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Date: Thu, 28 Mar 2024 21:48:24 -0400
From: Rich Felker <dalias@...c.org>
To: Max Filippov <jcmvbkbc@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: [RFC v2 0/2] xtensa FDPIC port
On Thu, Mar 28, 2024 at 05:48:50PM -0700, Max Filippov wrote:
> On Thu, Mar 28, 2024 at 4:00 PM Rich Felker <dalias@...c.org> wrote:
> > On Thu, Mar 28, 2024 at 01:03:17PM -0700, Max Filippov wrote:
> > > functional/dlopen fails with the
> > > src/functional/dlopen.c:39: dlsym main failed: (null)
> > > There's no failure in the dlsym call, but the pointers don't match.
> >
> > Is this something related to canonical function descriptors? Is it
> > musl's fault or a bug in the tooling? I suspect the latter.
>
> Yes, dlsym() returns the pointer into def.dso->funcdescs,
> but (void *)main returns the pointer to the canonical function
> descriptor. I understand that the linker must use the
> R_XTENSA_FUNCDESC relocation for the locally defined
> global symbol instead of the .rofixup entries.
If the xtensa FDPIC ABI is going to be that the linker makes canonical
function descriptors, I think that's workable, but the dynamic linker
would need a way to find and usee them. I'm not sure how that would
work.
The simple (but probably less efficient) way is to copy what SH did
and have the dynamic linker always be responsible for them (load
descriptor address from GOT).
Rich
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