* Mathieu Desnoyers:
>> It's the registration from libc.so which needs some care. In
>> particular, we must not override an existing registration.
>
> OK, so it could check if __rseq_abi.cpu_id is -1, and only
> perform registration if it is the case. Or do you have another
> approach in mind ?
No, __rseq_abi will not be shared with the outer libc, so the inner libc
will always see -1 there, even if the outer libc has performed
registration.
libio/vtables.c has some example what you can do:
/* In case this libc copy is in a non-default namespace, we always
need to accept foreign vtables because there is always a
possibility that FILE * objects are passed across the linking
boundary. */
{
Dl_info di;
struct link_map *l;
if (!rtld_active ()
|| (_dl_addr (_IO_vtable_check, &di, &l, NULL) != 0
&& l->l_ns != LM_ID_BASE))
return;
}
_IO_vtable_check would have to be replaced with your own function; the
actual function doesn't really matter.
The rtld_active check covers the static dlopen case, where
rtld_active () is false in the inner libc.
Thanks,
Florian
