Commit 1b715e1b authored by Yafang Shao's avatar Yafang Shao Committed by Alexei Starovoitov
Browse files

bpf: Support ->fill_link_info for perf_event 



By introducing support for ->fill_link_info to the perf_event link, users
gain the ability to inspect it using `bpftool link show`. While the current
approach involves accessing this information via `bpftool perf show`,
consolidating link information for all link types in one place offers
greater convenience. Additionally, this patch extends support to the
generic perf event, which is not currently accommodated by
`bpftool perf show`. While only the perf type and config are exposed to
userspace, other attributes such as sample_period and sample_freq are
ignored. It's important to note that if kptr_restrict is not permitted, the
probed address will not be exposed, maintaining security measures.

A new enum bpf_perf_event_type is introduced to help the user understand
which struct is relevant.

Signed-off-by: default avatarYafang Shao <laoar.shao@gmail.com>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230709025630.3735-9-laoar.shao@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 57d48537

include/uapi/linux/bpf.h

+35 −0
Original line number Diff line number Diff line
@@ -1057,6 +1057,16 @@ enum bpf_link_type { 
	MAX_BPF_LINK_TYPE,

};



enum bpf_perf_event_type {

	BPF_PERF_EVENT_UNSPEC = 0,

	BPF_PERF_EVENT_UPROBE = 1,

	BPF_PERF_EVENT_URETPROBE = 2,

	BPF_PERF_EVENT_KPROBE = 3,

	BPF_PERF_EVENT_KRETPROBE = 4,

	BPF_PERF_EVENT_TRACEPOINT = 5,

	BPF_PERF_EVENT_EVENT = 6,

};



/* cgroup-bpf attach flags used in BPF_PROG_ATTACH command

 *

 * NONE(default): No further bpf programs allowed in the subtree.
@@ -6444,6 +6454,31 @@ struct bpf_link_info { 
			__u32 count; /* in/out: kprobe_multi function count */

			__u32 flags;

		} kprobe_multi;

		struct {

			__u32 type; /* enum bpf_perf_event_type */

			__u32 :32;

			union {

				struct {

					__aligned_u64 file_name; /* in/out */

					__u32 name_len;

					__u32 offset; /* offset from file_name */

				} uprobe; /* BPF_PERF_EVENT_UPROBE, BPF_PERF_EVENT_URETPROBE */

				struct {

					__aligned_u64 func_name; /* in/out */

					__u32 name_len;

					__u32 offset; /* offset from func_name */

					__u64 addr;

				} kprobe; /* BPF_PERF_EVENT_KPROBE, BPF_PERF_EVENT_KRETPROBE */

				struct {

					__aligned_u64 tp_name;   /* in/out */

					__u32 name_len;

				} tracepoint; /* BPF_PERF_EVENT_TRACEPOINT */

				struct {

					__u64 config;

					__u32 type;

				} event; /* BPF_PERF_EVENT_EVENT */

			};

		} perf_event;

	};

} __attribute__((aligned(8)));

kernel/bpf/syscall.c

+146 −0
Original line number Diff line number Diff line
@@ -3364,9 +3364,155 @@ static void bpf_perf_link_dealloc(struct bpf_link *link) 
	kfree(perf_link);

}



static int bpf_perf_link_fill_common(const struct perf_event *event,

				     char __user *uname, u32 ulen,

				     u64 *probe_offset, u64 *probe_addr,

				     u32 *fd_type)

{

	const char *buf;

	u32 prog_id;

	size_t len;

	int err;



	if (!ulen ^ !uname)

		return -EINVAL;

	if (!uname)

		return 0;



	err = bpf_get_perf_event_info(event, &prog_id, fd_type, &buf,

				      probe_offset, probe_addr);

	if (err)

		return err;



	if (buf) {

		len = strlen(buf);

		err = bpf_copy_to_user(uname, buf, ulen, len);

		if (err)

			return err;

	} else {

		char zero = '\0';



		if (put_user(zero, uname))

			return -EFAULT;

	}

	return 0;

}



#ifdef CONFIG_KPROBE_EVENTS

static int bpf_perf_link_fill_kprobe(const struct perf_event *event,

				     struct bpf_link_info *info)

{

	char __user *uname;

	u64 addr, offset;

	u32 ulen, type;

	int err;



	uname = u64_to_user_ptr(info->perf_event.kprobe.func_name);

	ulen = info->perf_event.kprobe.name_len;

	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,

					&type);

	if (err)

		return err;

	if (type == BPF_FD_TYPE_KRETPROBE)

		info->perf_event.type = BPF_PERF_EVENT_KRETPROBE;

	else

		info->perf_event.type = BPF_PERF_EVENT_KPROBE;



	info->perf_event.kprobe.offset = offset;

	if (!kallsyms_show_value(current_cred()))

		addr = 0;

	info->perf_event.kprobe.addr = addr;

	return 0;

}

#endif



#ifdef CONFIG_UPROBE_EVENTS

static int bpf_perf_link_fill_uprobe(const struct perf_event *event,

				     struct bpf_link_info *info)

{

	char __user *uname;

	u64 addr, offset;

	u32 ulen, type;

	int err;



	uname = u64_to_user_ptr(info->perf_event.uprobe.file_name);

	ulen = info->perf_event.uprobe.name_len;

	err = bpf_perf_link_fill_common(event, uname, ulen, &offset, &addr,

					&type);

	if (err)

		return err;



	if (type == BPF_FD_TYPE_URETPROBE)

		info->perf_event.type = BPF_PERF_EVENT_URETPROBE;

	else

		info->perf_event.type = BPF_PERF_EVENT_UPROBE;

	info->perf_event.uprobe.offset = offset;

	return 0;

}

#endif



static int bpf_perf_link_fill_probe(const struct perf_event *event,

				    struct bpf_link_info *info)

{

#ifdef CONFIG_KPROBE_EVENTS

	if (event->tp_event->flags & TRACE_EVENT_FL_KPROBE)

		return bpf_perf_link_fill_kprobe(event, info);

#endif

#ifdef CONFIG_UPROBE_EVENTS

	if (event->tp_event->flags & TRACE_EVENT_FL_UPROBE)

		return bpf_perf_link_fill_uprobe(event, info);

#endif

	return -EOPNOTSUPP;

}



static int bpf_perf_link_fill_tracepoint(const struct perf_event *event,

					 struct bpf_link_info *info)

{

	char __user *uname;

	u32 ulen;



	uname = u64_to_user_ptr(info->perf_event.tracepoint.tp_name);

	ulen = info->perf_event.tracepoint.name_len;

	info->perf_event.type = BPF_PERF_EVENT_TRACEPOINT;

	return bpf_perf_link_fill_common(event, uname, ulen, NULL, NULL, NULL);

}



static int bpf_perf_link_fill_perf_event(const struct perf_event *event,

					 struct bpf_link_info *info)

{

	info->perf_event.event.type = event->attr.type;

	info->perf_event.event.config = event->attr.config;

	info->perf_event.type = BPF_PERF_EVENT_EVENT;

	return 0;

}



static int bpf_perf_link_fill_link_info(const struct bpf_link *link,

					struct bpf_link_info *info)

{

	struct bpf_perf_link *perf_link;

	const struct perf_event *event;



	perf_link = container_of(link, struct bpf_perf_link, link);

	event = perf_get_event(perf_link->perf_file);

	if (IS_ERR(event))

		return PTR_ERR(event);



	switch (event->prog->type) {

	case BPF_PROG_TYPE_PERF_EVENT:

		return bpf_perf_link_fill_perf_event(event, info);

	case BPF_PROG_TYPE_TRACEPOINT:

		return bpf_perf_link_fill_tracepoint(event, info);

	case BPF_PROG_TYPE_KPROBE:

		return bpf_perf_link_fill_probe(event, info);

	default:

		return -EOPNOTSUPP;

	}

}



static const struct bpf_link_ops bpf_perf_link_lops = {

	.release = bpf_perf_link_release,

	.dealloc = bpf_perf_link_dealloc,

	.fill_link_info = bpf_perf_link_fill_link_info,

};



static int bpf_perf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)

kernel/trace/bpf_trace.c

+7 −3
Original line number Diff line number Diff line
@@ -2369,8 +2369,12 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id, 
	if (is_tracepoint || is_syscall_tp) {

		*buf = is_tracepoint ? event->tp_event->tp->name

				     : event->tp_event->name;

		/* We allow NULL pointer for tracepoint */

		if (fd_type)

			*fd_type = BPF_FD_TYPE_TRACEPOINT;

		if (probe_offset)

			*probe_offset = 0x0;

		if (probe_addr)

			*probe_addr = 0x0;

	} else {

		/* kprobe/uprobe */

tools/include/uapi/linux/bpf.h

+35 −0
Original line number Diff line number Diff line
@@ -1057,6 +1057,16 @@ enum bpf_link_type { 
	MAX_BPF_LINK_TYPE,

};



enum bpf_perf_event_type {

	BPF_PERF_EVENT_UNSPEC = 0,

	BPF_PERF_EVENT_UPROBE = 1,

	BPF_PERF_EVENT_URETPROBE = 2,

	BPF_PERF_EVENT_KPROBE = 3,

	BPF_PERF_EVENT_KRETPROBE = 4,

	BPF_PERF_EVENT_TRACEPOINT = 5,

	BPF_PERF_EVENT_EVENT = 6,

};



/* cgroup-bpf attach flags used in BPF_PROG_ATTACH command

 *

 * NONE(default): No further bpf programs allowed in the subtree.
@@ -6444,6 +6454,31 @@ struct bpf_link_info { 
			__u32 count; /* in/out: kprobe_multi function count */

			__u32 flags;

		} kprobe_multi;

		struct {

			__u32 type; /* enum bpf_perf_event_type */

			__u32 :32;

			union {

				struct {

					__aligned_u64 file_name; /* in/out */

					__u32 name_len;

					__u32 offset; /* offset from file_name */

				} uprobe; /* BPF_PERF_EVENT_UPROBE, BPF_PERF_EVENT_URETPROBE */

				struct {

					__aligned_u64 func_name; /* in/out */

					__u32 name_len;

					__u32 offset; /* offset from func_name */

					__u64 addr;

				} kprobe; /* BPF_PERF_EVENT_KPROBE, BPF_PERF_EVENT_KRETPROBE */

				struct {

					__aligned_u64 tp_name;   /* in/out */

					__u32 name_len;

				} tracepoint; /* BPF_PERF_EVENT_TRACEPOINT */

				struct {

					__u64 config;

					__u32 type;

				} event; /* BPF_PERF_EVENT_EVENT */

			};

		} perf_event;

	};

} __attribute__((aligned(8)));