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powerpc64-linux toc edit
- From: Alan Modra <amodra at bigpond dot net dot au>
- To: binutils at sources dot redhat dot com
- Date: Thu, 4 Nov 2004 22:49:55 +1030
- Subject: powerpc64-linux toc edit
This implements a fairly conservative TOC edit for powerpc64-linux,
just throwing away unused entries. I'll throw together some code to
merge duplicates later.
Why do we want to edit the TOC? Well, there's only one .toc section
per object file, and this doesn't play nicely with section groups,
linkonce sections, or with -ffunction-sections and --gc-sections. When
tossing out unused sections, it's not a simple matter of tossing out
some associated .toc.* sub-section, because the .toc section is shared
by all functions in the object file.
bfd/
* elf64-ppc.h (ppc64_elf_edit_toc): Declare.
* elf64-ppc.c (struct ppc_link_hash_entry <adjust_done>): Update
comment.
(struct adjust_toc_info): New.
(adjust_toc_syms, ppc64_elf_edit_toc): New functions.
ld/
* emultempl/ppc64elf.em (no_tls_opt): Rename from notlsopt.
(no_opd_opt, no_toc_opt): New static vars.
(ppc_before_allocation): Don't edit opt if no_opd_opt. Call
ppc64_elf_edit_toc.
(OPTION_NO_OPD_OPT, OPTION_NO_TOC_OPT): Define.
(PARSE_AND_LIST_LONGOPTS): Add no-opd-optimize and no-toc-optimize.
(PARSE_AND_LIST_OPTIONS): Describe new options.
(PARSE_AND_LIST_ARGS_CASES): Handle them.
Index: bfd/elf64-ppc.h
===================================================================
RCS file: /cvs/src/src/bfd/elf64-ppc.h,v
retrieving revision 1.17
diff -u -p -r1.17 elf64-ppc.h
--- bfd/elf64-ppc.h 19 Aug 2004 07:47:25 -0000 1.17
+++ bfd/elf64-ppc.h 4 Nov 2004 11:39:00 -0000
@@ -25,6 +25,8 @@ asection *ppc64_elf_tls_setup
(bfd *, struct bfd_link_info *);
bfd_boolean ppc64_elf_tls_optimize
(bfd *, struct bfd_link_info *);
+bfd_boolean ppc64_elf_edit_toc
+ (bfd *, struct bfd_link_info *);
bfd_vma ppc64_elf_toc
(bfd *);
int ppc64_elf_setup_section_lists
Index: bfd/elf64-ppc.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-ppc.c,v
retrieving revision 1.177
diff -u -p -r1.177 elf64-ppc.c
--- bfd/elf64-ppc.c 21 Oct 2004 15:28:25 -0000 1.177
+++ bfd/elf64-ppc.c 4 Nov 2004 11:39:00 -0000
@@ -3206,9 +3208,9 @@ struct ppc_link_hash_entry
unsigned int is_func:1;
unsigned int is_func_descriptor:1;
- /* Whether global opd sym has been adjusted or not.
- After ppc64_elf_edit_opd has run, this flag should be set for all
- globals defined in any opd section. */
+ /* Whether global opd/toc sym has been adjusted or not.
+ After ppc64_elf_edit_opd/ppc64_elf_edit_toc has run, this flag
+ should be set for all globals defined in any opd/toc section. */
unsigned int adjust_done:1;
/* Set if we twiddled this symbol to weak at some stage. */
@@ -6645,6 +6647,445 @@ ppc64_elf_tls_optimize (bfd *obfd ATTRIB
return TRUE;
}
+/* Called via elf_link_hash_traverse from ppc64_elf_edit_toc to adjust
+ the values of any global symbols in a toc section that has been
+ edited. Globals in toc sections should be a rarity, so this function
+ sets a flag if any are found in toc sections other than the one just
+ edited, so that futher hash table traversals can be avoided. */
+
+struct adjust_toc_info
+{
+ asection *toc;
+ unsigned long *skip;
+ bfd_boolean global_toc_syms;
+};
+
+static bfd_boolean
+adjust_toc_syms (struct elf_link_hash_entry *h, void *inf)
+{
+ struct ppc_link_hash_entry *eh;
+ struct adjust_toc_info *toc_inf = (struct adjust_toc_info *) inf;
+
+ if (h->root.type == bfd_link_hash_indirect)
+ return TRUE;
+
+ if (h->root.type == bfd_link_hash_warning)
+ h = (struct elf_link_hash_entry *) h->root.u.i.link;
+
+ if (h->root.type != bfd_link_hash_defined
+ && h->root.type != bfd_link_hash_defweak)
+ return TRUE;
+
+ eh = (struct ppc_link_hash_entry *) h;
+ if (eh->adjust_done)
+ return TRUE;
+
+ if (eh->elf.root.u.def.section == toc_inf->toc)
+ {
+ unsigned long skip = toc_inf->skip[eh->elf.root.u.def.value >> 3];
+ if (skip != (unsigned long) -1)
+ eh->elf.root.u.def.value -= skip;
+ else
+ {
+ (*_bfd_error_handler)
+ (_("%s defined in removed toc entry"), eh->elf.root.root.string);
+ eh->elf.root.u.def.section = &bfd_abs_section;
+ eh->elf.root.u.def.value = 0;
+ }
+ eh->adjust_done = 1;
+ }
+ else if (strcmp (eh->elf.root.u.def.section->name, ".toc") == 0)
+ toc_inf->global_toc_syms = TRUE;
+
+ return TRUE;
+}
+
+/* Examine all relocs referencing .toc sections in order to remove
+ unused .toc entries. */
+
+bfd_boolean
+ppc64_elf_edit_toc (bfd *obfd ATTRIBUTE_UNUSED, struct bfd_link_info *info)
+{
+ bfd *ibfd;
+ struct adjust_toc_info toc_inf;
+
+ toc_inf.global_toc_syms = TRUE;
+ for (ibfd = info->input_bfds; ibfd != NULL; ibfd = ibfd->link_next)
+ {
+ asection *toc, *sec;
+ Elf_Internal_Shdr *symtab_hdr;
+ Elf_Internal_Sym *local_syms;
+ struct elf_link_hash_entry **sym_hashes;
+ Elf_Internal_Rela *relstart, *rel, *wrel;
+ unsigned long *skip, *drop;
+ unsigned char *used;
+ unsigned char *keep, last, some_unused;
+
+ toc = bfd_get_section_by_name (ibfd, ".toc");
+ if (toc == NULL
+ || toc->sec_info_type == ELF_INFO_TYPE_JUST_SYMS
+ || elf_discarded_section (toc))
+ continue;
+
+ local_syms = NULL;
+ symtab_hdr = &elf_tdata (ibfd)->symtab_hdr;
+ sym_hashes = elf_sym_hashes (ibfd);
+
+ /* Look at sections dropped from the final link. */
+ skip = NULL;
+ relstart = NULL;
+ for (sec = ibfd->sections; sec != NULL; sec = sec->next)
+ {
+ if (sec->reloc_count == 0
+ || !elf_discarded_section (sec)
+ || get_opd_info (sec)
+ || (sec->flags & SEC_ALLOC) == 0
+ || (sec->flags & SEC_DEBUGGING) != 0)
+ continue;
+
+ relstart = _bfd_elf_link_read_relocs (ibfd, sec, NULL, NULL, FALSE);
+ if (relstart == NULL)
+ goto error_ret;
+
+ /* Run through the relocs to see which toc entries might be
+ unused. */
+ for (rel = relstart; rel < relstart + sec->reloc_count; ++rel)
+ {
+ enum elf_ppc64_reloc_type r_type;
+ unsigned long r_symndx;
+ asection *sym_sec;
+ struct elf_link_hash_entry *h;
+ Elf_Internal_Sym *sym;
+ bfd_vma val;
+
+ r_type = ELF64_R_TYPE (rel->r_info);
+ switch (r_type)
+ {
+ default:
+ continue;
+
+ case R_PPC64_TOC16:
+ case R_PPC64_TOC16_LO:
+ case R_PPC64_TOC16_HI:
+ case R_PPC64_TOC16_HA:
+ case R_PPC64_TOC16_DS:
+ case R_PPC64_TOC16_LO_DS:
+ break;
+ }
+
+ r_symndx = ELF64_R_SYM (rel->r_info);
+ if (!get_sym_h (&h, &sym, &sym_sec, NULL, &local_syms,
+ r_symndx, ibfd))
+ goto error_ret;
+
+ if (sym_sec != toc)
+ continue;
+
+ if (h != NULL)
+ val = h->root.u.def.value;
+ else
+ val = sym->st_value;
+ val += rel->r_addend;
+
+ if (val >= toc->size)
+ continue;
+
+ /* Anything in the toc ought to be aligned to 8 bytes.
+ If not, don't mark as unused. */
+ if (val & 7)
+ continue;
+
+ if (skip == NULL)
+ {
+ skip = bfd_zmalloc (sizeof (*skip) * (toc->size + 7) / 8);
+ if (skip == NULL)
+ goto error_ret;
+ }
+
+ skip[val >> 3] = 1;
+ }
+
+ if (elf_section_data (sec)->relocs != relstart)
+ free (relstart);
+ }
+
+ if (skip == NULL)
+ continue;
+
+ used = bfd_zmalloc (sizeof (*used) * (toc->size + 7) / 8);
+ if (used == NULL)
+ {
+ error_ret:
+ if (local_syms != NULL
+ && symtab_hdr->contents != (unsigned char *) local_syms)
+ free (local_syms);
+ if (sec != NULL
+ && relstart != NULL
+ && elf_section_data (sec)->relocs != relstart)
+ free (relstart);
+ if (skip != NULL)
+ free (skip);
+ return FALSE;
+ }
+
+ /* Now check all kept sections that might reference the toc. */
+ for (sec = ibfd->sections;
+ sec != NULL;
+ /* Check the toc itself last. */
+ sec = (sec == toc ? NULL
+ : sec->next == toc && sec->next->next ? sec->next->next
+ : sec->next == NULL ? toc
+ : sec->next))
+ {
+ int repeat;
+
+ if (sec->reloc_count == 0
+ || elf_discarded_section (sec)
+ || get_opd_info (sec)
+ || (sec->flags & SEC_ALLOC) == 0
+ || (sec->flags & SEC_DEBUGGING) != 0)
+ continue;
+
+ relstart = _bfd_elf_link_read_relocs (ibfd, sec, NULL, NULL, TRUE);
+ if (relstart == NULL)
+ goto error_ret;
+
+ /* Mark toc entries referenced as used. */
+ repeat = 0;
+ do
+ for (rel = relstart; rel < relstart + sec->reloc_count; ++rel)
+ {
+ enum elf_ppc64_reloc_type r_type;
+ unsigned long r_symndx;
+ asection *sym_sec;
+ struct elf_link_hash_entry *h;
+ Elf_Internal_Sym *sym;
+ bfd_vma val;
+
+ r_type = ELF64_R_TYPE (rel->r_info);
+ switch (r_type)
+ {
+ case R_PPC64_TOC16:
+ case R_PPC64_TOC16_LO:
+ case R_PPC64_TOC16_HI:
+ case R_PPC64_TOC16_HA:
+ case R_PPC64_TOC16_DS:
+ case R_PPC64_TOC16_LO_DS:
+ /* In case we're taking addresses of toc entries. */
+ case R_PPC64_ADDR64:
+ break;
+
+ default:
+ continue;
+ }
+
+ r_symndx = ELF64_R_SYM (rel->r_info);
+ if (!get_sym_h (&h, &sym, &sym_sec, NULL, &local_syms,
+ r_symndx, ibfd))
+ {
+ free (used);
+ goto error_ret;
+ }
+
+ if (sym_sec != toc)
+ continue;
+
+ if (h != NULL)
+ val = h->root.u.def.value;
+ else
+ val = sym->st_value;
+ val += rel->r_addend;
+
+ if (val >= toc->size)
+ continue;
+
+ /* For the toc section, we only mark as used if
+ this entry itself isn't unused. */
+ if (sec == toc
+ && !used[val >> 3]
+ && (used[rel->r_offset >> 3]
+ || !skip[rel->r_offset >> 3]))
+ /* Do all the relocs again, to catch reference
+ chains. */
+ repeat = 1;
+
+ used[val >> 3] = 1;
+ }
+ while (repeat);
+ }
+
+ /* Merge the used and skip arrays. Assume that TOC
+ doublewords not appearing as either used or unused belong
+ to to an entry more than one doubleword in size. */
+ for (drop = skip, keep = used, last = 0, some_unused = 0;
+ drop < skip + (toc->size + 7) / 8;
+ ++drop, ++keep)
+ {
+ if (*keep)
+ {
+ *drop = 0;
+ last = 0;
+ }
+ else if (*drop)
+ {
+ some_unused = 1;
+ last = 1;
+ }
+ else
+ *drop = last;
+ }
+
+ free (used);
+
+ if (some_unused)
+ {
+ bfd_byte *contents, *src;
+ unsigned long off;
+
+ /* Shuffle the toc contents, and at the same time convert the
+ skip array from booleans into offsets. */
+ if (!bfd_malloc_and_get_section (ibfd, toc, &contents))
+ goto error_ret;
+
+ elf_section_data (toc)->this_hdr.contents = contents;
+
+ for (src = contents, off = 0, drop = skip;
+ src < contents + toc->size;
+ src += 8, ++drop)
+ {
+ if (*drop)
+ {
+ *drop = (unsigned long) -1;
+ off += 8;
+ }
+ else if (off != 0)
+ {
+ *drop = off;
+ memcpy (src - off, src, 8);
+ }
+ }
+ toc->rawsize = toc->size;
+ toc->size = src - contents - off;
+
+ /* Read toc relocs. */
+ relstart = _bfd_elf_link_read_relocs (ibfd, toc, NULL, NULL, TRUE);
+ if (relstart == NULL)
+ goto error_ret;
+
+ /* Remove unused toc relocs, and adjust those we keep. */
+ wrel = relstart;
+ for (rel = relstart; rel < relstart + toc->reloc_count; ++rel)
+ if (skip[rel->r_offset >> 3] != (unsigned long) -1)
+ {
+ wrel->r_offset = rel->r_offset - skip[rel->r_offset >> 3];
+ wrel->r_info = rel->r_info;
+ wrel->r_addend = rel->r_addend;
+ ++wrel;
+ }
+ toc->reloc_count = wrel - relstart;
+
+ /* Adjust addends for relocs against the toc section sym. */
+ for (sec = ibfd->sections; sec != NULL; sec = sec->next)
+ {
+ if (sec->reloc_count == 0
+ || elf_discarded_section (sec))
+ continue;
+
+ relstart = _bfd_elf_link_read_relocs (ibfd, sec, NULL, NULL,
+ TRUE);
+ if (relstart == NULL)
+ goto error_ret;
+
+ for (rel = relstart; rel < relstart + sec->reloc_count; ++rel)
+ {
+ enum elf_ppc64_reloc_type r_type;
+ unsigned long r_symndx;
+ asection *sym_sec;
+ struct elf_link_hash_entry *h;
+ Elf_Internal_Sym *sym;
+
+ r_type = ELF64_R_TYPE (rel->r_info);
+ switch (r_type)
+ {
+ default:
+ continue;
+
+ case R_PPC64_TOC16:
+ case R_PPC64_TOC16_LO:
+ case R_PPC64_TOC16_HI:
+ case R_PPC64_TOC16_HA:
+ case R_PPC64_TOC16_DS:
+ case R_PPC64_TOC16_LO_DS:
+ case R_PPC64_ADDR64:
+ break;
+ }
+
+ r_symndx = ELF64_R_SYM (rel->r_info);
+ if (!get_sym_h (&h, &sym, &sym_sec, NULL, &local_syms,
+ r_symndx, ibfd))
+ goto error_ret;
+
+ if (sym_sec != toc || h != NULL || sym->st_value != 0)
+ continue;
+
+ rel->r_addend -= skip[rel->r_addend >> 3];
+ }
+ }
+
+ /* We shouldn't have local or global symbols defined in the TOC,
+ but handle them anyway. */
+ if (local_syms != NULL)
+ {
+ Elf_Internal_Sym *sym;
+
+ for (sym = local_syms;
+ sym < local_syms + symtab_hdr->sh_info;
+ ++sym)
+ if (sym->st_shndx != SHN_UNDEF
+ && (sym->st_shndx < SHN_LORESERVE
+ || sym->st_shndx > SHN_HIRESERVE)
+ && sym->st_value != 0
+ && bfd_section_from_elf_index (ibfd, sym->st_shndx) == toc)
+ {
+ if (skip[sym->st_value >> 3] != (unsigned long) -1)
+ sym->st_value -= skip[sym->st_value >> 3];
+ else
+ {
+ (*_bfd_error_handler)
+ (_("%s defined in removed toc entry"),
+ bfd_elf_local_sym_name (ibfd, sym));
+ sym->st_value = 0;
+ sym->st_shndx = SHN_ABS;
+ }
+ symtab_hdr->contents = (unsigned char *) local_syms;
+ }
+ }
+
+ /* Finally, adjust any global syms defined in the toc. */
+ if (toc_inf.global_toc_syms)
+ {
+ toc_inf.toc = toc;
+ toc_inf.skip = skip;
+ toc_inf.global_toc_syms = FALSE;
+ elf_link_hash_traverse (elf_hash_table (info), adjust_toc_syms,
+ &toc_inf);
+ }
+ }
+
+ if (local_syms != NULL
+ && symtab_hdr->contents != (unsigned char *) local_syms)
+ {
+ if (!info->keep_memory)
+ free (local_syms);
+ else
+ symtab_hdr->contents = (unsigned char *) local_syms;
+ }
+ free (skip);
+ }
+
+ return TRUE;
+}
+
/* Allocate space in .plt, .got and associated reloc sections for
dynamic relocs. */
Index: ld/emultempl/ppc64elf.em
===================================================================
RCS file: /cvs/src/src/ld/emultempl/ppc64elf.em,v
retrieving revision 1.34
diff -u -p -r1.34 ppc64elf.em
--- ld/emultempl/ppc64elf.em 26 Sep 2004 23:42:30 -0000 1.34
+++ ld/emultempl/ppc64elf.em 4 Nov 2004 11:39:29 -0000
@@ -44,7 +44,13 @@ static bfd_signed_vma group_size = 1;
static int dotsyms = 1;
/* Whether to run tls optimization. */
-static int notlsopt = 0;
+static int no_tls_opt = 0;
+
+/* Whether to run opd optimization. */
+static int no_opd_opt = 0;
+
+/* Whether to run toc optimization. */
+static int no_toc_opt = 0;
/* Whether to emit symbols for stubs. */
static int emit_stub_syms = 0;
@@ -92,13 +98,14 @@ ppc_before_allocation (void)
{
if (stub_file != NULL)
{
- if (!ppc64_elf_edit_opd (output_bfd, &link_info, non_overlapping_opd))
+ if (!no_opd_opt
+ && !ppc64_elf_edit_opd (output_bfd, &link_info, non_overlapping_opd))
{
- einfo ("%X%P: can not edit opd %E\n");
+ einfo ("%X%P: can not edit %s %E\n", "opd");
return;
}
- if (ppc64_elf_tls_setup (output_bfd, &link_info) && !notlsopt)
+ if (ppc64_elf_tls_setup (output_bfd, &link_info) && !no_tls_opt)
{
/* Size the sections. This is premature, but we want to know the
TLS segment layout so that certain optimizations can be done. */
@@ -115,6 +122,14 @@ ppc_before_allocation (void)
elf_tdata (output_bfd)->program_header_size = 0;
lang_reset_memory_regions ();
}
+
+ if (!no_toc_opt
+ && !link_info.relocatable
+ && !ppc64_elf_edit_toc (output_bfd, &link_info))
+ {
+ einfo ("%X%P: can not edit %s %E\n", "toc");
+ return;
+ }
}
gld${EMULATION_NAME}_before_allocation ();
@@ -467,7 +482,9 @@ PARSE_AND_LIST_PROLOGUE='
#define OPTION_DOTSYMS (OPTION_STUBSYMS + 1)
#define OPTION_NO_DOTSYMS (OPTION_DOTSYMS + 1)
#define OPTION_NO_TLS_OPT (OPTION_NO_DOTSYMS + 1)
-#define OPTION_NON_OVERLAPPING_OPD (OPTION_NO_TLS_OPT + 1)
+#define OPTION_NO_OPD_OPT (OPTION_NO_TLS_OPT + 1)
+#define OPTION_NO_TOC_OPT (OPTION_NO_OPD_OPT + 1)
+#define OPTION_NON_OVERLAPPING_OPD (OPTION_NO_TOC_OPT + 1)
'
PARSE_AND_LIST_LONGOPTS='
@@ -476,6 +493,8 @@ PARSE_AND_LIST_LONGOPTS='
{ "dotsyms", no_argument, NULL, OPTION_DOTSYMS },
{ "no-dotsyms", no_argument, NULL, OPTION_NO_DOTSYMS },
{ "no-tls-optimize", no_argument, NULL, OPTION_NO_TLS_OPT },
+ { "no-opd-optimize", no_argument, NULL, OPTION_NO_OPD_OPT },
+ { "no-toc-optimize", no_argument, NULL, OPTION_NO_TOC_OPT },
{ "non-overlapping-opd", no_argument, NULL, OPTION_NON_OVERLAPPING_OPD },
'
@@ -505,6 +524,12 @@ PARSE_AND_LIST_OPTIONS='
--no-tls-optimize Don'\''t try to optimize TLS accesses.\n"
));
fprintf (file, _("\
+ --no-opd-optimize Don'\''t optimize the OPD section.\n"
+ ));
+ fprintf (file, _("\
+ --no-toc-optimize Don'\''t optimize the TOC section.\n"
+ ));
+ fprintf (file, _("\
--non-overlapping-opd Canonicalize .opd, so that there are no overlapping\n\
.opd entries.\n"
));
@@ -533,7 +558,15 @@ PARSE_AND_LIST_ARGS_CASES='
break;
case OPTION_NO_TLS_OPT:
- notlsopt = 1;
+ no_tls_opt = 1;
+ break;
+
+ case OPTION_NO_OPD_OPT:
+ no_opd_opt = 1;
+ break;
+
+ case OPTION_NO_TOC_OPT:
+ no_toc_opt = 1;
break;
case OPTION_NON_OVERLAPPING_OPD:
--
Alan Modra
IBM OzLabs - Linux Technology Centre