perf, bpf: add support for bpf in sw/hw perf_events

PATCH In review Alexei Starovoitov 3 participants 9 messages Sep 2, 2016

Subsystems (8)

Networking Network drivers BPF perf events +4 more subsystems

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Alexei Starovoitov

author

2016-09-02 01:37 UTC #0 lore raw

v3 cover perf, bpf: add support for bpf in sw/hw perf_events

Hi Peter, Dave,

this patch set is a follow up to the discussion:
https://lkml.kernel.org/r/20160804142853.GO6862%20()%20twins%20!%20programming%20!%20kicks-ass%20!%20net
It turned out to be simpler than what we discussed.

Patches 1-3 is bpf-side prep for the main patch 4
that adds bpf program as an overflow_handler to sw and hw perf_events.

Patches 5 and 6 are examples from myself and Brendan.

Peter,
to implement your suggestion to add ifdef CONFIG_BPF_SYSCALL inside struct perf_event, I had to shuffle ifdefs in events/core.c Please double check whether that is what you wanted to see.

v2->v3: fixed few more minor issues
v1->v2: fixed issues spotted by Peter and Daniel.

Thanks!

Alexei Starovoitov (5):
bpf: support 8-byte metafield access
bpf: introduce BPF_PROG_TYPE_PERF_EVENT program type
bpf: perf_event progs should only use preallocated maps perf, bpf: add perf events core support for BPF_PROG_TYPE_PERF_EVENT
programs
samples/bpf: add perf_event+bpf example

Brendan Gregg (1):
samples/bpf: add sampleip example

 include/linux/bpf.h                 |   4 +
 include/linux/perf_event.h          |   9 ++
 include/uapi/linux/Kbuild           |   1 +
 include/uapi/linux/bpf.h            |   1 +
 include/uapi/linux/bpf_perf_event.h |  18 +++
 kernel/bpf/verifier.c               |  31 +++++-
 kernel/events/core.c                |  89 ++++++++++++++-
 kernel/trace/bpf_trace.c            |  61 +++++++++++
 samples/bpf/Makefile                |   8 ++
 samples/bpf/bpf_helpers.h           |   2 +
 samples/bpf/bpf_load.c              |   7 +-
 samples/bpf/sampleip_kern.c         |  38 +++++++
 samples/bpf/sampleip_user.c         | 196 +++++++++++++++++++++++++++++++++
 samples/bpf/trace_event_kern.c      |  65 +++++++++++
 samples/bpf/trace_event_user.c      | 213 ++++++++++++++++++++++++++++++++++++
 15 files changed, 737 insertions(+), 6 deletions(-)
 create mode 100644 include/uapi/linux/bpf_perf_event.h
 create mode 100644 samples/bpf/sampleip_kern.c
 create mode 100644 samples/bpf/sampleip_user.c
 create mode 100644 samples/bpf/trace_event_kern.c
 create mode 100644 samples/bpf/trace_event_user.c

Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #1 lore raw

PATCH v3 1/6 bpf: support 8-byte metafield access

The verifier supported only 4-byte metafields in
struct __sk_buff and struct xdp_md. The metafields in upcoming struct bpf_perf_event are 8-byte to match register width in struct pt_regs. Teach verifier to recognize 8-byte metafield access.
The patch doesn't affect safety of sockets and xdp programs. They check for 4-byte only ctx access before these conditions are hit.

Signed-off-by Alexei Starovoitov <[email protected]>

Acked-by Daniel Borkmann <[email protected]>

---
 kernel/bpf/verifier.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

kernel/bpf/verifier.c +6 -3

index abb61f3f6900..c1c9e441f0f5 100644
@@ -2333,7 +2333,8 @@ static int do_check(struct verifier_env *env)
 			if (err)
 				return err;
 
-			if (BPF_SIZE(insn->code) != BPF_W) {
+			if (BPF_SIZE(insn->code) != BPF_W &&
+			    BPF_SIZE(insn->code) != BPF_DW) {
 				insn_idx++;
 				continue;
 			}

@@ -2642,9 +2643,11 @@ static int convert_ctx_accesses(struct verifier_env *env)
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		u32 insn_delta, cnt;
 
-		if (insn->code == (BPF_LDX | BPF_MEM | BPF_W))
+		if (insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
+		    insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
 			type = BPF_READ;
-		else if (insn->code == (BPF_STX | BPF_MEM | BPF_W))
+		else if (insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
+			 insn->code == (BPF_STX | BPF_MEM | BPF_DW))
 			type = BPF_WRITE;
 		else
 			continue;

Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #2 lore raw

PATCH v3 2/6 bpf: introduce BPF_PROG_TYPE_PERF_EVENT program type

In reply to Alexei Starovoitov

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 Alexei Starovoitov <[email protected]>

Acked-by Daniel Borkmann <[email protected]>

---
 include/linux/perf_event.h          |  5 +++
 include/uapi/linux/Kbuild           |  1 +
 include/uapi/linux/bpf.h            |  1 +
 include/uapi/linux/bpf_perf_event.h | 18 +++++++++++
 kernel/trace/bpf_trace.c            | 61 +++++++++++++++++++++++++++++++++++++
 5 files changed, 86 insertions(+)
 create mode 100644 include/uapi/linux/bpf_perf_event.h

include/linux/perf_event.h +5 -0

index 2b6b43cc0dd5..97bfe62f30d7 100644
@@ -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

index 185f8ea2702f..d0352a971ebd 100644
@@ -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

index e4c5a1baa993..f896dfac4ac0 100644
@@ -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 new file +18 -0

new file mode 100644
index 000000000000..067427259820
@@ -0,0 +1,18 @@
+/* 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

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Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #3 lore raw

PATCH v3 3/6 bpf: perf_event progs should only use preallocated maps

In reply to Alexei Starovoitov

Make sure that BPF_PROG_TYPE_PERF_EVENT programs only use preallocated hash maps, since doing memory allocation
in overflow_handler can crash depending on where nmi got triggered.

Signed-off-by Alexei Starovoitov <[email protected]>

Acked-by Daniel Borkmann <[email protected]>

---
 kernel/bpf/verifier.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

kernel/bpf/verifier.c +21 -1

index c1c9e441f0f5..48c2705db22c 100644
@@ -2511,6 +2511,20 @@ static int do_check(struct verifier_env *env)
 	return 0;
 }
 
+static int check_map_prog_compatibility(struct bpf_map *map,
+					struct bpf_prog *prog)
+
+{
+	if (prog->type == BPF_PROG_TYPE_PERF_EVENT &&
+	    (map->map_type == BPF_MAP_TYPE_HASH ||
+	     map->map_type == BPF_MAP_TYPE_PERCPU_HASH) &&
+	    (map->map_flags & BPF_F_NO_PREALLOC)) {
+		verbose("perf_event programs can only use preallocated hash map\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
 /* look for pseudo eBPF instructions that access map FDs and
  * replace them with actual map pointers
  */

@@ -2518,7 +2532,7 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
 {
 	struct bpf_insn *insn = env->prog->insnsi;
 	int insn_cnt = env->prog->len;
-	int i, j;
+	int i, j, err;
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		if (BPF_CLASS(insn->code) == BPF_LDX &&

@@ -2562,6 +2576,12 @@ static int replace_map_fd_with_map_ptr(struct verifier_env *env)
 				return PTR_ERR(map);
 			}
 
+			err = check_map_prog_compatibility(map, env->prog);
+			if (err) {
+				fdput(f);
+				return err;
+			}
+
 			/* store map pointer inside BPF_LD_IMM64 instruction */
 			insn[0].imm = (u32) (unsigned long) map;
 			insn[1].imm = ((u64) (unsigned long) map) >> 32;

Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #4 lore raw

PATCH v3 4/6 perf, bpf: add perf events core support for BPF_PROG_TYPE_PERF_EVENT programs

In reply to Alexei Starovoitov

Allow attaching BPF_PROG_TYPE_PERF_EVENT programs to sw and hw perf events via overflow_handler mechanism.
When program is attached the overflow_handlers become stacked.
The program acts as a filter.
Returning zero from the program means that the normal perf_event_output handler will not be called and sampling event won't be stored in the ring buffer.

The overflow_handler_context==NULL is an additional safety check to make sure programs are not attached to hw breakpoints and watchdog in case other checks (that prevent that now anyway) get accidentally relaxed in the future.

The program refcnt is incremented in case perf_events are inhereted when target task is forked.
Similar to kprobe and tracepoint programs there is no ioctl to detach the program or swap already attached program. The user space expected to close(perf_event_fd) like it does right now for kprobe+bpf. That restriction simplifies the code quite a bit.

The invocation of overflow_handler in __perf_event_overflow() is now done via READ_ONCE, since that pointer can be replaced when the program is attached while perf_event itself could have been active already. There is no need to do similar treatment for event->prog, since it's assigned only once before it's accessed.

Signed-off-by Alexei Starovoitov <[email protected]>

---
 include/linux/bpf.h        |  4 +++
 include/linux/perf_event.h |  4 +++
 kernel/events/core.c       | 89 +++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 96 insertions(+), 1 deletion(-)

include/linux/bpf.h +4 -0

index 11134238417d..9a904f63f8c1 100644
@@ -297,6 +297,10 @@ static inline struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i)
 static inline void bpf_prog_put(struct bpf_prog *prog)
 {
 }
+static inline struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
 #endif /* CONFIG_BPF_SYSCALL */
 
 /* verifier prototypes for helper functions called from eBPF programs */

include/linux/perf_event.h +4 -0

index 97bfe62f30d7..ccb73a58113d 100644
@@ -679,6 +679,10 @@ struct perf_event {
 	u64				(*clock)(void);
 	perf_overflow_handler_t		overflow_handler;
 	void				*overflow_handler_context;
+#ifdef CONFIG_BPF_SYSCALL
+	perf_overflow_handler_t		orig_overflow_handler;
+	struct bpf_prog			*prog;
+#endif
 
 #ifdef CONFIG_EVENT_TRACING
 	struct trace_event_call		*tp_event;

kernel/events/core.c +88 -1

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Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #5 lore raw

PATCH v3 5/6 samples/bpf: add perf_event+bpf example

In reply to Alexei Starovoitov

The bpf program is called 50 times a second and does hashmap[kern&user_stackid]++ It's primary purpose to check that key bpf helpers like map lookup, update, get_stackid, trace_printk and ctx access are all working.
It checks:
- PERF_COUNT_HW_CPU_CYCLES on all cpus
- PERF_COUNT_HW_CPU_CYCLES for current process and inherited perf_events to children
- PERF_COUNT_SW_CPU_CLOCK on all cpus
- PERF_COUNT_SW_CPU_CLOCK for current process

Signed-off-by Alexei Starovoitov <[email protected]>

---
 samples/bpf/Makefile           |   4 +
 samples/bpf/bpf_helpers.h      |   2 +
 samples/bpf/bpf_load.c         |   7 +-
 samples/bpf/trace_event_kern.c |  65 +++++++++++++
 samples/bpf/trace_event_user.c | 213 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 290 insertions(+), 1 deletion(-)
 create mode 100644 samples/bpf/trace_event_kern.c
 create mode 100644 samples/bpf/trace_event_user.c

samples/bpf/Makefile +4 -0

index db3cb061bfcd..a69cf9045285 100644
@@ -25,6 +25,7 @@ hostprogs-y += test_cgrp2_array_pin
 hostprogs-y += xdp1
 hostprogs-y += xdp2
 hostprogs-y += test_current_task_under_cgroup
+hostprogs-y += trace_event
 
 test_verifier-objs := test_verifier.o libbpf.o
 test_maps-objs := test_maps.o libbpf.o

@@ -52,6 +53,7 @@ xdp1-objs := bpf_load.o libbpf.o xdp1_user.o
 xdp2-objs := bpf_load.o libbpf.o xdp1_user.o
 test_current_task_under_cgroup-objs := bpf_load.o libbpf.o \
 				       test_current_task_under_cgroup_user.o
+trace_event-objs := bpf_load.o libbpf.o trace_event_user.o
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)

@@ -79,6 +81,7 @@ always += test_cgrp2_tc_kern.o
 always += xdp1_kern.o
 always += xdp2_kern.o
 always += test_current_task_under_cgroup_kern.o
+always += trace_event_kern.o
 
 HOSTCFLAGS += -I$(objtree)/usr/include

@@ -103,6 +106,7 @@ HOSTLOADLIBES_test_overhead += -lelf -lrt
 HOSTLOADLIBES_xdp1 += -lelf
 HOSTLOADLIBES_xdp2 += -lelf
 HOSTLOADLIBES_test_current_task_under_cgroup += -lelf
+HOSTLOADLIBES_trace_event += -lelf
 
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
 #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang

samples/bpf/bpf_helpers.h +2 -0

index bbdf62a1e45e..90f44bd2045e 100644
@@ -55,6 +55,8 @@ static int (*bpf_skb_get_tunnel_opt)(void *ctx, void *md, int size) =
 	(void *) BPF_FUNC_skb_get_tunnel_opt;
 static int (*bpf_skb_set_tunnel_opt)(void *ctx, void *md, int size) =
 	(void *) BPF_FUNC_skb_set_tunnel_opt;
+static unsigned long long (*bpf_get_prandom_u32)(void) =
+	(void *) BPF_FUNC_get_prandom_u32;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions

samples/bpf/bpf_load.c +6 -1

index 0cfda2320320..97913e109b14 100644
@@ -51,6 +51,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 	bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
 	bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
 	bool is_xdp = strncmp(event, "xdp", 3) == 0;
+	bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
 	enum bpf_prog_type prog_type;
 	char buf[256];
 	int fd, efd, err, id;

@@ -69,6 +70,8 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 		prog_type = BPF_PROG_TYPE_TRACEPOINT;
 	} else if (is_xdp) {
 		prog_type = BPF_PROG_TYPE_XDP;
+	} else if (is_perf_event) {
+		prog_type = BPF_PROG_TYPE_PERF_EVENT;
 	} else {
 		printf("Unknown event '%s'\n", event);
 		return -1;

@@ -82,7 +85,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 
 	prog_fd[prog_cnt++] = fd;
 
-	if (is_xdp)
+	if (is_xdp || is_perf_event)
 		return 0;
 
 	if (is_socket) {

@@ -326,6 +329,7 @@ int load_bpf_file(char *path)
 			    memcmp(shname_prog, "kretprobe/", 10) == 0 ||
 			    memcmp(shname_prog, "tracepoint/", 11) == 0 ||
 			    memcmp(shname_prog, "xdp", 3) == 0 ||
+			    memcmp(shname_prog, "perf_event", 10) == 0 ||
 			    memcmp(shname_prog, "socket", 6) == 0)
 				load_and_attach(shname_prog, insns, data_prog->d_size);
 		}

@@ -344,6 +348,7 @@ int load_bpf_file(char *path)
 		    memcmp(shname, "kretprobe/", 10) == 0 ||
 		    memcmp(shname, "tracepoint/", 11) == 0 ||
 		    memcmp(shname, "xdp", 3) == 0 ||
+		    memcmp(shname, "perf_event", 10) == 0 ||
 		    memcmp(shname, "socket", 6) == 0)
 			load_and_attach(shname, data->d_buf, data->d_size);
 	}

samples/bpf/trace_event_kern.c new file +65 -0

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samples/bpf/trace_event_user.c new file +213 -0

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Signature · 1 line

2.8.0

Alexei Starovoitov

author

2016-09-02 01:37 UTC #6 lore raw

PATCH v3 6/6 samples/bpf: add sampleip example

In reply to Alexei Starovoitov

From: Brendan Gregg <[email protected]>

sample instruction pointer and frequency count in a BPF map

Signed-off-by Brendan Gregg <[email protected]>

Signed-off-by Alexei Starovoitov <[email protected]>

---
 samples/bpf/Makefile        |   4 +
 samples/bpf/sampleip_kern.c |  38 +++++++++
 samples/bpf/sampleip_user.c | 196 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 238 insertions(+)
 create mode 100644 samples/bpf/sampleip_kern.c
 create mode 100644 samples/bpf/sampleip_user.c

samples/bpf/Makefile +4 -0

index a69cf9045285..12b7304d55dc 100644
@@ -26,6 +26,7 @@ hostprogs-y += xdp1
 hostprogs-y += xdp2
 hostprogs-y += test_current_task_under_cgroup
 hostprogs-y += trace_event
+hostprogs-y += sampleip
 
 test_verifier-objs := test_verifier.o libbpf.o
 test_maps-objs := test_maps.o libbpf.o

@@ -54,6 +55,7 @@ xdp2-objs := bpf_load.o libbpf.o xdp1_user.o
 test_current_task_under_cgroup-objs := bpf_load.o libbpf.o \
 				       test_current_task_under_cgroup_user.o
 trace_event-objs := bpf_load.o libbpf.o trace_event_user.o
+sampleip-objs := bpf_load.o libbpf.o sampleip_user.o
 
 # Tell kbuild to always build the programs
 always := $(hostprogs-y)

@@ -82,6 +84,7 @@ always += xdp1_kern.o
 always += xdp2_kern.o
 always += test_current_task_under_cgroup_kern.o
 always += trace_event_kern.o
+always += sampleip_kern.o
 
 HOSTCFLAGS += -I$(objtree)/usr/include

@@ -107,6 +110,7 @@ HOSTLOADLIBES_xdp1 += -lelf
 HOSTLOADLIBES_xdp2 += -lelf
 HOSTLOADLIBES_test_current_task_under_cgroup += -lelf
 HOSTLOADLIBES_trace_event += -lelf
+HOSTLOADLIBES_sampleip += -lelf
 
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
 #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang

samples/bpf/sampleip_kern.c new file +38 -0

new file mode 100644
index 000000000000..774a681f374a
@@ -0,0 +1,38 @@
+/* Copyright 2016 Netflix, Inc.
+ *
+ * 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.
+ */
+#include <linux/version.h>
+#include <linux/ptrace.h>
+#include <uapi/linux/bpf.h>
+#include <uapi/linux/bpf_perf_event.h>
+#include "bpf_helpers.h"
+
+#define MAX_IPS		8192
+
+struct bpf_map_def SEC("maps") ip_map = {
+	.type = BPF_MAP_TYPE_HASH,
+	.key_size = sizeof(u64),
+	.value_size = sizeof(u32),
+	.max_entries = MAX_IPS,
+};
+
+SEC("perf_event")
+int do_sample(struct bpf_perf_event_data *ctx)
+{
+	u64 ip;
+	u32 *value, init_val = 1;
+
+	ip = ctx->regs.ip;
+	value = bpf_map_lookup_elem(&ip_map, &ip);
+	if (value)
+		*value += 1;
+	else
+		/* E2BIG not tested for this example only */
+		bpf_map_update_elem(&ip_map, &ip, &init_val, BPF_NOEXIST);
+
+	return 0;
+}
+char _license[] SEC("license") = "GPL";

samples/bpf/sampleip_user.c new file +196 -0

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Signature · 1 line

2.8.0

Peter Zijlstra

maintainer Acked-by on the v3 series

2016-09-02 09:32 UTC #7 lore raw

In reply to Alexei Starovoitov

Quoted 4 lines · Alexei Starovoitov

Peter,
to implement your suggestion to add ifdef CONFIG_BPF_SYSCALL inside struct perf_event, I had to shuffle ifdefs in events/core.c Please double check whether that is what you wanted to see.

Looks fine, Thanks!

Acked-by Peter Zijlstra (Intel) <[email protected]>

David Miller

maintainer

2016-09-02 17:56 UTC #8 lore raw

In reply to Alexei Starovoitov

From: Alexei Starovoitov <[email protected]>
Date: Thu, 1 Sep 2016 18:37:20 -0700

Quoted 11 lines

Hi Peter, Dave,
this patch set is a follow up to the discussion:
https://lkml.kernel.org/r/20160804142853.GO6862%20()%20twins%20!%20programming%20!%20kicks-ass%20!%20net
It turned out to be simpler than what we discussed.
Patches 1-3 is bpf-side prep for the main patch 4
that adds bpf program as an overflow_handler to sw and hw perf_events.
Patches 5 and 6 are examples from myself and Brendan.

Quoted 7 lines

Peter,
to implement your suggestion to add ifdef CONFIG_BPF_SYSCALL inside struct perf_event, I had to shuffle ifdefs in events/core.c Please double check whether that is what you wanted to see.
v2->v3: fixed few more minor issues
v1->v2: fixed issues spotted by Peter and Daniel.

Series applied, thanks.