On Thu, Oct 26, 2023 at 07:57:27PM +0800, Yafang Shao wrote:
> On Thu, Oct 26, 2023 at 4:24 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 | 68 ++++++++++++++++++++++++++++++++++
> > tools/include/uapi/linux/bpf.h | 10 +++++
> > 3 files changed, 88 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 0f6cdf52b1da..960cf2914d63 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;
>
> The bpf cookie for the perf_event link is exposed through
> 'pid_iter.bpf.c,' while the cookies for the tracing link and
> kprobe_multi link are not exposed at all. This inconsistency can be
> confusing. I believe it would be better to include all of them in the
> link_info. The reason is that 'pid_iter' depends on the task holding
> the links, which may not exist. However, I think we handle this in a
> separate patchset. What do you think?
right, I think we should add cookies for both kprobe_multi
and tracing link, I'll add that in new version
thanks,
jirka
>
> > + __u32 path_max; /* in/out: uprobe_multi 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 843b3846d3f8..9f8ad19a1a93 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -3042,6 +3042,7 @@ struct bpf_uprobe_multi_link {
> > u32 cnt;
> > struct bpf_uprobe *uprobes;
> > struct task_struct *task;
> > + u32 flags;
> > };
> >
> > struct bpf_uprobe_multi_run_ctx {
> > @@ -3081,9 +3082,75 @@ 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_max = info->uprobe_multi.path_max;
> > + struct bpf_uprobe_multi_link *umulti_link;
> > + u32 ucount = info->uprobe_multi.count;
> > + int err = 0, i;
> > + char *p, *buf;
> > + long left;
> > +
> > + if (!upath ^ !upath_max)
> > + return -EINVAL;
> > +
> > + if (!uoffsets ^ !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(umulti_link->task) : (u32) -1;
> > +
> > + if (upath) {
> > + if (upath_max > PATH_MAX)
> > + return -E2BIG;
> > + buf = kmalloc(upath_max, GFP_KERNEL);
> > + if (!buf)
> > + return -ENOMEM;
> > + p = d_path(&umulti_link->path, buf, upath_max);
> > + if (IS_ERR(p)) {
> > + kfree(buf);
> > + return -ENOSPC;
> > + }
> > + left = copy_to_user(upath, p, buf + upath_max - p);
> > + kfree(buf);
> > + if (left)
> > + return -EFAULT;
> > + }
> > +
> > + if (!uoffsets)
> > + return 0;
> > +
> > + 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,
> > @@ -3272,6 +3339,7 @@ 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..960cf2914d63 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_max; /* in/out: uprobe_multi 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
> >
>
>
> --
> Regards
> Yafang
