Rewrite __start and __stop symbol handling
This arranges for __start and __stop symbols to be defined before garbage collection, for all target formats. That should allow the COFF and PE --gc-sections to keep a singleton orphan input section, a feature lost by 2017-06-13 commitcbd0eecf26. The fancier ELF treatment of keeping all input sections associated with a __start or __stop symbol, from 2015-10-23 commit1cce69b9dc, is retained. .startof. and .sizeof. symbols are deliberately not defined before garbage collection, so these won't affect garbage collection of sections. The patch also ensures __start, __stop, .startof. and .sizeof. symbols are defined before target size_dynamic_sections is called, albeit with a preliminary value, so that target code doesn't need to cope with a symbol changing from undefined at size_dynamic_sections to defined at relocate_section. Also, a number of problems with the testcases have been fixed. PR ld/20022 PR ld/21557 PR ld/21562 PR ld/21571 include/ * bfdlink.h (struct bfd_link_hash_entry): Delete undef.section. bfd/ * targets.c (struct bfd_target): Add _bfd_define_start_stop. (BFD_JUMP_TABLE_LINK): Likewise. * elf-bfd.h (bfd_elf_define_start_stop): Declare. * elflink.c (_bfd_elf_gc_mark_rsec): Update comment. (bfd_elf_define_start_stop): New function. * linker.c (bfd_generic_define_start_stop): New function. * coff64-rs6000.c (rs6000_xcoff64_vec, rs6000_xcoff64_aix_vec): Init new field. * aout-adobe.c (aout_32_bfd_define_start_stop): Define. * aout-target.h (MY_bfd_define_start_stop): Define. * aout-tic30.c (MY_bfd_define_start_stop): Define. * binary.c (binary_bfd_define_start_stop): Define. * bout.c (b_out_bfd_define_start_stop): Define. * coff-alpha.c (_bfd_ecoff_bfd_define_start_stop): Define. * coff-mips.c (_bfd_ecoff_bfd_define_start_stop): Define. * coff-rs6000.c (_bfd_xcoff_bfd_define_start_stop): Define. * coffcode.h (coff_bfd_define_start_stop): Define. * elfxx-target.h (bfd_elfNN_bfd_define_start_stop): Define. * i386msdos.c (msdos_bfd_define_start_stop): Define. * i386os9k.c (os9k_bfd_define_start_stop): Define. * ieee.c (ieee_bfd_define_start_stop): Define. * ihex.c (ihex_bfd_define_start_stop): Define. * libbfd-in.h (_bfd_nolink_bfd_define_start_stop): Define. * mach-o-target.c (bfd_mach_o_bfd_define_start_stop): Define. * mmo.c (mmo_bfd_define_start_stop): Define. * nlm-target.h (nlm_bfd_define_start_stop): Define. * oasys.c (oasys_bfd_define_start_stop): Define. * pef.c (bfd_pef_bfd_define_start_stop): Define. * plugin.c (bfd_plugin_bfd_define_start_stop): Define. * ppcboot.c (ppcboot_bfd_define_start_stop): Define. * som.c (som_bfd_define_start_stop): Define. * srec.c (srec_bfd_define_start_stop): Define. * tekhex.c (tekhex_bfd_define_start_stop): Define. * versados.c (versados_bfd_define_start_stop): Define. * vms-alpha.c (vms_bfd_define_start_stop): Define. (alpha_vms_bfd_define_start_stop): Define. * xsym.c (bfd_sym_bfd_define_start_stop): Define. * bfd-in2.h: Regenerate. * libbfd.h: Regenerate. ld/ * emultempl/elf32.em (gld${EMULATION_NAME}_after_open): Don't set __start/__stop syms here. * ldlang.c (lang_set_startof): Delete. (start_stop_syms, start_stop_count, start_stop_alloc): New vars. (lang_define_start_stop, lang_init_start_stop, foreach_start_stop, undef_start_stop, lang_undef_start_stop, lang_init_startof_sizeof, set_start_stop, lang_finalize_start_stop): New functions. (lang_process): Call _start_stop functions. * testsuite/ld-elf/pr21562a.d: Use xfail rather than notarget. Correct typos and list of xfail targets. * testsuite/ld-elf/pr21562b.d: Likewise. * testsuite/ld-elf/pr21562c.d: Likewise. * testsuite/ld-elf/pr21562d.d: Likewise. * testsuite/ld-elf/pr21562e.d: Likewise. * testsuite/ld-elf/pr21562f.d: Likewise. * testsuite/ld-elf/pr21562g.d: Likewise. * testsuite/ld-elf/pr21562h.d: Likewise. * testsuite/ld-elf/pr21562i.d: Likewise. * testsuite/ld-elf/pr21562j.d: Likewise. * testsuite/ld-elf/pr21562k.d: Likewise. * testsuite/ld-elf/pr21562l.d: Likewise. * testsuite/ld-elf/pr21562m.d: Likewise. * testsuite/ld-elf/pr21562n.d: Likewise. * testsuite/ld-elf/sizeofa.d: Likewise. Adjust to pass for generic ELF. * testsuite/ld-elf/sizeofb.d: Likewise. * testsuite/ld-elf/startofa.d: Likewise. * testsuite/ld-elf/startofb.d: Likewise.
This commit is contained in:
Alan Modra
parent
d68f19767d
commit
7dba9362c1
59 changed files with 492 additions and 242 deletions
249
ld/ldlang.c
249
ld/ldlang.c
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@ -5878,97 +5878,173 @@ section_for_dot (void)
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return bfd_abs_section_ptr;
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}
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/* Fix any .startof., .sizeof., __start or __stop symbols. When the
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assemblers see the operator .startof. (section_name), it produces
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an undefined symbol .startof.section_name. Similarly, when it sees
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.sizeof. (section_name), it produces an undefined symbol
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.sizeof.section_name. Also for ELF linker, __start_XXX or __stop_XXX
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symbols should be resolved to the start and end of section XXX. For
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all the output sections, we look for such symbols, and set them to
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the correct value. */
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/* Array of __start/__stop/.startof./.sizeof/ symbols. */
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static struct bfd_link_hash_entry **start_stop_syms;
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static size_t start_stop_count = 0;
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static size_t start_stop_alloc = 0;
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/* Give start/stop SYMBOL for SEC a preliminary definition, and add it
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to start_stop_syms. */
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static void
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lang_set_startof (void)
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lang_define_start_stop (const char *symbol, asection *sec)
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{
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asection *s;
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char leading_char;
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bfd_boolean is_elf;
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bfd_boolean is_relocatable;
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struct bfd_link_hash_entry *h;
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if (!config.build_constructors)
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h = bfd_define_start_stop (link_info.output_bfd, &link_info, symbol, sec);
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if (h != NULL)
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{
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if (start_stop_count == start_stop_alloc)
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{
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start_stop_alloc = 2 * start_stop_alloc + 10;
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start_stop_syms
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= xrealloc (start_stop_syms,
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start_stop_alloc * sizeof (*start_stop_syms));
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}
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start_stop_syms[start_stop_count++] = h;
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}
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}
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/* Check for input sections whose names match references to
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__start_SECNAME or __stop_SECNAME symbols. Give the symbols
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preliminary definitions. */
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static void
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lang_init_start_stop (void)
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{
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bfd *abfd;
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asection *s;
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char leading_char = bfd_get_symbol_leading_char (link_info.output_bfd);
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for (abfd = link_info.input_bfds; abfd != NULL; abfd = abfd->link.next)
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for (s = abfd->sections; s != NULL; s = s->next)
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{
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const char *ps;
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const char *secname = s->name;
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for (ps = secname; *ps != '\0'; ps++)
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if (!ISALNUM ((unsigned char) *ps) && *ps != '_')
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break;
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if (*ps == '\0')
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{
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char *symbol = (char *) xmalloc (10 + strlen (secname));
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symbol[0] = leading_char;
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sprintf (symbol + (leading_char != 0), "__start_%s", secname);
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lang_define_start_stop (symbol, s);
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symbol[1] = leading_char;
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memcpy (symbol + 1 + (leading_char != 0), "__stop", 6);
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lang_define_start_stop (symbol + 1, s);
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free (symbol);
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}
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}
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}
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/* Iterate over start_stop_syms. */
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static void
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foreach_start_stop (void (*func) (struct bfd_link_hash_entry *))
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{
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size_t i;
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for (i = 0; i < start_stop_count; ++i)
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func (start_stop_syms[i]);
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}
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/* __start and __stop symbols are only supposed to be defined by the
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linker for orphan sections, but we now extend that to sections that
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map to an output section of the same name. The symbols were
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defined early for --gc-sections, before we mapped input to output
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sections, so undo those that don't satisfy this rule. */
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static void
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undef_start_stop (struct bfd_link_hash_entry *h)
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{
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if (h->ldscript_def)
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return;
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is_elf = (bfd_get_flavour (link_info.output_bfd)
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== bfd_target_elf_flavour);
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is_relocatable = bfd_link_relocatable (&link_info);
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if (h->u.def.section->output_section == NULL
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|| h->u.def.section->output_section->owner != link_info.output_bfd
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|| strcmp (h->u.def.section->name,
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h->u.def.section->output_section->name) != 0)
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{
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h->type = bfd_link_hash_undefined;
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h->u.undef.abfd = NULL;
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}
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}
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leading_char = bfd_get_symbol_leading_char (link_info.output_bfd);
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static void
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lang_undef_start_stop (void)
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{
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foreach_start_stop (undef_start_stop);
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}
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/* Check for output sections whose names match references to
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.startof.SECNAME or .sizeof.SECNAME symbols. Give the symbols
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preliminary definitions. */
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static void
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lang_init_startof_sizeof (void)
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{
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asection *s;
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for (s = link_info.output_bfd->sections; s != NULL; s = s->next)
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{
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const char *secname;
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char *buf;
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struct bfd_link_hash_entry *h;
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const char *secname = s->name;
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char *symbol = (char *) xmalloc (10 + strlen (secname));
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secname = bfd_get_section_name (link_info.output_bfd, s);
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buf = (char *) xmalloc (10 + strlen (secname));
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sprintf (symbol, ".startof.%s", secname);
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lang_define_start_stop (symbol, s);
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if (!is_relocatable)
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{
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sprintf (buf, ".startof.%s", secname);
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h = bfd_link_hash_lookup (link_info.hash, buf, FALSE, FALSE,
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TRUE);
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if (h != NULL && h->type == bfd_link_hash_undefined)
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{
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h->type = bfd_link_hash_defined;
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h->u.def.value = 0;
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h->u.def.section = s;
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}
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sprintf (buf, ".sizeof.%s", secname);
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h = bfd_link_hash_lookup (link_info.hash, buf, FALSE, FALSE,
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TRUE);
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if (h != NULL && h->type == bfd_link_hash_undefined)
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{
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h->type = bfd_link_hash_defined;
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h->u.def.value = TO_ADDR (s->size);
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h->u.def.section = bfd_abs_section_ptr;
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}
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}
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buf[0] = leading_char;
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sprintf (buf + (buf[0] != 0), "__start_%s", secname);
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h = bfd_link_hash_lookup (link_info.hash, buf, FALSE, FALSE,
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TRUE);
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if (h != NULL
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&& (h->type == bfd_link_hash_undefined
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|| h->type == bfd_link_hash_undefweak))
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{
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h->type = bfd_link_hash_defined;
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h->u.def.value = 0;
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h->u.def.section = s;
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if (is_elf)
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((struct elf_link_hash_entry *) h)->def_regular = 1;
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}
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buf[0] = leading_char;
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sprintf (buf + (buf[0] != 0), "__stop_%s", secname);
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h = bfd_link_hash_lookup (link_info.hash, buf, FALSE, FALSE,
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TRUE);
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if (h != NULL
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&& (h->type == bfd_link_hash_undefined
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|| h->type == bfd_link_hash_undefweak))
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{
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h->type = bfd_link_hash_defined;
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h->u.def.value = TO_ADDR (s->size);
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h->u.def.section = s;
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if (is_elf)
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((struct elf_link_hash_entry *) h)->def_regular = 1;
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}
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free (buf);
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memcpy (symbol + 1, ".size", 5);
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lang_define_start_stop (symbol + 1, s);
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free (symbol);
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}
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}
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/* Set .startof., .sizeof., __start and __stop symbols final values. */
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static void
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set_start_stop (struct bfd_link_hash_entry *h)
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{
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if (h->ldscript_def
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|| h->type != bfd_link_hash_defined)
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return;
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if (h->root.string[0] == '.')
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{
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/* .startof. or .sizeof. symbol.
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.startof. already has final value. */
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if (h->root.string[2] == 'i')
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{
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/* .sizeof. */
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h->u.def.value = TO_ADDR (h->u.def.section->size);
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h->u.def.section = bfd_abs_section_ptr;
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}
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}
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else
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{
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/* __start or __stop symbol. */
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int has_lead = bfd_get_symbol_leading_char (link_info.output_bfd) != 0;
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h->u.def.section = h->u.def.section->output_section;
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if (h->root.string[4 + has_lead] == 'o')
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{
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/* __stop_ */
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h->u.def.value = TO_ADDR (h->u.def.section->size);
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}
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}
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}
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static void
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lang_finalize_start_stop (void)
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{
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foreach_start_stop (set_start_stop);
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}
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static void
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lang_end (void)
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{
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@ -7035,6 +7111,12 @@ lang_process (void)
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files. */
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ldctor_build_sets ();
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/* Give initial values for __start and __stop symbols, so that ELF
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gc_sections will keep sections referenced by these symbols. Must
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be done before lang_do_assignments below. */
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if (config.build_constructors)
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lang_init_start_stop ();
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/* PR 13683: We must rerun the assignments prior to running garbage
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collection in order to make sure that all symbol aliases are resolved. */
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lang_do_assignments (lang_mark_phase_enum);
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@ -7089,6 +7171,17 @@ lang_process (void)
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/* Copy forward lma regions for output sections in same lma region. */
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lang_propagate_lma_regions ();
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/* Defining __start/__stop symbols early for --gc-sections to work
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around a glibc build problem can result in these symbols being
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defined when they should not be. Fix them now. */
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if (config.build_constructors)
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lang_undef_start_stop ();
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/* Define .startof./.sizeof. symbols with preliminary values before
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dynamic symbols are created. */
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if (!bfd_link_relocatable (&link_info))
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lang_init_startof_sizeof ();
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/* Do anything special before sizing sections. This is where ELF
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and other back-ends size dynamic sections. */
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ldemul_before_allocation ();
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@ -7108,8 +7201,8 @@ lang_process (void)
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everything is. This is where relaxation is done. */
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ldemul_after_allocation ();
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/* Fix any .startof. or .sizeof. symbols. */
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lang_set_startof ();
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/* Fix any __start, __stop, .startof. or .sizeof. symbols. */
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lang_finalize_start_stop ();
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/* Do all the assignments, now that we know the final resting places
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of all the symbols. */
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