[PATCH 4/5 v1] LoongArch: Move ifunc info to rela.dyn from rela.plt.
liuzhensong
liuzhensong@loongson.cn
Mon Jul 18 08:43:19 GMT 2022
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
---
bfd/elfnn-loongarch.c | 322 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 310 insertions(+), 12 deletions(-)
diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index 4eeaeb44eff..5bb7596e5d0 100644
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -1207,6 +1207,259 @@ allocate_dynrelocs (struct elf_link_hash_entry *h, void *inf)
return true;
}
+/* Based function _bfd_elf_allocate_ifunc_dyn_relocs.
+ For local def and ref ifunc,
+ dynamic relocations are stored in
+ 1. rel[a].irelifunc section in PIC object.
+ 2. rel[a].srelgot section in dynamic executable.
+ 3. rel[a].irelplt section in static executable.
+ Change ifunc dynamic info from srelplt to srelgot.
+ In loader, remove R_LARCH_IRELACTIVE from rela lazy in ld.so. */
+
+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
+ rel[a].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 rel[a].plt/.rel[a].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. rel[a].srelgot section in PIC object.
+ 2. rel[a].srelgot section in dynamic executable.
+ 3. rel[a].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
+ rel[a].got section, but for static executable, it is
+ in rel[a].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 +1487,23 @@ 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,
+ {
+ 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;
}
@@ -2175,7 +2439,7 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
+ h->root.u.def.section->output_offset);
if (htab->elf.splt != NULL)
- sreloc = htab->elf.srelplt;
+ sreloc = htab->elf.srelgot;
else
sreloc = htab->elf.irelplt;
}
@@ -2818,10 +3082,7 @@ 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;
@@ -3239,7 +3500,10 @@ 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;
@@ -3274,11 +3538,45 @@ 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)
{
--
2.31.1
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