Re: [PATCH 2/2] LoongArch: Fix R_LARCH_IRELATIVE insertion after elf_link_sort_relocs

[Xi Ruoyao <xry111@xry111.site>]

On Thu, 2022-09-15 at 21:03 +0800, liuzhensong wrote:
> It May be unnecessary find the slot in section of .rela.dyn.
> 
> The slot of R_LARCH_IRELATIVE is within the scope relplt->contents (the 
> space
> 
> is calculated in function local_allocate_ifunc_dyn_relocs).
> 
> We can find the slot just in relplt->contents(Only for dynamic ifunc. I 
> did not test for static ifunc.).

The problem is loongarch_elf_finish_dynamic_symbol runs after
elf_link_sort_relocs.  elf_link_sort_relocs basically does:

(pseudo code)

buffer = []
for section in {input of .rela.dyn}
    buffer += (section.content) as [RELA]

buffer.sort_by(some_comparator)

buffer = buffer as [byte]
for section in {input of .rela.dyn}
    section.content = buffer[..section.content.len()]
    buffer = buffer[section.content.len()..]

So a "slot" in relplt->contents can end up elsewhere.  You can read the
code of elf_link_sort_relocs to see it...

I can try to write a test case for this, but it's 04:00 AM now so I'd do
it after a sleep...
-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University