On Wed, Jul 10, 2024 at 12:38 PM Jiri Olsa <olsaj...@gmail.com> wrote:
>
> On Wed, Jul 10, 2024 at 11:23:10AM -0700, Andrii Nakryiko wrote:
> > On Wed, Jul 10, 2024 at 9:49 AM Jiri Olsa <olsaj...@gmail.com> wrote:
> > >
> > > On Wed, Jul 10, 2024 at 06:31:33PM +0200, Oleg Nesterov wrote:
> > >
> > > SNIP
> > >
> > > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > > > index 467f358c8ce7..7571811127a2 100644
> > > > --- a/kernel/trace/bpf_trace.c
> > > > +++ b/kernel/trace/bpf_trace.c
> > > > @@ -3157,6 +3157,7 @@ struct bpf_uprobe {
> > > > loff_t offset;
> > > > unsigned long ref_ctr_offset;
> > > > u64 cookie;
> > > > + struct uprobe *uprobe;
> > > > struct uprobe_consumer consumer;
> > > > };
> > > >
> > > > @@ -3180,10 +3181,8 @@ static void bpf_uprobe_unregister(struct path
> > > > *path, struct bpf_uprobe *uprobes,
> > > > {
> > > > u32 i;
> > > >
> > > > - for (i = 0; i < cnt; i++) {
> > > > - uprobe_unregister(d_real_inode(path->dentry),
> > > > uprobes[i].offset,
> > > > - &uprobes[i].consumer);
> > > > - }
> > >
> > > nice, we could also drop path argument now
> >
> > see my comments to Oleg, I think we can/should get rid of link->path
> > altogether if uprobe itself keeps inode alive.
>
> yea, I was thinking of that, but then it's kind of useful to have it in
> bpf_uprobe_multi_link_fill_link_info, otherwise we have to take it from
> first uprobe in the link, but ok, still probably worth to remove it ;-)
if we need it for link_info, probably cleaner to just keep it, no big deal then
>
> anyway as you wrote it's ok for follow up cleanup, I'll check on that
>
> >
> > BTW, Jiri, do we have any test for multi-uprobe that simulates partial
> > attachment success/failure (whichever way you want to look at it). It
> > would be super useful to have to check at least some error handling
> > code in the uprobe code base. If we don't, do you mind adding
> > something simple to BPF selftests?
>
> there's test_attach_api_fails, but I think all checked fails are before
> actually calling uprobe_register function
>
> I think there are few ways to fail the uprobe_register, like install it
> on top of int3.. will check add some test for that
>
great, thank you!
> jirka
>
> >
> > >
> > > jirka
> > >
> > > > + for (i = 0; i < cnt; i++)
> > > > + uprobe_unregister(uprobes[i].uprobe,
> > > > &uprobes[i].consumer);
> > > > }
> > > >
> > > > static void bpf_uprobe_multi_link_release(struct bpf_link *link)
> > > > @@ -3477,11 +3476,12 @@ int bpf_uprobe_multi_link_attach(const union
> > > > bpf_attr *attr, struct bpf_prog *pr
> > > > &bpf_uprobe_multi_link_lops, prog);
> > > >
> > > > for (i = 0; i < cnt; i++) {
> > > > - err = uprobe_register(d_real_inode(link->path.dentry),
> > > > + uprobes[i].uprobe =
> > > > uprobe_register(d_real_inode(link->path.dentry),
> > > > uprobes[i].offset,
> > > > uprobes[i].ref_ctr_offset,
> > > > &uprobes[i].consumer);
> > > > - if (err) {
> > > > + if (IS_ERR(uprobes[i].uprobe)) {
> > > > + err = PTR_ERR(uprobes[i].uprobe);
> > > > bpf_uprobe_unregister(&path, uprobes, i);
> > > > goto error_free;
> > > > }
