Merge branch 'bpf-add-link_info-support-for-uprobe-multi-link'

Jiri Olsa says:

====================
bpf: Add link_info support for uprobe multi link

hi,
this patchset adds support to get bpf_link_info details for
uprobe_multi links and adding support for bpftool link to
display them.

v4 changes:
  - move flags field up in bpf_uprobe_multi_link [Andrii]
  - include zero terminating byte in path_size [Andrii]
  - return d_path error directly [Yonghong]
  - use SEC(".probes") for semaphores [Yonghong]
  - fix ref_ctr_offsets leak in test [Yonghong]
  - other smaller fixes [Yonghong]

thanks,
jirka
---
====================

Link: https://lore.kernel.org/r/20231125193130.834322-1-jolsa@kernel.org
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

include/uapi/linux/bpf.h

@@ -6562,6 +6562,16 @@ struct bpf_link_info {
 			__u32 flags;
 			__u64 missed;
 		} kprobe_multi;
+		struct {
+			__aligned_u64 path;
+			__aligned_u64 offsets;
+			__aligned_u64 ref_ctr_offsets;
+			__aligned_u64 cookies;
+			__u32 path_size; /* in/out: real path size on success, including zero byte */
+			__u32 count; /* in/out: uprobe_multi offsets/ref_ctr_offsets/cookies count */
+			__u32 flags;
+			__u32 pid;
+		} uprobe_multi;
 		struct {
 			__u32 type; /* enum bpf_perf_event_type */
 			__u32 :32;

kernel/trace/bpf_trace.c

@@ -3033,6 +3033,7 @@ struct bpf_uprobe_multi_link;
 struct bpf_uprobe {
 	struct bpf_uprobe_multi_link *link;
 	loff_t offset;
+	unsigned long ref_ctr_offset;
 	u64 cookie;
 	struct uprobe_consumer consumer;
 };
@@ -3041,6 +3042,7 @@ struct bpf_uprobe_multi_link {
 	struct path path;
 	struct bpf_link link;
 	u32 cnt;
+	u32 flags;
 	struct bpf_uprobe *uprobes;
 	struct task_struct *task;
 };
@@ -3082,9 +3084,79 @@ static void bpf_uprobe_multi_link_dealloc(struct bpf_link *link)
 	kfree(umulti_link);
 }
 
+static int bpf_uprobe_multi_link_fill_link_info(const struct bpf_link *link,
+						struct bpf_link_info *info)
+{
+	u64 __user *uref_ctr_offsets = u64_to_user_ptr(info->uprobe_multi.ref_ctr_offsets);
+	u64 __user *ucookies = u64_to_user_ptr(info->uprobe_multi.cookies);
+	u64 __user *uoffsets = u64_to_user_ptr(info->uprobe_multi.offsets);
+	u64 __user *upath = u64_to_user_ptr(info->uprobe_multi.path);
+	u32 upath_size = info->uprobe_multi.path_size;
+	struct bpf_uprobe_multi_link *umulti_link;
+	u32 ucount = info->uprobe_multi.count;
+	int err = 0, i;
+	long left;
+
+	if (!upath ^ !upath_size)
+		return -EINVAL;
+
+	if ((uoffsets || uref_ctr_offsets || ucookies) && !ucount)
+		return -EINVAL;
+
+	umulti_link = container_of(link, struct bpf_uprobe_multi_link, link);
+	info->uprobe_multi.count = umulti_link->cnt;
+	info->uprobe_multi.flags = umulti_link->flags;
+	info->uprobe_multi.pid = umulti_link->task ?
+				 task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;
+
+	if (upath) {
+		char *p, *buf;
+
+		upath_size = min_t(u32, upath_size, PATH_MAX);
+
+		buf = kmalloc(upath_size, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+		p = d_path(&umulti_link->path, buf, upath_size);
+		if (IS_ERR(p)) {
+			kfree(buf);
+			return PTR_ERR(p);
+		}
+		upath_size = buf + upath_size - p;
+		left = copy_to_user(upath, p, upath_size);
+		kfree(buf);
+		if (left)
+			return -EFAULT;
+		info->uprobe_multi.path_size = upath_size;
+	}
+
+	if (!uoffsets && !ucookies && !uref_ctr_offsets)
+		return 0;
+
+	if (ucount < umulti_link->cnt)
+		err = -ENOSPC;
+	else
+		ucount = umulti_link->cnt;
+
+	for (i = 0; i < ucount; i++) {
+		if (uoffsets &&
+		    put_user(umulti_link->uprobes[i].offset, uoffsets + i))
+			return -EFAULT;
+		if (uref_ctr_offsets &&
+		    put_user(umulti_link->uprobes[i].ref_ctr_offset, uref_ctr_offsets + i))
+			return -EFAULT;
+		if (ucookies &&
+		    put_user(umulti_link->uprobes[i].cookie, ucookies + i))
+			return -EFAULT;
+	}
+
+	return err;
+}
+
 static const struct bpf_link_ops bpf_uprobe_multi_link_lops = {
 	.release = bpf_uprobe_multi_link_release,
 	.dealloc = bpf_uprobe_multi_link_dealloc,
+	.fill_link_info = bpf_uprobe_multi_link_fill_link_info,
 };
 
 static int uprobe_prog_run(struct bpf_uprobe *uprobe,
@@ -3172,7 +3244,6 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 {
 	struct bpf_uprobe_multi_link *link = NULL;
 	unsigned long __user *uref_ctr_offsets;
-	unsigned long *ref_ctr_offsets = NULL;
 	struct bpf_link_primer link_primer;
 	struct bpf_uprobe *uprobes = NULL;
 	struct task_struct *task = NULL;
@@ -3245,18 +3316,12 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	if (!uprobes || !link)
 		goto error_free;
 
-	if (uref_ctr_offsets) {
-		ref_ctr_offsets = kvcalloc(cnt, sizeof(*ref_ctr_offsets), GFP_KERNEL);
-		if (!ref_ctr_offsets)
-			goto error_free;
-	}
-
 	for (i = 0; i < cnt; i++) {
 		if (ucookies && __get_user(uprobes[i].cookie, ucookies + i)) {
 			err = -EFAULT;
 			goto error_free;
 		}
-		if (uref_ctr_offsets && __get_user(ref_ctr_offsets[i], uref_ctr_offsets + i)) {
+		if (uref_ctr_offsets && __get_user(uprobes[i].ref_ctr_offset, uref_ctr_offsets + i)) {
 			err = -EFAULT;
 			goto error_free;
 		}
@@ -3280,14 +3345,15 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	link->uprobes = uprobes;
 	link->path = path;
 	link->task = task;
+	link->flags = flags;
 
 	bpf_link_init(&link->link, BPF_LINK_TYPE_UPROBE_MULTI,
 		      &bpf_uprobe_multi_link_lops, prog);
 
 	for (i = 0; i < cnt; i++) {
 		err = uprobe_register_refctr(d_real_inode(link->path.dentry),
 					     uprobes[i].offset,
-					     ref_ctr_offsets ? ref_ctr_offsets[i] : 0,
+					     uprobes[i].ref_ctr_offset,
 					     &uprobes[i].consumer);
 		if (err) {
 			bpf_uprobe_unregister(&path, uprobes, i);
@@ -3299,11 +3365,9 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	if (err)
 		goto error_free;
 
-	kvfree(ref_ctr_offsets);
 	return bpf_link_settle(&link_primer);
 
 error_free:
-	kvfree(ref_ctr_offsets);
 	kvfree(uprobes);
 	kfree(link);
 	if (task)

tools/bpf/bpftool/link.c

@@ -294,6 +294,37 @@ show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr)
 	jsonw_end_array(json_wtr);
 }
 
+static __u64 *u64_to_arr(__u64 val)
+{
+	return (__u64 *) u64_to_ptr(val);
+}
+
+static void
+show_uprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr)
+{
+	__u32 i;
+
+	jsonw_bool_field(json_wtr, "retprobe",
+			 info->uprobe_multi.flags & BPF_F_UPROBE_MULTI_RETURN);
+	jsonw_string_field(json_wtr, "path", (char *) u64_to_ptr(info->uprobe_multi.path));
+	jsonw_uint_field(json_wtr, "func_cnt", info->uprobe_multi.count);
+	jsonw_int_field(json_wtr, "pid", (int) info->uprobe_multi.pid);
+	jsonw_name(json_wtr, "funcs");
+	jsonw_start_array(json_wtr);
+
+	for (i = 0; i < info->uprobe_multi.count; i++) {
+		jsonw_start_object(json_wtr);
+		jsonw_uint_field(json_wtr, "offset",
+				 u64_to_arr(info->uprobe_multi.offsets)[i]);
+		jsonw_uint_field(json_wtr, "ref_ctr_offset",
+				 u64_to_arr(info->uprobe_multi.ref_ctr_offsets)[i]);
+		jsonw_uint_field(json_wtr, "cookie",
+				 u64_to_arr(info->uprobe_multi.cookies)[i]);
+		jsonw_end_object(json_wtr);
+	}
+	jsonw_end_array(json_wtr);
+}
+
 static void
 show_perf_event_kprobe_json(struct bpf_link_info *info, json_writer_t *wtr)
 {
@@ -465,6 +496,9 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 	case BPF_LINK_TYPE_KPROBE_MULTI:
 		show_kprobe_multi_json(info, json_wtr);
 		break;
+	case BPF_LINK_TYPE_UPROBE_MULTI:
+		show_uprobe_multi_json(info, json_wtr);
+		break;
 	case BPF_LINK_TYPE_PERF_EVENT:
 		switch (info->perf_event.type) {
 		case BPF_PERF_EVENT_EVENT:
@@ -674,6 +708,33 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info)
 	}
 }
 
+static void show_uprobe_multi_plain(struct bpf_link_info *info)
+{
+	__u32 i;
+
+	if (!info->uprobe_multi.count)
+		return;
+
+	if (info->uprobe_multi.flags & BPF_F_UPROBE_MULTI_RETURN)
+		printf("\n\turetprobe.multi  ");
+	else
+		printf("\n\tuprobe.multi  ");
+
+	printf("path %s  ", (char *) u64_to_ptr(info->uprobe_multi.path));
+	printf("func_cnt %u  ", info->uprobe_multi.count);
+
+	if (info->uprobe_multi.pid)
+		printf("pid %d  ", info->uprobe_multi.pid);
+
+	printf("\n\t%-16s   %-16s   %-16s", "offset", "ref_ctr_offset", "cookies");
+	for (i = 0; i < info->uprobe_multi.count; i++) {
+		printf("\n\t0x%-16llx 0x%-16llx 0x%-16llx",
+			u64_to_arr(info->uprobe_multi.offsets)[i],
+			u64_to_arr(info->uprobe_multi.ref_ctr_offsets)[i],
+			u64_to_arr(info->uprobe_multi.cookies)[i]);
+	}
+}
+
 static void show_perf_event_kprobe_plain(struct bpf_link_info *info)
 {
 	const char *buf;
@@ -807,6 +868,9 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 	case BPF_LINK_TYPE_KPROBE_MULTI:
 		show_kprobe_multi_plain(info);
 		break;
+	case BPF_LINK_TYPE_UPROBE_MULTI:
+		show_uprobe_multi_plain(info);
+		break;
 	case BPF_LINK_TYPE_PERF_EVENT:
 		switch (info->perf_event.type) {
 		case BPF_PERF_EVENT_EVENT:
@@ -846,8 +910,10 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 
 static int do_show_link(int fd)
 {
+	__u64 *ref_ctr_offsets = NULL, *offsets = NULL, *cookies = NULL;
 	struct bpf_link_info info;
 	__u32 len = sizeof(info);
+	char path_buf[PATH_MAX];
 	__u64 *addrs = NULL;
 	char buf[PATH_MAX];
 	int count;
@@ -889,6 +955,39 @@ static int do_show_link(int fd)
 			goto again;
 		}
 	}
+	if (info.type == BPF_LINK_TYPE_UPROBE_MULTI &&
+	    !info.uprobe_multi.offsets) {
+		count = info.uprobe_multi.count;
+		if (count) {
+			offsets = calloc(count, sizeof(__u64));
+			if (!offsets) {
+				p_err("mem alloc failed");
+				close(fd);
+				return -ENOMEM;
+			}
+			info.uprobe_multi.offsets = ptr_to_u64(offsets);
+			ref_ctr_offsets = calloc(count, sizeof(__u64));
+			if (!ref_ctr_offsets) {
+				p_err("mem alloc failed");
+				free(offsets);
+				close(fd);
+				return -ENOMEM;
+			}
+			info.uprobe_multi.ref_ctr_offsets = ptr_to_u64(ref_ctr_offsets);
+			cookies = calloc(count, sizeof(__u64));
+			if (!cookies) {
+				p_err("mem alloc failed");
+				free(cookies);
+				free(offsets);
+				close(fd);
+				return -ENOMEM;
+			}
+			info.uprobe_multi.cookies = ptr_to_u64(cookies);
+			info.uprobe_multi.path = ptr_to_u64(path_buf);
+			info.uprobe_multi.path_size = sizeof(path_buf);
+			goto again;
+		}
+	}
 	if (info.type == BPF_LINK_TYPE_PERF_EVENT) {
 		switch (info.perf_event.type) {
 		case BPF_PERF_EVENT_TRACEPOINT:
@@ -924,8 +1023,10 @@ static int do_show_link(int fd)
 	else
 		show_link_close_plain(fd, &info);
 
-	if (addrs)
-		free(addrs);
+	free(ref_ctr_offsets);
+	free(cookies);
+	free(offsets);
+	free(addrs);
 	close(fd);
 	return 0;
 }

tools/include/uapi/linux/bpf.h

@@ -6562,6 +6562,16 @@ struct bpf_link_info {
 			__u32 flags;
 			__u64 missed;
 		} kprobe_multi;
+		struct {
+			__aligned_u64 path;
+			__aligned_u64 offsets;
+			__aligned_u64 ref_ctr_offsets;
+			__aligned_u64 cookies;
+			__u32 path_size; /* in/out: real path size on success, including zero byte */
+			__u32 count; /* in/out: uprobe_multi offsets/ref_ctr_offsets/cookies count */
+			__u32 flags;
+			__u32 pid;
+		} uprobe_multi;
 		struct {
 			__u32 type; /* enum bpf_perf_event_type */
 			__u32 :32;

tools/lib/bpf/elf.c

@@ -407,7 +407,8 @@ static int symbol_cmp(const void *a, const void *b)
  * size, that needs to be released by the caller.
  */
 int elf_resolve_syms_offsets(const char *binary_path, int cnt,
-			     const char **syms, unsigned long **poffsets)
+			     const char **syms, unsigned long **poffsets,
+			     int st_type)
 {
 	int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
 	int err = 0, i, cnt_done = 0;
@@ -438,7 +439,7 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
 		struct elf_sym_iter iter;
 		struct elf_sym *sym;
 
-		err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], STT_FUNC);
+		err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], st_type);
 		if (err == -ENOENT)
 			continue;
 		if (err)

tools/lib/bpf/libbpf.c

@@ -11447,7 +11447,7 @@ bpf_program__attach_uprobe_multi(const struct bpf_program *prog,
 			return libbpf_err_ptr(err);
 		offsets = resolved_offsets;
 	} else if (syms) {
-		err = elf_resolve_syms_offsets(path, cnt, syms, &resolved_offsets);
+		err = elf_resolve_syms_offsets(path, cnt, syms, &resolved_offsets, STT_FUNC);
 		if (err < 0)
 			return libbpf_err_ptr(err);
 		offsets = resolved_offsets;

tools/lib/bpf/libbpf_internal.h

@@ -594,7 +594,8 @@ int elf_open(const char *binary_path, struct elf_fd *elf_fd);
 void elf_close(struct elf_fd *elf_fd);
 
 int elf_resolve_syms_offsets(const char *binary_path, int cnt,
-			     const char **syms, unsigned long **poffsets);
+			     const char **syms, unsigned long **poffsets,
+			     int st_type);
 int elf_resolve_pattern_offsets(const char *binary_path, const char *pattern,
 				 unsigned long **poffsets, size_t *pcnt);