Re: [PATCH v2] RISC-V: Fix IFUNC resolver cannot access gp pointer

[Florian Weimer <fweimer@redhat.com>]

* Yangyu Chen:

> I proposed an idea to bypass the GP initialization by restricting
> the use of the norelax attribute for all callees of IFUNC. In this
> case, the linker will retain auipc + load/store instructions to
> access global variables based on pc-relative address mode instead
> of relaxing them to a single load/store at a +- 2KB offset from the
> GP.

What do you mean by “all callees of IFUNC”?  This issue only affects the
resolver, not the IFUNC implementation itself.

As I said, if the glibc dynamic linker has a reliable way to identify
the expected GP value, it can set GP before calling the resolver.  That
requires some form of ABI change, but it would be backwards compatible.
(We just won't be able to do it if the binary doesn't contain the required
information, and the __global_pointer$ dynamic symbol is absent as
well.)

The technical side should be easy to implement.

Thanks,
Florian