Re: [PATCH v6 bpf-next 10/10] selftests/bpf: add build ID tests

[Eduard Zingerman <eddyz87@gmail.com>]

On Thu, 2024-08-22 at 15:55 -0700, Andrii Nakryiko wrote:

> > > +     madvise(addr, page_sz, MADV_POPULATE_READ);
> > 
> > Nit: check error code?
>
> Well, even if this errors out there is no one to notice and do
> anything about it, given this is in a forked process. The idea,
> though, is that if this doesn't work, we'll catch it as part of the
> actual selftest.

Ok.

[...]

> In my QEMU I only get 3:
> 
> FRAME #00: BUILD ID = d370860567af6d28316d45726045f1c59bbfc416 OFFSET = 2c4156
> FRAME #01: BUILD ID = d370860567af6d28316d45726045f1c59bbfc416 OFFSET = 393ac7
> FRAME #02: BUILD ID = 8bfe03f6bf9b6a6e2591babd0bbc266837d8f658 OFFSET = 27cd0
> 
> But see below, for my actual devserver there are 4 frames. My bet
> would be that 568ef is libc. A bit confused why you get frame 04 from
> uprobe_multi, but maybe that's how things work with musl or whatever?
> Don't know. Check libc.so.

Oh, right, I had to check libc build-id inside QEMU, not outside...
Yes, this is libc signature.
This figures, thank you for explaining.

[...]