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Large data sections support
- From: Jan Hubicka <hubicka at ucw dot cz>
- To: binutils at sources dot redhat dot com, rth at redhat dot com
- Date: Sun, 12 Jun 2005 14:41:35 +0200
- Subject: Large data sections support
Hi,
this patch adds support for .ldata/.lbbs and .lrodata as needed by x86-64 ABI
draft for medium model. The idea actually came from rth after my initial patch
to use .sdata/sbbs/srodata in medium model. The .l sections come last in the
file and are allowed to exceed 2GB. (unlike for other architecutres the
"small" datas are big enought for most of common use so using .l section
instead of .s buys us some additional compatibility in between models and some
nasty hacks to get GOT table before large datas).
The patch was tested together with patches GCC to build medium model libraries
on older version of GCC. I've just compiled it and run x86-64 testsuite on
current. I am not sure if the approach of modifying global linker
script sounds acceptable, but I don't see any negatives it would have
for other architectures (as we do the same for sdata too).
Does this look OK?
Honza
2005-06-12 Jan Hubicka <jh@suse.cz>
* elf.c (bfd_get_section_by_name): Add .ldata support.
* elf64-x86-64.c (elf64_x86_64_add_symbol_hook): New.
(elf_backend_add_symbol_hook): Define.
* elf.sc: Add .ldata, .lbbs and .lrodata support.
Index: bfd/elf.c
===================================================================
RCS file: /cvs/src/src/bfd/elf.c,v
retrieving revision 1.242
diff -c -3 -p -r1.242 elf.c
*** bfd/elf.c 6 Sep 2004 20:55:22 -0000 1.242
--- bfd/elf.c 8 Sep 2004 21:49:06 -0000
*************** get_program_header_size (bfd *abfd)
*** 4360,4365 ****
--- 4360,4371 ----
segs += 2;
}
+ if (bfd_get_section_by_name (abfd, ".ldata") != NULL)
+ {
+ /* We need a large data area segment. */
+ ++segs;
+ }
+
if (bfd_get_section_by_name (abfd, ".dynamic") != NULL)
{
/* We need a PT_DYNAMIC segment. */
Index: bfd/elf64-x86-64.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-x86-64.c,v
retrieving revision 1.83
diff -c -3 -p -r1.83 elf64-x86-64.c
*** bfd/elf64-x86-64.c 13 Aug 2004 03:15:59 -0000 1.83
--- bfd/elf64-x86-64.c 8 Sep 2004 21:49:06 -0000
*************** elf64_x86_64_check_relocs (bfd *abfd, st
*** 973,978 ****
--- 989,1029 ----
return TRUE;
}
+ /* Hook called by the linker routine which adds symbols from an object
+ file. We use it to put .comm items in .lbss, and not .bss. */
+
+ static bfd_boolean
+ elf64_x86_64_add_symbol_hook (bfd *abfd, struct bfd_link_info *info,
+ Elf_Internal_Sym *sym, const char **namep,
+ flagword *flagsp, asection **secp, bfd_vma *valp)
+ {
+ if (sym->st_shndx == SHN_COMMON
+ && !info->relocatable
+ && sym->st_size > elf_gp_size (abfd))
+ {
+ /* Common symbols greater than -G nn bytes are
+ automatically put into .lbss. */
+
+ asection *lcomm = bfd_get_section_by_name (abfd, ".lbss");
+
+ if (lcomm == NULL)
+ {
+ lcomm = bfd_make_section (abfd, ".lbss");
+ if (lcomm == NULL
+ || !bfd_set_section_flags (abfd, lcomm, (SEC_ALLOC
+ | SEC_IS_COMMON
+ | SEC_LINKER_CREATED)))
+ return FALSE;
+ }
+
+ *secp = lcomm;
+ *valp = sym->st_size;
+ }
+
+ return TRUE;
+ }
+
+
/* Return the section that should be marked against GC for a given
relocation. */
*************** elf64_x86_64_plt_sym_val (bfd_vma i, con
*** 2809,2814 ****
--- 2883,2889 ----
#define bfd_elf64_bfd_reloc_type_lookup elf64_x86_64_reloc_type_lookup
#define elf_backend_adjust_dynamic_symbol elf64_x86_64_adjust_dynamic_symbol
+ #define elf_backend_add_symbol_hook elf64_x86_64_add_symbol_hook
#define elf_backend_check_relocs elf64_x86_64_check_relocs
#define elf_backend_copy_indirect_symbol elf64_x86_64_copy_indirect_symbol
#define elf_backend_create_dynamic_sections elf64_x86_64_create_dynamic_sections
Index: ld/scripttempl/elf.sc
===================================================================
RCS file: /cvs/src/src/ld/scripttempl/elf.sc,v
retrieving revision 1.46
diff -c -3 -p -r1.46 elf.sc
*** ld/scripttempl/elf.sc 5 Jul 2004 20:00:13 -0000 1.46
--- ld/scripttempl/elf.sc 8 Sep 2004 21:49:09 -0000
***************
*** 69,74 ****
--- 69,77 ----
# .debug_info .gnu.linkonce.wi.foo
# .tdata .gnu.linkonce.td.foo
# .tbss .gnu.linkonce.tb.foo
+ # .ldata .gnu.linkonce.l.foo
+ # .lbss .gnu.linkonce.lb.foo
+ # .lrodata .gnu.linkonce.lr.foo
#
# Each of these can also have corresponding .rel.* and .rela.* sections.
*************** if test -z "${NO_SMALL_DATA}"; then
*** 141,146 ****
--- 143,173 ----
else
NO_SMALL_DATA=" "
fi
+ if test -z "${NO_LARGE_DATA}"; then
+ LBSS=".lbss ${RELOCATING-0} :
+ {
+ ${RELOCATING+PROVIDE (__lbss_start = .);}
+ ${RELOCATING+PROVIDE (___lbss_start = .);}
+ *(.dynlbss)
+ *(.lbss${RELOCATING+ .sbss.* .gnu.linkonce.sb.*})
+ *(.lcommon)
+ ${RELOCATING+PROVIDE (__lbss_end = .);}
+ ${RELOCATING+PROVIDE (___lbss_end = .);}
+ }"
+ LDATA="
+ .ldata ${RELOCATING-0} :
+ {
+ ${RELOCATING+${LDATA_START_SYMBOLS}}
+ *(.ldata${RELOCATING+ .ldata.* .gnu.linkonce.l.*})
+ }"
+ LRODATA=".lrodata ${RELOCATING-0} : { *(.lrodata${RELOCATING+ .lrodata.* .gnu.linkonce.lr.*}) }"
+ REL_LDATA=".rel.ldata ${RELOCATING-0} : { *(.rel.ldata${RELOCATING+ .rel.ldata.* .rel.gnu.linkonce.l.*}) }
+ .rela.ldata ${RELOCATING-0} : { *(.rela.ldata${RELOCATING+ .rela.ldata.* .rela.gnu.linkonce.l.*}) }"
+ REL_LBSS=".rel.lbss ${RELOCATING-0} : { *(.rel.sbss${RELOCATING+ .rel.sbss.* .rel.gnu.linkonce.lb.*}) }
+ .rela.lbss ${RELOCATING-0} : { *(.rela.sbss${RELOCATING+ .rela.sbss.* .rela.gnu.linkonce.lb.*}) }"
+ else
+ NO_LARGE_DATA=" "
+ fi
test -n "$SEPARATE_GOTPLT" && SEPARATE_GOTPLT=" "
CTOR=".ctors ${CONSTRUCTING-0} :
{
*************** eval $COMBRELOCCAT <<EOF
*** 258,263 ****
--- 285,294 ----
${REL_SBSS2}
.rel.bss ${RELOCATING-0} : { *(.rel.bss${RELOCATING+ .rel.bss.* .rel.gnu.linkonce.b.*}) }
.rela.bss ${RELOCATING-0} : { *(.rela.bss${RELOCATING+ .rela.bss.* .rela.gnu.linkonce.b.*}) }
+ ${REL_LDATA}
+ ${REL_LBSS}
+ ${REL_LDATA2}
+ ${REL_LBSS2}
EOF
if [ -n "$COMBRELOC" ]; then
cat <<EOF
*************** cat <<EOF
*** 401,406 ****
--- 432,440 ----
${RELOCATING+${OTHER_BSS_END_SYMBOLS}}
${RELOCATING+PROVIDE (end = .);}
${RELOCATING+${DATA_SEGMENT_END}}
+ ${LRODATA}
+ ${LDATA}
+ ${LBSS}
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }