stub symbols and relocs for powerpc64-linux
Alan Modra
amodra@bigpond.net.au
Tue Sep 7 12:41:00 GMT 2004
This patch does a few things to make it easier for FDPR to process
powerpc64-linux binaries.
Symbols output with --emit-stub-syms now include the stub type in the
name, and lose the trailing "+0" in most cases. Typical stub symbols
for globals now look like
00000010.long_branch_r2off.debug_tree
000007a3.plt_call.fprintf@@GLIBC_2.3
while a stub for a local sym might look like
0000002a.long_branch_r2off.13b0:2
ie. You lose the name of the local sym and instead get two hex numbers
separated by a colon.
Relocs are now created on powerpc64-linux long branch stubs when
--emit-relocs is used. The relocations emitted will have a symbol index
of zero when the destination was originally a local sym, which is a
little unusual. I chose to do it this way rather than giving a proper
symbol because the stub sections, and their associated relocations, are
not attached to any of the normal input files. This makes it difficult
to attach the real destination symbol you might expect to see on these
relocations. In any case, a local symbol destination is nearly always a
section symbol, so no better than the zero symbol in finding a
destination function. I did manage to attach a proper symbol on stub
relocs where the destination is a global sym.
* elf64-ppc.c (struct ppc_link_hash_table): Add stub_globals.
(is_ppc64_elf_target): Rename from is_ppc64_target. Update all
callers.
(ppc_stub_name): Remove trailing "+0" on stub name.
(create_linkage_sections): Create relocations for
branch lookup table when --emit-relocs as well as when --shared.
(ppc_build_one_stub): Emit relocs for long branch stubs. Adjust
relbrlt test. For --emit-stub-syms, always output a sym even when
one already exists on a plt call stub. Put stub type in the stub
symbol name.
(ppc_size_one_stub): Size long branch stub relocs. Adjust relbrlt
test.
(ppc64_elf_size_stubs): Count global sym stubs added. Zero
reloc_count in stub sections. Adjust relbrlt test.
(ppc64_elf_build_stubs): Adjust relbrlt test. Tweak stats output.
* elflink.c (bfd_elf_size_dynamic_sections): Fix comment typo.
(elf_link_input_bfd): Ignore symbol index zero relocs when checking
for relocs against discarded symbols. Fix comments.
Index: bfd/elf64-ppc.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-ppc.c,v
retrieving revision 1.172
diff -u -p -r1.172 elf64-ppc.c
--- bfd/elf64-ppc.c 6 Sep 2004 12:37:12 -0000 1.172
+++ bfd/elf64-ppc.c 7 Sep 2004 12:34:32 -0000
@@ -2400,8 +2400,10 @@ ppc64_elf_mkobject (bfd *abfd)
return TRUE;
}
+/* Return 1 if target is one of ours. */
+
static bfd_boolean
-is_ppc64_target (const struct bfd_target *targ)
+is_ppc64_elf_target (const struct bfd_target *targ)
{
extern const bfd_target bfd_elf64_powerpc_vec;
extern const bfd_target bfd_elf64_powerpcle_vec;
@@ -3290,6 +3292,9 @@ struct ppc_link_hash_table
/* Statistics. */
unsigned long stub_count[ppc_stub_plt_call];
+ /* Number of stubs against global syms. */
+ unsigned long stub_globals;
+
/* Set if we should emit symbols for stubs. */
unsigned int emit_stub_syms:1;
@@ -3533,6 +3538,8 @@ ppc_stub_name (const asection *input_sec
(int) rel->r_addend & 0xffffffff);
}
}
+ if (stub_name[len - 2] == '+' && stub_name[len - 1] == '0')
+ stub_name[len - 2] = 0;
return stub_name;
}
@@ -3671,7 +3678,7 @@ create_linkage_sections (bfd *dynobj, st
|| ! bfd_set_section_alignment (dynobj, htab->brlt, 3))
return FALSE;
- if (info->shared)
+ if (info->shared || info->emitrelocations)
{
flags = (SEC_ALLOC | SEC_LOAD | SEC_READONLY
| SEC_HAS_CONTENTS | SEC_IN_MEMORY | SEC_LINKER_CREATED);
@@ -4038,7 +4045,7 @@ ppc64_elf_check_directives (bfd *abfd AT
struct ppc_link_hash_table *htab;
htab = ppc_hash_table (info);
- if (!is_ppc64_target (htab->elf.root.creator))
+ if (!is_ppc64_elf_target (htab->elf.root.creator))
return TRUE;
elf_link_hash_traverse (&htab->elf, add_symbol_adjust, info);
@@ -6898,7 +6905,7 @@ ppc64_elf_size_dynamic_sections (bfd *ou
Elf_Internal_Shdr *symtab_hdr;
asection *srel;
- if (!is_ppc64_target (ibfd->xvec))
+ if (!is_ppc64_elf_target (ibfd->xvec))
continue;
if (ppc64_tlsld_got (ibfd)->refcount > 0)
@@ -7068,7 +7075,7 @@ ppc64_elf_size_dynamic_sections (bfd *ou
for (ibfd = info->input_bfds; ibfd != NULL; ibfd = ibfd->link_next)
{
- if (!is_ppc64_target (ibfd->xvec))
+ if (!is_ppc64_elf_target (ibfd->xvec))
continue;
s = ppc64_elf_tdata (ibfd)->got;
@@ -7252,7 +7259,7 @@ ppc_build_one_stub (struct bfd_hash_entr
bfd_byte *p;
unsigned int indx;
struct plt_entry *ent;
- bfd_vma off;
+ bfd_vma dest, off;
int size;
/* Massage our args to the form they really have. */
@@ -7271,9 +7278,9 @@ ppc_build_one_stub (struct bfd_hash_entr
case ppc_stub_long_branch:
case ppc_stub_long_branch_r2off:
/* Branches are relative. This is where we are going to. */
- off = (stub_entry->target_value
- + stub_entry->target_section->output_offset
- + stub_entry->target_section->output_section->vma);
+ off = dest = (stub_entry->target_value
+ + stub_entry->target_section->output_offset
+ + stub_entry->target_section->output_section->vma);
/* And this is where we are coming from. */
off -= (stub_entry->stub_offset
@@ -7300,6 +7307,67 @@ ppc_build_one_stub (struct bfd_hash_entr
bfd_put_32 (htab->stub_bfd, B_DOT | (off & 0x3fffffc), loc);
BFD_ASSERT (off + (1 << 25) < (bfd_vma) (1 << 26));
+
+ if (info->emitrelocations)
+ {
+ Elf_Internal_Rela *relocs, *r;
+ struct bfd_elf_section_data *elfsec_data;
+
+ elfsec_data = elf_section_data (stub_entry->stub_sec);
+ relocs = elfsec_data->relocs;
+ if (relocs == NULL)
+ {
+ bfd_size_type relsize;
+ relsize = stub_entry->stub_sec->reloc_count * sizeof (*relocs);
+ relocs = bfd_alloc (htab->stub_bfd, relsize);
+ if (relocs == NULL)
+ return FALSE;
+ elfsec_data->relocs = relocs;
+ elfsec_data->rel_hdr.sh_size = relsize;
+ elfsec_data->rel_hdr.sh_entsize = 24;
+ stub_entry->stub_sec->reloc_count = 0;
+ }
+ r = relocs + stub_entry->stub_sec->reloc_count;
+ stub_entry->stub_sec->reloc_count += 1;
+ r->r_offset = loc - stub_entry->stub_sec->contents;
+ r->r_info = ELF64_R_INFO (0, R_PPC64_REL24);
+ r->r_addend = dest;
+ if (stub_entry->h != NULL)
+ {
+ struct elf_link_hash_entry **hashes;
+ unsigned long symndx;
+ struct ppc_link_hash_entry *h;
+
+ hashes = elf_sym_hashes (htab->stub_bfd);
+ if (hashes == NULL)
+ {
+ bfd_size_type hsize;
+
+ hsize = (htab->stub_globals + 1) * sizeof (*hashes);
+ hashes = bfd_zalloc (htab->stub_bfd, hsize);
+ if (hashes == NULL)
+ return FALSE;
+ elf_sym_hashes (htab->stub_bfd) = hashes;
+ htab->stub_globals = 1;
+ }
+ symndx = htab->stub_globals++;
+ h = stub_entry->h;
+ hashes[symndx] = &h->elf;
+ r->r_info = ELF64_R_INFO (symndx, R_PPC64_REL24);
+ if (h->oh != NULL && h->oh->is_func)
+ h = h->oh;
+ if (h->elf.root.u.def.section != stub_entry->target_section)
+ /* H is an opd symbol. The addend must be zero. */
+ r->r_addend = 0;
+ else
+ {
+ off = (h->elf.root.u.def.value
+ + h->elf.root.u.def.section->output_offset
+ + h->elf.root.u.def.section->output_section->vma);
+ r->r_addend -= off;
+ }
+ }
+ }
break;
case ppc_stub_plt_branch:
@@ -7322,7 +7390,7 @@ ppc_build_one_stub (struct bfd_hash_entr
bfd_put_64 (htab->brlt->owner, off,
htab->brlt->contents + br_entry->offset);
- if (info->shared)
+ if (htab->relbrlt != NULL)
{
/* Create a reloc for the branch lookup table entry. */
Elf_Internal_Rela rela;
@@ -7442,16 +7510,26 @@ ppc_build_one_stub (struct bfd_hash_entr
stub_entry->stub_sec->size += size;
- if (htab->emit_stub_syms
- && !(stub_entry->stub_type == ppc_stub_plt_call
- && stub_entry->h->oh != NULL
- && stub_entry->h->oh->elf.root.type == bfd_link_hash_defined
- && stub_entry->h->oh->elf.root.u.def.section == stub_entry->stub_sec
- && stub_entry->h->oh->elf.root.u.def.value == stub_entry->stub_offset))
+ if (htab->emit_stub_syms)
{
struct elf_link_hash_entry *h;
- h = elf_link_hash_lookup (&htab->elf, stub_entry->root.string,
- TRUE, FALSE, FALSE);
+ size_t len1, len2;
+ char *name;
+ const char *const stub_str[] = { "long_branch",
+ "long_branch_r2off",
+ "plt_branch",
+ "plt_branch_r2off",
+ "plt_call" };
+
+ len1 = strlen (stub_str[stub_entry->stub_type - 1]);
+ len2 = strlen (stub_entry->root.string);
+ name = bfd_malloc (len1 + len2 + 2);
+ if (name == NULL)
+ return FALSE;
+ memcpy (name, stub_entry->root.string, 9);
+ memcpy (name + 9, stub_str[stub_entry->stub_type - 1], len1);
+ memcpy (name + len1 + 9, stub_entry->root.string + 8, len2 - 8 + 1);
+ h = elf_link_hash_lookup (&htab->elf, name, TRUE, FALSE, FALSE);
if (h == NULL)
return FALSE;
if (h->root.type == bfd_link_hash_new)
@@ -7554,7 +7632,7 @@ ppc_size_one_stub (struct bfd_hash_entry
br_entry->offset = htab->brlt->size;
htab->brlt->size += 8;
- if (info->shared)
+ if (htab->relbrlt != NULL)
htab->relbrlt->size += sizeof (Elf64_External_Rela);
}
@@ -7563,6 +7641,11 @@ ppc_size_one_stub (struct bfd_hash_entry
if (stub_entry->stub_type != ppc_stub_plt_branch)
size = 28;
}
+
+ if (info->emitrelocations
+ && (stub_entry->stub_type == ppc_stub_long_branch
+ || stub_entry->stub_type == ppc_stub_long_branch_r2off))
+ stub_entry->stub_sec->reloc_count += 1;
}
stub_entry->stub_sec->size += size;
@@ -8149,6 +8232,10 @@ ppc64_elf_size_stubs (bfd *output_bfd,
stub_entry->target_section = code_sec;
stub_entry->h = hash;
stub_entry->addend = irela->r_addend;
+
+ if (stub_entry->h != NULL)
+ htab->stub_globals += 1;
+
stub_changed = TRUE;
}
@@ -8176,10 +8263,13 @@ ppc64_elf_size_stubs (bfd *output_bfd,
stub_sec != NULL;
stub_sec = stub_sec->next)
if ((stub_sec->flags & SEC_LINKER_CREATED) == 0)
- stub_sec->size = 0;
+ {
+ stub_sec->size = 0;
+ stub_sec->reloc_count = 0;
+ }
htab->brlt->size = 0;
- if (info->shared)
+ if (htab->relbrlt != NULL)
htab->relbrlt->size = 0;
bfd_hash_traverse (&htab->stub_hash_table, ppc_size_one_stub, info);
@@ -8384,7 +8474,7 @@ ppc64_elf_build_stubs (bfd_boolean emit_
if (htab->brlt->contents == NULL)
return FALSE;
}
- if (info->shared && htab->relbrlt->size != 0)
+ if (htab->relbrlt != NULL && htab->relbrlt->size != 0)
{
htab->relbrlt->contents = bfd_zalloc (htab->relbrlt->owner,
htab->relbrlt->size);
@@ -8421,13 +8511,14 @@ ppc64_elf_build_stubs (bfd_boolean emit_
if (*stats == NULL)
return FALSE;
- sprintf (*stats, _("linker stubs in %u groups\n"
+ sprintf (*stats, _("linker stubs in %u group%s\n"
" branch %lu\n"
" toc adjust %lu\n"
" long branch %lu\n"
" long toc adj %lu\n"
" plt call %lu"),
stub_sec_count,
+ stub_sec_count == 1 ? "" : "s",
htab->stub_count[ppc_stub_long_branch - 1],
htab->stub_count[ppc_stub_long_branch_r2off - 1],
htab->stub_count[ppc_stub_plt_branch - 1],
@@ -8526,6 +8617,11 @@ ppc64_elf_relocate_section (bfd *output_
ppc_howto_init ();
htab = ppc_hash_table (info);
+
+ /* Don't relocate stub sections. */
+ if (input_section->owner == htab->stub_bfd)
+ return TRUE;
+
local_got_ents = elf_local_got_ents (input_bfd);
TOCstart = elf_gp (output_bfd);
symtab_hdr = &elf_tdata (input_bfd)->symtab_hdr;
@@ -10116,7 +10212,7 @@ ppc64_elf_finish_dynamic_sections (bfd *
{
asection *s;
- if (!is_ppc64_target (dynobj->xvec))
+ if (!is_ppc64_elf_target (dynobj->xvec))
continue;
s = ppc64_elf_tdata (dynobj)->got;
Index: bfd/elflink.c
===================================================================
RCS file: /cvs/src/src/bfd/elflink.c,v
retrieving revision 1.99
diff -u -p -r1.99 elflink.c
--- bfd/elflink.c 3 Sep 2004 17:15:34 -0000 1.99
+++ bfd/elflink.c 7 Sep 2004 12:34:37 -0000
@@ -4911,7 +4911,7 @@ bfd_elf_size_dynamic_sections (bfd *outp
return FALSE;
/* Add some entries to the .dynamic section. We fill in some of the
- values later, in elf_bfd_final_link, but we must add the entries
+ values later, in bfd_elf_final_link, but we must add the entries
now so that we know the final size of the .dynamic section. */
/* If there are initialization and/or finalization functions to
@@ -6645,6 +6645,9 @@ elf_link_input_bfd (struct elf_final_lin
struct elf_link_hash_entry *h = NULL;
const char *sym_name;
+ if (r_symndx == STN_UNDEF)
+ continue;
+
if (r_symndx >= locsymcount
|| (elf_bad_symtab (input_bfd)
&& finfo->sections[r_symndx] == NULL))
@@ -6837,7 +6840,7 @@ elf_link_input_bfd (struct elf_final_lin
symbol. We set the rel_hash entry for this
reloc to point to the global hash table entry
for this symbol. The symbol index is then
- set at the end of elf_bfd_final_link. */
+ set at the end of bfd_elf_final_link. */
indx = r_symndx - extsymoff;
rh = elf_sym_hashes (input_bfd)[indx];
while (rh->root.type == bfd_link_hash_indirect
@@ -7577,8 +7580,7 @@ bfd_elf_final_link (bfd *abfd, struct bf
if (! _bfd_elf_compute_section_file_positions (abfd, info))
goto error_return;
- /* That created the reloc sections. Set their sizes, and assign
- them file positions, and allocate some buffers. */
+ /* Set sizes, and assign file positions for reloc sections. */
for (o = abfd->sections; o != NULL; o = o->next)
{
if ((o->flags & SEC_RELOC) != 0)
--
Alan Modra
IBM OzLabs - Linux Technology Centre
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