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Re: PATCH for i386: --no-copy-relocs
On Thu, Jun 21, 2001 at 05:33:25PM -0700, Ian Lance Taylor wrote:
>
> If a symbol is only referenced from writable sections, then omitting
> the COPY relocation is OK because those sections can not be shared anyhow.
Here's a first pass at this change. Not overmuch tested yet ;)
but I need to sleep. HJ, you said you'd happily test this for me,
so here it is. ChangeLog coming later.
Index: elf32-i386.c
===================================================================
RCS file: /cvs/src/src/bfd/elf32-i386.c,v
retrieving revision 1.28
diff -u -p -r1.28 elf32-i386.c
--- elf32-i386.c 2001/06/20 18:54:52 1.28
+++ elf32-i386.c 2001/06/22 17:03:50
@@ -43,12 +43,10 @@ static boolean elf_i386_check_relocs
const Elf_Internal_Rela *));
static boolean elf_i386_adjust_dynamic_symbol
PARAMS ((struct bfd_link_info *, struct elf_link_hash_entry *));
-static boolean allocate_plt_and_got
+static boolean allocate_plt_and_got_and_discard_relocs
PARAMS ((struct elf_link_hash_entry *, PTR));
static boolean elf_i386_size_dynamic_sections
PARAMS ((bfd *, struct bfd_link_info *));
-static boolean discard_copies
- PARAMS ((struct elf_link_hash_entry *, PTR));
static boolean elf_i386_relocate_section
PARAMS ((bfd *, struct bfd_link_info *, bfd *, asection *, bfd_byte *,
Elf_Internal_Rela *, Elf_Internal_Sym *, asection **));
@@ -591,14 +589,15 @@ elf_i386_check_relocs (abfd, info, sec,
h = sym_hashes[r_symndx - symtab_hdr->sh_info];
/* Some relocs require a global offset table. */
- if (dynobj == NULL)
+ if (htab->sgot == NULL)
{
switch (ELF32_R_TYPE (rel->r_info))
{
case R_386_GOT32:
case R_386_GOTOFF:
case R_386_GOTPC:
- elf_hash_table (info)->dynobj = dynobj = abfd;
+ if (dynobj == NULL)
+ htab->root.dynobj = dynobj = abfd;
if (!create_got_section (dynobj, info))
return false;
break;
@@ -673,19 +672,19 @@ elf_i386_check_relocs (abfd, info, sec,
case R_386_32:
case R_386_PC32:
- if (h != NULL)
+ if (h != NULL && !info->shared)
{
- h->elf_link_hash_flags |= ELF_LINK_NON_GOT_REF;
-
- if (!info->shared)
- {
- /* We may need a .plt entry if the function this
- reloc refers to is in a shared lib. */
- if (h->plt.refcount == -1)
- h->plt.refcount = 1;
- else
- h->plt.refcount += 1;
- }
+ /* If this reloc is in a read-only section, we might
+ need a copy reloc. */
+ if ((sec->flags & SEC_READONLY) != 0)
+ h->elf_link_hash_flags |= ELF_LINK_NON_GOT_REF;
+
+ /* We may need a .plt entry if the function this reloc
+ refers to is in a shared lib. */
+ if (h->plt.refcount == -1)
+ h->plt.refcount = 1;
+ else
+ h->plt.refcount += 1;
}
/* If we are creating a shared library, and this is a reloc
@@ -703,19 +702,32 @@ elf_i386_check_relocs (abfd, info, sec,
storing information in the relocs_copied field of the hash
table entry. A similar situation occurs when creating
shared libraries and symbol visibility changes render the
- symbol local. */
- if (info->shared
- && (sec->flags & SEC_ALLOC) != 0
- && (ELF32_R_TYPE (rel->r_info) != R_386_PC32
- || (h != NULL
- && (! info->symbolic
- || h->root.type == bfd_link_hash_defweak
- || (h->elf_link_hash_flags
- & ELF_LINK_HASH_DEF_REGULAR) == 0))))
+ symbol local.
+ If on the other hand, we are creating an executable, we
+ may need to keep relocations for symbols satisfied by a
+ dynamic library if we manage to avoid copy relocs for the
+ symbol. */
+ if ((info->shared
+ && (sec->flags & SEC_ALLOC) != 0
+ && (ELF32_R_TYPE (rel->r_info) != R_386_PC32
+ || (h != NULL
+ && (! info->symbolic
+ || h->root.type == bfd_link_hash_defweak
+ || (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0))))
+ || (!info->shared
+ && (sec->flags & SEC_ALLOC) != 0
+ && h != NULL
+ && (h->elf_link_hash_flags & ELF_LINK_NON_GOT_REF) == 0
+ && (h->root.type == bfd_link_hash_defweak
+ || (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0)))
{
- /* When creating a shared object, we must copy these
- reloc types into the output file. We create a reloc
- section in dynobj and make room for this reloc. */
+ /* We must copy these reloc types into the output file.
+ Create a reloc section in dynobj and make room for
+ this reloc. */
+ if (dynobj == NULL)
+ htab->root.dynobj = dynobj = abfd;
if (sreloc == NULL)
{
const char *name;
@@ -767,8 +779,9 @@ elf_i386_check_relocs (abfd, info, sec,
that this function is only called if we are using an
elf_i386 linker hash table, which means that h is
really a pointer to an elf_i386_link_hash_entry. */
- if (h != NULL
- && ELF32_R_TYPE (rel->r_info) == R_386_PC32)
+ if (!info->shared
+ || (h != NULL
+ && ELF32_R_TYPE (rel->r_info) == R_386_PC32))
{
struct elf_i386_link_hash_entry *eh;
struct elf_i386_pcrel_relocs_copied *p;
@@ -1095,10 +1108,12 @@ elf_i386_adjust_dynamic_symbol (info, h)
|| ((H)->elf_link_hash_flags & ELF_LINK_FORCED_LOCAL) != 0))
/* Allocate space in .plt, .got and associated reloc sections for
- global syms. */
+ global syms. Also discards space allocated for relocs in the
+ check_relocs function that we subsequently have found to be
+ unneeded. */
static boolean
-allocate_plt_and_got (h, inf)
+allocate_plt_and_got_and_discard_relocs (h, inf)
struct elf_link_hash_entry *h;
PTR inf;
{
@@ -1175,6 +1190,29 @@ allocate_plt_and_got (h, inf)
else
h->got.offset = (bfd_vma) -1;
+ /* In the shared -Bsymbolic case, discard space allocated to copy
+ PC relative relocs against symbols which turn out to be defined
+ in regular objects. For the normal shared case, discard space
+ for relocs that have become local due to symbol visibility
+ changes. For the non-shared case, discard space for symbols
+ which turn out to need copy relocs or are not dynamic. */
+
+ if ((info->shared
+ && (h->elf_link_hash_flags & ELF_LINK_HASH_DEF_REGULAR) != 0
+ && ((h->elf_link_hash_flags & ELF_LINK_FORCED_LOCAL) != 0
+ || info->symbolic))
+ || (!info->shared
+ && ((h->elf_link_hash_flags & ELF_LINK_NON_GOT_REF) != 0
+ || h->dynindx == -1)))
+ {
+ struct elf_i386_link_hash_entry *eh;
+ struct elf_i386_pcrel_relocs_copied *c;
+
+ eh = (struct elf_i386_link_hash_entry *) h;
+ for (c = eh->pcrel_relocs_copied; c != NULL; c = c->next)
+ c->section->_raw_size -= c->count * sizeof (Elf32_External_Rel);
+ }
+
return true;
}
@@ -1198,7 +1236,6 @@ elf_i386_size_dynamic_sections (output_b
if (htab->root.dynamic_sections_created)
{
-
/* Set the contents of the .interp section to the interpreter. */
if (! info->shared)
{
@@ -1244,20 +1281,12 @@ elf_i386_size_dynamic_sections (output_b
}
}
- /* Allocate global sym .plt and .got entries. */
+ /* Allocate global sym .plt and .got entries. Also discard all
+ unneeded relocs. */
elf_link_hash_traverse (&htab->root,
- allocate_plt_and_got,
+ allocate_plt_and_got_and_discard_relocs,
(PTR) info);
- /* If this is a -Bsymbolic shared link, then we need to discard all
- PC relative relocs against symbols defined in a regular object.
- We allocated space for them in the check_relocs routine, but we
- will not fill them in in the relocate_section routine. */
- if (info->shared)
- elf_link_hash_traverse (&htab->root,
- discard_copies,
- (PTR) info);
-
/* The check_relocs and adjust_dynamic_symbol entry points have
determined the sizes of the various dynamic sections. Allocate
memory for them. */
@@ -1384,41 +1413,6 @@ elf_i386_size_dynamic_sections (output_b
return true;
}
-/* This function is called via elf_link_hash_traverse if we are
- creating a shared object. In the -Bsymbolic case, it discards the
- space allocated to copy PC relative relocs against symbols which
- are defined in regular objects. For the normal non-symbolic case,
- we also discard space for relocs that have become local due to
- symbol visibility changes. We allocated space for them in the
- check_relocs routine, but we won't fill them in in the
- relocate_section routine. */
-
-static boolean
-discard_copies (h, inf)
- struct elf_link_hash_entry *h;
- PTR inf;
-{
- struct elf_i386_pcrel_relocs_copied *s;
- struct bfd_link_info *info;
- struct elf_i386_link_hash_entry *eh;
-
- info = (struct bfd_link_info *) inf;
- eh = (struct elf_i386_link_hash_entry *) h;
-
- /* If a symbol has been forced local or we have found a regular
- definition for the symbolic link case, then we won't be needing
- any relocs. */
- if ((eh->root.elf_link_hash_flags & ELF_LINK_HASH_DEF_REGULAR) != 0
- && ((eh->root.elf_link_hash_flags & ELF_LINK_FORCED_LOCAL) != 0
- || info->symbolic))
- {
- for (s = eh->pcrel_relocs_copied; s != NULL; s = s->next)
- s->section->_raw_size -= s->count * sizeof (Elf32_External_Rel);
- }
-
- return true;
-}
-
/* Relocate an i386 ELF section. */
static boolean
@@ -1539,12 +1533,18 @@ elf_i386_relocate_section (output_bfd, i
& ELF_LINK_FORCED_LOCAL))
&& (h->elf_link_hash_flags
& ELF_LINK_HASH_DEF_REGULAR)))
- || (info->shared
- && ((! info->symbolic && h->dynindx != -1)
- || (h->elf_link_hash_flags
- & ELF_LINK_HASH_DEF_REGULAR) == 0)
- && (r_type == R_386_32
- || r_type == R_386_PC32)
+ || ((r_type == R_386_32
+ || r_type == R_386_PC32)
+ && ((info->shared
+ && ((!info->symbolic && h->dynindx != -1)
+ || (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0))
+ || (!info->shared
+ && h->dynindx != -1
+ && (h->elf_link_hash_flags
+ & ELF_LINK_NON_GOT_REF) == 0
+ && (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0))
&& ((input_section->flags & SEC_ALLOC) != 0
/* DWARF will emit R_386_32 relocations in its
sections against symbols defined externally
@@ -1723,14 +1723,22 @@ elf_i386_relocate_section (output_bfd, i
case R_386_32:
case R_386_PC32:
- if (info->shared
- && (input_section->flags & SEC_ALLOC) != 0
- && (r_type != R_386_PC32
- || (h != NULL
- && h->dynindx != -1
- && (! info->symbolic
- || (h->elf_link_hash_flags
- & ELF_LINK_HASH_DEF_REGULAR) == 0))))
+ if ((info->shared
+ && (input_section->flags & SEC_ALLOC) != 0
+ && (r_type != R_386_PC32
+ || (h != NULL
+ && h->dynindx != -1
+ && (! info->symbolic
+ || (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0))))
+ || (!info->shared
+ && (input_section->flags & SEC_ALLOC) != 0
+ && h != NULL
+ && h->dynindx != -1
+ && (h->elf_link_hash_flags & ELF_LINK_NON_GOT_REF) == 0
+ && (h->root.type == bfd_link_hash_defweak
+ || (h->elf_link_hash_flags
+ & ELF_LINK_HASH_DEF_REGULAR) == 0)))
{
Elf_Internal_Rel outrel;
boolean skip, relocate;
@@ -1780,8 +1788,7 @@ elf_i386_relocate_section (output_bfd, i
bfd_vma off;
off = (_bfd_stab_section_offset
- (output_bfd, &elf_hash_table (info)->stab_info,
- input_section,
+ (output_bfd, htab->root.stab_info, input_section,
&elf_section_data (input_section)->stab_info,
rel->r_offset));
if (off == (bfd_vma) -1)
@@ -1808,7 +1815,8 @@ elf_i386_relocate_section (output_bfd, i
/* h->dynindx may be -1 if this symbol was marked to
become local. */
if (h == NULL
- || ((info->symbolic || h->dynindx == -1)
+ || (info->shared
+ && (info->symbolic || h->dynindx == -1)
&& (h->elf_link_hash_flags
& ELF_LINK_HASH_DEF_REGULAR) != 0))
{
@@ -2056,15 +2064,13 @@ elf_i386_finish_dynamic_sections (output
htab = elf_i386_hash_table (info);
dynobj = htab->root.dynobj;
-
- BFD_ASSERT (htab->sgot != NULL);
sdyn = bfd_get_section_by_name (dynobj, ".dynamic");
if (htab->root.dynamic_sections_created)
{
Elf32_External_Dyn *dyncon, *dynconend;
- BFD_ASSERT (sdyn != NULL);
+ BFD_ASSERT (sdyn != NULL && htab->sgot != NULL);
dyncon = (Elf32_External_Dyn *) sdyn->contents;
dynconend = (Elf32_External_Dyn *) (sdyn->contents + sdyn->_raw_size);
@@ -2148,19 +2154,21 @@ elf_i386_finish_dynamic_sections (output
}
}
- /* Fill in the first three entries in the global offset table. */
- if (htab->sgotplt->_raw_size > 0)
+ if (htab->sgotplt)
{
- bfd_put_32 (output_bfd,
- (sdyn == NULL ? (bfd_vma) 0
- : sdyn->output_section->vma + sdyn->output_offset),
- htab->sgotplt->contents);
- bfd_put_32 (output_bfd, (bfd_vma) 0, htab->sgotplt->contents + 4);
- bfd_put_32 (output_bfd, (bfd_vma) 0, htab->sgotplt->contents + 8);
- }
-
- elf_section_data (htab->sgotplt->output_section)->this_hdr.sh_entsize = 4;
+ /* Fill in the first three entries in the global offset table. */
+ if (htab->sgotplt->_raw_size > 0)
+ {
+ bfd_put_32 (output_bfd,
+ (sdyn == NULL ? (bfd_vma) 0
+ : sdyn->output_section->vma + sdyn->output_offset),
+ htab->sgotplt->contents);
+ bfd_put_32 (output_bfd, (bfd_vma) 0, htab->sgotplt->contents + 4);
+ bfd_put_32 (output_bfd, (bfd_vma) 0, htab->sgotplt->contents + 8);
+ }
+ elf_section_data (htab->sgotplt->output_section)->this_hdr.sh_entsize = 4;
+ }
return true;
}