,

};



static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,

				    enum bpf_reg_type *reg_type)

{

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

		return false;

	if (type != BPF_READ)

		return false;

	if (off % size != 0)

		return false;

	if (off == offsetof(struct bpf_perf_event_data, sample_period)) {

		if (size != sizeof(u64))

			return false;

	} else {

		if (size != sizeof(long))

			return false;

	}

	return true;

}



static u32 pe_prog_convert_ctx_access(enum bpf_access_type type, int dst_reg,

				      int src_reg, int ctx_off,

				      struct bpf_insn *insn_buf,

				      struct bpf_prog *prog)

{

	struct bpf_insn *insn = insn_buf;



	switch (ctx_off) {

	case offsetof(struct bpf_perf_event_data, sample_period):

		BUILD_BUG_ON(FIELD_SIZEOF(struct perf_sample_data, period) != sizeof(u64));

		*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct bpf_perf_event_data_kern, data)),

				      dst_reg, src_reg,

				      offsetof(struct bpf_perf_event_data_kern, data));

		*insn++ = BPF_LDX_MEM(BPF_DW, dst_reg, dst_reg,

				      offsetof(struct perf_sample_data, period));

		break;

	default:

		*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct bpf_perf_event_data_kern, regs)),

				      dst_reg, src_reg,

				      offsetof(struct bpf_perf_event_data_kern, regs));

		*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(sizeof(long)),

				      dst_reg, dst_reg, ctx_off);

		break;

	}



	return insn - insn_buf;

}



static const struct bpf_verifier_ops perf_event_prog_ops = {

	.get_func_proto		= tp_prog_func_proto,

	.is_valid_access	= pe_prog_is_valid_access,

	.convert_ctx_access	= pe_prog_convert_ctx_access,

};



static struct bpf_prog_type_list perf_event_tl = {

	.ops	= &perf_event_prog_ops,

	.type	= BPF_PROG_TYPE_PERF_EVENT,

};



static int __init register_kprobe_prog_ops(void)

{

	bpf_register_prog_type(&kprobe_tl);

	bpf_register_prog_type(&tracepoint_tl);

	bpf_register_prog_type(&perf_event_tl);

	return 0;

}

late_initcall(register_kprobe_prog_ops);

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