Support multiple .eh_frame sections

	This patch is based on MULTIPLE_FRAME_SECTIONS and EH_FRAME_LINKONCE,
	it allows backend to enable this feature and use '--gc-sections' simply.

	* gas/dw2gencfi.h (TARGET_MULTIPLE_EH_FRAME_SECTIONS): New.
	(MULTIPLE_FRAME_SECTIONS): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS.
	* gas/dw2gencfi.c (EH_FRAME_LINKONCE): Add TARGET_MULTIPLE_EH_FRAME_SECTIONS.
	(is_now_linkonce_segment): Likewise.
	(get_cfi_seg): Create relocation info between .eh_frame.* and .text.* section.

	* bfd/elf-bfd.h (elf_backend_can_make_multiple_eh_frame): New.
	* bfd/elfxx-target.h (elf_backend_can_make_multiple_eh_frame): Likewise.
	* bfd/elflink.c (_bfd_elf_default_action_discarded): Add checking for
	elf_backend_can_make_multiple_eh_frame.

3 files changed, 35 insertions, 3 deletions

diff --git a/gas/doc/internals.texi b/gas/doc/internals.texi
index a91d2ab..f028874 100644
--- a/gas/doc/internals.texi
+++ b/gas/doc/internals.texi
@@ -1581,6 +1581,10 @@ If defined, GAS will check this macro before performing any optimizations on
 the DWARF call frame debug information that is emitted.  Targets which
 implement link time relaxation may need to define this macro and set it to zero
 if it is possible to change the size of a function's prologue.
+
+@item TARGET_MULTIPLE_EH_FRAME_SECTIONS
+If defined, GAS will create multiple .eh_frame.* sections according to
+the name of owner's function sections.
 @end table
 
 @node Object format backend
diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c
index 6be8cb5..80b2628 100644
--- a/gas/dw2gencfi.c
+++ b/gas/dw2gencfi.c
@@ -75,7 +75,8 @@
 # define tc_cfi_endproc(fde) ((void) (fde))
 #endif
 
-#define EH_FRAME_LINKONCE (SUPPORT_FRAME_LINKONCE || compact_eh)
+#define EH_FRAME_LINKONCE (SUPPORT_FRAME_LINKONCE || compact_eh \
+			   || TARGET_MULTIPLE_EH_FRAME_SECTIONS)
 
 #ifndef DWARF2_FORMAT
 #define DWARF2_FORMAT(SEC) dwarf2_format_32bit
@@ -277,6 +278,9 @@ is_now_linkonce_segment (void)
   if (compact_eh)
     return now_seg;
 
+  if (TARGET_MULTIPLE_EH_FRAME_SECTIONS)
+    return now_seg;
+
   if ((bfd_section_flags (now_seg)
        & (SEC_LINK_ONCE | SEC_LINK_DUPLICATES_DISCARD
 	  | SEC_LINK_DUPLICATES_ONE_ONLY | SEC_LINK_DUPLICATES_SAME_SIZE
@@ -1333,14 +1337,33 @@ static segT
 get_cfi_seg (segT cseg, const char *base, flagword flags, int align)
 {
   /* Exclude .debug_frame sections for Compact EH.  */
-  if (SUPPORT_FRAME_LINKONCE || ((flags & SEC_DEBUGGING) == 0 && compact_eh))
+  if (SUPPORT_FRAME_LINKONCE || ((flags & SEC_DEBUGGING) == 0 && compact_eh)
+      || ((flags & SEC_DEBUGGING) == 0 && TARGET_MULTIPLE_EH_FRAME_SECTIONS))
     {
+      segT iseg = cseg;
       struct dwcfi_seg_list *l;
 
       l = dwcfi_hash_find_or_make (cseg, base, flags);
 
       cseg = l->seg;
       subseg_set (cseg, l->subseg);
+
+      if (TARGET_MULTIPLE_EH_FRAME_SECTIONS
+	  && (flags & DWARF2_EH_FRAME_READ_ONLY))
+	{
+	  const frchainS *ifrch = seg_info (iseg)->frchainP;
+	  const frchainS *frch = seg_info (cseg)->frchainP;
+	  expressionS exp;
+
+	  exp.X_op = O_symbol;
+	  exp.X_add_symbol = (symbolS *) local_symbol_make (cseg->name, cseg, frch->frch_root, 0);
+	  exp.X_add_number = 0;
+	  subseg_set (iseg, ifrch->frch_subseg);
+	  fix_new_exp (ifrch->frch_root, 0, 0, &exp, 0, BFD_RELOC_NONE);
+
+	  /* Restore the original segment info.  */
+	  subseg_set (cseg, l->subseg);
+	}
     }
   else
     {
diff --git a/gas/dw2gencfi.h b/gas/dw2gencfi.h
index d570cdb..0f5ae77 100644
--- a/gas/dw2gencfi.h
+++ b/gas/dw2gencfi.h
@@ -66,7 +66,12 @@ extern void cfi_add_CFA_restore_state (void);
 #define SUPPORT_COMPACT_EH 0
 #endif
 
-#define MULTIPLE_FRAME_SECTIONS (SUPPORT_FRAME_LINKONCE || SUPPORT_COMPACT_EH)
+#ifndef TARGET_MULTIPLE_EH_FRAME_SECTIONS
+#define TARGET_MULTIPLE_EH_FRAME_SECTIONS 0
+#endif
+
+#define MULTIPLE_FRAME_SECTIONS (SUPPORT_FRAME_LINKONCE || SUPPORT_COMPACT_EH \
+				 || TARGET_MULTIPLE_EH_FRAME_SECTIONS)
 
 struct cfi_insn_data
 {