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rtld-elf: Support upcoming new ABI for R_MORELLO_JUMP_SLOT #2081

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Apr 30, 2024
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rtld-elf: Support upcoming new ABI for R_MORELLO_JUMP_SLOT #2081

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37 changes: 28 additions & 9 deletions libexec/rtld-elf/aarch64/reloc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -349,20 +349,39 @@ reloc_plt(Obj_Entry *obj, int flags, RtldLockState *lockstate)
FUNC_PTR_REMOVE_PERMS);
#endif
for (rela = obj->pltrela; rela < relalim; rela++) {
Elf_Addr *where;
uintptr_t *where;
#ifdef __CHERI_PURE_CAPABILITY__
Elf_Addr *fragment;
#endif

where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
where = (uintptr_t *)(obj->relocbase + rela->r_offset);
#ifdef __CHERI_PURE_CAPABILITY__
fragment = (Elf_Addr *)where;
#endif

switch(ELF_R_TYPE(rela->r_info)) {
#ifdef __CHERI_PURE_CAPABILITY__
case R_MORELLO_JUMP_SLOT:
/*
* XXX: This would be far more natural if the linker
* made it an R_MORELLO_RELATIVE-like fragment instead.
* https://git.morello-project.org/morello/llvm-project/-/issues/19
* Old ABI:
* - Treat as R_AARCH64_JUMP_SLOT
*
* New ABI:
* - Same representation as R_MORELLO_RELATIVE
*
* Determine which this is based on whether there's
* non-zero metadata next to the address. Remove once
* the new ABI is old enough that we can assume it is
* in use.
*/
*(uintptr_t *)where = cheri_sealentry(jump_slot_base +
*where);
if (fragment[1] == 0)
*where = cheri_sealentry(jump_slot_base +
fragment[0]);
else
*where = init_cap_from_fragment(fragment,
obj->relocbase, obj->text_rodata_cap,
(Elf_Addr)(uintptr_t)obj->relocbase,
rela->r_addend);
break;
#else
case R_AARCH64_JUMP_SLOT:
Expand All @@ -374,8 +393,8 @@ reloc_plt(Obj_Entry *obj, int flags, RtldLockState *lockstate)
#else
case R_AARCH64_TLSDESC:
#endif
reloc_tlsdesc(obj, rela, where, SYMLOOK_IN_PLT | flags,
lockstate);
reloc_tlsdesc(obj, rela, (Elf_Addr *)where,
SYMLOOK_IN_PLT | flags, lockstate);
break;
#ifdef __CHERI_PURE_CAPABILITY__
case R_MORELLO_IRELATIVE:
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