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

A global flag use_perf_type_probe 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 | 56 ++++++++++++++++++++++++++++++++------------------
samples/bpf/bpf_load.h | 8 ++++++++
2 files changed, 44 insertions(+), 20 deletions(-)

diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 2325d7a..dc6d843 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>
@@ -42,6 +41,7 @@ int prog_array_fd = -1;

struct bpf_map_data map_data[MAX_MAPS];
int map_data_count = 0;
+bool use_perf_type_probe = true;

static int populate_prog_array(const char *event, int prog_fd)
{
@@ -70,8 +70,9 @@ 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 = {};
+ struct probe_desc pd;

attr.type = PERF_TYPE_TRACEPOINT;
attr.sample_type = PERF_SAMPLE_RAW;
@@ -128,7 +129,7 @@ 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_type_probe && (is_kprobe || is_kretprobe)) {
if (is_kprobe)
event += 7;
else
@@ -169,27 +170,42 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
strcat(buf, "/id");
}

- 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));
- return -1;
+ if (use_perf_type_probe && (is_kprobe || is_kretprobe)) {
+ attr.type = PERF_TYPE_PROBE;
+ pd.func = ptr_to_u64(event + strlen(is_kprobe ? "kprobe/"
+ : "kretprobe/"));
+ pd.offset = 0;
+ attr.is_return = !!is_kretprobe;
+ attr.probe_desc = ptr_to_u64(&pd);
+ } 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));
+ return -1;
+ }
+ close(efd);
+ buf[err] = 0;
+ id = atoi(buf);
+ attr.config = id;
}

- 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_type_probe && (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..e7a8a21 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 +39,8 @@ extern int map_fd[MAX_MAPS];
extern struct bpf_map_data map_data[MAX_MAPS];
extern int map_data_count;

+extern bool use_perf_type_probe;
+
/* 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 +62,11 @@ 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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