On Thu, Nov 9, 2023 at 1:29 AM Jiri Olsa <jolsa@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> include/uapi/linux/bpf.h | 10 +++++
> kernel/trace/bpf_trace.c | 69 ++++++++++++++++++++++++++++++++++
> tools/include/uapi/linux/bpf.h | 10 +++++
> 3 files changed, 89 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 0f6cdf52b1da..05b355da4508 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -6556,6 +6556,16 @@ 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;
> + __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 52c1ec3a0467..1ea54f3b3f73 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3046,6 +3046,7 @@ struct bpf_uprobe_multi_link {
> u32 cnt;
> struct bpf_uprobe *uprobes;
> struct task_struct *task;
> + u32 flags;
> };
>
> struct bpf_uprobe_multi_run_ctx {
> @@ -3085,9 +3086,76 @@ 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 ^ !ucount)
uoffsets is not the only one that requires ucount, right?
> + 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;
> + }
> + left = copy_to_user(upath, p, buf + upath_size - p);
> + kfree(buf);
> + if (left)
> + return -EFAULT;
hmm.. I expected the actual path_size to be reported back to the
user?.. Is there a problem with doing that?
> + }
> +
> + if (!uoffsets)
> + return 0;
why guard by uoffsets? what if users only wanted cookies? I think each
array should do its own checking and be independent, no?
> +
> + if (ucount < umulti_link->cnt)
> + err = -ENOSPC;
> + else
> + ucount = umulti_link->cnt;
> +
> + for (i = 0; i < ucount; i++) {
> + if (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,
> @@ -3276,6 +3344,7 @@ 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 0f6cdf52b1da..05b355da4508 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -6556,6 +6556,16 @@ 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;
> + __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;
> --
> 2.41.0
>
