On Wed, Jul 10, 2024 at 11:23:10AM -0700, Andrii Nakryiko wrote:
> On Wed, Jul 10, 2024 at 9:49 AM Jiri Olsa <[email protected]> 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 ;-)
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
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;
> > > }
