[PATCH bpf-next 0/7] libbpf: add tracing attach APIs

[PATCH bpf-next 0/7] libbpf: add tracing attach APIs

[Andrii Nakryiko]

This patchset adds the following APIs to allow attaching BPF programs to
tracing entities:
- bpf_program__attach_perf_event for attaching to any opened perf event FD,
  allowing users full control;
- bpf_program__attach_kprobe for attaching to kernel probes (both entry and
  return probes);
- bpf_program__attach_uprobe for attaching to user probes (both entry/return);
- bpf_program__attach_tracepoint for attaching to kernel tracepoints;
- bpf_program__attach_raw_tracepoint for attaching to raw kernel tracepoint
  (wrapper around bpf_raw_tracepoint_open);

This set of APIs makes libbpf more useful for tracing applications.

Pre-patch #1 makes internal libbpf_strerror_r helper function work w/ negative
error codes, lifting the burder off callers to keep track of error sign.
Patch #2 adds attach_perf_event, which is the base for all other APIs.
Patch #3 adds kprobe/uprobe APIs.
Patch #4 adds tracepoint/raw_tracepoint APIs.
Patch #5 converts one existing test to use attach_perf_event.
Patch #6 adds new kprobe/uprobe tests.
Patch #7 converts all the selftests currently using tracepoint to new APIs.

Andrii Nakryiko (7):
  libbpf: make libbpf_strerror_r agnostic to sign of error
  libbpf: add ability to attach/detach BPF to perf event
  libbpf: add kprobe/uprobe attach API
  libbpf: add tracepoint/raw tracepoint attach API
  selftests/bpf: switch test to new attach_perf_event API
  selftests/bpf: add kprobe/uprobe selftests
  selftests/bpf: convert existing tracepoint tests to new APIs

 tools/lib/bpf/libbpf.c                        | 347 ++++++++++++++++++
 tools/lib/bpf/libbpf.h                        |  17 +
 tools/lib/bpf/libbpf.map                      |   6 +
 tools/lib/bpf/str_error.c                     |   2 +-
 .../selftests/bpf/prog_tests/attach_probe.c   | 151 ++++++++
 .../bpf/prog_tests/stacktrace_build_id.c      |  49 +--
 .../bpf/prog_tests/stacktrace_build_id_nmi.c  |  16 +-
 .../selftests/bpf/prog_tests/stacktrace_map.c |  42 +--
 .../bpf/prog_tests/stacktrace_map_raw_tp.c    |  14 +-
 .../bpf/prog_tests/task_fd_query_rawtp.c      |  10 +-
 .../bpf/prog_tests/task_fd_query_tp.c         |  51 +--
 .../bpf/prog_tests/tp_attach_query.c          |  56 +--
 .../selftests/bpf/progs/test_attach_probe.c   |  55 +++
 13 files changed, 650 insertions(+), 166 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_probe.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_attach_probe.c

-- 
2.17.1

[PATCH bpf-next 1/7] libbpf: make libbpf_strerror_r agnostic to sign of error

[Andrii Nakryiko]

It's often inconvenient to switch sign of error when passing it into
libbpf_strerror_r. It's better for it to handle that automatically.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/str_error.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/str_error.c b/tools/lib/bpf/str_error.c
index 00e48ac5b806..b8064eedc177 100644
--- a/tools/lib/bpf/str_error.c
+++ b/tools/lib/bpf/str_error.c
@@ -11,7 +11,7 @@
  */
 char *libbpf_strerror_r(int err, char *dst, int len)
 {
-	int ret = strerror_r(err, dst, len);
+	int ret = strerror_r(err < 0 ? -err : err, dst, len);
 	if (ret)
 		snprintf(dst, len, "ERROR: strerror_r(%d)=%d", err, ret);
 	return dst;
-- 
2.17.1

[PATCH bpf-next 2/7] libbpf: add ability to attach/detach BPF to perf event

[Andrii Nakryiko]

bpf_program__attach_perf_event allows to attach BPF program to existing
perf event, providing most generic and most low-level way to attach BPF
programs.

libbpf_perf_event_disable_and_close API is added to disable and close
existing perf event by its FD.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c   | 41 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  4 ++++
 tools/lib/bpf/libbpf.map |  2 ++
 3 files changed, 47 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 8ce3beba8551..2bb1fa008be3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -32,6 +32,7 @@
 #include <linux/limits.h>
 #include <linux/perf_event.h>
 #include <linux/ring_buffer.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
@@ -3928,6 +3929,46 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
 	return 0;
 }
 
+int libbpf_perf_event_disable_and_close(int pfd)
+{
+	int err;
+
+	if (pfd < 0)
+		return 0;
+
+	err = ioctl(pfd, PERF_EVENT_IOC_DISABLE, 0);
+	close(pfd);
+	return err;
+}
+
+int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
+{
+	char errmsg[STRERR_BUFSIZE];
+	int bpf_fd, err;
+
+	bpf_fd = bpf_program__fd(prog);
+	if (bpf_fd < 0) {
+		pr_warning("program '%s': can't attach before loaded\n",
+			   bpf_program__title(prog, false));
+		return -EINVAL;
+	}
+	if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, bpf_fd) < 0) {
+		err = -errno;
+		pr_warning("program '%s': failed to attach to pfd %d: %s\n",
+			   bpf_program__title(prog, false), pfd,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
+		err = -errno;
+		pr_warning("program '%s': failed to enable pfd %d: %s\n",
+			   bpf_program__title(prog, false), pfd,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return 0;
+}
+
 enum bpf_perf_event_ret
 bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 			   void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d639f47e3110..76db1bbc0dac 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -165,6 +165,10 @@ LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
 LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
 LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
 
+LIBBPF_API int libbpf_perf_event_disable_and_close(int pfd);
+LIBBPF_API int bpf_program__attach_perf_event(struct bpf_program *prog,
+					      int pfd);
+
 struct bpf_insn;
 
 /*
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 2c6d835620d2..d27406982b5a 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -172,5 +172,7 @@ LIBBPF_0.0.4 {
 		btf_dump__new;
 		btf__parse_elf;
 		bpf_object__load_xattr;
+		bpf_program__attach_perf_event;
 		libbpf_num_possible_cpus;
+		libbpf_perf_event_disable_and_close;
 } LIBBPF_0.0.3;
-- 
2.17.1

[PATCH bpf-next 3/7] libbpf: add kprobe/uprobe attach API

[Andrii Nakryiko]

Add ability to attach to kernel and user probes and retprobes.
Implementation depends on perf event support for kprobes/uprobes.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c   | 207 +++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |   8 ++
 tools/lib/bpf/libbpf.map |   2 +
 3 files changed, 217 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2bb1fa008be3..11329e05530e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3969,6 +3969,213 @@ int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
 	return 0;
 }
 
+static int parse_uint(const char *buf)
+{
+	int ret;
+
+	errno = 0;
+	ret = (int)strtol(buf, NULL, 10);
+	if (errno) {
+		ret = -errno;
+		pr_debug("failed to parse '%s' as unsigned int\n", buf);
+		return ret;
+	}
+	if (ret < 0) {
+		pr_debug("failed to parse '%s' as unsigned int\n", buf);
+		return -EINVAL;
+	}
+	return ret;
+}
+
+static int parse_uint_from_file(const char* file)
+{
+	char buf[STRERR_BUFSIZE];
+	int fd, ret;
+
+	fd = open(file, O_RDONLY);
+	if (fd < 0) {
+		ret = -errno;
+		pr_debug("failed to open '%s': %s\n", file,
+			 libbpf_strerror_r(ret, buf, sizeof(buf)));
+		return ret;
+	}
+	ret = read(fd, buf, sizeof(buf));
+	close(fd);
+	if (ret < 0) {
+		ret = -errno;
+		pr_debug("failed to read '%s': %s\n", file,
+			libbpf_strerror_r(ret, buf, sizeof(buf)));
+		return ret;
+	}
+	if (ret == 0 || ret >= sizeof(buf)) {
+		buf[sizeof(buf) - 1] = 0;
+		pr_debug("unexpected input from '%s': '%s'\n", file, buf);
+		return -EINVAL;
+	}
+	return parse_uint(buf);
+}
+
+static int determine_kprobe_perf_type(void)
+{
+	const char *file = "/sys/bus/event_source/devices/kprobe/type";
+	return parse_uint_from_file(file);
+}
+
+static int determine_uprobe_perf_type(void)
+{
+	const char *file = "/sys/bus/event_source/devices/uprobe/type";
+	return parse_uint_from_file(file);
+}
+
+static int parse_config_from_file(const char *file)
+{
+	char buf[STRERR_BUFSIZE];
+	int fd, ret;
+
+	fd = open(file, O_RDONLY);
+	if (fd < 0) {
+		ret = -errno;
+		pr_debug("failed to open '%s': %s\n", file,
+			 libbpf_strerror_r(ret, buf, sizeof(buf)));
+		return ret;
+	}
+	ret = read(fd, buf, sizeof(buf));
+	close(fd);
+	if (ret < 0) {
+		ret = -errno;
+		pr_debug("failed to read '%s': %s\n", file,
+			libbpf_strerror_r(ret, buf, sizeof(buf)));
+		return ret;
+	}
+	if (ret == 0 || ret >= sizeof(buf)) {
+		buf[sizeof(buf) - 1] = 0;
+		pr_debug("unexpected input from '%s': '%s'\n", file, buf);
+		return -EINVAL;
+	}
+	if (strncmp(buf, "config:", 7)) {
+		pr_debug("expected 'config:' prefix, found '%s'\n", buf);
+		return -EINVAL;
+	}
+	return parse_uint(buf + 7);
+}
+
+static int determine_kprobe_retprobe_bit(void)
+{
+	const char *file = "/sys/bus/event_source/devices/kprobe/format/retprobe";
+	return parse_config_from_file(file);
+}
+
+static int determine_uprobe_retprobe_bit(void)
+{
+	const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
+	return parse_config_from_file(file);
+}
+
+static int perf_event_open_probe(bool uprobe, bool retprobe, const char* name,
+				 uint64_t offset, int pid)
+{
+	struct perf_event_attr attr = {};
+	char errmsg[STRERR_BUFSIZE];
+	int type, pfd, err;
+
+	type = uprobe ? determine_uprobe_perf_type()
+		      : determine_kprobe_perf_type();
+	if (type < 0) {
+		pr_warning("failed to determine %s perf type: %s\n",
+			   uprobe ? "uprobe" : "kprobe",
+			   libbpf_strerror_r(type, errmsg, sizeof(errmsg)));
+		return type;
+	}
+	if (retprobe) {
+		int bit = uprobe ? determine_uprobe_retprobe_bit()
+				 : determine_kprobe_retprobe_bit();
+
+		if (bit < 0) {
+			pr_warning("failed to determine %s retprobe bit: %s\n",
+				   uprobe ? "uprobe" : "kprobe",
+				   libbpf_strerror_r(bit, errmsg,
+						     sizeof(errmsg)));
+			return bit;
+		}
+		attr.config |= 1 << bit;
+	}
+	attr.size = sizeof(attr);
+	attr.type = type;
+	attr.config1 = (uint64_t)(void *)name; /* kprobe_func or uprobe_path */
+	attr.config2 = offset;		       /* kprobe_addr or probe_offset */
+
+	/* pid filter is meaningful only for uprobes */
+	pfd = syscall(__NR_perf_event_open, &attr,
+		      pid < 0 ? -1 : pid /* pid */,
+		      pid == -1 ? 0 : -1 /* cpu */,
+		      -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
+	if (pfd < 0) {
+		err = -errno;
+		pr_warning("%s perf_event_open() failed: %s\n",
+			   uprobe ? "uprobe" : "kprobe",
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return pfd;
+}
+
+int bpf_program__attach_kprobe(struct bpf_program *prog, bool retprobe,
+			       const char *func_name)
+{
+	char errmsg[STRERR_BUFSIZE];
+	int pfd, err;
+
+	pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name,
+				    0 /* offset */, -1 /* pid */);
+	if (pfd < 0) {
+		pr_warning("program '%s': failed to create %s '%s' perf event: %s\n",
+			   bpf_program__title(prog, false),
+			   retprobe ? "kretprobe" : "kprobe", func_name,
+			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+		return pfd;
+	}
+	err = bpf_program__attach_perf_event(prog, pfd);
+	if (err) {
+		libbpf_perf_event_disable_and_close(pfd);
+		pr_warning("program '%s': failed to attach to %s '%s': %s\n",
+			   bpf_program__title(prog, false),
+			   retprobe ? "kretprobe" : "kprobe", func_name,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return pfd;
+}
+
+int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
+			       pid_t pid, const char *binary_path,
+			       size_t func_offset)
+{
+	char errmsg[STRERR_BUFSIZE];
+	int pfd, err;
+
+	pfd = perf_event_open_probe(true /* uprobe */, retprobe,
+				    binary_path, func_offset, pid);
+	if (pfd < 0) {
+		pr_warning("program '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
+			   bpf_program__title(prog, false),
+			   retprobe ? "uretprobe" : "uprobe",
+			   binary_path, func_offset,
+			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+		return pfd;
+	}
+	err = bpf_program__attach_perf_event(prog, pfd);
+	if (err) {
+		libbpf_perf_event_disable_and_close(pfd);
+		pr_warning("program '%s': failed to attach to %s '%s:0x%zx': %s\n",
+			   bpf_program__title(prog, false),
+			   retprobe ? "uretprobe" : "uprobe",
+			   binary_path, func_offset,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return pfd;
+}
+
 enum bpf_perf_event_ret
 bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 			   void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 76db1bbc0dac..a7264f06aa5f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -168,6 +168,14 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
 LIBBPF_API int libbpf_perf_event_disable_and_close(int pfd);
 LIBBPF_API int bpf_program__attach_perf_event(struct bpf_program *prog,
 					      int pfd);
+LIBBPF_API int bpf_program__attach_kprobe(struct bpf_program *prog,
+					  bool retprobe,
+					  const char *func_name);
+LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog,
+					  bool retprobe,
+					  pid_t pid,
+					  const char *binary_path,
+					  size_t func_offset);
 
 struct bpf_insn;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index d27406982b5a..1a982c2e1751 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -172,7 +172,9 @@ LIBBPF_0.0.4 {
 		btf_dump__new;
 		btf__parse_elf;
 		bpf_object__load_xattr;
+		bpf_program__attach_kprobe;
 		bpf_program__attach_perf_event;
+		bpf_program__attach_uprobe;
 		libbpf_num_possible_cpus;
 		libbpf_perf_event_disable_and_close;
 } LIBBPF_0.0.3;
-- 
2.17.1

[PATCH bpf-next 4/7] libbpf: add tracepoint/raw tracepoint attach API

[Andrii Nakryiko]

Add APIs allowing to attach BPF program to kernel tracepoints. Raw
tracepoint attach API is also added for uniform per-BPF-program API,
but is mostly a wrapper around existing bpf_raw_tracepoint_open call.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/lib/bpf/libbpf.c   | 99 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  5 ++
 tools/lib/bpf/libbpf.map |  2 +
 3 files changed, 106 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 11329e05530e..cefe67ba160b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
 	return pfd;
 }
 
+static int determine_tracepoint_id(const char* tp_category, const char* tp_name)
+{
+	char file[PATH_MAX];
+	int ret;
+
+	ret = snprintf(file, sizeof(file),
+		       "/sys/kernel/debug/tracing/events/%s/%s/id",
+		       tp_category, tp_name);
+	if (ret < 0)
+		return -errno;
+	if (ret >= sizeof(file)) {
+		pr_debug("tracepoint %s/%s path is too long\n",
+			 tp_category, tp_name);
+		return -E2BIG;
+	}
+	return parse_uint_from_file(file);
+}
+
+static int perf_event_open_tracepoint(const char* tp_category,
+				      const char* tp_name)
+{
+	struct perf_event_attr attr = {};
+	char errmsg[STRERR_BUFSIZE];
+	int tp_id, pfd, err;
+
+	tp_id = determine_tracepoint_id(tp_category, tp_name);
+	if (tp_id < 0){
+		pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n",
+			   tp_category, tp_name,
+			   libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
+		return tp_id;
+	}
+
+	memset(&attr, 0, sizeof(attr));
+	attr.type = PERF_TYPE_TRACEPOINT;
+	attr.size = sizeof(attr);
+	attr.config = tp_id;
+
+	pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
+			-1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
+	if (pfd < 0) {
+		err = -errno;
+		pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",
+			   tp_category, tp_name,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return pfd;
+}
+
+int bpf_program__attach_tracepoint(struct bpf_program *prog,
+				   const char *tp_category,
+				   const char *tp_name)
+{
+	char errmsg[STRERR_BUFSIZE];
+	int pfd, err;
+
+	pfd = perf_event_open_tracepoint(tp_category, tp_name);
+	if (pfd < 0) {
+		pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
+			   bpf_program__title(prog, false),
+			   tp_category, tp_name,
+			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+		return pfd;
+	}
+	err = bpf_program__attach_perf_event(prog, pfd);
+	if (err) {
+		libbpf_perf_event_disable_and_close(pfd);
+		pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n",
+			   bpf_program__title(prog, false),
+			   tp_category, tp_name,
+			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
+		return err;
+	}
+	return pfd;
+}
+
+int bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
+				       const char *tp_name)
+{
+	char errmsg[STRERR_BUFSIZE];
+	int bpf_fd, pfd;
+
+	bpf_fd = bpf_program__fd(prog);
+	if (bpf_fd < 0) {
+		pr_warning("program '%s': can't attach before loaded\n",
+			   bpf_program__title(prog, false));
+		return -EINVAL;
+	}
+	pfd = bpf_raw_tracepoint_open(tp_name, bpf_fd);
+	if (pfd < 0) {
+		pr_warning("program '%s': failed to attach to raw tracepoint '%s': %s\n",
+			   bpf_program__title(prog, false), tp_name,
+			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
+		return pfd;
+	}
+	return pfd;
+}
+
 enum bpf_perf_event_ret
 bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
 			   void **copy_mem, size_t *copy_size,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index a7264f06aa5f..bf7020a565c6 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -176,6 +176,11 @@ LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog,
 					  pid_t pid,
 					  const char *binary_path,
 					  size_t func_offset);
+LIBBPF_API int bpf_program__attach_tracepoint(struct bpf_program *prog,
+					      const char *tp_category,
+					      const char *tp_name);
+LIBBPF_API int bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
+						  const char *tp_name);
 
 struct bpf_insn;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 1a982c2e1751..2382fbda4cbb 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -174,6 +174,8 @@ LIBBPF_0.0.4 {
 		bpf_object__load_xattr;
 		bpf_program__attach_kprobe;
 		bpf_program__attach_perf_event;
+		bpf_program__attach_raw_tracepoint;
+		bpf_program__attach_tracepoint;
 		bpf_program__attach_uprobe;
 		libbpf_num_possible_cpus;
 		libbpf_perf_event_disable_and_close;
-- 
2.17.1

[PATCH bpf-next 5/7] selftests/bpf: switch test to new attach_perf_event API

[Andrii Nakryiko]

Use new bpf_program__attach_perf_event() in test previously relying on
direct ioctl manipulations.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 .../bpf/prog_tests/stacktrace_build_id_nmi.c     | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
index 1c1a2f75f3d8..1bbdb0b82ac5 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
@@ -17,6 +17,7 @@ static __u64 read_perf_max_sample_freq(void)
 void test_stacktrace_build_id_nmi(void)
 {
 	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
+	const char *prog_name = "tracepoint/random/urandom_read";
 	const char *file = "./test_stacktrace_build_id.o";
 	int err, pmu_fd, prog_fd;
 	struct perf_event_attr attr = {
@@ -25,6 +26,7 @@ void test_stacktrace_build_id_nmi(void)
 		.config = PERF_COUNT_HW_CPU_CYCLES,
 	};
 	__u32 key, previous_key, val, duration = 0;
+	struct bpf_program *prog;
 	struct bpf_object *obj;
 	char buf[256];
 	int i, j;
@@ -39,6 +41,10 @@ void test_stacktrace_build_id_nmi(void)
 	if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
 		return;
 
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
+		goto close_prog;
+
 	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
 			 0 /* cpu 0 */, -1 /* group id */,
 			 0 /* flags */);
@@ -47,16 +53,10 @@ void test_stacktrace_build_id_nmi(void)
 		  pmu_fd, errno))
 		goto close_prog;
 
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
-	if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
-		  err, errno))
+	err = bpf_program__attach_perf_event(prog, pmu_fd);
+	if (CHECK(err, "attach_perf_event", "err %d\n", err))
 		goto close_pmu;
 
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
-	if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
-		  err, errno))
-		goto disable_pmu;
-
 	/* find map fds */
 	control_map_fd = bpf_find_map(__func__, obj, "control_map");
 	if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
-- 
2.17.1

[PATCH bpf-next 6/7] selftests/bpf: add kprobe/uprobe selftests

[Andrii Nakryiko]

Add tests verifying kprobe/kretprobe/uprobe/uretprobe APIs work as
expected.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 .../selftests/bpf/prog_tests/attach_probe.c   | 151 ++++++++++++++++++
 .../selftests/bpf/progs/test_attach_probe.c   |  55 +++++++
 2 files changed, 206 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/attach_probe.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_attach_probe.c

diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
new file mode 100644
index 000000000000..5cc7e674a513
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+
+ssize_t get_base_addr() {
+	size_t start;
+	char buf[256];
+	FILE *f;
+
+	f = fopen("/proc/self/maps", "r");
+	if (!f)
+		return -errno;
+
+	while (fscanf(f, "%zx-%*x %s %*s\n", &start, buf) == 2) {
+		if (strcmp(buf, "r-xp") == 0) {
+			fclose(f);
+			return start;
+		}
+	}
+
+	fclose(f);
+	return -EINVAL;
+}
+
+void test_attach_probe(void)
+{
+	const char *kprobe_name = "kprobe/sys_nanosleep";
+	const char *kretprobe_name = "kretprobe/sys_nanosleep";
+	const char *uprobe_name = "uprobe/trigger_func";
+	const char *uretprobe_name = "uretprobe/trigger_func";
+	const int kprobe_idx = 0, kretprobe_idx = 1;
+	const int uprobe_idx = 2, uretprobe_idx = 3;
+	const char *file = "./test_attach_probe.o";
+	struct bpf_program *kprobe_prog, *kretprobe_prog;
+	struct bpf_program *uprobe_prog, *uretprobe_prog;
+	struct bpf_object *obj;
+	int err, prog_fd, duration = 0, res;
+	int kprobe_pfd = -1, kretprobe_pfd = -1;
+	int uprobe_pfd = -1, uretprobe_pfd = -1;
+	int results_map_fd;
+	size_t uprobe_offset;
+	ssize_t base_addr;
+
+	base_addr = get_base_addr();
+	if (CHECK(base_addr < 0, "get_base_addr",
+		  "failed to find base addr: %zd", base_addr))
+		return;
+	uprobe_offset = (size_t)&get_base_addr - base_addr;
+
+	/* load programs */
+	err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
+	if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
+		return;
+
+	kprobe_prog = bpf_object__find_program_by_title(obj, kprobe_name);
+	if (CHECK(!kprobe_prog, "find_probe",
+		  "prog '%s' not found\n", kprobe_name))
+		goto cleanup;
+	kretprobe_prog = bpf_object__find_program_by_title(obj, kretprobe_name);
+	if (CHECK(!kretprobe_prog, "find_probe",
+		  "prog '%s' not found\n", kretprobe_name))
+		goto cleanup;
+	uprobe_prog = bpf_object__find_program_by_title(obj, uprobe_name);
+	if (CHECK(!uprobe_prog, "find_probe",
+		  "prog '%s' not found\n", uprobe_name))
+		goto cleanup;
+	uretprobe_prog = bpf_object__find_program_by_title(obj, uretprobe_name);
+	if (CHECK(!uretprobe_prog, "find_probe",
+		  "prog '%s' not found\n", uretprobe_name))
+		goto cleanup;
+
+	/* load maps */
+	results_map_fd = bpf_find_map(__func__, obj, "results_map");
+	if (CHECK(results_map_fd < 0, "find_results_map",
+		  "err %d\n", results_map_fd))
+		goto cleanup;
+
+	kprobe_pfd = bpf_program__attach_kprobe(kprobe_prog,
+						false /* retprobe */,
+						"sys_nanosleep");
+	if (CHECK(kprobe_pfd < 0, "attach_kprobe", "err %d\n", kprobe_pfd))
+		goto cleanup;
+
+	kretprobe_pfd = bpf_program__attach_kprobe(kretprobe_prog,
+						   true /* retprobe */,
+						   "sys_nanosleep");
+	if (CHECK(kretprobe_pfd < 0, "attach_kretprobe",
+		  "err %d\n", kretprobe_pfd))
+		goto cleanup;
+
+	uprobe_pfd = bpf_program__attach_uprobe(uprobe_prog,
+						false /* retprobe */,
+						0 /* self pid */,
+						"/proc/self/exe",
+						uprobe_offset);
+	if (CHECK(uprobe_pfd < 0, "attach_uprobe", "err %d\n", uprobe_pfd))
+		goto cleanup;
+
+	uretprobe_pfd = bpf_program__attach_uprobe(uretprobe_prog,
+						   true /* retprobe */,
+						   -1 /* any pid */,
+						   "/proc/self/exe",
+						   uprobe_offset);
+	if (CHECK(uretprobe_pfd < 0, "attach_uretprobe",
+		  "err %d\n", uretprobe_pfd))
+		goto cleanup;
+
+	/* trigger & validate kprobe && kretprobe */
+	usleep(1);
+
+	err = bpf_map_lookup_elem(results_map_fd, &kprobe_idx, &res);
+	if (CHECK(err, "get_kprobe_res",
+		  "failed to get kprobe res: %d\n", err))
+		goto cleanup;
+	if (CHECK(res != kprobe_idx + 1, "check_kprobe_res",
+		  "wrong kprobe res: %d\n", res))
+		goto cleanup;
+
+	err = bpf_map_lookup_elem(results_map_fd, &kretprobe_idx, &res);
+	if (CHECK(err, "get_kretprobe_res",
+		  "failed to get kretprobe res: %d\n", err))
+		goto cleanup;
+	if (CHECK(res != kretprobe_idx + 1, "check_kretprobe_res",
+		  "wrong kretprobe res: %d\n", res))
+		goto cleanup;
+
+	/* trigger & validate uprobe & uretprobe */
+	get_base_addr();
+
+	err = bpf_map_lookup_elem(results_map_fd, &uprobe_idx, &res);
+	if (CHECK(err, "get_uprobe_res",
+		  "failed to get uprobe res: %d\n", err))
+		goto cleanup;
+	if (CHECK(res != uprobe_idx + 1, "check_uprobe_res",
+		  "wrong uprobe res: %d\n", res))
+		goto cleanup;
+
+	err = bpf_map_lookup_elem(results_map_fd, &uretprobe_idx, &res);
+	if (CHECK(err, "get_uretprobe_res",
+		  "failed to get uretprobe res: %d\n", err))
+		goto cleanup;
+	if (CHECK(res != uretprobe_idx + 1, "check_uretprobe_res",
+		  "wrong uretprobe res: %d\n", res))
+		goto cleanup;
+
+cleanup:
+	libbpf_perf_event_disable_and_close(kprobe_pfd);
+	libbpf_perf_event_disable_and_close(kretprobe_pfd);
+	libbpf_perf_event_disable_and_close(uprobe_pfd);
+	libbpf_perf_event_disable_and_close(uretprobe_pfd);
+	bpf_object__close(obj);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_attach_probe.c b/tools/testing/selftests/bpf/progs/test_attach_probe.c
new file mode 100644
index 000000000000..7a7c5cd728c8
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_attach_probe.c
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2017 Facebook
+
+#include <linux/ptrace.h>
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+
+struct {
+	int type;
+	int max_entries;
+	int *key;
+	int *value;
+} results_map SEC(".maps") = {
+	.type = BPF_MAP_TYPE_ARRAY,
+	.max_entries = 4,
+};
+
+SEC("kprobe/sys_nanosleep")
+int handle_sys_nanosleep_entry(struct pt_regs *ctx)
+{
+	const int key = 0, value = 1;
+
+	bpf_map_update_elem(&results_map, &key, &value, 0);
+	return 0;
+}
+
+SEC("kretprobe/sys_nanosleep")
+int handle_sys_getpid_return(struct pt_regs *ctx)
+{
+	const int key = 1, value = 2;
+
+	bpf_map_update_elem(&results_map, &key, &value, 0);
+	return 0;
+}
+
+SEC("uprobe/trigger_func")
+int handle_uprobe_entry(struct pt_regs *ctx)
+{
+	const int key = 2, value = 3;
+
+	bpf_map_update_elem(&results_map, &key, &value, 0);
+	return 0;
+}
+
+SEC("uretprobe/trigger_func")
+int handle_uprobe_return(struct pt_regs *ctx)
+{
+	const int key = 3, value = 4;
+
+	bpf_map_update_elem(&results_map, &key, &value, 0);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+__u32 _version SEC("version") = 1;
-- 
2.17.1

[PATCH bpf-next 7/7] selftests/bpf: convert existing tracepoint tests to new APIs

[Andrii Nakryiko]

Convert existing tests that attach to tracepoints to use
bpf_program__attach_tracepoint API instead.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 .../bpf/prog_tests/stacktrace_build_id.c      | 49 +++-------------
 .../selftests/bpf/prog_tests/stacktrace_map.c | 42 +++-----------
 .../bpf/prog_tests/stacktrace_map_raw_tp.c    | 14 ++++-
 .../bpf/prog_tests/task_fd_query_rawtp.c      | 10 +++-
 .../bpf/prog_tests/task_fd_query_tp.c         | 51 +++++------------
 .../bpf/prog_tests/tp_attach_query.c          | 56 ++++++-------------
 6 files changed, 65 insertions(+), 157 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
index 3aab2b083c71..9ef3b66f3644 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c
@@ -4,10 +4,11 @@
 void test_stacktrace_build_id(void)
 {
 	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
+	const char *prog_name = "tracepoint/random/urandom_read";
 	const char *file = "./test_stacktrace_build_id.o";
-	int bytes, efd, err, pmu_fd, prog_fd, stack_trace_len;
-	struct perf_event_attr attr = {};
+	int err, pmu_fd, prog_fd, stack_trace_len;
 	__u32 key, previous_key, val, duration = 0;
+	struct bpf_program *prog;
 	struct bpf_object *obj;
 	char buf[256];
 	int i, j;
@@ -20,42 +21,14 @@ void test_stacktrace_build_id(void)
 	if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
 		goto out;
 
-	/* Get the ID for the sched/sched_switch tracepoint */
-	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/random/urandom_read/id");
-	efd = open(buf, O_RDONLY, 0);
-	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
 		goto close_prog;
 
-	bytes = read(efd, buf, sizeof(buf));
-	close(efd);
-	if (CHECK(bytes <= 0 || bytes >= sizeof(buf),
-		  "read", "bytes %d errno %d\n", bytes, errno))
+	pmu_fd = bpf_program__attach_tracepoint(prog, "random", "urandom_read");
+	if (CHECK(pmu_fd < 0, "attach_tp", "err %d\n", pmu_fd))
 		goto close_prog;
 
-	/* Open the perf event and attach bpf progrram */
-	attr.config = strtol(buf, NULL, 0);
-	attr.type = PERF_TYPE_TRACEPOINT;
-	attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
-	attr.sample_period = 1;
-	attr.wakeup_events = 1;
-	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
-			 0 /* cpu 0 */, -1 /* group id */,
-			 0 /* flags */);
-	if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
-		  pmu_fd, errno))
-		goto close_prog;
-
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
-	if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
-		  err, errno))
-		goto close_pmu;
-
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
-	if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
-		  err, errno))
-		goto disable_pmu;
-
 	/* find map fds */
 	control_map_fd = bpf_find_map(__func__, obj, "control_map");
 	if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
@@ -133,8 +106,7 @@ void test_stacktrace_build_id(void)
 	 * try it one more time.
 	 */
 	if (build_id_matches < 1 && retry--) {
-		ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
-		close(pmu_fd);
+		libbpf_perf_event_disable_and_close(pmu_fd);
 		bpf_object__close(obj);
 		printf("%s:WARN:Didn't find expected build ID from the map, retrying\n",
 		       __func__);
@@ -152,10 +124,7 @@ void test_stacktrace_build_id(void)
 	      "err %d errno %d\n", err, errno);
 
 disable_pmu:
-	ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
-
-close_pmu:
-	close(pmu_fd);
+	libbpf_perf_event_disable_and_close(pmu_fd);
 
 close_prog:
 	bpf_object__close(obj);
diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
index 2bfd50a0d6d1..df0716e69b96 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
@@ -4,50 +4,25 @@
 void test_stacktrace_map(void)
 {
 	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
+	const char *prog_name = "tracepoint/sched/sched_switch";
+	int efd, err, prog_fd, stack_trace_len;
 	const char *file = "./test_stacktrace_map.o";
-	int bytes, efd, err, pmu_fd, prog_fd, stack_trace_len;
-	struct perf_event_attr attr = {};
 	__u32 key, val, duration = 0;
+	struct bpf_program *prog;
 	struct bpf_object *obj;
-	char buf[256];
 
 	err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
 	if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
 		return;
 
-	/* Get the ID for the sched/sched_switch tracepoint */
-	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/sched/sched_switch/id");
-	efd = open(buf, O_RDONLY, 0);
-	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
 		goto close_prog;
 
-	bytes = read(efd, buf, sizeof(buf));
-	close(efd);
-	if (bytes <= 0 || bytes >= sizeof(buf))
-		goto close_prog;
-
-	/* Open the perf event and attach bpf progrram */
-	attr.config = strtol(buf, NULL, 0);
-	attr.type = PERF_TYPE_TRACEPOINT;
-	attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
-	attr.sample_period = 1;
-	attr.wakeup_events = 1;
-	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
-			 0 /* cpu 0 */, -1 /* group id */,
-			 0 /* flags */);
-	if (CHECK(pmu_fd < 0, "perf_event_open", "err %d errno %d\n",
-		  pmu_fd, errno))
+	efd = bpf_program__attach_tracepoint(prog, "sched", "sched_switch");
+	if (CHECK(efd < 0, "attach_tp", "err %d\n", efd))
 		goto close_prog;
 
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
-	if (err)
-		goto disable_pmu;
-
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
-	if (err)
-		goto disable_pmu;
-
 	/* find map fds */
 	control_map_fd = bpf_find_map(__func__, obj, "control_map");
 	if (control_map_fd < 0)
@@ -96,8 +71,7 @@ void test_stacktrace_map(void)
 disable_pmu:
 	error_cnt++;
 disable_pmu_noerr:
-	ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
-	close(pmu_fd);
+	close(efd);
 close_prog:
 	bpf_object__close(obj);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_map_raw_tp.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_map_raw_tp.c
index 1f8387d80fd7..4d14a08b1d99 100644
--- a/tools/testing/selftests/bpf/prog_tests/stacktrace_map_raw_tp.c
+++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_map_raw_tp.c
@@ -3,18 +3,24 @@
 
 void test_stacktrace_map_raw_tp(void)
 {
+	const char *prog_name = "tracepoint/sched/sched_switch";
 	int control_map_fd, stackid_hmap_fd, stackmap_fd;
 	const char *file = "./test_stacktrace_map.o";
-	int efd, err, prog_fd;
 	__u32 key, val, duration = 0;
+	int efd = -1, err, prog_fd;
+	struct bpf_program *prog;
 	struct bpf_object *obj;
 
 	err = bpf_prog_load(file, BPF_PROG_TYPE_RAW_TRACEPOINT, &obj, &prog_fd);
 	if (CHECK(err, "prog_load raw tp", "err %d errno %d\n", err, errno))
 		return;
 
-	efd = bpf_raw_tracepoint_open("sched_switch", prog_fd);
-	if (CHECK(efd < 0, "raw_tp_open", "err %d errno %d\n", efd, errno))
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
+		goto close_prog;
+
+	efd = bpf_program__attach_raw_tracepoint(prog, "sched_switch");
+	if (CHECK(efd < 0, "attach_raw_tp", "err %d\n", efd))
 		goto close_prog;
 
 	/* find map fds */
@@ -55,5 +61,7 @@ void test_stacktrace_map_raw_tp(void)
 close_prog:
 	error_cnt++;
 close_prog_noerr:
+	if (efd >= 0)
+		close(efd);
 	bpf_object__close(obj);
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/task_fd_query_rawtp.c b/tools/testing/selftests/bpf/prog_tests/task_fd_query_rawtp.c
index 958a3d88de99..6ad73cb8c7e3 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_fd_query_rawtp.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_fd_query_rawtp.c
@@ -3,9 +3,11 @@
 
 void test_task_fd_query_rawtp(void)
 {
+	const char *prog_name = "tracepoint/raw_syscalls/sys_enter";
 	const char *file = "./test_get_stack_rawtp.o";
 	__u64 probe_offset, probe_addr;
 	__u32 len, prog_id, fd_type;
+	struct bpf_program *prog;
 	struct bpf_object *obj;
 	int efd, err, prog_fd;
 	__u32 duration = 0;
@@ -15,8 +17,12 @@ void test_task_fd_query_rawtp(void)
 	if (CHECK(err, "prog_load raw tp", "err %d errno %d\n", err, errno))
 		return;
 
-	efd = bpf_raw_tracepoint_open("sys_enter", prog_fd);
-	if (CHECK(efd < 0, "raw_tp_open", "err %d errno %d\n", efd, errno))
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
+		goto close_prog;
+
+	efd = bpf_program__attach_raw_tracepoint(prog, "sys_enter");
+	if (CHECK(efd < 0, "attach_raw_tp", "err %d\n", efd))
 		goto close_prog;
 
 	/* query (getpid(), efd) */
diff --git a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
index f9b70e81682b..034870692636 100644
--- a/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_fd_query_tp.c
@@ -1,15 +1,16 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 
-static void test_task_fd_query_tp_core(const char *probe_name,
+static void test_task_fd_query_tp_core(const char *tp_category,
 				       const char *tp_name)
 {
+	const char *prog_name = "tracepoint/sched/sched_switch";
 	const char *file = "./test_tracepoint.o";
-	int err, bytes, efd, prog_fd, pmu_fd;
-	struct perf_event_attr attr = {};
 	__u64 probe_offset, probe_addr;
 	__u32 len, prog_id, fd_type;
+	int err, prog_fd, pmu_fd;
 	struct bpf_object *obj = NULL;
+	struct bpf_program *prog;
 	__u32 duration = 0;
 	char buf[256];
 
@@ -17,37 +18,13 @@ static void test_task_fd_query_tp_core(const char *probe_name,
 	if (CHECK(err, "bpf_prog_load", "err %d errno %d\n", err, errno))
 		goto close_prog;
 
-	snprintf(buf, sizeof(buf),
-		 "/sys/kernel/debug/tracing/events/%s/id", probe_name);
-	efd = open(buf, O_RDONLY, 0);
-	if (CHECK(efd < 0, "open", "err %d errno %d\n", efd, errno))
+	prog = bpf_object__find_program_by_title(obj, prog_name);
+	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
 		goto close_prog;
-	bytes = read(efd, buf, sizeof(buf));
-	close(efd);
-	if (CHECK(bytes <= 0 || bytes >= sizeof(buf), "read",
-		  "bytes %d errno %d\n", bytes, errno))
-		goto close_prog;
-
-	attr.config = strtol(buf, NULL, 0);
-	attr.type = PERF_TYPE_TRACEPOINT;
-	attr.sample_type = PERF_SAMPLE_RAW;
-	attr.sample_period = 1;
-	attr.wakeup_events = 1;
-	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
-			 0 /* cpu 0 */, -1 /* group id */,
-			 0 /* flags */);
-	if (CHECK(err, "perf_event_open", "err %d errno %d\n", err, errno))
-		goto close_pmu;
 
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
-	if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n", err,
-		  errno))
-		goto close_pmu;
-
-	err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
-	if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n", err,
-		  errno))
-		goto close_pmu;
+	pmu_fd = bpf_program__attach_tracepoint(prog, tp_category, tp_name);
+	if (CHECK(pmu_fd < 0, "attach_tp", "err %d\n", pmu_fd))
+		goto close_prog;
 
 	/* query (getpid(), pmu_fd) */
 	len = sizeof(buf);
@@ -62,11 +39,11 @@ static void test_task_fd_query_tp_core(const char *probe_name,
 		  fd_type, buf))
 		goto close_pmu;
 
-	close(pmu_fd);
+	libbpf_perf_event_disable_and_close(pmu_fd);
 	goto close_prog_noerr;
 
 close_pmu:
-	close(pmu_fd);
+	libbpf_perf_event_disable_and_close(pmu_fd);
 close_prog:
 	error_cnt++;
 close_prog_noerr:
@@ -75,8 +52,6 @@ static void test_task_fd_query_tp_core(const char *probe_name,
 
 void test_task_fd_query_tp(void)
 {
-	test_task_fd_query_tp_core("sched/sched_switch",
-				   "sched_switch");
-	test_task_fd_query_tp_core("syscalls/sys_enter_read",
-				   "sys_enter_read");
+	test_task_fd_query_tp_core("sched", "sched_switch");
+	test_task_fd_query_tp_core("syscalls", "sys_enter_read");
 }
diff --git a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
index fb095e5cd9af..5e129eb3eb47 100644
--- a/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
+++ b/tools/testing/selftests/bpf/prog_tests/tp_attach_query.c
@@ -6,9 +6,9 @@ void test_tp_attach_query(void)
 	const int num_progs = 3;
 	int i, j, bytes, efd, err, prog_fd[num_progs], pmu_fd[num_progs];
 	__u32 duration = 0, info_len, saved_prog_ids[num_progs];
+	const char *prog_name = "tracepoint/sched/sched_switch";
 	const char *file = "./test_tracepoint.o";
 	struct perf_event_query_bpf *query;
-	struct perf_event_attr attr = {};
 	struct bpf_object *obj[num_progs];
 	struct bpf_prog_info prog_info;
 	char buf[256];
@@ -27,19 +27,19 @@ void test_tp_attach_query(void)
 		  "read", "bytes %d errno %d\n", bytes, errno))
 		return;
 
-	attr.config = strtol(buf, NULL, 0);
-	attr.type = PERF_TYPE_TRACEPOINT;
-	attr.sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN;
-	attr.sample_period = 1;
-	attr.wakeup_events = 1;
-
 	query = malloc(sizeof(*query) + sizeof(__u32) * num_progs);
 	for (i = 0; i < num_progs; i++) {
+		struct bpf_program *prog;
+
 		err = bpf_prog_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj[i],
 				    &prog_fd[i]);
 		if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
 			goto cleanup1;
 
+		prog = bpf_object__find_program_by_title(obj[i], prog_name);
+		if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
+			goto cleanup1;
+
 		bzero(&prog_info, sizeof(prog_info));
 		prog_info.jited_prog_len = 0;
 		prog_info.xlated_prog_len = 0;
@@ -51,32 +51,10 @@ void test_tp_attach_query(void)
 			goto cleanup1;
 		saved_prog_ids[i] = prog_info.id;
 
-		pmu_fd[i] = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
-				    0 /* cpu 0 */, -1 /* group id */,
-				    0 /* flags */);
-		if (CHECK(pmu_fd[i] < 0, "perf_event_open", "err %d errno %d\n",
-			  pmu_fd[i], errno))
+		pmu_fd[i] = bpf_program__attach_tracepoint(prog, "sched",
+							   "sched_switch");
+		if (CHECK(pmu_fd[i] < 0, "attach_tp", "err %d\n", pmu_fd[i]))
 			goto cleanup2;
-		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE, 0);
-		if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
-			  err, errno))
-			goto cleanup3;
-
-		if (i == 0) {
-			/* check NULL prog array query */
-			query->ids_len = num_progs;
-			err = ioctl(pmu_fd[i], PERF_EVENT_IOC_QUERY_BPF, query);
-			if (CHECK(err || query->prog_cnt != 0,
-				  "perf_event_ioc_query_bpf",
-				  "err %d errno %d query->prog_cnt %u\n",
-				  err, errno, query->prog_cnt))
-				goto cleanup3;
-		}
-
-		err = ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[i]);
-		if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
-			  err, errno))
-			goto cleanup3;
 
 		if (i == 1) {
 			/* try to get # of programs only */
@@ -86,7 +64,7 @@ void test_tp_attach_query(void)
 				  "perf_event_ioc_query_bpf",
 				  "err %d errno %d query->prog_cnt %u\n",
 				  err, errno, query->prog_cnt))
-				goto cleanup3;
+				goto cleanup2;
 
 			/* try a few negative tests */
 			/* invalid query pointer */
@@ -95,7 +73,7 @@ void test_tp_attach_query(void)
 			if (CHECK(!err || errno != EFAULT,
 				  "perf_event_ioc_query_bpf",
 				  "err %d errno %d\n", err, errno))
-				goto cleanup3;
+				goto cleanup2;
 
 			/* no enough space */
 			query->ids_len = 1;
@@ -104,7 +82,7 @@ void test_tp_attach_query(void)
 				  "perf_event_ioc_query_bpf",
 				  "err %d errno %d query->prog_cnt %u\n",
 				  err, errno, query->prog_cnt))
-				goto cleanup3;
+				goto cleanup2;
 		}
 
 		query->ids_len = num_progs;
@@ -113,21 +91,19 @@ void test_tp_attach_query(void)
 			  "perf_event_ioc_query_bpf",
 			  "err %d errno %d query->prog_cnt %u\n",
 			  err, errno, query->prog_cnt))
-			goto cleanup3;
+			goto cleanup2;
 		for (j = 0; j < i + 1; j++)
 			if (CHECK(saved_prog_ids[j] != query->ids[j],
 				  "perf_event_ioc_query_bpf",
 				  "#%d saved_prog_id %x query prog_id %x\n",
 				  j, saved_prog_ids[j], query->ids[j]))
-				goto cleanup3;
+				goto cleanup2;
 	}
 
 	i = num_progs - 1;
 	for (; i >= 0; i--) {
- cleanup3:
-		ioctl(pmu_fd[i], PERF_EVENT_IOC_DISABLE);
  cleanup2:
-		close(pmu_fd[i]);
+		libbpf_perf_event_disable_and_close(pmu_fd[i]);
  cleanup1:
 		bpf_object__close(obj[i]);
 	}
-- 
2.17.1

Re: [PATCH bpf-next 2/7] libbpf: add ability to attach/detach BPF to perf event

[Stanislav Fomichev]

On 06/20, Andrii Nakryiko wrote:
> bpf_program__attach_perf_event allows to attach BPF program to existing
> perf event, providing most generic and most low-level way to attach BPF
> programs.
> 
> libbpf_perf_event_disable_and_close API is added to disable and close
> existing perf event by its FD.
> 
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>  tools/lib/bpf/libbpf.c   | 41 ++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   |  4 ++++
>  tools/lib/bpf/libbpf.map |  2 ++
>  3 files changed, 47 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 8ce3beba8551..2bb1fa008be3 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -32,6 +32,7 @@
>  #include <linux/limits.h>
>  #include <linux/perf_event.h>
>  #include <linux/ring_buffer.h>
> +#include <sys/ioctl.h>
>  #include <sys/stat.h>
>  #include <sys/types.h>
>  #include <sys/vfs.h>
> @@ -3928,6 +3929,46 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
>  	return 0;
>  }
>  
[..]
> +int libbpf_perf_event_disable_and_close(int pfd)
nit: why not call it libbpf_perf_event_detach[_and_close]?
It's usually attach/detach.

> +{
> +	int err;
> +
> +	if (pfd < 0)
> +		return 0;
> +
> +	err = ioctl(pfd, PERF_EVENT_IOC_DISABLE, 0);
> +	close(pfd);
> +	return err;
> +}
> +
> +int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
> +{
> +	char errmsg[STRERR_BUFSIZE];
> +	int bpf_fd, err;
> +
> +	bpf_fd = bpf_program__fd(prog);
> +	if (bpf_fd < 0) {
> +		pr_warning("program '%s': can't attach before loaded\n",
> +			   bpf_program__title(prog, false));
> +		return -EINVAL;
> +	}
> +	if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, bpf_fd) < 0) {
> +		err = -errno;
> +		pr_warning("program '%s': failed to attach to pfd %d: %s\n",
> +			   bpf_program__title(prog, false), pfd,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
> +		err = -errno;
> +		pr_warning("program '%s': failed to enable pfd %d: %s\n",
> +			   bpf_program__title(prog, false), pfd,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return 0;
> +}
> +
>  enum bpf_perf_event_ret
>  bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
>  			   void **copy_mem, size_t *copy_size,
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index d639f47e3110..76db1bbc0dac 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -165,6 +165,10 @@ LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
>  LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
>  LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
>  
> +LIBBPF_API int libbpf_perf_event_disable_and_close(int pfd);
> +LIBBPF_API int bpf_program__attach_perf_event(struct bpf_program *prog,
> +					      int pfd);
> +
>  struct bpf_insn;
>  
>  /*
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 2c6d835620d2..d27406982b5a 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -172,5 +172,7 @@ LIBBPF_0.0.4 {
>  		btf_dump__new;
>  		btf__parse_elf;
>  		bpf_object__load_xattr;
> +		bpf_program__attach_perf_event;
>  		libbpf_num_possible_cpus;
> +		libbpf_perf_event_disable_and_close;
>  } LIBBPF_0.0.3;
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next 3/7] libbpf: add kprobe/uprobe attach API

[Stanislav Fomichev]

On 06/20, Andrii Nakryiko wrote:
> Add ability to attach to kernel and user probes and retprobes.
> Implementation depends on perf event support for kprobes/uprobes.
> 
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>  tools/lib/bpf/libbpf.c   | 207 +++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   |   8 ++
>  tools/lib/bpf/libbpf.map |   2 +
>  3 files changed, 217 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 2bb1fa008be3..11329e05530e 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -3969,6 +3969,213 @@ int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
>  	return 0;
>  }
>  
> +static int parse_uint(const char *buf)
> +{
> +	int ret;
> +
> +	errno = 0;
> +	ret = (int)strtol(buf, NULL, 10);
> +	if (errno) {
> +		ret = -errno;
> +		pr_debug("failed to parse '%s' as unsigned int\n", buf);
> +		return ret;
> +	}
> +	if (ret < 0) {
> +		pr_debug("failed to parse '%s' as unsigned int\n", buf);
> +		return -EINVAL;
> +	}
> +	return ret;
> +}
> +
> +static int parse_uint_from_file(const char* file)
> +{
> +	char buf[STRERR_BUFSIZE];
> +	int fd, ret;
> +
> +	fd = open(file, O_RDONLY);
> +	if (fd < 0) {
> +		ret = -errno;
> +		pr_debug("failed to open '%s': %s\n", file,
> +			 libbpf_strerror_r(ret, buf, sizeof(buf)));
> +		return ret;
> +	}
> +	ret = read(fd, buf, sizeof(buf));
> +	close(fd);
> +	if (ret < 0) {
> +		ret = -errno;
Is -errno still valid here after a close(fd) above? Do we have any
guarantee of errno preservation when we do another syscall?

> +		pr_debug("failed to read '%s': %s\n", file,
> +			libbpf_strerror_r(ret, buf, sizeof(buf)));
> +		return ret;
> +	}
> +	if (ret == 0 || ret >= sizeof(buf)) {
> +		buf[sizeof(buf) - 1] = 0;
> +		pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> +		return -EINVAL;
> +	}
> +	return parse_uint(buf);
> +}
> +
> +static int determine_kprobe_perf_type(void)
> +{
> +	const char *file = "/sys/bus/event_source/devices/kprobe/type";
> +	return parse_uint_from_file(file);
> +}
> +
> +static int determine_uprobe_perf_type(void)
> +{
> +	const char *file = "/sys/bus/event_source/devices/uprobe/type";
> +	return parse_uint_from_file(file);
> +}
> +
> +static int parse_config_from_file(const char *file)
> +{
> +	char buf[STRERR_BUFSIZE];
> +	int fd, ret;
> +
> +	fd = open(file, O_RDONLY);
> +	if (fd < 0) {
> +		ret = -errno;
> +		pr_debug("failed to open '%s': %s\n", file,
> +			 libbpf_strerror_r(ret, buf, sizeof(buf)));
> +		return ret;
> +	}
> +	ret = read(fd, buf, sizeof(buf));
> +	close(fd);
> +	if (ret < 0) {
> +		ret = -errno;
> +		pr_debug("failed to read '%s': %s\n", file,
> +			libbpf_strerror_r(ret, buf, sizeof(buf)));
> +		return ret;
> +	}
> +	if (ret == 0 || ret >= sizeof(buf)) {
> +		buf[sizeof(buf) - 1] = 0;
> +		pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> +		return -EINVAL;
> +	}
> +	if (strncmp(buf, "config:", 7)) {
> +		pr_debug("expected 'config:' prefix, found '%s'\n", buf);
> +		return -EINVAL;
> +	}
> +	return parse_uint(buf + 7);
> +}
> +
> +static int determine_kprobe_retprobe_bit(void)
> +{
> +	const char *file = "/sys/bus/event_source/devices/kprobe/format/retprobe";
> +	return parse_config_from_file(file);
> +}
> +
> +static int determine_uprobe_retprobe_bit(void)
> +{
> +	const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
> +	return parse_config_from_file(file);
> +}
> +
> +static int perf_event_open_probe(bool uprobe, bool retprobe, const char* name,
> +				 uint64_t offset, int pid)
> +{
> +	struct perf_event_attr attr = {};
> +	char errmsg[STRERR_BUFSIZE];
> +	int type, pfd, err;
> +
> +	type = uprobe ? determine_uprobe_perf_type()
> +		      : determine_kprobe_perf_type();
> +	if (type < 0) {
> +		pr_warning("failed to determine %s perf type: %s\n",
> +			   uprobe ? "uprobe" : "kprobe",
> +			   libbpf_strerror_r(type, errmsg, sizeof(errmsg)));
> +		return type;
> +	}
> +	if (retprobe) {
> +		int bit = uprobe ? determine_uprobe_retprobe_bit()
> +				 : determine_kprobe_retprobe_bit();
> +
> +		if (bit < 0) {
> +			pr_warning("failed to determine %s retprobe bit: %s\n",
> +				   uprobe ? "uprobe" : "kprobe",
> +				   libbpf_strerror_r(bit, errmsg,
> +						     sizeof(errmsg)));
> +			return bit;
> +		}
> +		attr.config |= 1 << bit;
> +	}
> +	attr.size = sizeof(attr);
> +	attr.type = type;
> +	attr.config1 = (uint64_t)(void *)name; /* kprobe_func or uprobe_path */
> +	attr.config2 = offset;		       /* kprobe_addr or probe_offset */
> +
> +	/* pid filter is meaningful only for uprobes */
> +	pfd = syscall(__NR_perf_event_open, &attr,
> +		      pid < 0 ? -1 : pid /* pid */,
> +		      pid == -1 ? 0 : -1 /* cpu */,
> +		      -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> +	if (pfd < 0) {
> +		err = -errno;
> +		pr_warning("%s perf_event_open() failed: %s\n",
> +			   uprobe ? "uprobe" : "kprobe",
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return pfd;
> +}
> +
> +int bpf_program__attach_kprobe(struct bpf_program *prog, bool retprobe,
> +			       const char *func_name)
> +{
> +	char errmsg[STRERR_BUFSIZE];
> +	int pfd, err;
> +
> +	pfd = perf_event_open_probe(false /* uprobe */, retprobe, func_name,
> +				    0 /* offset */, -1 /* pid */);
> +	if (pfd < 0) {
> +		pr_warning("program '%s': failed to create %s '%s' perf event: %s\n",
> +			   bpf_program__title(prog, false),
> +			   retprobe ? "kretprobe" : "kprobe", func_name,
> +			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> +		return pfd;
> +	}
> +	err = bpf_program__attach_perf_event(prog, pfd);
> +	if (err) {
> +		libbpf_perf_event_disable_and_close(pfd);
> +		pr_warning("program '%s': failed to attach to %s '%s': %s\n",
> +			   bpf_program__title(prog, false),
> +			   retprobe ? "kretprobe" : "kprobe", func_name,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return pfd;
> +}
> +
> +int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
> +			       pid_t pid, const char *binary_path,
> +			       size_t func_offset)
> +{
> +	char errmsg[STRERR_BUFSIZE];
> +	int pfd, err;
> +
> +	pfd = perf_event_open_probe(true /* uprobe */, retprobe,
> +				    binary_path, func_offset, pid);
> +	if (pfd < 0) {
> +		pr_warning("program '%s': failed to create %s '%s:0x%zx' perf event: %s\n",
> +			   bpf_program__title(prog, false),
> +			   retprobe ? "uretprobe" : "uprobe",
> +			   binary_path, func_offset,
> +			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> +		return pfd;
> +	}
> +	err = bpf_program__attach_perf_event(prog, pfd);
> +	if (err) {
> +		libbpf_perf_event_disable_and_close(pfd);
> +		pr_warning("program '%s': failed to attach to %s '%s:0x%zx': %s\n",
> +			   bpf_program__title(prog, false),
> +			   retprobe ? "uretprobe" : "uprobe",
> +			   binary_path, func_offset,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return pfd;
> +}
> +
>  enum bpf_perf_event_ret
>  bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
>  			   void **copy_mem, size_t *copy_size,
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 76db1bbc0dac..a7264f06aa5f 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -168,6 +168,14 @@ LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
>  LIBBPF_API int libbpf_perf_event_disable_and_close(int pfd);
>  LIBBPF_API int bpf_program__attach_perf_event(struct bpf_program *prog,
>  					      int pfd);
> +LIBBPF_API int bpf_program__attach_kprobe(struct bpf_program *prog,
> +					  bool retprobe,
> +					  const char *func_name);
> +LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog,
> +					  bool retprobe,
> +					  pid_t pid,
> +					  const char *binary_path,
> +					  size_t func_offset);
>  
>  struct bpf_insn;
>  
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index d27406982b5a..1a982c2e1751 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -172,7 +172,9 @@ LIBBPF_0.0.4 {
>  		btf_dump__new;
>  		btf__parse_elf;
>  		bpf_object__load_xattr;
> +		bpf_program__attach_kprobe;
>  		bpf_program__attach_perf_event;
> +		bpf_program__attach_uprobe;
>  		libbpf_num_possible_cpus;
>  		libbpf_perf_event_disable_and_close;
>  } LIBBPF_0.0.3;
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next 4/7] libbpf: add tracepoint/raw tracepoint attach API

[Stanislav Fomichev]

On 06/20, Andrii Nakryiko wrote:
> Add APIs allowing to attach BPF program to kernel tracepoints. Raw
> tracepoint attach API is also added for uniform per-BPF-program API,
> but is mostly a wrapper around existing bpf_raw_tracepoint_open call.
> 
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>  tools/lib/bpf/libbpf.c   | 99 ++++++++++++++++++++++++++++++++++++++++
>  tools/lib/bpf/libbpf.h   |  5 ++
>  tools/lib/bpf/libbpf.map |  2 +
>  3 files changed, 106 insertions(+)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 11329e05530e..cefe67ba160b 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
>  	return pfd;
>  }
>  
> +static int determine_tracepoint_id(const char* tp_category, const char* tp_name)
> +{
> +	char file[PATH_MAX];
> +	int ret;
> +
> +	ret = snprintf(file, sizeof(file),
> +		       "/sys/kernel/debug/tracing/events/%s/%s/id",
> +		       tp_category, tp_name);
> +	if (ret < 0)
> +		return -errno;
> +	if (ret >= sizeof(file)) {
> +		pr_debug("tracepoint %s/%s path is too long\n",
> +			 tp_category, tp_name);
> +		return -E2BIG;
> +	}
> +	return parse_uint_from_file(file);
> +}
> +
> +static int perf_event_open_tracepoint(const char* tp_category,
> +				      const char* tp_name)
> +{
> +	struct perf_event_attr attr = {};
> +	char errmsg[STRERR_BUFSIZE];
> +	int tp_id, pfd, err;
> +
[..]
> +	tp_id = determine_tracepoint_id(tp_category, tp_name);
Why no assign to attr.config directly here?
You can move all other constants to the initialization as well:

struct perf_event_attr attr = {
	.type = PERF_TYPE_TRACEPON,
	.size = sizeof(struct perf_event_attr),
};

attr.config = determine_tracepoint_id(...);

(I guess that's a matter of style, but something to consider).

> +	if (tp_id < 0){
> +		pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n",
> +			   tp_category, tp_name,
> +			   libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
> +		return tp_id;
> +	}
> +
[..]
> +	memset(&attr, 0, sizeof(attr));
Not needed since you do attr = {}; above?

> +	attr.type = PERF_TYPE_TRACEPOINT;
> +	attr.size = sizeof(attr);
> +	attr.config = tp_id;
> +
> +	pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
> +			-1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> +	if (pfd < 0) {
> +		err = -errno;
> +		pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",
> +			   tp_category, tp_name,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return pfd;
> +}
> +
> +int bpf_program__attach_tracepoint(struct bpf_program *prog,
> +				   const char *tp_category,
> +				   const char *tp_name)
> +{
> +	char errmsg[STRERR_BUFSIZE];
> +	int pfd, err;
> +
> +	pfd = perf_event_open_tracepoint(tp_category, tp_name);
> +	if (pfd < 0) {
> +		pr_warning("program '%s': failed to create tracepoint '%s/%s' perf event: %s\n",
> +			   bpf_program__title(prog, false),
> +			   tp_category, tp_name,
> +			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> +		return pfd;
> +	}
> +	err = bpf_program__attach_perf_event(prog, pfd);
> +	if (err) {
> +		libbpf_perf_event_disable_and_close(pfd);
> +		pr_warning("program '%s': failed to attach to tracepoint '%s/%s': %s\n",
> +			   bpf_program__title(prog, false),
> +			   tp_category, tp_name,
> +			   libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> +		return err;
> +	}
> +	return pfd;
> +}
> +
> +int bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
> +				       const char *tp_name)
> +{
> +	char errmsg[STRERR_BUFSIZE];
> +	int bpf_fd, pfd;
> +
> +	bpf_fd = bpf_program__fd(prog);
> +	if (bpf_fd < 0) {
> +		pr_warning("program '%s': can't attach before loaded\n",
> +			   bpf_program__title(prog, false));
> +		return -EINVAL;
> +	}
> +	pfd = bpf_raw_tracepoint_open(tp_name, bpf_fd);
> +	if (pfd < 0) {
> +		pr_warning("program '%s': failed to attach to raw tracepoint '%s': %s\n",
> +			   bpf_program__title(prog, false), tp_name,
> +			   libbpf_strerror_r(pfd, errmsg, sizeof(errmsg)));
> +		return pfd;
> +	}
> +	return pfd;
> +}
> +
>  enum bpf_perf_event_ret
>  bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
>  			   void **copy_mem, size_t *copy_size,
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index a7264f06aa5f..bf7020a565c6 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -176,6 +176,11 @@ LIBBPF_API int bpf_program__attach_uprobe(struct bpf_program *prog,
>  					  pid_t pid,
>  					  const char *binary_path,
>  					  size_t func_offset);
> +LIBBPF_API int bpf_program__attach_tracepoint(struct bpf_program *prog,
> +					      const char *tp_category,
> +					      const char *tp_name);
> +LIBBPF_API int bpf_program__attach_raw_tracepoint(struct bpf_program *prog,
> +						  const char *tp_name);
>  
>  struct bpf_insn;
>  
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 1a982c2e1751..2382fbda4cbb 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -174,6 +174,8 @@ LIBBPF_0.0.4 {
>  		bpf_object__load_xattr;
>  		bpf_program__attach_kprobe;
>  		bpf_program__attach_perf_event;
> +		bpf_program__attach_raw_tracepoint;
> +		bpf_program__attach_tracepoint;
>  		bpf_program__attach_uprobe;
>  		libbpf_num_possible_cpus;
>  		libbpf_perf_event_disable_and_close;
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next 5/7] selftests/bpf: switch test to new attach_perf_event API

[Stanislav Fomichev]

On 06/20, Andrii Nakryiko wrote:
> Use new bpf_program__attach_perf_event() in test previously relying on
> direct ioctl manipulations.
Maybe use new detach/disable routine at the end of the
test_stacktrace_build_id_nmi as well?

> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>  .../bpf/prog_tests/stacktrace_build_id_nmi.c     | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> index 1c1a2f75f3d8..1bbdb0b82ac5 100644
> --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c
> @@ -17,6 +17,7 @@ static __u64 read_perf_max_sample_freq(void)
>  void test_stacktrace_build_id_nmi(void)
>  {
>  	int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
> +	const char *prog_name = "tracepoint/random/urandom_read";
>  	const char *file = "./test_stacktrace_build_id.o";
>  	int err, pmu_fd, prog_fd;
>  	struct perf_event_attr attr = {
> @@ -25,6 +26,7 @@ void test_stacktrace_build_id_nmi(void)
>  		.config = PERF_COUNT_HW_CPU_CYCLES,
>  	};
>  	__u32 key, previous_key, val, duration = 0;
> +	struct bpf_program *prog;
>  	struct bpf_object *obj;
>  	char buf[256];
>  	int i, j;
> @@ -39,6 +41,10 @@ void test_stacktrace_build_id_nmi(void)
>  	if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
>  		return;
>  
> +	prog = bpf_object__find_program_by_title(obj, prog_name);
> +	if (CHECK(!prog, "find_prog", "prog '%s' not found\n", prog_name))
> +		goto close_prog;
> +
>  	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
>  			 0 /* cpu 0 */, -1 /* group id */,
>  			 0 /* flags */);
> @@ -47,16 +53,10 @@ void test_stacktrace_build_id_nmi(void)
>  		  pmu_fd, errno))
>  		goto close_prog;
>  
> -	err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0);
> -	if (CHECK(err, "perf_event_ioc_enable", "err %d errno %d\n",
> -		  err, errno))
> +	err = bpf_program__attach_perf_event(prog, pmu_fd);
> +	if (CHECK(err, "attach_perf_event", "err %d\n", err))
>  		goto close_pmu;
>  
> -	err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd);
> -	if (CHECK(err, "perf_event_ioc_set_bpf", "err %d errno %d\n",
> -		  err, errno))
> -		goto disable_pmu;
> -
>  	/* find map fds */
>  	control_map_fd = bpf_find_map(__func__, obj, "control_map");
>  	if (CHECK(control_map_fd < 0, "bpf_find_map control_map",
> -- 
> 2.17.1
> 

Re: [PATCH bpf-next 2/7] libbpf: add ability to attach/detach BPF to perf event

[Andrii Nakryiko]

On Thu, Jun 20, 2019 at 5:01 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
>
> On 06/20, Andrii Nakryiko wrote:
> > bpf_program__attach_perf_event allows to attach BPF program to existing
> > perf event, providing most generic and most low-level way to attach BPF
> > programs.
> >
> > libbpf_perf_event_disable_and_close API is added to disable and close
> > existing perf event by its FD.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> >  tools/lib/bpf/libbpf.c   | 41 ++++++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/libbpf.h   |  4 ++++
> >  tools/lib/bpf/libbpf.map |  2 ++
> >  3 files changed, 47 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 8ce3beba8551..2bb1fa008be3 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -32,6 +32,7 @@
> >  #include <linux/limits.h>
> >  #include <linux/perf_event.h>
> >  #include <linux/ring_buffer.h>
> > +#include <sys/ioctl.h>
> >  #include <sys/stat.h>
> >  #include <sys/types.h>
> >  #include <sys/vfs.h>
> > @@ -3928,6 +3929,46 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
> >       return 0;
> >  }
> >
> [..]
> > +int libbpf_perf_event_disable_and_close(int pfd)
> nit: why not call it libbpf_perf_event_detach[_and_close]?
> It's usually attach/detach.

I think detach is actually confusing for perf event. Here's what you
do for tracing:

1. open perf event
2. enable perf event
3. attach BPF program to perf event
...
4. <is there a way to detach BPF program?>
5. disable perf event
6. close perf event

So open/close event, enable/disable event, attach / (auto-detach on
close right now) BPF program.

It seems like there should be explicit "detach this BPF program from
perf event without killing event itself", but I haven't found it.

But my point is that for event open/close and enable/disable seems
very complementary.


>
> > +{
> > +     int err;
> > +
> > +     if (pfd < 0)
> > +             return 0;
> > +
> > +     err = ioctl(pfd, PERF_EVENT_IOC_DISABLE, 0);
> > +     close(pfd);
> > +     return err;
> > +}
> > +
> > +int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
> > +{
> > +     char errmsg[STRERR_BUFSIZE];
> > +     int bpf_fd, err;
> > +
> > +     bpf_fd = bpf_program__fd(prog);
> > +     if (bpf_fd < 0) {
> > +             pr_warning("program '%s': can't attach before loaded\n",
> > +                        bpf_program__title(prog, false));
> > +             return -EINVAL;
> > +     }
> > +     if (ioctl(pfd, PERF_EVENT_IOC_SET_BPF, bpf_fd) < 0) {
> > +             err = -errno;
> > +             pr_warning("program '%s': failed to attach to pfd %d: %s\n",
> > +                        bpf_program__title(prog, false), pfd,
> > +                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> > +             return err;
> > +     }
> > +     if (ioctl(pfd, PERF_EVENT_IOC_ENABLE, 0) < 0) {
> > +             err = -errno;
> > +             pr_warning("program '%s': failed to enable pfd %d: %s\n",
> > +                        bpf_program__title(prog, false), pfd,
> > +                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> > +             return err;
> > +     }
> > +     return 0;
> > +}
> > +
> >  enum bpf_perf_event_ret
> >  bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size,
> >                          void **copy_mem, size_t *copy_size,
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index d639f47e3110..76db1bbc0dac 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -165,6 +165,10 @@ LIBBPF_API int bpf_program__pin(struct bpf_program *prog, const char *path);
> >  LIBBPF_API int bpf_program__unpin(struct bpf_program *prog, const char *path);
> >  LIBBPF_API void bpf_program__unload(struct bpf_program *prog);
> >
> > +LIBBPF_API int libbpf_perf_event_disable_and_close(int pfd);
> > +LIBBPF_API int bpf_program__attach_perf_event(struct bpf_program *prog,
> > +                                           int pfd);
> > +
> >  struct bpf_insn;
> >
> >  /*
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index 2c6d835620d2..d27406982b5a 100644
> > --- a/tools/lib/bpf/libbpf.map
> > +++ b/tools/lib/bpf/libbpf.map
> > @@ -172,5 +172,7 @@ LIBBPF_0.0.4 {
> >               btf_dump__new;
> >               btf__parse_elf;
> >               bpf_object__load_xattr;
> > +             bpf_program__attach_perf_event;
> >               libbpf_num_possible_cpus;
> > +             libbpf_perf_event_disable_and_close;
> >  } LIBBPF_0.0.3;
> > --
> > 2.17.1
> >

Re: [PATCH bpf-next 3/7] libbpf: add kprobe/uprobe attach API

[Andrii Nakryiko]

On Thu, Jun 20, 2019 at 5:04 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
>
> On 06/20, Andrii Nakryiko wrote:
> > Add ability to attach to kernel and user probes and retprobes.
> > Implementation depends on perf event support for kprobes/uprobes.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> >  tools/lib/bpf/libbpf.c   | 207 +++++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/libbpf.h   |   8 ++
> >  tools/lib/bpf/libbpf.map |   2 +
> >  3 files changed, 217 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 2bb1fa008be3..11329e05530e 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3969,6 +3969,213 @@ int bpf_program__attach_perf_event(struct bpf_program *prog, int pfd)
> >       return 0;
> >  }
> >
> > +static int parse_uint(const char *buf)
> > +{
> > +     int ret;
> > +
> > +     errno = 0;
> > +     ret = (int)strtol(buf, NULL, 10);
> > +     if (errno) {
> > +             ret = -errno;
> > +             pr_debug("failed to parse '%s' as unsigned int\n", buf);
> > +             return ret;
> > +     }
> > +     if (ret < 0) {
> > +             pr_debug("failed to parse '%s' as unsigned int\n", buf);
> > +             return -EINVAL;
> > +     }
> > +     return ret;
> > +}
> > +
> > +static int parse_uint_from_file(const char* file)
> > +{
> > +     char buf[STRERR_BUFSIZE];
> > +     int fd, ret;
> > +
> > +     fd = open(file, O_RDONLY);
> > +     if (fd < 0) {
> > +             ret = -errno;
> > +             pr_debug("failed to open '%s': %s\n", file,
> > +                      libbpf_strerror_r(ret, buf, sizeof(buf)));
> > +             return ret;
> > +     }
> > +     ret = read(fd, buf, sizeof(buf));
> > +     close(fd);
> > +     if (ret < 0) {
> > +             ret = -errno;
> Is -errno still valid here after a close(fd) above? Do we have any
> guarantee of errno preservation when we do another syscall?

Good catch! No, close() can change errno. Fixed. Also fixed for
parse_config_from_file below.

>
> > +             pr_debug("failed to read '%s': %s\n", file,
> > +                     libbpf_strerror_r(ret, buf, sizeof(buf)));
> > +             return ret;
> > +     }
> > +     if (ret == 0 || ret >= sizeof(buf)) {
> > +             buf[sizeof(buf) - 1] = 0;
> > +             pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> > +             return -EINVAL;
> > +     }
> > +     return parse_uint(buf);
> > +}
> > +
> > +static int determine_kprobe_perf_type(void)
> > +{
> > +     const char *file = "/sys/bus/event_source/devices/kprobe/type";
> > +     return parse_uint_from_file(file);
> > +}
> > +
> > +static int determine_uprobe_perf_type(void)
> > +{
> > +     const char *file = "/sys/bus/event_source/devices/uprobe/type";
> > +     return parse_uint_from_file(file);
> > +}
> > +
> > +static int parse_config_from_file(const char *file)
> > +{
> > +     char buf[STRERR_BUFSIZE];
> > +     int fd, ret;
> > +
> > +     fd = open(file, O_RDONLY);
> > +     if (fd < 0) {
> > +             ret = -errno;
> > +             pr_debug("failed to open '%s': %s\n", file,
> > +                      libbpf_strerror_r(ret, buf, sizeof(buf)));
> > +             return ret;
> > +     }
> > +     ret = read(fd, buf, sizeof(buf));
> > +     close(fd);
> > +     if (ret < 0) {
> > +             ret = -errno;
> > +             pr_debug("failed to read '%s': %s\n", file,
> > +                     libbpf_strerror_r(ret, buf, sizeof(buf)));
> > +             return ret;
> > +     }
> > +     if (ret == 0 || ret >= sizeof(buf)) {
> > +             buf[sizeof(buf) - 1] = 0;
> > +             pr_debug("unexpected input from '%s': '%s'\n", file, buf);
> > +             return -EINVAL;
> > +     }
> > +     if (strncmp(buf, "config:", 7)) {
> > +             pr_debug("expected 'config:' prefix, found '%s'\n", buf);
> > +             return -EINVAL;
> > +     }
> > +     return parse_uint(buf + 7);
> > +}
> > +

<snip>

Re: [PATCH bpf-next 4/7] libbpf: add tracepoint/raw tracepoint attach API

[Andrii Nakryiko]

On Thu, Jun 20, 2019 at 5:07 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
>
> On 06/20, Andrii Nakryiko wrote:
> > Add APIs allowing to attach BPF program to kernel tracepoints. Raw
> > tracepoint attach API is also added for uniform per-BPF-program API,
> > but is mostly a wrapper around existing bpf_raw_tracepoint_open call.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> >  tools/lib/bpf/libbpf.c   | 99 ++++++++++++++++++++++++++++++++++++++++
> >  tools/lib/bpf/libbpf.h   |  5 ++
> >  tools/lib/bpf/libbpf.map |  2 +
> >  3 files changed, 106 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 11329e05530e..cefe67ba160b 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -4176,6 +4176,105 @@ int bpf_program__attach_uprobe(struct bpf_program *prog, bool retprobe,
> >       return pfd;
> >  }
> >
> > +static int determine_tracepoint_id(const char* tp_category, const char* tp_name)
> > +{
> > +     char file[PATH_MAX];
> > +     int ret;
> > +
> > +     ret = snprintf(file, sizeof(file),
> > +                    "/sys/kernel/debug/tracing/events/%s/%s/id",
> > +                    tp_category, tp_name);
> > +     if (ret < 0)
> > +             return -errno;
> > +     if (ret >= sizeof(file)) {
> > +             pr_debug("tracepoint %s/%s path is too long\n",
> > +                      tp_category, tp_name);
> > +             return -E2BIG;
> > +     }
> > +     return parse_uint_from_file(file);
> > +}
> > +
> > +static int perf_event_open_tracepoint(const char* tp_category,
> > +                                   const char* tp_name)
> > +{
> > +     struct perf_event_attr attr = {};
> > +     char errmsg[STRERR_BUFSIZE];
> > +     int tp_id, pfd, err;
> > +
> [..]
> > +     tp_id = determine_tracepoint_id(tp_category, tp_name);
> Why no assign to attr.config directly here?

It's used in few places for error-handling branch, so it would look a
bit weird and make lines longer.


> You can move all other constants to the initialization as well:
>
> struct perf_event_attr attr = {
>         .type = PERF_TYPE_TRACEPON,
>         .size = sizeof(struct perf_event_attr),
> };
>
> attr.config = determine_tracepoint_id(...);
>
> (I guess that's a matter of style, but something to consider).

Yeah. It seems like explicit initialization of each member of
attribute structs is prevalent in libbpf.c. I also don't want to have
some fields initialized at declaration site, and some other in code.
Better to group all initialization together.

>
> > +     if (tp_id < 0){
> > +             pr_warning("failed to determine tracepoint '%s/%s' perf ID: %s\n",
> > +                        tp_category, tp_name,
> > +                        libbpf_strerror_r(tp_id, errmsg, sizeof(errmsg)));
> > +             return tp_id;
> > +     }
> > +
> [..]
> > +     memset(&attr, 0, sizeof(attr));
> Not needed since you do attr = {}; above?

Yep, removed.

>
> > +     attr.type = PERF_TYPE_TRACEPOINT;
> > +     attr.size = sizeof(attr);
> > +     attr.config = tp_id;
> > +
> > +     pfd = syscall( __NR_perf_event_open, &attr, -1 /* pid */, 0 /* cpu */,
> > +                     -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> > +     if (pfd < 0) {
> > +             err = -errno;
> > +             pr_warning("tracepoint '%s/%s' perf_event_open() failed: %s\n",
> > +                        tp_category, tp_name,
> > +                        libbpf_strerror_r(err, errmsg, sizeof(errmsg)));
> > +             return err;
> > +     }
> > +     return pfd;
> > +}
> > +

<snip>

Re: [PATCH bpf-next 5/7] selftests/bpf: switch test to new attach_perf_event API

[Andrii Nakryiko]

On Thu, Jun 20, 2019 at 5:08 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
>
> On 06/20, Andrii Nakryiko wrote:
> > Use new bpf_program__attach_perf_event() in test previously relying on
> > direct ioctl manipulations.
> Maybe use new detach/disable routine at the end of the
> test_stacktrace_build_id_nmi as well?
>

yeah, totally, missed that.

> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> >  .../bpf/prog_tests/stacktrace_build_id_nmi.c     | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> >

<snip>