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 commit cbd0eecf26.  The fancier ELF
treatment of keeping all input sections associated with a __start or
__stop symbol, from 2015-10-23 commit 1cce69b9dc, 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.

1 files changed, 14 insertions, 1 deletions

diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index a23bb98..4348793 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -7593,7 +7593,8 @@ typedef struct bfd_target
   NAME##_bfd_is_group_section, \
   NAME##_bfd_discard_group, \
   NAME##_section_already_linked, \
-  NAME##_bfd_define_common_symbol
+  NAME##_bfd_define_common_symbol, \
+  NAME##_bfd_define_start_stop
 
   int         (*_bfd_sizeof_headers) (bfd *, struct bfd_link_info *);
   bfd_byte *  (*_bfd_get_relocated_section_contents)
@@ -7657,6 +7658,11 @@ typedef struct bfd_target
   bfd_boolean (*_bfd_define_common_symbol) (bfd *, struct bfd_link_info *,
                                             struct bfd_link_hash_entry *);
 
+  /* Define a __start, __stop, .startof. or .sizeof. symbol.  */
+  struct bfd_link_hash_entry *(*_bfd_define_start_stop) (struct bfd_link_info *,
+                                                         const char *,
+                                                         asection *);
+
   /* Routines to handle dynamic symbols and relocs.  */
 #define BFD_JUMP_TABLE_DYNAMIC(NAME) \
   NAME##_get_dynamic_symtab_upper_bound, \
@@ -7736,6 +7742,13 @@ bfd_boolean bfd_generic_define_common_symbol
 #define bfd_define_common_symbol(output_bfd, info, h) \
        BFD_SEND (output_bfd, _bfd_define_common_symbol, (output_bfd, info, h))
 
+struct bfd_link_hash_entry *bfd_generic_define_start_stop
+   (struct bfd_link_info *info,
+    const char *symbol, asection *sec);
+
+#define bfd_define_start_stop(output_bfd, info, symbol, sec) \
+       BFD_SEND (output_bfd, _bfd_define_start_stop, (info, symbol, sec))
+
 struct bfd_elf_version_tree * bfd_find_version_for_sym
    (struct bfd_elf_version_tree *verdefs,
     const char *sym_name, bfd_boolean *hide);