[PATCHv3 bpf-next 0/6] bpf: Add link_info support for uprobe multi link

[PATCHv3 bpf-next 0/6] bpf: Add link_info support for uprobe multi link

[Jiri Olsa]

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

v3 changes:
  - allow to return offset/ref_ctr_offset/cookies independently
    and changed the test accordingly [Andrii]
  - use path_size also as out argument [Andrii]

thanks,
jirka


---
Jiri Olsa (6):
      libbpf: Add st_type argument to elf_resolve_syms_offsets function
      bpf: Store ref_ctr_offsets values in bpf_uprobe array
      bpf: Add link_info support for uprobe multi link
      selftests/bpf: Use bpf_link__destroy in fill_link_info tests
      selftests/bpf: Add link_info test for uprobe_multi link
      bpftool: Add support to display uprobe_multi links

 include/uapi/linux/bpf.h                                   |  10 ++++
 kernel/trace/bpf_trace.c                                   |  86 +++++++++++++++++++++++++++++-----
 tools/bpf/bpftool/link.c                                   | 105 ++++++++++++++++++++++++++++++++++++++++-
 tools/include/uapi/linux/bpf.h                             |  10 ++++
 tools/lib/bpf/elf.c                                        |   5 +-
 tools/lib/bpf/libbpf.c                                     |   2 +-
 tools/lib/bpf/libbpf_internal.h                            |   3 +-
 tools/testing/selftests/bpf/prog_tests/fill_link_info.c    | 235 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---------
 tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c |   2 +-
 tools/testing/selftests/bpf/progs/test_fill_link_info.c    |   6 +++
 10 files changed, 425 insertions(+), 39 deletions(-)

[PATCHv3 bpf-next 1/6] libbpf: Add st_type argument to elf_resolve_syms_offsets function

[Jiri Olsa]

We need to get offsets for static variables in following changes,
so making elf_resolve_syms_offsets to take st_type value as argument
and passing it to elf_sym_iter_new.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/lib/bpf/elf.c                                        | 5 +++--
 tools/lib/bpf/libbpf.c                                     | 2 +-
 tools/lib/bpf/libbpf_internal.h                            | 3 ++-
 tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c | 2 +-
 4 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
index 2a62bf411bb3..b02faec748a5 100644
--- a/tools/lib/bpf/elf.c
+++ b/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)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e067be95da3c..ea9b8158c20d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/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;
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index f0f08635adb0..b5d334754e5d 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/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);
 
diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
index cd051d3901a9..ece260cf2c0b 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_multi_test.c
@@ -249,7 +249,7 @@ static void __test_link_api(struct child *child)
 	int link_extra_fd = -1;
 	int err;
 
-	err = elf_resolve_syms_offsets(path, 3, syms, (unsigned long **) &offsets);
+	err = elf_resolve_syms_offsets(path, 3, syms, (unsigned long **) &offsets, STT_FUNC);
 	if (!ASSERT_OK(err, "elf_resolve_syms_offsets"))
 		return;
 
-- 
2.42.0

[PATCHv3 bpf-next 2/6] bpf: Store ref_ctr_offsets values in bpf_uprobe array

[Jiri Olsa]

We will need to return ref_ctr_offsets values through link_info
interface in following change, so we need to keep them around.

Storing ref_ctr_offsets values directly into bpf_uprobe array.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/bpf_trace.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f0b8b7c29126..ad0323f27288 100644
--- a/kernel/trace/bpf_trace.c
+++ b/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;
 };
@@ -3172,7 +3173,6 @@ 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 +3245,12 @@ 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;
 		}
@@ -3287,7 +3281,7 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
 	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 +3293,9 @@ 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)
-- 
2.42.0

[PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Jiri Olsa]

Adding support to get uprobe_link details through bpf_link_info
interface.

Adding new struct uprobe_multi to struct bpf_link_info to carry
the uprobe_multi link details.

The uprobe_multi.count is passed from user space to denote size
of array fields (offsets/ref_ctr_offsets/cookies). The actual
array size is stored back to uprobe_multi.count (allowing user
to find out the actual array size) and array fields are populated
up to the user passed size.

All the non-array fields (path/count/flags/pid) are always set.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/uapi/linux/bpf.h       | 10 +++++
 kernel/trace/bpf_trace.c       | 72 ++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h | 10 +++++
 3 files changed, 92 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7a5498242eaa..a63b5eb7f9ec 100644
--- a/include/uapi/linux/bpf.h
+++ b/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 */
+			__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;
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index ad0323f27288..ca453b642819 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3044,6 +3044,7 @@ struct bpf_uprobe_multi_link {
 	u32 cnt;
 	struct bpf_uprobe *uprobes;
 	struct task_struct *task;
+	u32 flags;
 };
 
 struct bpf_uprobe_multi_run_ctx {
@@ -3083,9 +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 -ENOSPC;
+		}
+		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 - 1 /* NULL */;
+	}
+
+	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,
@@ -3274,6 +3345,7 @@ 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);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7a5498242eaa..a63b5eb7f9ec 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/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 */
+			__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;
-- 
2.42.0

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Yonghong Song]

On 11/20/23 9:56 AM, Jiri Olsa wrote:
> Adding support to get uprobe_link details through bpf_link_info
> interface.
>
> Adding new struct uprobe_multi to struct bpf_link_info to carry
> the uprobe_multi link details.
>
> The uprobe_multi.count is passed from user space to denote size
> of array fields (offsets/ref_ctr_offsets/cookies). The actual
> array size is stored back to uprobe_multi.count (allowing user
> to find out the actual array size) and array fields are populated
> up to the user passed size.
>
> All the non-array fields (path/count/flags/pid) are always set.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>   include/uapi/linux/bpf.h       | 10 +++++
>   kernel/trace/bpf_trace.c       | 72 ++++++++++++++++++++++++++++++++++
>   tools/include/uapi/linux/bpf.h | 10 +++++
>   3 files changed, 92 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7a5498242eaa..a63b5eb7f9ec 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/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 */
> +			__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;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index ad0323f27288..ca453b642819 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3044,6 +3044,7 @@ struct bpf_uprobe_multi_link {
>   	u32 cnt;
>   	struct bpf_uprobe *uprobes;
>   	struct task_struct *task;
> +	u32 flags;
>   };
>   
>   struct bpf_uprobe_multi_run_ctx {
> @@ -3083,9 +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 -ENOSPC;

Should we just return PTR_ERR(p)? In d_path, it is possible that
-ENAMETOOLONG is returned. But path->dentry->d_op->d_dname() might
return a different error reason than  -ENAMETOOLONG or -ENOSPC?

> +		}
> +		upath_size = buf + upath_size - p;
> +		left = copy_to_user(upath, p, upath_size);

Here, the data copied to user may contain more than
actual path itself. I am okay with this since this
is not in critical path. But early buf allocation is using
kmalloc whose content could be arbitrary. Should we
use kzalloc for the above 'buf' allocation?


> +		kfree(buf);
> +		if (left)
> +			return -EFAULT;
> +		info->uprobe_multi.path_size = upath_size - 1 /* NULL */;
> +	}
> +
> +	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;
> +}
> +
>   [...]

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Jiri Olsa]

On Mon, Nov 20, 2023 at 10:04:16AM -0800, Yonghong Song wrote:

SNIP

> > +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 -ENOSPC;
> 
> Should we just return PTR_ERR(p)? In d_path, it is possible that
> -ENAMETOOLONG is returned. But path->dentry->d_op->d_dname() might
> return a different error reason than  -ENAMETOOLONG or -ENOSPC?

true, will change

> 
> > +		}
> > +		upath_size = buf + upath_size - p;
> > +		left = copy_to_user(upath, p, upath_size);
> 
> Here, the data copied to user may contain more than
> actual path itself. I am okay with this since this
> is not in critical path. But early buf allocation is using
> kmalloc whose content could be arbitrary. Should we
> use kzalloc for the above 'buf' allocation?

good catch, will use kzalloc

thanks,
jirka

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Jiri Olsa]

On Wed, Nov 22, 2023 at 10:50:06PM +0100, Jiri Olsa wrote:
> On Mon, Nov 20, 2023 at 10:04:16AM -0800, Yonghong Song wrote:
> 
> SNIP
> 
> > > +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 -ENOSPC;
> > 
> > Should we just return PTR_ERR(p)? In d_path, it is possible that
> > -ENAMETOOLONG is returned. But path->dentry->d_op->d_dname() might
> > return a different error reason than  -ENAMETOOLONG or -ENOSPC?
> 
> true, will change
> 
> > 
> > > +		}
> > > +		upath_size = buf + upath_size - p;
> > > +		left = copy_to_user(upath, p, upath_size);
> > 
> > Here, the data copied to user may contain more than
> > actual path itself. I am okay with this since this
> > is not in critical path. But early buf allocation is using
> > kmalloc whose content could be arbitrary. Should we
> > use kzalloc for the above 'buf' allocation?
> 
> good catch, will use kzalloc

hum, actually.. after checking d_path IIUC it copies into the end of buffer,
so I can't see this code copying more data to user buffer

jirka

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Yonghong Song]

On 11/23/23 4:20 AM, Jiri Olsa wrote:
> On Wed, Nov 22, 2023 at 10:50:06PM +0100, Jiri Olsa wrote:
>> On Mon, Nov 20, 2023 at 10:04:16AM -0800, Yonghong Song wrote:
>>
>> SNIP
>>
>>>> +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 -ENOSPC;
>>> Should we just return PTR_ERR(p)? In d_path, it is possible that
>>> -ENAMETOOLONG is returned. But path->dentry->d_op->d_dname() might
>>> return a different error reason than  -ENAMETOOLONG or -ENOSPC?
>> true, will change
>>
>>>> +		}
>>>> +		upath_size = buf + upath_size - p;
>>>> +		left = copy_to_user(upath, p, upath_size);
>>> Here, the data copied to user may contain more than
>>> actual path itself. I am okay with this since this
>>> is not in critical path. But early buf allocation is using
>>> kmalloc whose content could be arbitrary. Should we
>>> use kzalloc for the above 'buf' allocation?
>> good catch, will use kzalloc
> hum, actually.. after checking d_path IIUC it copies into the end of buffer,
> so I can't see this code copying more data to user buffer

Double checked as well. Indeed, the path is copied to the end of buffer,
so kmalloc() should be okay. Sorry for noise.

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Andrii Nakryiko]

On Mon, Nov 20, 2023 at 6:57 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding support to get uprobe_link details through bpf_link_info
> interface.
>
> Adding new struct uprobe_multi to struct bpf_link_info to carry
> the uprobe_multi link details.
>
> The uprobe_multi.count is passed from user space to denote size
> of array fields (offsets/ref_ctr_offsets/cookies). The actual
> array size is stored back to uprobe_multi.count (allowing user
> to find out the actual array size) and array fields are populated
> up to the user passed size.
>
> All the non-array fields (path/count/flags/pid) are always set.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  include/uapi/linux/bpf.h       | 10 +++++
>  kernel/trace/bpf_trace.c       | 72 ++++++++++++++++++++++++++++++++++
>  tools/include/uapi/linux/bpf.h | 10 +++++
>  3 files changed, 92 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7a5498242eaa..a63b5eb7f9ec 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/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 */
> +                       __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;
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index ad0323f27288..ca453b642819 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3044,6 +3044,7 @@ struct bpf_uprobe_multi_link {
>         u32 cnt;
>         struct bpf_uprobe *uprobes;
>         struct task_struct *task;
> +       u32 flags;

this fits better after cnt to avoid increasing the size of
bpf_uprobe_multi_link, please it move up

>  };
>
>  struct bpf_uprobe_multi_run_ctx {
> @@ -3083,9 +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 -ENOSPC;
> +               }
> +               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 - 1 /* NULL */;

why subtract zero terminating byte? I think we should drop this -1 and
return filled out buffer content size, including zero terminator.


> +       }
> +
> +       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,
> @@ -3274,6 +3345,7 @@ 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);
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 7a5498242eaa..a63b5eb7f9ec 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/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 */
> +                       __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;
> --
> 2.42.0
>

Re: [PATCHv3 bpf-next 3/6] bpf: Add link_info support for uprobe multi link

[Jiri Olsa]

On Tue, Nov 21, 2023 at 10:41:24AM -0800, Andrii Nakryiko wrote:
> On Mon, Nov 20, 2023 at 6:57 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Adding support to get uprobe_link details through bpf_link_info
> > interface.
> >
> > Adding new struct uprobe_multi to struct bpf_link_info to carry
> > the uprobe_multi link details.
> >
> > The uprobe_multi.count is passed from user space to denote size
> > of array fields (offsets/ref_ctr_offsets/cookies). The actual
> > array size is stored back to uprobe_multi.count (allowing user
> > to find out the actual array size) and array fields are populated
> > up to the user passed size.
> >
> > All the non-array fields (path/count/flags/pid) are always set.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  include/uapi/linux/bpf.h       | 10 +++++
> >  kernel/trace/bpf_trace.c       | 72 ++++++++++++++++++++++++++++++++++
> >  tools/include/uapi/linux/bpf.h | 10 +++++
> >  3 files changed, 92 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 7a5498242eaa..a63b5eb7f9ec 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/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 */
> > +                       __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;
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index ad0323f27288..ca453b642819 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -3044,6 +3044,7 @@ struct bpf_uprobe_multi_link {
> >         u32 cnt;
> >         struct bpf_uprobe *uprobes;
> >         struct task_struct *task;
> > +       u32 flags;
> 
> this fits better after cnt to avoid increasing the size of
> bpf_uprobe_multi_link, please it move up

ok

> 
> >  };
> >
> >  struct bpf_uprobe_multi_run_ctx {
> > @@ -3083,9 +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 -ENOSPC;
> > +               }
> > +               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 - 1 /* NULL */;
> 
> why subtract zero terminating byte? I think we should drop this -1 and
> return filled out buffer content size, including zero terminator.

I wanted to return the same as strlen would:

       The strlen() function calculates the length of the string pointed to by s, excluding the terminating null byte ('\0').

either way works for me, but perhaps we should document it in the uapi header

jirka

[PATCHv3 bpf-next 4/6] selftests/bpf: Use bpf_link__destroy in fill_link_info tests

[Jiri Olsa]

The fill_link_info test keeps skeleton open and just creates
various links. We are wrongly calling bpf_link__detach after
each test to close them, we need to call bpf_link__destroy.

Acked-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../selftests/bpf/prog_tests/fill_link_info.c | 44 ++++++++++---------
 1 file changed, 23 insertions(+), 21 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index 97142a4db374..9294cb8d7743 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
@@ -140,14 +140,14 @@ static void test_kprobe_fill_link_info(struct test_fill_link_info *skel,
 		.retprobe = type == BPF_PERF_EVENT_KRETPROBE,
 	);
 	ssize_t entry_offset = 0;
+	struct bpf_link *link;
 	int link_fd, err;
 
-	skel->links.kprobe_run = bpf_program__attach_kprobe_opts(skel->progs.kprobe_run,
-								 KPROBE_FUNC, &opts);
-	if (!ASSERT_OK_PTR(skel->links.kprobe_run, "attach_kprobe"))
+	link = bpf_program__attach_kprobe_opts(skel->progs.kprobe_run, KPROBE_FUNC, &opts);
+	if (!ASSERT_OK_PTR(link, "attach_kprobe"))
 		return;
 
-	link_fd = bpf_link__fd(skel->links.kprobe_run);
+	link_fd = bpf_link__fd(link);
 	if (!invalid) {
 		/* See also arch_adjust_kprobe_addr(). */
 		if (skel->kconfig->CONFIG_X86_KERNEL_IBT)
@@ -157,39 +157,41 @@ static void test_kprobe_fill_link_info(struct test_fill_link_info *skel,
 	} else {
 		kprobe_fill_invalid_user_buffer(link_fd);
 	}
-	bpf_link__detach(skel->links.kprobe_run);
+	bpf_link__destroy(link);
 }
 
 static void test_tp_fill_link_info(struct test_fill_link_info *skel)
 {
+	struct bpf_link *link;
 	int link_fd, err;
 
-	skel->links.tp_run = bpf_program__attach_tracepoint(skel->progs.tp_run, TP_CAT, TP_NAME);
-	if (!ASSERT_OK_PTR(skel->links.tp_run, "attach_tp"))
+	link = bpf_program__attach_tracepoint(skel->progs.tp_run, TP_CAT, TP_NAME);
+	if (!ASSERT_OK_PTR(link, "attach_tp"))
 		return;
 
-	link_fd = bpf_link__fd(skel->links.tp_run);
+	link_fd = bpf_link__fd(link);
 	err = verify_perf_link_info(link_fd, BPF_PERF_EVENT_TRACEPOINT, 0, 0, 0);
 	ASSERT_OK(err, "verify_perf_link_info");
-	bpf_link__detach(skel->links.tp_run);
+	bpf_link__destroy(link);
 }
 
 static void test_uprobe_fill_link_info(struct test_fill_link_info *skel,
 				       enum bpf_perf_event_type type)
 {
+	struct bpf_link *link;
 	int link_fd, err;
 
-	skel->links.uprobe_run = bpf_program__attach_uprobe(skel->progs.uprobe_run,
-							    type == BPF_PERF_EVENT_URETPROBE,
-							    0, /* self pid */
-							    UPROBE_FILE, uprobe_offset);
-	if (!ASSERT_OK_PTR(skel->links.uprobe_run, "attach_uprobe"))
+	link = bpf_program__attach_uprobe(skel->progs.uprobe_run,
+					  type == BPF_PERF_EVENT_URETPROBE,
+					  0, /* self pid */
+					  UPROBE_FILE, uprobe_offset);
+	if (!ASSERT_OK_PTR(link, "attach_uprobe"))
 		return;
 
-	link_fd = bpf_link__fd(skel->links.uprobe_run);
+	link_fd = bpf_link__fd(link);
 	err = verify_perf_link_info(link_fd, type, 0, uprobe_offset, 0);
 	ASSERT_OK(err, "verify_perf_link_info");
-	bpf_link__detach(skel->links.uprobe_run);
+	bpf_link__destroy(link);
 }
 
 static int verify_kmulti_link_info(int fd, bool retprobe)
@@ -278,24 +280,24 @@ static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
 					     bool retprobe, bool invalid)
 {
 	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+	struct bpf_link *link;
 	int link_fd, err;
 
 	opts.syms = kmulti_syms;
 	opts.cnt = KMULTI_CNT;
 	opts.retprobe = retprobe;
-	skel->links.kmulti_run = bpf_program__attach_kprobe_multi_opts(skel->progs.kmulti_run,
-								       NULL, &opts);
-	if (!ASSERT_OK_PTR(skel->links.kmulti_run, "attach_kprobe_multi"))
+	link = bpf_program__attach_kprobe_multi_opts(skel->progs.kmulti_run, NULL, &opts);
+	if (!ASSERT_OK_PTR(link, "attach_kprobe_multi"))
 		return;
 
-	link_fd = bpf_link__fd(skel->links.kmulti_run);
+	link_fd = bpf_link__fd(link);
 	if (!invalid) {
 		err = verify_kmulti_link_info(link_fd, retprobe);
 		ASSERT_OK(err, "verify_kmulti_link_info");
 	} else {
 		verify_kmulti_invalid_user_buffer(link_fd);
 	}
-	bpf_link__detach(skel->links.kmulti_run);
+	bpf_link__destroy(link);
 }
 
 void test_fill_link_info(void)
-- 
2.42.0

Re: [PATCHv3 bpf-next 4/6] selftests/bpf: Use bpf_link__destroy in fill_link_info tests

[Yonghong Song]

On 11/20/23 9:56 AM, Jiri Olsa wrote:
> The fill_link_info test keeps skeleton open and just creates
> various links. We are wrongly calling bpf_link__detach after
> each test to close them, we need to call bpf_link__destroy.
>
> Acked-by: Yafang Shao <laoar.shao@gmail.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>

Acked-by: Yonghong Song <yonghong.song@linux.dev>

[PATCHv3 bpf-next 5/6] selftests/bpf: Add link_info test for uprobe_multi link

[Jiri Olsa]

Adding fill_link_info test for uprobe_multi link.

Setting up uprobes with bogus ref_ctr_offsets and cookie values
to test all the bpf_link_info::uprobe_multi fields.

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 .../selftests/bpf/prog_tests/fill_link_info.c | 191 ++++++++++++++++++
 .../selftests/bpf/progs/test_fill_link_info.c |   6 +
 2 files changed, 197 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
index 9294cb8d7743..fdf2c6b8c0cf 100644
--- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
+++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
@@ -7,6 +7,7 @@
 #include <test_progs.h>
 #include "trace_helpers.h"
 #include "test_fill_link_info.skel.h"
+#include "bpf/libbpf_internal.h"
 
 #define TP_CAT "sched"
 #define TP_NAME "sched_switch"
@@ -300,6 +301,189 @@ static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
 	bpf_link__destroy(link);
 }
 
+/* Initialize semaphore variables so they don't end up in bss
+ * section and we could get retrieve their offsets.
+ */
+static short uprobe_link_info_sema_1 = 1;
+static short uprobe_link_info_sema_2 = 1;
+static short uprobe_link_info_sema_3 = 1;
+
+noinline void uprobe_link_info_func_1(void)
+{
+	uprobe_link_info_sema_1++;
+	asm volatile ("");
+}
+
+noinline void uprobe_link_info_func_2(void)
+{
+	uprobe_link_info_sema_2++;
+	asm volatile ("");
+}
+
+noinline void uprobe_link_info_func_3(void)
+{
+	uprobe_link_info_sema_3++;
+	asm volatile ("");
+}
+
+static int
+verify_umulti_link_info(int fd, bool retprobe, __u64 *offsets,
+			__u64 *cookies, __u64 *ref_ctr_offsets)
+{
+	char path[PATH_MAX], path_buf[PATH_MAX];
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	__u64 ref_ctr_offsets_buf[3];
+	__u64 offsets_buf[3];
+	__u64 cookies_buf[3];
+	int i, err, bit;
+	__u32 count = 0;
+
+	memset(path, 0, sizeof(path));
+	err = readlink("/proc/self/exe", path, sizeof(path));
+	if (!ASSERT_NEQ(err, -1, "readlink"))
+		return -1;
+
+	for (bit = 0; bit < 8; bit++) {
+		memset(&info, 0, sizeof(info));
+		info.uprobe_multi.path = ptr_to_u64(path_buf);
+		info.uprobe_multi.path_size = sizeof(path_buf);
+		info.uprobe_multi.count = count;
+
+		if (bit & 0x1)
+			info.uprobe_multi.offsets = ptr_to_u64(offsets_buf);
+		if (bit & 0x2)
+			info.uprobe_multi.cookies = ptr_to_u64(cookies_buf);
+		if (bit & 0x4)
+			info.uprobe_multi.ref_ctr_offsets = ptr_to_u64(ref_ctr_offsets_buf);
+
+		err = bpf_link_get_info_by_fd(fd, &info, &len);
+		if (!ASSERT_OK(err, "bpf_link_get_info_by_fd"))
+			return -1;
+
+		if (!ASSERT_EQ(info.type, BPF_LINK_TYPE_UPROBE_MULTI, "info.type"))
+			return -1;
+
+		ASSERT_EQ(info.uprobe_multi.pid, getpid(), "info.uprobe_multi.pid");
+		ASSERT_EQ(info.uprobe_multi.count, 3, "info.uprobe_multi.count");
+		ASSERT_EQ(info.uprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN,
+			  retprobe, "info.uprobe_multi.flags.retprobe");
+		ASSERT_EQ(info.uprobe_multi.path_size, strlen(path), "info.uprobe_multi.path_size");
+		ASSERT_STREQ(path_buf, path, "info.uprobe_multi.path");
+
+		for (i = 0; i < info.uprobe_multi.count; i++) {
+			if (info.uprobe_multi.offsets)
+				ASSERT_EQ(offsets_buf[i], offsets[i], "info.uprobe_multi.offsets");
+			if (info.uprobe_multi.cookies)
+				ASSERT_EQ(cookies_buf[i], cookies[i], "info.uprobe_multi.cookies");
+			if (info.uprobe_multi.ref_ctr_offsets) {
+				ASSERT_EQ(ref_ctr_offsets_buf[i], ref_ctr_offsets[i],
+					  "info.uprobe_multi.ref_ctr_offsets");
+			}
+		}
+		count = count ?: info.uprobe_multi.count;
+	}
+
+	return 0;
+}
+
+static void verify_umulti_invalid_user_buffer(int fd)
+{
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	__u64 buf[3];
+	int err;
+
+	/* upath_size defined, not path */
+	memset(&info, 0, sizeof(info));
+	info.uprobe_multi.path_size = 3;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "failed_upath_size");
+
+	/* path has wrong pointer */
+	memset(&info, 0, sizeof(info));
+	info.uprobe_multi.path_size = PATH_MAX;
+	info.uprobe_multi.path = 123;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EFAULT, "failed_bad_path_ptr");
+
+	/* count zero, with offsets */
+	memset(&info, 0, sizeof(info));
+	info.uprobe_multi.offsets = ptr_to_u64(buf);
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "failed_count");
+
+	/* offsets not big enough */
+	memset(&info, 0, sizeof(info));
+	info.uprobe_multi.offsets = ptr_to_u64(buf);
+	info.uprobe_multi.count = 2;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -ENOSPC, "failed_small_count");
+
+	/* offsets has wrong pointer */
+	memset(&info, 0, sizeof(info));
+	info.uprobe_multi.offsets = 123;
+	info.uprobe_multi.count = 3;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EFAULT, "failed_wrong_offsets");
+}
+
+static void test_uprobe_multi_fill_link_info(struct test_fill_link_info *skel,
+					     bool retprobe, bool invalid)
+{
+	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
+		.retprobe = retprobe,
+	);
+	const char *syms[3] = {
+		"uprobe_link_info_func_1",
+		"uprobe_link_info_func_2",
+		"uprobe_link_info_func_3",
+	};
+	__u64 cookies[3] = {
+		0xdead,
+		0xbeef,
+		0xcafe,
+	};
+	const char *sema[3] = {
+		"uprobe_link_info_sema_1",
+		"uprobe_link_info_sema_2",
+		"uprobe_link_info_sema_3",
+	};
+	__u64 *offsets, *ref_ctr_offsets;
+	struct bpf_link *link;
+	int link_fd, err;
+
+	err = elf_resolve_syms_offsets("/proc/self/exe", 3, sema,
+				       (unsigned long **) &ref_ctr_offsets, STT_OBJECT);
+	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_object"))
+		return;
+
+	err = elf_resolve_syms_offsets("/proc/self/exe", 3, syms,
+				       (unsigned long **) &offsets, STT_FUNC);
+	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_func"))
+		return;
+
+	opts.syms = syms;
+	opts.cookies = &cookies[0];
+	opts.ref_ctr_offsets = (unsigned long *) &ref_ctr_offsets[0];
+	opts.cnt = ARRAY_SIZE(syms);
+
+	link = bpf_program__attach_uprobe_multi(skel->progs.umulti_run, 0,
+						"/proc/self/exe", NULL, &opts);
+	if (!ASSERT_OK_PTR(link, "bpf_program__attach_uprobe_multi"))
+		goto out;
+
+	link_fd = bpf_link__fd(link);
+	if (invalid)
+		verify_umulti_invalid_user_buffer(link_fd);
+	else
+		verify_umulti_link_info(link_fd, retprobe, offsets, cookies, ref_ctr_offsets);
+
+	bpf_link__destroy(link);
+out:
+	free(offsets);
+}
+
 void test_fill_link_info(void)
 {
 	struct test_fill_link_info *skel;
@@ -339,6 +523,13 @@ void test_fill_link_info(void)
 	if (test__start_subtest("kprobe_multi_invalid_ubuff"))
 		test_kprobe_multi_fill_link_info(skel, true, true);
 
+	if (test__start_subtest("uprobe_multi_link_info"))
+		test_uprobe_multi_fill_link_info(skel, false, false);
+	if (test__start_subtest("uretprobe_multi_link_info"))
+		test_uprobe_multi_fill_link_info(skel, true, false);
+	if (test__start_subtest("uprobe_multi_invalid"))
+		test_uprobe_multi_fill_link_info(skel, false, true);
+
 cleanup:
 	test_fill_link_info__destroy(skel);
 }
diff --git a/tools/testing/selftests/bpf/progs/test_fill_link_info.c b/tools/testing/selftests/bpf/progs/test_fill_link_info.c
index 564f402d56fe..69509f8bb680 100644
--- a/tools/testing/selftests/bpf/progs/test_fill_link_info.c
+++ b/tools/testing/selftests/bpf/progs/test_fill_link_info.c
@@ -39,4 +39,10 @@ int BPF_PROG(kmulti_run)
 	return 0;
 }
 
+SEC("uprobe.multi")
+int BPF_PROG(umulti_run)
+{
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.42.0

Re: [PATCHv3 bpf-next 5/6] selftests/bpf: Add link_info test for uprobe_multi link

[Yonghong Song]

On 11/20/23 9:56 AM, Jiri Olsa wrote:
> Adding fill_link_info test for uprobe_multi link.
>
> Setting up uprobes with bogus ref_ctr_offsets and cookie values
> to test all the bpf_link_info::uprobe_multi fields.
>
> Acked-by: Song Liu <song@kernel.org>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>   .../selftests/bpf/prog_tests/fill_link_info.c | 191 ++++++++++++++++++
>   .../selftests/bpf/progs/test_fill_link_info.c |   6 +
>   2 files changed, 197 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> index 9294cb8d7743..fdf2c6b8c0cf 100644
> --- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> +++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> @@ -7,6 +7,7 @@
>   #include <test_progs.h>
>   #include "trace_helpers.h"
>   #include "test_fill_link_info.skel.h"
> +#include "bpf/libbpf_internal.h"
>   
>   #define TP_CAT "sched"
>   #define TP_NAME "sched_switch"
> @@ -300,6 +301,189 @@ static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
>   	bpf_link__destroy(link);
>   }
>   
> +/* Initialize semaphore variables so they don't end up in bss
> + * section and we could get retrieve their offsets.
> + */
> +static short uprobe_link_info_sema_1 = 1;
> +static short uprobe_link_info_sema_2 = 1;
> +static short uprobe_link_info_sema_3 = 1;

I guess The typical sema value starting value should be 0, right?
If this is the case, the above is not a good example.
So the issue is that current libbpf does not support
retrieving offset from .bss section? Do you know why?

In selftest udst.c, we have semaphore defined as
usdt.c:unsigned short test_usdt0_semaphore SEC(".probes");
usdt.c:unsigned short test_usdt3_semaphore SEC(".probes");
usdt.c:unsigned short test_usdt12_semaphore SEC(".probes");

Will the following work?
static short uprobe_link_info_sema_1 SEC(".probes");
...

> +
> +noinline void uprobe_link_info_func_1(void)
> +{
> +	uprobe_link_info_sema_1++;
> +	asm volatile ("");

The 'asm volatile' above intends to prevent compiler from
doing 'implicit' inlining. So as a convention let us
switch statement order to

	asm volatile ("");
	uprobe_link_info_sema_1++;

Similarly for below.

> +}
> +
> +noinline void uprobe_link_info_func_2(void)
> +{
> +	uprobe_link_info_sema_2++;
> +	asm volatile ("");
> +}
> +
> +noinline void uprobe_link_info_func_3(void)
> +{
> +	uprobe_link_info_sema_3++;
> +	asm volatile ("");
> +}
> +
> +static int
> +verify_umulti_link_info(int fd, bool retprobe, __u64 *offsets,
> +			__u64 *cookies, __u64 *ref_ctr_offsets)
> +{
> +	char path[PATH_MAX], path_buf[PATH_MAX];
> +	struct bpf_link_info info;
> +	__u32 len = sizeof(info);
> +	__u64 ref_ctr_offsets_buf[3];
> +	__u64 offsets_buf[3];
> +	__u64 cookies_buf[3];
> +	int i, err, bit;
> +	__u32 count = 0;
> +
> +	memset(path, 0, sizeof(path));
> +	err = readlink("/proc/self/exe", path, sizeof(path));
> +	if (!ASSERT_NEQ(err, -1, "readlink"))
> +		return -1;
> +
> +	for (bit = 0; bit < 8; bit++) {
> +		memset(&info, 0, sizeof(info));
> +		info.uprobe_multi.path = ptr_to_u64(path_buf);
> +		info.uprobe_multi.path_size = sizeof(path_buf);
> +		info.uprobe_multi.count = count;
> +
> +		if (bit & 0x1)
> +			info.uprobe_multi.offsets = ptr_to_u64(offsets_buf);
> +		if (bit & 0x2)
> +			info.uprobe_multi.cookies = ptr_to_u64(cookies_buf);
> +		if (bit & 0x4)
> +			info.uprobe_multi.ref_ctr_offsets = ptr_to_u64(ref_ctr_offsets_buf);
> +
> +		err = bpf_link_get_info_by_fd(fd, &info, &len);
> +		if (!ASSERT_OK(err, "bpf_link_get_info_by_fd"))
> +			return -1;
> +
> +		if (!ASSERT_EQ(info.type, BPF_LINK_TYPE_UPROBE_MULTI, "info.type"))
> +			return -1;
> +
> +		ASSERT_EQ(info.uprobe_multi.pid, getpid(), "info.uprobe_multi.pid");
> +		ASSERT_EQ(info.uprobe_multi.count, 3, "info.uprobe_multi.count");
> +		ASSERT_EQ(info.uprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN,
> +			  retprobe, "info.uprobe_multi.flags.retprobe");
> +		ASSERT_EQ(info.uprobe_multi.path_size, strlen(path), "info.uprobe_multi.path_size");
> +		ASSERT_STREQ(path_buf, path, "info.uprobe_multi.path");
> +
> +		for (i = 0; i < info.uprobe_multi.count; i++) {
> +			if (info.uprobe_multi.offsets)
> +				ASSERT_EQ(offsets_buf[i], offsets[i], "info.uprobe_multi.offsets");
> +			if (info.uprobe_multi.cookies)
> +				ASSERT_EQ(cookies_buf[i], cookies[i], "info.uprobe_multi.cookies");
> +			if (info.uprobe_multi.ref_ctr_offsets) {
> +				ASSERT_EQ(ref_ctr_offsets_buf[i], ref_ctr_offsets[i],
> +					  "info.uprobe_multi.ref_ctr_offsets");
> +			}
> +		}
> +		count = count ?: info.uprobe_multi.count;
> +	}
> +
> +	return 0;
> +}
> +
> +static void verify_umulti_invalid_user_buffer(int fd)
> +{
> +	struct bpf_link_info info;
> +	__u32 len = sizeof(info);
> +	__u64 buf[3];
> +	int err;
> +
> +	/* upath_size defined, not path */
> +	memset(&info, 0, sizeof(info));
> +	info.uprobe_multi.path_size = 3;
> +	err = bpf_link_get_info_by_fd(fd, &info, &len);
> +	ASSERT_EQ(err, -EINVAL, "failed_upath_size");
> +
> +	/* path has wrong pointer */
> +	memset(&info, 0, sizeof(info));
> +	info.uprobe_multi.path_size = PATH_MAX;
> +	info.uprobe_multi.path = 123;
> +	err = bpf_link_get_info_by_fd(fd, &info, &len);
> +	ASSERT_EQ(err, -EFAULT, "failed_bad_path_ptr");
> +
> +	/* count zero, with offsets */
> +	memset(&info, 0, sizeof(info));
> +	info.uprobe_multi.offsets = ptr_to_u64(buf);
> +	err = bpf_link_get_info_by_fd(fd, &info, &len);
> +	ASSERT_EQ(err, -EINVAL, "failed_count");
> +
> +	/* offsets not big enough */
> +	memset(&info, 0, sizeof(info));
> +	info.uprobe_multi.offsets = ptr_to_u64(buf);
> +	info.uprobe_multi.count = 2;
> +	err = bpf_link_get_info_by_fd(fd, &info, &len);
> +	ASSERT_EQ(err, -ENOSPC, "failed_small_count");
> +
> +	/* offsets has wrong pointer */
> +	memset(&info, 0, sizeof(info));
> +	info.uprobe_multi.offsets = 123;
> +	info.uprobe_multi.count = 3;
> +	err = bpf_link_get_info_by_fd(fd, &info, &len);
> +	ASSERT_EQ(err, -EFAULT, "failed_wrong_offsets");
> +}
> +
> +static void test_uprobe_multi_fill_link_info(struct test_fill_link_info *skel,
> +					     bool retprobe, bool invalid)
> +{
> +	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
> +		.retprobe = retprobe,
> +	);
> +	const char *syms[3] = {
> +		"uprobe_link_info_func_1",
> +		"uprobe_link_info_func_2",
> +		"uprobe_link_info_func_3",
> +	};
> +	__u64 cookies[3] = {
> +		0xdead,
> +		0xbeef,
> +		0xcafe,
> +	};
> +	const char *sema[3] = {
> +		"uprobe_link_info_sema_1",
> +		"uprobe_link_info_sema_2",
> +		"uprobe_link_info_sema_3",
> +	};
> +	__u64 *offsets, *ref_ctr_offsets;
> +	struct bpf_link *link;
> +	int link_fd, err;
> +
> +	err = elf_resolve_syms_offsets("/proc/self/exe", 3, sema,
> +				       (unsigned long **) &ref_ctr_offsets, STT_OBJECT);
> +	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_object"))
> +		return;
> +
> +	err = elf_resolve_syms_offsets("/proc/self/exe", 3, syms,
> +				       (unsigned long **) &offsets, STT_FUNC);
> +	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_func"))
> +		return;

potential leak of ref_ctr_offsets?

> +
> +	opts.syms = syms;
> +	opts.cookies = &cookies[0];
> +	opts.ref_ctr_offsets = (unsigned long *) &ref_ctr_offsets[0];
> +	opts.cnt = ARRAY_SIZE(syms);
> +
> +	link = bpf_program__attach_uprobe_multi(skel->progs.umulti_run, 0,
> +						"/proc/self/exe", NULL, &opts);
> +	if (!ASSERT_OK_PTR(link, "bpf_program__attach_uprobe_multi"))
> +		goto out;
> +
> +	link_fd = bpf_link__fd(link);
> +	if (invalid)
> +		verify_umulti_invalid_user_buffer(link_fd);
> +	else
> +		verify_umulti_link_info(link_fd, retprobe, offsets, cookies, ref_ctr_offsets);
> +
> +	bpf_link__destroy(link);
> +out:
> +	free(offsets);

Should we free ref_ctr_offsets here?

> +}
> +
> [...]

Re: [PATCHv3 bpf-next 5/6] selftests/bpf: Add link_info test for uprobe_multi link

[Jiri Olsa]

On Mon, Nov 20, 2023 at 10:22:26AM -0800, Yonghong Song wrote:
> 
> On 11/20/23 9:56 AM, Jiri Olsa wrote:
> > Adding fill_link_info test for uprobe_multi link.
> > 
> > Setting up uprobes with bogus ref_ctr_offsets and cookie values
> > to test all the bpf_link_info::uprobe_multi fields.
> > 
> > Acked-by: Song Liu <song@kernel.org>
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >   .../selftests/bpf/prog_tests/fill_link_info.c | 191 ++++++++++++++++++
> >   .../selftests/bpf/progs/test_fill_link_info.c |   6 +
> >   2 files changed, 197 insertions(+)
> > 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> > index 9294cb8d7743..fdf2c6b8c0cf 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/fill_link_info.c
> > @@ -7,6 +7,7 @@
> >   #include <test_progs.h>
> >   #include "trace_helpers.h"
> >   #include "test_fill_link_info.skel.h"
> > +#include "bpf/libbpf_internal.h"
> >   #define TP_CAT "sched"
> >   #define TP_NAME "sched_switch"
> > @@ -300,6 +301,189 @@ static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
> >   	bpf_link__destroy(link);
> >   }
> > +/* Initialize semaphore variables so they don't end up in bss
> > + * section and we could get retrieve their offsets.
> > + */
> > +static short uprobe_link_info_sema_1 = 1;
> > +static short uprobe_link_info_sema_2 = 1;
> > +static short uprobe_link_info_sema_3 = 1;
> 
> I guess The typical sema value starting value should be 0, right?
> If this is the case, the above is not a good example.
> So the issue is that current libbpf does not support
> retrieving offset from .bss section? Do you know why?

hum, I can't recall why it was the problem, because it seems to work
with .bss now when I try it ... anyway I think your suggestion below
is better

> 
> In selftest udst.c, we have semaphore defined as
> usdt.c:unsigned short test_usdt0_semaphore SEC(".probes");
> usdt.c:unsigned short test_usdt3_semaphore SEC(".probes");
> usdt.c:unsigned short test_usdt12_semaphore SEC(".probes");
> 
> Will the following work?
> static short uprobe_link_info_sema_1 SEC(".probes");

yes, that will work and it's better

> ...
> 
> > +
> > +noinline void uprobe_link_info_func_1(void)
> > +{
> > +	uprobe_link_info_sema_1++;
> > +	asm volatile ("");
> 
> The 'asm volatile' above intends to prevent compiler from
> doing 'implicit' inlining. So as a convention let us
> switch statement order to
> 
> 	asm volatile ("");
> 	uprobe_link_info_sema_1++;
> 
> Similarly for below.

ok

SNIP

> > +static void test_uprobe_multi_fill_link_info(struct test_fill_link_info *skel,
> > +					     bool retprobe, bool invalid)
> > +{
> > +	LIBBPF_OPTS(bpf_uprobe_multi_opts, opts,
> > +		.retprobe = retprobe,
> > +	);
> > +	const char *syms[3] = {
> > +		"uprobe_link_info_func_1",
> > +		"uprobe_link_info_func_2",
> > +		"uprobe_link_info_func_3",
> > +	};
> > +	__u64 cookies[3] = {
> > +		0xdead,
> > +		0xbeef,
> > +		0xcafe,
> > +	};
> > +	const char *sema[3] = {
> > +		"uprobe_link_info_sema_1",
> > +		"uprobe_link_info_sema_2",
> > +		"uprobe_link_info_sema_3",
> > +	};
> > +	__u64 *offsets, *ref_ctr_offsets;
> > +	struct bpf_link *link;
> > +	int link_fd, err;
> > +
> > +	err = elf_resolve_syms_offsets("/proc/self/exe", 3, sema,
> > +				       (unsigned long **) &ref_ctr_offsets, STT_OBJECT);
> > +	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_object"))
> > +		return;
> > +
> > +	err = elf_resolve_syms_offsets("/proc/self/exe", 3, syms,
> > +				       (unsigned long **) &offsets, STT_FUNC);
> > +	if (!ASSERT_OK(err, "elf_resolve_syms_offsets_func"))
> > +		return;
> 
> potential leak of ref_ctr_offsets?

ugh yep, will fix

> 
> > +
> > +	opts.syms = syms;
> > +	opts.cookies = &cookies[0];
> > +	opts.ref_ctr_offsets = (unsigned long *) &ref_ctr_offsets[0];
> > +	opts.cnt = ARRAY_SIZE(syms);
> > +
> > +	link = bpf_program__attach_uprobe_multi(skel->progs.umulti_run, 0,
> > +						"/proc/self/exe", NULL, &opts);
> > +	if (!ASSERT_OK_PTR(link, "bpf_program__attach_uprobe_multi"))
> > +		goto out;
> > +
> > +	link_fd = bpf_link__fd(link);
> > +	if (invalid)
> > +		verify_umulti_invalid_user_buffer(link_fd);
> > +	else
> > +		verify_umulti_link_info(link_fd, retprobe, offsets, cookies, ref_ctr_offsets);
> > +
> > +	bpf_link__destroy(link);
> > +out:
> > +	free(offsets);
> 
> Should we free ref_ctr_offsets here?

yes, thanks

jirka

[PATCHv3 bpf-next 6/6] bpftool: Add support to display uprobe_multi links

[Jiri Olsa]

Adding support to display details for uprobe_multi links,
both plain:

  # bpftool link -p
  ...
  24: uprobe_multi  prog 126
          uprobe.multi  path /home/jolsa/bpf/test_progs  func_cnt 3  pid 4143
          offset             ref_ctr_offset     cookies
          0xd1f88            0xf5d5a8           0xdead
          0xd1f8f            0xf5d5aa           0xbeef
          0xd1f96            0xf5d5ac           0xcafe

and json:

  # bpftool link -p
  [{
  ...
      },{
          "id": 24,
          "type": "uprobe_multi",
          "prog_id": 126,
          "retprobe": false,
          "path": "/home/jolsa/bpf/test_progs",
          "func_cnt": 3,
          "pid": 4143,
          "funcs": [{
                  "offset": 860040,
                  "ref_ctr_offset": 16111016,
                  "cookie": 57005
              },{
                  "offset": 860047,
                  "ref_ctr_offset": 16111018,
                  "cookie": 48879
              },{
                  "offset": 860054,
                  "ref_ctr_offset": 16111020,
                  "cookie": 51966
              }
          ]
      }
  ]

Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/bpf/bpftool/link.c | 105 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 103 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index a1528cde81ab..d198adf77d81 100644
--- a/tools/bpf/bpftool/link.c
+++ b/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 != (__u32) -1)
+		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;
 }
-- 
2.42.0

Re: [PATCHv3 bpf-next 6/6] bpftool: Add support to display uprobe_multi links

[Yonghong Song]

On 11/20/23 9:56 AM, Jiri Olsa wrote:
> Adding support to display details for uprobe_multi links,
> both plain:
>
>    # bpftool link -p
>    ...
>    24: uprobe_multi  prog 126
>            uprobe.multi  path /home/jolsa/bpf/test_progs  func_cnt 3  pid 4143
>            offset             ref_ctr_offset     cookies
>            0xd1f88            0xf5d5a8           0xdead
>            0xd1f8f            0xf5d5aa           0xbeef
>            0xd1f96            0xf5d5ac           0xcafe
>
> and json:
>
>    # bpftool link -p
>    [{
>    ...
>        },{
>            "id": 24,
>            "type": "uprobe_multi",
>            "prog_id": 126,
>            "retprobe": false,
>            "path": "/home/jolsa/bpf/test_progs",
>            "func_cnt": 3,
>            "pid": 4143,
>            "funcs": [{
>                    "offset": 860040,
>                    "ref_ctr_offset": 16111016,
>                    "cookie": 57005
>                },{
>                    "offset": 860047,
>                    "ref_ctr_offset": 16111018,
>                    "cookie": 48879
>                },{
>                    "offset": 860054,
>                    "ref_ctr_offset": 16111020,
>                    "cookie": 51966
>                }
>            ]
>        }
>    ]
>
> Acked-by: Song Liu <song@kernel.org>
> Reviewed-by: Quentin Monnet <quentin@isovalent.com>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>   tools/bpf/bpftool/link.c | 105 ++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 103 insertions(+), 2 deletions(-)
>
> diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
> index a1528cde81ab..d198adf77d81 100644
> --- a/tools/bpf/bpftool/link.c
> +++ b/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 != (__u32) -1)
> +		printf("pid %d  ", info->uprobe_multi.pid);

Could you explain when info->uprobe_multi.pid could be -1?
 From patch 3, I see:
	info->uprobe_multi.pid = umulti_link->task ?
			 task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;
and cannot find how -1 could be assigned to 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;
> [...]

Re: [PATCHv3 bpf-next 6/6] bpftool: Add support to display uprobe_multi links

[Jiri Olsa]

On Mon, Nov 20, 2023 at 10:32:02AM -0800, Yonghong Song wrote:

SNIP

> > +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 != (__u32) -1)
> > +		printf("pid %d  ", info->uprobe_multi.pid);
> 
> Could you explain when info->uprobe_multi.pid could be -1?
> From patch 3, I see:
> 	info->uprobe_multi.pid = umulti_link->task ?
> 			 task_pid_nr_ns(umulti_link->task, task_active_pid_ns(current)) : 0;
> and cannot find how -1 could be assigned to info->uprobe_multi.pid.

ah it's leftover from previous version fix.. and I forgot to update
the bpftool code.. nice catch, thanks

jirka

> 
> > +
> > +	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;
> > [...]