Add --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi]

This patch adds --compress-debug-sections=[none|zlib|zlib-gnu|zlib-gabi]
to ld for ELF targets to support generating compressed DWARF debug
sections.  We always generate .zdebug_* section since section names have
been finalized and they can't be changed easily when compression is
being performed.

bfd/

	* bfd-in.h (compressed_debug_section_type): New.
	* compress.c (bfd_compress_section_contents): Add an argument
	for linker write compression and always generate .zdebug_*
	section when linking.
	(bfd_init_section_compress_status): Pass FALSE to
	bfd_compress_section_contents.
	(bfd_compress_section): New function.
	* elf.c (elf_fake_sections): For linking, set SEC_ELF_COMPRESS
	on DWARF debug sections if COMPRESS_DEBUG is set and rename
	section if COMPRESS_DEBUG_GABI_ZLIB isn't set.
	(assign_file_positions_for_non_load_sections): Set sh_offset
	to -1 if SEC_ELF_COMPRESS is set.
	(assign_file_positions_except_relocs): Likwise.
	(_bfd_elf_assign_file_positions_for_relocs): Renamed to ...
	(_bfd_elf_assign_file_positions_for_non_load): This.  Change
	return time to bfd_boolean.  Compress the section if
	SEC_ELF_COMPRESS is set.
	(_bfd_elf_write_object_contents): Updated.
	(_bfd_elf_set_section_contents): Write section contents to
	the buffer if SEC_ELF_COMPRESS is set.
	* merge.c: Include "elf-bfd.h".
	(sec_merge_emit): Add arguments for contents and offset.  Write
	to contents with offset if contents isn't NULL.
	(_bfd_write_merged_section): Write section contents to the
	buffer if SEC_ELF_COMPRESS is set.  Pass contents and
	output_offset to sec_merge_emit.
	* elflink.c (bfd_elf_final_link): Allocate the buffer for
	output section contents if SEC_ELF_COMPRESS is set.
	* section.c (SEC_ELF_COMPRESS): New.
	* bfd-in2.h: Regenerated.

gas/

	* as.h (compressed_debug_section_type): Removed.

include/

	* bfdlink.h (bfd_link_info): Add compress_debug.

ld/

	* ld.texinfo: Document --compress-debug-sections=.
	* ldmain.c (main): Set BFD_COMPRESS on output_bfd if
	COMPRESS_DEBUG is set.  Set BFD_COMPRESS_GABI on output_bfd
	for COMPRESS_DEBUG_GABI_ZLIB.
	* lexsup.c (elf_static_list_options): Add
	--compress-debug-sections=.
	* emultempl/elf32.em (OPTION_COMPRESS_DEBUG): New.
	(xtra_long): Add "compress-debug-sections".
	(gld${EMULATION_NAME}_handle_option): Handle
	OPTION_COMPRESS_DEBUG.

ld/testsuite/

	* ld-elf/compress.exp (build_tests): Add tests for
	--compress-debug-sections=.
	(run_tests): Likewise.
	Add additonal tests for --compress-debug-sections=.
	* ld-elf/gabiend.rt: New file.
	* ld-elf/gabinormal.rt: Likewise.
	* ld-elf/gnubegin.rS: Likewise.
	* ld-elf/gnunormal.rS: Likewise.
	* ld-elf/zlibbegin.rS: Likewise.
	* ld-elf/zlibnormal.rS: Likewise.

8 files changed, 253 insertions, 21 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 17610e0..abb87dc 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,36 @@
+2015-04-14  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* bfd-in.h (compressed_debug_section_type): New.
+	* compress.c (bfd_compress_section_contents): Add an argument
+	for linker write compression and always generate .zdebug_*
+	section when linking.
+	(bfd_init_section_compress_status): Pass FALSE to
+	bfd_compress_section_contents.
+	(bfd_compress_section): New function.
+	* elf.c (elf_fake_sections): For linking, set SEC_ELF_COMPRESS
+	on DWARF debug sections if COMPRESS_DEBUG is set and rename
+	section if COMPRESS_DEBUG_GABI_ZLIB isn't set.
+	(assign_file_positions_for_non_load_sections): Set sh_offset
+	to -1 if SEC_ELF_COMPRESS is set.
+	(assign_file_positions_except_relocs): Likwise.
+	(_bfd_elf_assign_file_positions_for_relocs): Renamed to ...
+	(_bfd_elf_assign_file_positions_for_non_load): This.  Change
+	return time to bfd_boolean.  Compress the section if
+	SEC_ELF_COMPRESS is set.
+	(_bfd_elf_write_object_contents): Updated.
+	(_bfd_elf_set_section_contents): Write section contents to
+	the buffer if SEC_ELF_COMPRESS is set.
+	* merge.c: Include "elf-bfd.h".
+	(sec_merge_emit): Add arguments for contents and offset.  Write
+	to contents with offset if contents isn't NULL.
+	(_bfd_write_merged_section): Write section contents to the
+	buffer if SEC_ELF_COMPRESS is set.  Pass contents and
+	output_offset to sec_merge_emit.
+	* elflink.c (bfd_elf_final_link): Allocate the buffer for
+	output section contents if SEC_ELF_COMPRESS is set.
+	* section.c (SEC_ELF_COMPRESS): New.
+	* bfd-in2.h: Regenerated.
+
 2015-04-15  Alan Modra  <amodra@gmail.com>
 
 	* elf32-rl78.c (rl78_elf_relocate_section): Typo fix.
diff --git a/bfd/bfd-in.h b/bfd/bfd-in.h
index 1f8a72c..2e324cd 100644
--- a/bfd/bfd-in.h
+++ b/bfd/bfd-in.h
@@ -437,6 +437,17 @@ extern void bfd_hash_traverse
    this size.  */
 extern unsigned long bfd_hash_set_default_size (unsigned long);
 
+/* Types of compressed DWARF debug sections.  We currently support
+   zlib.  */
+enum compressed_debug_section_type
+{
+  COMPRESS_DEBUG_NONE = 0,
+  COMPRESS_DEBUG = 1 << 0,
+  COMPRESS_DEBUG_ZLIB = COMPRESS_DEBUG | 1 << 1,
+  COMPRESS_DEBUG_GNU_ZLIB = COMPRESS_DEBUG | 1 << 2,
+  COMPRESS_DEBUG_GABI_ZLIB = COMPRESS_DEBUG | 1 << 3
+};
+
 /* This structure is used to keep track of stabs in sections
    information while linking.  */
 
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 679595e..122caa0 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -444,6 +444,17 @@ extern void bfd_hash_traverse
    this size.  */
 extern unsigned long bfd_hash_set_default_size (unsigned long);
 
+/* Types of compressed DWARF debug sections.  We currently support
+   zlib.  */
+enum compressed_debug_section_type
+{
+  COMPRESS_DEBUG_NONE = 0,
+  COMPRESS_DEBUG = 1 << 0,
+  COMPRESS_DEBUG_ZLIB = COMPRESS_DEBUG | 1 << 1,
+  COMPRESS_DEBUG_GNU_ZLIB = COMPRESS_DEBUG | 1 << 2,
+  COMPRESS_DEBUG_GABI_ZLIB = COMPRESS_DEBUG | 1 << 3
+};
+
 /* This structure is used to keep track of stabs in sections
    information while linking.  */
 
@@ -1378,6 +1389,10 @@ typedef struct bfd_section
      executables or shared objects. This is for COFF only.  */
 #define SEC_COFF_SHARED 0x8000000
 
+  /* This section should be compressed.  This is for ELF linker
+     internal use only.  */
+#define SEC_ELF_COMPRESS 0x8000000
+
   /* When a section with this flag is being linked, then if the size of
      the input section is less than a page, it should not cross a page
      boundary.  If the size of the input section is one page or more,
@@ -7316,6 +7331,9 @@ bfd_boolean bfd_init_section_decompress_status
 bfd_boolean bfd_init_section_compress_status
    (bfd *abfd, asection *section);
 
+bfd_boolean bfd_compress_section
+   (bfd *abfd, asection *section, bfd_byte *uncompressed_buffer);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/bfd/compress.c b/bfd/compress.c
index 770ea57..dfde50e 100644
--- a/bfd/compress.c
+++ b/bfd/compress.c
@@ -72,7 +72,8 @@ decompress_contents (bfd_byte *compressed_buffer,
 static bfd_size_type
 bfd_compress_section_contents (bfd *abfd, sec_ptr sec,
 			       bfd_byte *uncompressed_buffer,
-			       bfd_size_type uncompressed_size)
+			       bfd_size_type uncompressed_size,
+			       bfd_boolean write_compress)
 {
   uLong compressed_size;
   bfd_byte *buffer;
@@ -176,8 +177,11 @@ bfd_compress_section_contents (bfd *abfd, sec_ptr sec,
 
       compressed_size += header_size;
       /* PR binutils/18087: If compression didn't make the section smaller,
-	 just keep it uncompressed.  */
-      if (compressed_size < uncompressed_size)
+	 just keep it uncompressed.  We always generate .zdebug_* section
+	 when linking since section names have been finalized and they
+	 can't be changed easily.  */
+      if ((write_compress && compression_header_size == 0)
+	   || compressed_size < uncompressed_size)
 	{
 	  bfd_update_compression_header (abfd, buffer, sec);
 
@@ -543,9 +547,48 @@ bfd_init_section_compress_status (bfd *abfd, sec_ptr sec)
     {
       uncompressed_size = bfd_compress_section_contents (abfd, sec,
 							 uncompressed_buffer,
-							 uncompressed_size);
+							 uncompressed_size,
+							 FALSE);
       ret = uncompressed_size != 0;
     }
 
   return ret;
 }
+
+/*
+FUNCTION
+	bfd_compress_section
+
+SYNOPSIS
+	bfd_boolean bfd_compress_section
+	  (bfd *abfd, asection *section, bfd_byte *uncompressed_buffer);
+
+DESCRIPTION
+	If open for write, compress section, update section size with
+	compressed size and set compress_status to COMPRESS_SECTION_DONE.
+
+	Return @code{FALSE} if compression fail.  Otherwise, return
+	@code{TRUE}.
+*/
+
+bfd_boolean
+bfd_compress_section (bfd *abfd, sec_ptr sec, bfd_byte *uncompressed_buffer)
+{
+  bfd_size_type uncompressed_size = sec->size;
+
+  /* Error if not opened for write.  */
+  if (abfd->direction != write_direction
+      || uncompressed_size == 0
+      || uncompressed_buffer == NULL
+      || sec->contents != NULL
+      || sec->compressed_size != 0
+      || sec->compress_status != COMPRESS_SECTION_NONE)
+    {
+      bfd_set_error (bfd_error_invalid_operation);
+      return FALSE;
+    }
+
+  /* Compress it.  */
+  return bfd_compress_section_contents (abfd, sec, uncompressed_buffer,
+					uncompressed_size, TRUE) != 0;
+}
diff --git a/bfd/elf.c b/bfd/elf.c
index 41fb023..85a4b6b 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -2752,6 +2752,7 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
   struct bfd_elf_section_data *esd = elf_section_data (asect);
   Elf_Internal_Shdr *this_hdr;
   unsigned int sh_type;
+  const char *name = asect->name;
 
   if (arg->failed)
     {
@@ -2762,8 +2763,38 @@ elf_fake_sections (bfd *abfd, asection *asect, void *fsarg)
 
   this_hdr = &esd->this_hdr;
 
+  /* For linking, compress DWARF debug sections with names: .debug_*.  */
+  if (arg->link_info
+      && (arg->link_info->compress_debug & COMPRESS_DEBUG)
+      && (asect->flags & SEC_DEBUGGING)
+      && name[1] == 'd'
+      && name[6] == '_')
+    {
+      /* Set SEC_ELF_COMPRESS to indicate this section should be
+	 compressed.  */
+      asect->flags |= SEC_ELF_COMPRESS;
+
+      if (arg->link_info->compress_debug != COMPRESS_DEBUG_GABI_ZLIB)
+	{
+	  /* If SHF_COMPRESSED isn't used, rename compressed DWARF
+	     debug section to .zdebug_*.  */
+	  unsigned int len = strlen (name);
+	  char *new_name = bfd_alloc (abfd, len + 2);
+	  if (new_name == NULL)
+	    {
+	      arg->failed = TRUE;
+	      return;
+	    }
+	  new_name[0] = '.';
+	  new_name[1] = 'z';
+	  memcpy (new_name + 2, name + 1, len);
+	  bfd_rename_section (abfd, asect, new_name);
+	  name = asect->name;
+	}
+    }
+
   this_hdr->sh_name = (unsigned int) _bfd_elf_strtab_add (elf_shstrtab (abfd),
-							  asect->name, FALSE);
+							  name, FALSE);
   if (this_hdr->sh_name == (unsigned int) -1)
     {
       arg->failed = TRUE;
@@ -5116,6 +5147,9 @@ assign_file_positions_for_non_load_sections (bfd *abfd,
 	}
       else if (((hdr->sh_type == SHT_REL || hdr->sh_type == SHT_RELA)
 		&& hdr->bfd_section == NULL)
+	       || (hdr->bfd_section != NULL
+		   && (hdr->bfd_section->flags & SEC_ELF_COMPRESS))
+		   /* Compress DWARF debug sections.  */
 	       || hdr == i_shdrpp[elf_onesymtab (abfd)]
 	       || hdr == i_shdrpp[elf_symtab_shndx (abfd)]
 	       || hdr == i_shdrpp[elf_strtab_sec (abfd)])
@@ -5365,6 +5399,9 @@ assign_file_positions_except_relocs (bfd *abfd,
 	  hdr = *hdrpp;
 	  if (((hdr->sh_type == SHT_REL || hdr->sh_type == SHT_RELA)
 	       && hdr->bfd_section == NULL)
+	      || (hdr->bfd_section != NULL
+		  && (hdr->bfd_section->flags & SEC_ELF_COMPRESS))
+		  /* Compress DWARF debug sections.  */
 	      || i == elf_onesymtab (abfd)
 	      || i == elf_symtab_shndx (abfd)
 	      || i == elf_strtab_sec (abfd))
@@ -5518,8 +5555,8 @@ prep_headers (bfd *abfd)
 /* Assign file positions for all the reloc sections which are not part
    of the loadable file image, and the file position of section headers.  */
 
-static void
-_bfd_elf_assign_file_positions_for_relocs (bfd *abfd)
+static bfd_boolean
+_bfd_elf_assign_file_positions_for_non_load (bfd *abfd)
 {
   file_ptr off;
   unsigned int i, num_sec;
@@ -5535,9 +5572,30 @@ _bfd_elf_assign_file_positions_for_relocs (bfd *abfd)
       Elf_Internal_Shdr *shdrp;
 
       shdrp = *shdrpp;
-      if ((shdrp->sh_type == SHT_REL || shdrp->sh_type == SHT_RELA)
-	  && shdrp->sh_offset == -1)
-	off = _bfd_elf_assign_file_position_for_section (shdrp, off, TRUE);
+      if (shdrp->sh_offset == -1)
+	{
+	  bfd_boolean is_rel = (shdrp->sh_type == SHT_REL
+				|| shdrp->sh_type == SHT_RELA);
+	  if (is_rel
+	      || (shdrp->bfd_section != NULL
+		  && (shdrp->bfd_section->flags & SEC_ELF_COMPRESS)))
+	    {
+	      if (!is_rel)
+		{
+		  /* Compress DWARF debug sections.  */
+		  if (!bfd_compress_section (abfd, shdrp->bfd_section,
+					     shdrp->contents))
+		    return FALSE;
+		  /* Update section size and contents.  */
+		  shdrp->sh_size = shdrp->bfd_section->size;
+		  shdrp->contents = shdrp->bfd_section->contents;
+		  shdrp->bfd_section->contents = NULL;
+		}
+	      off = _bfd_elf_assign_file_position_for_section (shdrp,
+							       off,
+							       TRUE);
+	    }
+	}
     }
 
 /* Place the section headers.  */
@@ -5547,6 +5605,8 @@ _bfd_elf_assign_file_positions_for_relocs (bfd *abfd)
   i_ehdrp->e_shoff = off;
   off += i_ehdrp->e_shnum * i_ehdrp->e_shentsize;
   elf_next_file_pos (abfd) = off;
+
+  return TRUE;
 }
 
 bfd_boolean
@@ -5569,7 +5629,8 @@ _bfd_elf_write_object_contents (bfd *abfd)
   if (failed)
     return FALSE;
 
-  _bfd_elf_assign_file_positions_for_relocs (abfd);
+  if (!_bfd_elf_assign_file_positions_for_non_load (abfd))
+    return FALSE;
 
   /* After writing the headers, we need to write the sections too...  */
   num_sec = elf_numsections (abfd);
@@ -7922,7 +7983,21 @@ _bfd_elf_set_section_contents (bfd *abfd,
       && ! _bfd_elf_compute_section_file_positions (abfd, NULL))
     return FALSE;
 
+  if (!count)
+    return TRUE;
+
   hdr = &elf_section_data (section)->this_hdr;
+  if (hdr->sh_offset == (file_ptr) -1)
+    {
+      /* We must compress this section.  Write output to the buffer.  */
+      unsigned char *contents = hdr->contents;
+      if ((offset + count) > hdr->sh_size
+	  || (section->flags & SEC_ELF_COMPRESS) == 0
+	  || contents == NULL)
+	abort ();
+      memcpy (contents + offset, location, count);
+      return TRUE;
+    }
   pos = hdr->sh_offset + offset;
   if (bfd_seek (abfd, pos, SEEK_SET) != 0
       || bfd_bwrite (location, count, abfd) != count)
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ea9246b..6efe1e4 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -10890,6 +10890,21 @@ bfd_elf_final_link (bfd *abfd, struct bfd_link_info *info)
 	 to count upwards while actually outputting the relocations.  */
       esdo->rel.count = 0;
       esdo->rela.count = 0;
+
+      if (esdo->this_hdr.sh_offset == (file_ptr) -1)
+	{
+	  /* Cache the section contents so that they can be compressed
+	     later.  Use bfd_malloc since it will be freed by
+	     bfd_compress_section_contents.  */
+	  unsigned char *contents = esdo->this_hdr.contents;
+	  if ((o->flags & SEC_ELF_COMPRESS) == 0 || contents != NULL)
+	    abort ();
+	  contents
+	    = (unsigned char *) bfd_malloc (esdo->this_hdr.sh_size);
+	  if (contents == NULL)
+	    goto error_return;
+	  esdo->this_hdr.contents = contents;
+	}
     }
 
   /* We have now assigned file positions for all the sections except
diff --git a/bfd/merge.c b/bfd/merge.c
index 5f45ba6..174ec90 100644
--- a/bfd/merge.c
+++ b/bfd/merge.c
@@ -25,6 +25,7 @@
 
 #include "sysdep.h"
 #include "bfd.h"
+#include "elf-bfd.h"
 #include "libbfd.h"
 #include "hashtab.h"
 #include "libiberty.h"
@@ -283,7 +284,8 @@ sec_merge_add (struct sec_merge_hash *tab, const char *str,
 }
 
 static bfd_boolean
-sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry)
+sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry,
+		unsigned char *contents, file_ptr offset)
 {
   struct sec_merge_sec_info *secinfo = entry->secinfo;
   asection *sec = secinfo->sec;
@@ -306,7 +308,12 @@ sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry)
       len = -off & (entry->alignment - 1);
       if (len != 0)
 	{
-	  if (bfd_bwrite (pad, len, abfd) != len)
+	  if (contents)
+	    {
+	      memcpy (contents + offset, pad, len);
+	      offset += len;
+	    }
+	  else if (bfd_bwrite (pad, len, abfd) != len)
 	    goto err;
 	  off += len;
 	}
@@ -314,7 +321,12 @@ sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry)
       str = entry->root.string;
       len = entry->len;
 
-      if (bfd_bwrite (str, len, abfd) != len)
+      if (contents)
+	{
+	  memcpy (contents + offset, str, len);
+	  offset += len;
+	}
+      else if (bfd_bwrite (str, len, abfd) != len)
 	goto err;
 
       off += len;
@@ -322,9 +334,13 @@ sec_merge_emit (bfd *abfd, struct sec_merge_hash_entry *entry)
 
   /* Trailing alignment needed?  */
   off = sec->size - off;
-  if (off != 0
-      && bfd_bwrite (pad, off, abfd) != off)
-    goto err;
+  if (off != 0)
+    {
+      if (contents)
+	memcpy (contents + offset, pad, off);
+      else if (bfd_bwrite (pad, off, abfd) != off)
+	goto err;
+    }
 
   if (pad != NULL)
     free (pad);
@@ -785,6 +801,8 @@ _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
 {
   struct sec_merge_sec_info *secinfo;
   file_ptr pos;
+  unsigned char *contents;
+  Elf_Internal_Shdr *hdr;
 
   secinfo = (struct sec_merge_sec_info *) psecinfo;
 
@@ -795,11 +813,26 @@ _bfd_write_merged_section (bfd *output_bfd, asection *sec, void *psecinfo)
     return TRUE;
 
   /* FIXME: octets_per_byte.  */
-  pos = sec->output_section->filepos + sec->output_offset;
-  if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
-    return FALSE;
+  hdr = &elf_section_data (sec->output_section)->this_hdr;
+  if (hdr->sh_offset == (file_ptr) -1)
+    {
+      /* We must compress this section.  Write output to the
+	 buffer.  */
+      contents = hdr->contents;
+      if ((sec->output_section->flags & SEC_ELF_COMPRESS) == 0
+	  || contents == NULL)
+	abort ();
+    }
+  else
+    {
+      contents = NULL;
+      pos = sec->output_section->filepos + sec->output_offset;
+      if (bfd_seek (output_bfd, pos, SEEK_SET) != 0)
+	return FALSE;
+    }
 
-  if (! sec_merge_emit (output_bfd, secinfo->first_str))
+  if (! sec_merge_emit (output_bfd, secinfo->first_str, contents,
+			sec->output_offset))
     return FALSE;
 
   return TRUE;
diff --git a/bfd/section.c b/bfd/section.c
index 4a6f2e4..d59a0e3 100644
--- a/bfd/section.c
+++ b/bfd/section.c
@@ -334,6 +334,10 @@ CODE_FRAGMENT
 .     executables or shared objects. This is for COFF only.  *}
 .#define SEC_COFF_SHARED 0x8000000
 .
+.  {* This section should be compressed.  This is for ELF linker
+.     internal use only.  *}
+.#define SEC_ELF_COMPRESS 0x8000000
+.
 .  {* When a section with this flag is being linked, then if the size of
 .     the input section is less than a page, it should not cross a page
 .     boundary.  If the size of the input section is one page or more,