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LoongArch: Move ifunc info to rela.dyn from rela.plt.

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Delete R_LARCH_IRELATIVE from dynamic loader (glibc ld.so) when
  loading lazy function (rela.plt section).

  In dynamic programes, move ifunc dynamic relocate info to section
  srelgot from srelplt.

  bfd/
    elfnn-loongarch.c
This commit is contained in:
liuzhensong
2022-07-15 16:07:48 +08:00
parent f09482a874
commit bc2a35c0b4
1 changed files with 345 additions and 30 deletions
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375
bfd/elfnn-loongarch.c
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@ -1207,6 +1207,259 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
return true;
}
/* A modified version of _bfd_elf_allocate_ifunc_dyn_relocs.
For local def and ref ifunc,
dynamic relocations are stored in
1. rela.srelgot section in dynamic object (dll or exec).
2. rela.irelplt section in static executable.
Unlike _bfd_elf_allocate_ifunc_dyn_relocs, rela.srelgot is used
instead of rela.srelplt. Glibc ELF loader will not support
R_LARCH_IRELATIVE relocation in rela.plt. */
static bool
local_allocate_ifunc_dyn_relocs (struct bfd_link_info *info,
struct elf_link_hash_entry *h,
struct elf_dyn_relocs **head,
unsigned int plt_entry_size,
unsigned int plt_header_size,
unsigned int got_entry_size,
bool avoid_plt)
{
asection *plt, *gotplt, *relplt;
struct elf_dyn_relocs *p;
unsigned int sizeof_reloc;
const struct elf_backend_data *bed;
struct elf_link_hash_table *htab;
/* If AVOID_PLT is TRUE, don't use PLT if possible. */
bool use_plt = !avoid_plt || h->plt.refcount > 0;
bool need_dynreloc = !use_plt || bfd_link_pic (info);
/* When a PIC object references a STT_GNU_IFUNC symbol defined
in executable or it isn't referenced via PLT, the address of
the resolved function may be used. But in non-PIC executable,
the address of its plt slot may be used. Pointer equality may
not work correctly. PIE or non-PLT reference should be used if
pointer equality is required here.
If STT_GNU_IFUNC symbol is defined in position-dependent executable,
backend should change it to the normal function and set its address
to its PLT entry which should be resolved by R_*_IRELATIVE at
run-time. All external references should be resolved to its PLT in
executable. */
if (!need_dynreloc
&& !(bfd_link_pde (info) && h->def_regular)
&& (h->dynindx != -1
|| info->export_dynamic)
&& h->pointer_equality_needed)
{
info->callbacks->einfo
/* xgettext:c-format. */
(_("%F%P: dynamic STT_GNU_IFUNC symbol `%s' with pointer "
"equality in `%pB' can not be used when making an "
"executable; recompile with -fPIE and relink with -pie\n"),
h->root.root.string,
h->root.u.def.section->owner);
bfd_set_error (bfd_error_bad_value);
return false;
}
htab = elf_hash_table (info);
/* When the symbol is marked with regular reference, if PLT isn't used
or we are building a PIC object, we must keep dynamic relocation
if there is non-GOT reference and use PLT if there is PC-relative
reference. */
if (need_dynreloc && h->ref_regular)
{
bool keep = false;
for (p = *head; p != NULL; p = p->next)
if (p->count)
{
h->non_got_ref = 1;
/* Need dynamic relocations for non-GOT reference. */
keep = true;
if (p->pc_count)
{
/* Must use PLT for PC-relative reference. */
use_plt = true;
need_dynreloc = bfd_link_pic (info);
break;
}
}
if (keep)
goto keep;
}
/* Support garbage collection against STT_GNU_IFUNC symbols. */
if (h->plt.refcount <= 0 && h->got.refcount <= 0)
{
h->got = htab->init_got_offset;
h->plt = htab->init_plt_offset;
*head = NULL;
return true;
}
/* Return and discard space for dynamic relocations against it if
it is never referenced. */
if (!h->ref_regular)
{
if (h->plt.refcount > 0
|| h->got.refcount > 0)
abort ();
h->got = htab->init_got_offset;
h->plt = htab->init_plt_offset;
*head = NULL;
return true;
}
keep:
bed = get_elf_backend_data (info->output_bfd);
if (bed->rela_plts_and_copies_p)
sizeof_reloc = bed->s->sizeof_rela;
else
sizeof_reloc = bed->s->sizeof_rel;
/* When building a static executable, use iplt, igot.plt and
rela.iplt sections for STT_GNU_IFUNC symbols. */
if (htab->splt != NULL)
{
plt = htab->splt;
gotplt = htab->sgotplt;
/* Change dynamic info of ifunc gotplt from srelplt to srelgot. */
relplt = htab->srelgot;
/* If this is the first plt entry and PLT is used, make room for
the special first entry. */
if (plt->size == 0 && use_plt)
plt->size += plt_header_size;
}
else
{
plt = htab->iplt;
gotplt = htab->igotplt;
relplt = htab->irelplt;
}
if (use_plt)
{
/* Don't update value of STT_GNU_IFUNC symbol to PLT. We need
the original value for R_*_IRELATIVE. */
h->plt.offset = plt->size;
/* Make room for this entry in the plt/iplt section. */
plt->size += plt_entry_size;
/* We also need to make an entry in the got.plt/got.iplt section,
which will be placed in the got section by the linker script. */
gotplt->size += got_entry_size;
}
/* We also need to make an entry in the rela.plt/.rela.iplt
section for GOTPLT relocation if PLT is used. */
if (use_plt)
{
relplt->size += sizeof_reloc;
relplt->reloc_count++;
}
/* We need dynamic relocation for STT_GNU_IFUNC symbol only when
there is a non-GOT reference in a PIC object or PLT isn't used. */
if (!need_dynreloc || !h->non_got_ref)
*head = NULL;
/* Finally, allocate space. */
p = *head;
if (p != NULL)
{
bfd_size_type count = 0;
do
{
count += p->count;
p = p->next;
}
while (p != NULL);
htab->ifunc_resolvers = count != 0;
/* Dynamic relocations are stored in
1. rela.srelgot section in PIC object.
2. rela.srelgot section in dynamic executable.
3. rela.irelplt section in static executable. */
if (htab->splt != NULL)
htab->srelgot->size += count * sizeof_reloc;
else
{
relplt->size += count * sizeof_reloc;
relplt->reloc_count += count;
}
}
/* For STT_GNU_IFUNC symbol, got.plt has the real function address
and got has the PLT entry adddress. We will load the GOT entry
with the PLT entry in finish_dynamic_symbol if it is used. For
branch, it uses got.plt. For symbol value, if PLT is used,
1. Use got.plt in a PIC object if it is forced local or not
dynamic.
2. Use got.plt in a non-PIC object if pointer equality isn't
needed.
3. Use got.plt in PIE.
4. Use got.plt if got isn't used.
5. Otherwise use got so that it can be shared among different
objects at run-time.
If PLT isn't used, always use got for symbol value.
We only need to relocate got entry in PIC object or in dynamic
executable without PLT. */
if (use_plt
&& (h->got.refcount <= 0
|| (bfd_link_pic (info)
&& (h->dynindx == -1
|| h->forced_local))
|| (
!h->pointer_equality_needed)
|| htab->sgot == NULL))
{
/* Use got.plt. */
h->got.offset = (bfd_vma) -1;
}
else
{
if (!use_plt)
{
/* PLT isn't used. */
h->plt.offset = (bfd_vma) -1;
}
if (h->got.refcount <= 0)
{
/* GOT isn't need when there are only relocations for static
pointers. */
h->got.offset = (bfd_vma) -1;
}
else
{
h->got.offset = htab->sgot->size;
htab->sgot->size += got_entry_size;
/* Need to relocate the GOT entry in a PIC object or PLT isn't
used. Otherwise, the GOT entry will be filled with the PLT
entry and dynamic GOT relocation isn't needed. */
if (need_dynreloc)
{
/* For non-static executable, dynamic GOT relocation is in
rela.got section, but for static executable, it is
in rela.iplt section. */
if (htab->splt != NULL)
htab->srelgot->size += sizeof_reloc;
else
{
relplt->size += sizeof_reloc;
relplt->reloc_count++;
}
}
}
}
return true;
}
/* Allocate space in .plt, .got and associated reloc sections for
ifunc dynamic relocs. */
@ -1234,12 +1487,22 @@ elfNN_allocate_ifunc_dynrelocs (struct elf_link_hash_entry *h, void *inf)
/* Since STT_GNU_IFUNC symbol must go through PLT, we handle it
here if it is defined and referenced in a non-shared object. */
if (h->type == STT_GNU_IFUNC && h->def_regular)
return _bfd_elf_allocate_ifunc_dyn_relocs (info, h,
&h->dyn_relocs,
PLT_ENTRY_SIZE,
PLT_HEADER_SIZE,
GOT_ENTRY_SIZE,
false);
{
if (SYMBOL_REFERENCES_LOCAL (info, h))
return local_allocate_ifunc_dyn_relocs (info, h,
&h->dyn_relocs,
PLT_ENTRY_SIZE,
PLT_HEADER_SIZE,
GOT_ENTRY_SIZE,
false);
else
return _bfd_elf_allocate_ifunc_dyn_relocs (info, h,
&h->dyn_relocs,
PLT_ENTRY_SIZE,
PLT_HEADER_SIZE,
GOT_ENTRY_SIZE,
false);
}
return true;
}
@ -2162,22 +2425,40 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
outrel.r_offset += sec_addr (input_section);
/* A pointer point to a local ifunc symbol. */
if(h
&& h->type == STT_GNU_IFUNC
&& (h->dynindx == -1
|| h->forced_local
|| bfd_link_executable(info)))
/* A pointer point to a ifunc symbol. */
if (h && h->type == STT_GNU_IFUNC)
{
outrel.r_info = ELFNN_R_INFO (0, R_LARCH_IRELATIVE);
outrel.r_addend = (h->root.u.def.value
+ h->root.u.def.section->output_section->vma
+ h->root.u.def.section->output_offset);
if (htab->elf.splt != NULL)
sreloc = htab->elf.srelplt;
if (h->dynindx == -1)
{
outrel.r_info = ELFNN_R_INFO (0, R_LARCH_IRELATIVE);
outrel.r_addend = (h->root.u.def.value
+ h->root.u.def.section->output_section->vma
+ h->root.u.def.section->output_offset);
}
else
sreloc = htab->elf.irelplt;
{
outrel.r_info = ELFNN_R_INFO (h->dynindx, R_LARCH_NN);
outrel.r_addend = 0;
}
if (SYMBOL_REFERENCES_LOCAL (info, h))
{
if (htab->elf.splt != NULL)
sreloc = htab->elf.srelgot;
else
sreloc = htab->elf.irelplt;
}
else
{
if (bfd_link_pic (info))
sreloc = htab->elf.irelifunc;
else if (htab->elf.splt != NULL)
sreloc = htab->elf.srelgot;
else
sreloc = htab->elf.irelplt;
}
}
else if (resolved_dynly)
{
@ -2816,10 +3097,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
case R_LARCH_PCALA64_LO20:
case R_LARCH_PCALA64_HI12:
if (h && h->plt.offset != MINUS_ONE)
{
BFD_ASSERT (rel->r_addend == 0);
relocation = sec_addr (plt) + h->plt.offset;
}
relocation = sec_addr (plt) + h->plt.offset;
else
relocation += rel->r_addend;
@ -3237,7 +3515,10 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
plt = htab->elf.splt;
gotplt = htab->elf.sgotplt;
relplt = htab->elf.srelplt;
if (h->type == STT_GNU_IFUNC && SYMBOL_REFERENCES_LOCAL (info, h))
relplt = htab->elf.srelgot;
else
relplt = htab->elf.srelplt;
plt_idx = (h->plt.offset - PLT_HEADER_SIZE) / PLT_ENTRY_SIZE;
got_address =
sec_addr (gotplt) + GOTPLT_HEADER_SIZE + plt_idx * GOT_ENTRY_SIZE;
@ -3272,11 +3553,45 @@ loongarch_elf_finish_dynamic_symbol (bfd *output_bfd,
rela.r_offset = got_address;
/* Fill in the entry in the rela.plt section. */
rela.r_info = ELFNN_R_INFO (h->dynindx, R_LARCH_JUMP_SLOT);
rela.r_addend = 0;
loc = relplt->contents + plt_idx * sizeof (ElfNN_External_Rela);
bed->s->swap_reloca_out (output_bfd, &rela, loc);
/* TRUE if this is a PLT reference to a local IFUNC. */
if (PLT_LOCAL_IFUNC_P (info, h)
&& (relplt == htab->elf.srelgot
|| relplt == htab->elf.irelplt))
{
{
rela.r_info = ELFNN_R_INFO (0, R_LARCH_IRELATIVE);
rela.r_addend = (h->root.u.def.value
+ h->root.u.def.section->output_section->vma
+ h->root.u.def.section->output_offset);
}
/* Find the space after dyn sort. */
{
Elf_Internal_Rela *dyn = (Elf_Internal_Rela *)relplt->contents;
bool fill = false;
for (;dyn < dyn + relplt->size / sizeof (*dyn); dyn++)
{
if (0 == dyn->r_offset)
{
bed->s->swap_reloca_out (output_bfd, &rela,
(bfd_byte *)dyn);
relplt->reloc_count++;
fill = true;
break;
}
}
BFD_ASSERT (fill);
}
}
else
{
/* Fill in the entry in the rela.plt section. */
rela.r_info = ELFNN_R_INFO (h->dynindx, R_LARCH_JUMP_SLOT);
rela.r_addend = 0;
loc = relplt->contents + plt_idx * sizeof (ElfNN_External_Rela);
bed->s->swap_reloca_out (output_bfd, &rela, loc);
}
if (!h->def_regular)
{