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Subject[PATCH v4 5/6] bpf: add option for bpf_load.c to use perf_kprobe
Date
Function load_and_attach() is updated to be able to create kprobes
with either old text based API, or the new perf_event_open API.

A global flag use_perf_kprobe is added to select between the two
APIs.

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
---
samples/bpf/bpf_load.c | 59 +++++++++++++++++++++++++++++++++++++++++++-------
samples/bpf/bpf_load.h | 10 +++++++++
2 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 2325d7a..b11c1c1 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -8,7 +8,6 @@
#include <errno.h>
#include <unistd.h>
#include <string.h>
-#include <stdbool.h>
#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/filter.h>
@@ -29,6 +28,7 @@
#include "perf-sys.h"

#define DEBUGFS "/sys/kernel/debug/tracing/"
+#define KPROBE_TYPE_FILE "/sys/bus/event_source/devices/kprobe/type"

static char license[128];
static int kern_version;
@@ -42,6 +42,8 @@ int prog_array_fd = -1;

struct bpf_map_data map_data[MAX_MAPS];
int map_data_count = 0;
+bool use_perf_kprobe = true;
+int perf_kprobe_type = -1;

static int populate_prog_array(const char *event, int prog_fd)
{
@@ -55,6 +57,26 @@ static int populate_prog_array(const char *event, int prog_fd)
return 0;
}

+int get_perf_kprobe_type_id(void)
+{
+ int tfd;
+ int err;
+ char buf[16];
+
+ tfd = open(KPROBE_TYPE_FILE, O_RDONLY);
+ if (tfd < 0)
+ return -1;
+
+ err = read(tfd, buf, sizeof(buf));
+ close(tfd);
+
+ if (err < 0 || err >= sizeof(buf))
+ return -1;
+ buf[err] = 0;
+ perf_kprobe_type = atoi(buf);
+ return perf_kprobe_type;
+}
+
static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
bool is_socket = strncmp(event, "socket", 6) == 0;
@@ -70,7 +92,7 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
size_t insns_cnt = size / sizeof(struct bpf_insn);
enum bpf_prog_type prog_type;
char buf[256];
- int fd, efd, err, id;
+ int fd, efd, err, id = -1;
struct perf_event_attr attr = {};

attr.type = PERF_TYPE_TRACEPOINT;
@@ -128,7 +150,13 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
return populate_prog_array(event, fd);
}

- if (is_kprobe || is_kretprobe) {
+ if (use_perf_kprobe && perf_kprobe_type == -1) {
+ get_perf_kprobe_type_id();
+ if (perf_kprobe_type == -1)
+ use_perf_kprobe = false;
+ }
+
+ if (!use_perf_kprobe && (is_kprobe || is_kretprobe)) {
if (is_kprobe)
event += 7;
else
@@ -169,27 +197,42 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
strcat(buf, "/id");
}

+ if (use_perf_kprobe && (is_kprobe || is_kretprobe)) {
+ attr.type = perf_kprobe_type;
+ attr.kprobe_func = ptr_to_u64(
+ event + strlen(is_kprobe ? "kprobe/" : "kretprobe/"));
+ attr.probe_offset = 0;
+ if (is_kretprobe)
+ attr.config |= PERF_PROBE_CONFIG_IS_RETPROBE;
+ } else {
efd = open(buf, O_RDONLY, 0);
if (efd < 0) {
printf("failed to open event %s\n", event);
return -1;
}
-
err = read(efd, buf, sizeof(buf));
if (err < 0 || err >= sizeof(buf)) {
- printf("read from '%s' failed '%s'\n", event, strerror(errno));
+ printf("read from '%s' failed '%s'\n", event,
+ strerror(errno));
return -1;
}
-
close(efd);
-
buf[err] = 0;
id = atoi(buf);
attr.config = id;
+ }

efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
if (efd < 0) {
- printf("event %d fd %d err %s\n", id, efd, strerror(errno));
+ if (use_perf_kprobe && (is_kprobe || is_kretprobe))
+ printf("k%sprobe %s fd %d err %s\n",
+ is_kprobe ? "" : "ret",
+ event + strlen(is_kprobe ? "kprobe/"
+ : "kretprobe/"),
+ efd, strerror(errno));
+ else
+ printf("event %d fd %d err %s\n", id, efd,
+ strerror(errno));
return -1;
}
event_fd[prog_cnt - 1] = efd;
diff --git a/samples/bpf/bpf_load.h b/samples/bpf/bpf_load.h
index 7d57a42..95d6be5 100644
--- a/samples/bpf/bpf_load.h
+++ b/samples/bpf/bpf_load.h
@@ -2,6 +2,7 @@
#ifndef __BPF_LOAD_H
#define __BPF_LOAD_H

+#include <stdbool.h>
#include "libbpf.h"

#define MAX_MAPS 32
@@ -38,6 +39,10 @@ extern int map_fd[MAX_MAPS];
extern struct bpf_map_data map_data[MAX_MAPS];
extern int map_data_count;

+extern bool use_perf_kprobe;
+extern int perf_kprobe_type;
+extern int get_perf_kprobe_type_id(void);
+
/* parses elf file compiled by llvm .c->.o
* . parses 'maps' section and creates maps via BPF syscall
* . parses 'license' section and passes it to syscall
@@ -59,6 +64,11 @@ struct ksym {
char *name;
};

+static inline __u64 ptr_to_u64(const void *ptr)
+{
+ return (__u64) (unsigned long) ptr;
+}
+
int load_kallsyms(void);
struct ksym *ksym_search(long key);
int set_link_xdp_fd(int ifindex, int fd, __u32 flags);
--
2.9.5
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