Add SHF_COMPRESSED support to gas and objcopy

This patch adds --compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}
options to gas and objcopy for ELF files. They control how DWARF debug
sections are compressed.  --compress-debug-sections=none is equivalent to
--nocompress-debug-sections.  --compress-debug-sections=zlib and
--compress-debug-sections=zlib-gnu are equivalent to
--compress-debug-sections.  --compress-debug-sections=zlib-gabi compresses
DWARF debug sections with SHF_COMPRESSED from the ELF ABI.  No linker
changes are required to support SHF_COMPRESSED.

bfd/

	* archive.c (_bfd_get_elt_at_filepos): Also copy BFD_COMPRESS_GABI
	bit.
	* bfd.c (bfd::flags): Increase size to 18 bits.
	(BFD_COMPRESS_GABI): New.
	(BFD_FLAGS_SAVED): Add BFD_COMPRESS_GABI.
	(BFD_FLAGS_FOR_BFD_USE_MASK): Likewise.
	(bfd_update_compression_header): New fuction.
	(bfd_check_compression_header): Likewise.
	(bfd_get_compression_header_size): Likewise.
	(bfd_is_section_compressed_with_header): Likewise.
	* compress.c (MAX_COMPRESSION_HEADER_SIZE): New.
	(bfd_compress_section_contents): Return the uncompressed size if
	the full section contents is compressed successfully.  Support
	converting from/to .zdebug* sections.
	(bfd_get_full_section_contents): Call
	bfd_get_compression_header_size to get compression header size.
	(bfd_is_section_compressed): Renamed to ...
	(bfd_is_section_compressed_with_header): This.  Add a pointer
	argument to return compression header size.
	(bfd_is_section_compressed): Use it.
	(bfd_init_section_decompress_status): Call
	bfd_get_compression_header_size to get compression header size.
	Return FALSE if uncompressed section size is 0.
	* elf.c (_bfd_elf_make_section_from_shdr): Support converting
	from/to .zdebug* sections.
	* bfd-in2.h: Regenerated.

binutils/

	* objcopy.c (do_debug_sections): Add compress_zlib,
	compress_gnu_zlib and compress_gabi_zlib.
	(copy_options): Use optional_argument on compress-debug-sections.
	(copy_usage): Update --compress-debug-sections.
	(copy_file): Handle compress_zlib, compress_gnu_zlib and
	compress_gabi_zlib.
	(copy_main): Handle
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* doc/binutils.texi: Document
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.

binutils/testsuite/

	* compress.exp: Add tests for
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* binutils-all/dw2-3.rS: New file.
	* binutils-all/dw2-3.rt: Likewise.
	* binutils-all/libdw2-compressedgabi.out: Likewise.

gas/

	* as.c (show_usage): Update --compress-debug-sections.
	(std_longopts): Use optional_argument on compress-debug-sections.
	(parse_args): Handle
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* as.h (compressed_debug_section_type): New.
	(flag_compress_debug): Change type to compressed_debug_section_type.
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.
	* write.c (compress_debug): Set BFD_COMPRESS_GABI for
	--compress-debug-sections=zlib-gabi.  Call
	bfd_get_compression_header_size to get compression header size.
	Don't rename section name for --compress-debug-sections=zlib-gabi.
	* config/tc-i386.c (compressed_debug_section_type): Set to
	COMPRESS_DEBUG_ZLIB.
	* doc/as.texinfo: Document
	--compress-debug-sections={none|zlib|zlib-gnu|zlib-gabi}.

gas/testsuite/

	* gas/i386/dw2-compressed-1.d: New file.
	* gas/i386/dw2-compressed-2.d: Likewise.
	* gas/i386/dw2-compressed-3.d: Likewise.
	* gas/i386/x86-64-dw2-compressed-2.d: Likewise.
	* gas/i386/i386.exp: Run dw2-compressed-2, dw2-compressed-1,
	dw2-compressed-3 and x86-64-dw2-compressed-2.

ld/testsuite/

	* ld-elf/compress.exp: Add a test for
	--compress-debug-sections=zlib-gabi.
	(build_tests): Add 2 tests for --compress-debug-sections=zlib-gabi.
	(run_tests): Likewise.
	Verify linker output with zlib-gabi compressed debug input.
	* ld-elf/compressed1a.d: New file.
	* ld-elf/compressed1b.d: Likewise.
	* ld-elf/compressed1c.d: Likewise.

6 files changed, 457 insertions, 95 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 192d9aa..68e13c5 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,32 @@
+2015-04-08  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* archive.c (_bfd_get_elt_at_filepos): Also copy BFD_COMPRESS_GABI
+	bit.
+	* bfd.c (bfd::flags): Increase size to 18 bits.
+	(BFD_COMPRESS_GABI): New.
+	(BFD_FLAGS_SAVED): Add BFD_COMPRESS_GABI.
+	(BFD_FLAGS_FOR_BFD_USE_MASK): Likewise.
+	(bfd_update_compression_header): New fuction.
+	(bfd_check_compression_header): Likewise.
+	(bfd_get_compression_header_size): Likewise.
+	(bfd_is_section_compressed_with_header): Likewise.
+	* compress.c (MAX_COMPRESSION_HEADER_SIZE): New.
+	(bfd_compress_section_contents): Return the uncompressed size if
+	the full section contents is compressed successfully.  Support
+	converting from/to .zdebug* sections.
+	(bfd_get_full_section_contents): Call
+	bfd_get_compression_header_size to get compression header size.
+	(bfd_is_section_compressed): Renamed to ...
+	(bfd_is_section_compressed_with_header): This.  Add a pointer
+	argument to return compression header size.
+	(bfd_is_section_compressed): Use it.
+	(bfd_init_section_decompress_status): Call
+	bfd_get_compression_header_size to get compression header size.
+	Return FALSE if uncompressed section size is 0.
+	* elf.c (_bfd_elf_make_section_from_shdr): Support converting
+	from/to .zdebug* sections.
+	* bfd-in2.h: Regenerated.
+
 2015-04-07  Alan Modra  <amodra@gmail.com>
 
 	* elf.c (_bfd_elf_get_reloc_section): Allow for .got.plt being
diff --git a/bfd/archive.c b/bfd/archive.c
index 3899d84..31d86f3 100644
--- a/bfd/archive.c
+++ b/bfd/archive.c
@@ -725,8 +725,10 @@ _bfd_get_elt_at_filepos (bfd *archive, file_ptr filepos)
 
   n_bfd->arelt_data = new_areldata;
 
-  /* Copy BFD_COMPRESS and BFD_DECOMPRESS flags.  */
-  n_bfd->flags |= archive->flags & (BFD_COMPRESS | BFD_DECOMPRESS);
+  /* Copy BFD_COMPRESS, BFD_DECOMPRESS and BFD_COMPRESS_GABI flags.  */
+  n_bfd->flags |= archive->flags & (BFD_COMPRESS
+				    | BFD_DECOMPRESS
+				    | BFD_COMPRESS_GABI);
 
   if (_bfd_add_bfd_to_archive_cache (archive, filepos, n_bfd))
     return n_bfd;
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index 81def3f..679595e 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -6323,7 +6323,7 @@ struct bfd
   ENUM_BITFIELD (bfd_direction) direction : 2;
 
   /* Format_specific flags.  */
-  flagword flags : 17;
+  flagword flags : 18;
 
   /* Values that may appear in the flags field of a BFD.  These also
      appear in the object_flags field of the bfd_target structure, where
@@ -6400,14 +6400,19 @@ struct bfd
   /* BFD is a dummy, for plugins.  */
 #define BFD_PLUGIN 0x10000
 
+  /* Compress sections in this BFD with SHF_COMPRESSED from gABI.  */
+#define BFD_COMPRESS_GABI 0x20000
+
   /* Flags bits to be saved in bfd_preserve_save.  */
 #define BFD_FLAGS_SAVED \
-  (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_PLUGIN)
+  (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_PLUGIN \
+   | BFD_COMPRESS_GABI)
 
   /* Flags bits which are for BFD use only.  */
 #define BFD_FLAGS_FOR_BFD_USE_MASK \
   (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
-   | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT)
+   | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
+   | BFD_COMPRESS_GABI)
 
   /* Is the file descriptor being cached?  That is, can it be closed as
      needed, and re-opened when accessed later?  */
@@ -6777,6 +6782,15 @@ void bfd_emul_set_commonpagesize (const char *, bfd_vma);
 
 char *bfd_demangle (bfd *, const char *, int);
 
+void bfd_update_compression_header
+   (bfd *abfd, bfd_byte *contents, asection *sec);
+
+bfd_boolean bfd_check_compression_header
+   (bfd *abfd, bfd_byte *contents, asection *sec,
+    bfd_size_type uncompressed_size);
+
+int bfd_get_compression_header_size (bfd *abfd, asection *sec);
+
 /* Extracted from archive.c.  */
 symindex bfd_get_next_mapent
    (bfd *abfd, symindex previous, carsym **sym);
@@ -7289,6 +7303,10 @@ bfd_boolean bfd_get_full_section_contents
 void bfd_cache_section_contents
    (asection *sec, void *contents);
 
+bfd_boolean bfd_is_section_compressed_with_header
+   (bfd *abfd, asection *section,
+    int *compression_header_size_p);
+
 bfd_boolean bfd_is_section_compressed
    (bfd *abfd, asection *section);
 
diff --git a/bfd/bfd.c b/bfd/bfd.c
index 5ae5eca..ba78cf3 100644
--- a/bfd/bfd.c
+++ b/bfd/bfd.c
@@ -85,7 +85,7 @@ CODE_FRAGMENT
 .  ENUM_BITFIELD (bfd_direction) direction : 2;
 .
 .  {* Format_specific flags.  *}
-.  flagword flags : 17;
+.  flagword flags : 18;
 .
 .  {* Values that may appear in the flags field of a BFD.  These also
 .     appear in the object_flags field of the bfd_target structure, where
@@ -162,14 +162,19 @@ CODE_FRAGMENT
 .  {* BFD is a dummy, for plugins.  *}
 .#define BFD_PLUGIN 0x10000
 .
+.  {* Compress sections in this BFD with SHF_COMPRESSED from gABI.  *}
+.#define BFD_COMPRESS_GABI 0x20000
+.
 .  {* Flags bits to be saved in bfd_preserve_save.  *}
 .#define BFD_FLAGS_SAVED \
-.  (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_PLUGIN)
+.  (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_PLUGIN \
+.   | BFD_COMPRESS_GABI)
 .
 .  {* Flags bits which are for BFD use only.  *}
 .#define BFD_FLAGS_FOR_BFD_USE_MASK \
 .  (BFD_IN_MEMORY | BFD_COMPRESS | BFD_DECOMPRESS | BFD_LINKER_CREATED \
-.   | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT)
+.   | BFD_PLUGIN | BFD_TRADITIONAL_FORMAT | BFD_DETERMINISTIC_OUTPUT \
+.   | BFD_COMPRESS_GABI)
 .
 .  {* Is the file descriptor being cached?  That is, can it be closed as
 .     needed, and re-opened when accessed later?  *}
@@ -1940,3 +1945,145 @@ bfd_demangle (bfd *abfd, const char *name, int options)
 
   return res;
 }
+
+/*
+FUNCTION
+	bfd_update_compression_header
+
+SYNOPSIS
+	void bfd_update_compression_header
+	  (bfd *abfd, bfd_byte *contents, asection *sec);
+
+DESCRIPTION
+	Set the compression header at CONTENTS of SEC in ABFD and update
+	elf_section_flags for compression.
+*/
+
+void
+bfd_update_compression_header (bfd *abfd, bfd_byte *contents,
+			       asection *sec)
+{
+  if ((abfd->flags & BFD_COMPRESS) != 0)
+    {
+      if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
+	{
+	  if ((abfd->flags & BFD_COMPRESS_GABI) != 0)
+	    {
+	      const struct elf_backend_data *bed
+		= get_elf_backend_data (abfd);
+
+	      /* Set the SHF_COMPRESSED bit.  */
+	      elf_section_flags (sec) |= SHF_COMPRESSED;
+
+	      if (bed->s->elfclass == ELFCLASS32)
+		{
+		  Elf32_External_Chdr *echdr
+		    = (Elf32_External_Chdr *) contents;
+		  bfd_put_32 (abfd, ELFCOMPRESS_ZLIB, &echdr->ch_type);
+		  bfd_put_32 (abfd, sec->size, &echdr->ch_size);
+		  bfd_put_32 (abfd, 1 << sec->alignment_power,
+			      &echdr->ch_addralign);
+		}
+	      else
+		{
+		  Elf64_External_Chdr *echdr
+		    = (Elf64_External_Chdr *) contents;
+		  bfd_put_64 (abfd, ELFCOMPRESS_ZLIB, &echdr->ch_type);
+		  bfd_put_64 (abfd, sec->size, &echdr->ch_size);
+		  bfd_put_64 (abfd, 1 << sec->alignment_power,
+			      &echdr->ch_addralign);
+		}
+	    }
+	  else
+	    /* Clear the SHF_COMPRESSED bit.  */
+	    elf_section_flags (sec) &= ~SHF_COMPRESSED;
+	}
+    }
+  else
+    abort ();
+}
+
+/*
+   FUNCTION
+   bfd_check_compression_header
+
+   SYNOPSIS
+	bfd_boolean bfd_check_compression_header
+	  (bfd *abfd, bfd_byte *contents, asection *sec,
+	   bfd_size_type uncompressed_size);
+
+DESCRIPTION
+	Check the compression header at CONTENTS of SEC in ABFD with
+	the uncompressed size UNCOMPRESSED_SIZE.
+
+RETURNS
+	Return TRUE if the compression header is valid.
+*/
+
+bfd_boolean
+bfd_check_compression_header (bfd *abfd, bfd_byte *contents,
+			      asection *sec,
+			      bfd_size_type uncompressed_size)
+{
+  if (bfd_get_flavour (abfd) == bfd_target_elf_flavour
+      && (elf_section_flags (sec) & SHF_COMPRESSED) != 0)
+    {
+      Elf_Internal_Chdr chdr;
+      const struct elf_backend_data *bed = get_elf_backend_data (abfd);
+      if (bed->s->elfclass == ELFCLASS32)
+	{
+	  Elf32_External_Chdr *echdr = (Elf32_External_Chdr *) contents;
+	  chdr.ch_type = bfd_get_32 (abfd, &echdr->ch_type);
+	  chdr.ch_size = bfd_get_32 (abfd, &echdr->ch_size);
+	  chdr.ch_addralign = bfd_get_32 (abfd, &echdr->ch_addralign);
+	}
+      else
+	{
+	  Elf64_External_Chdr *echdr = (Elf64_External_Chdr *) contents;
+	  chdr.ch_type = bfd_get_64 (abfd, &echdr->ch_type);
+	  chdr.ch_size = bfd_get_64 (abfd, &echdr->ch_size);
+	  chdr.ch_addralign = bfd_get_64 (abfd, &echdr->ch_addralign);
+	}
+      return (chdr.ch_type == ELFCOMPRESS_ZLIB
+	      && chdr.ch_size == uncompressed_size
+	      && chdr.ch_addralign == 1U << sec->alignment_power);
+    }
+
+  return FALSE;
+}
+
+/*
+FUNCTION
+	bfd_get_compression_header_size
+
+SYNOPSIS
+	int bfd_get_compression_header_size (bfd *abfd, asection *sec);
+
+DESCRIPTION
+	Return the size of the compression header of SEC in ABFD.
+
+RETURNS
+	Return the size of the compression header in bytes.
+*/
+
+int
+bfd_get_compression_header_size (bfd *abfd, asection *sec)
+{
+  if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
+    {
+      if (sec == NULL)
+	{
+	  if (!(abfd->flags & BFD_COMPRESS_GABI))
+	    return 0;
+	}
+      else if (!(elf_section_flags (sec) & SHF_COMPRESSED))
+	return 0;
+
+      if (get_elf_backend_data (abfd)->s->elfclass == ELFCLASS32)
+	return sizeof (Elf32_External_Chdr);
+      else
+	return sizeof (Elf64_External_Chdr);
+    }
+
+  return 0;
+}
diff --git a/bfd/compress.c b/bfd/compress.c
index b57650f..ba9fc96 100644
--- a/bfd/compress.c
+++ b/bfd/compress.c
@@ -24,6 +24,8 @@
 #include "libbfd.h"
 #include "safe-ctype.h"
 
+#define MAX_COMPRESSION_HEADER_SIZE 24
+
 static bfd_boolean
 decompress_contents (bfd_byte *compressed_buffer,
 		     bfd_size_type compressed_size,
@@ -65,55 +67,136 @@ decompress_contents (bfd_byte *compressed_buffer,
    field was allocated using bfd_malloc() or equivalent.  If zlib
    is not installed on this machine, the input is unmodified.
 
-   Return @code{TRUE} if the full section contents is compressed
-   successfully.  */
+   Return the uncompressed size if the full section contents is
+   compressed successfully.  Otherwise return 0.  */
 
-static bfd_boolean
-bfd_compress_section_contents (bfd *abfd ATTRIBUTE_UNUSED, sec_ptr sec,
+static bfd_size_type
+bfd_compress_section_contents (bfd *abfd, sec_ptr sec,
 			       bfd_byte *uncompressed_buffer,
 			       bfd_size_type uncompressed_size)
 {
   uLong compressed_size;
-  bfd_byte *compressed_buffer;
-
-  compressed_size = compressBound (uncompressed_size) + 12;
-  compressed_buffer = (bfd_byte *) bfd_malloc (compressed_size);
+  bfd_byte *buffer;
+  bfd_size_type buffer_size;
+  bfd_boolean decompress;
+  int zlib_size;
+  int orig_compression_header_size;
+  int compression_header_size
+    = bfd_get_compression_header_size (abfd, NULL);
+  bfd_boolean compressed
+    = bfd_is_section_compressed_with_header (abfd, sec,
+					     &orig_compression_header_size);
+
+  if (compressed)
+    {
+      /* We shouldn't decompress unsupported compressed section.  */
+      if (orig_compression_header_size < 0)
+	abort ();
 
-  if (compressed_buffer == NULL)
-    return FALSE;
+      /* Different compression schemes.  Just move the compressed section
+	 contents to the right position. */
+      if (orig_compression_header_size == 0)
+	{
+	  /* Convert it from .zdebug* section.  Get the uncompressed
+	     size first.  */
+	  zlib_size = uncompressed_size;
+	  compressed_size = zlib_size + compression_header_size;
+	  uncompressed_size = bfd_getb64 (uncompressed_buffer + 4);
+	}
+      else
+	{
+	  /* Convert it to .zdebug* section. */
+	  zlib_size = uncompressed_size - orig_compression_header_size;
+	  compressed_size = zlib_size;
+	}
+    }
+  else
+    compressed_size = compressBound (uncompressed_size) + 12;
 
-  if (compress ((Bytef*) compressed_buffer + 12,
-		&compressed_size,
-		(const Bytef*) uncompressed_buffer,
-		uncompressed_size) != Z_OK)
+  /* When converting from .zdebug* section, uncompress if it leads to
+     smaller size.  */
+  if (compressed
+      && orig_compression_header_size == 0
+      && compressed_size > uncompressed_size)
     {
-      free (compressed_buffer);
-      bfd_set_error (bfd_error_bad_value);
-      return FALSE;
+      decompress = TRUE;
+      buffer_size = uncompressed_size;
     }
+  else
+    {
+      decompress = FALSE;
+      buffer_size = compressed_size + compression_header_size;
+    }
+  buffer = (bfd_byte *) bfd_malloc (buffer_size);
+  if (buffer == NULL)
+    return 0;
 
-  compressed_size += 12;
-
-  /* PR binutils/18087: If compression didn't make the section smaller,
-     just keep it uncompressed.  */
-  if (compressed_size < uncompressed_size)
+  if (compressed)
     {
-      /* Write the zlib header.  In this case, it should be "ZLIB" followed
-	 by the uncompressed section size, 8 bytes in big-endian order.  */
-      memcpy (compressed_buffer, "ZLIB", 4);
-      bfd_putb64 (uncompressed_size, compressed_buffer + 4);
-      free (uncompressed_buffer);
-      sec->contents = compressed_buffer;
-      sec->size = compressed_size;
-      sec->compress_status = COMPRESS_SECTION_DONE;
+      sec->size = uncompressed_size;
+      if (decompress)
+	{
+	  if (!decompress_contents (uncompressed_buffer, zlib_size,
+				    buffer, uncompressed_size))
+	    {
+	      bfd_set_error (bfd_error_bad_value);
+	      free (buffer);
+	      return 0;
+	    }
+	  free (uncompressed_buffer);
+	  sec->contents = buffer;
+	  sec->compress_status = COMPRESS_SECTION_DONE;
+	  return uncompressed_size;
+	}
+      else
+	{
+	  bfd_update_compression_header (abfd, buffer, sec);
+	  memmove (buffer + compression_header_size,
+		   uncompressed_buffer + orig_compression_header_size,
+		   zlib_size);
+	}
     }
   else
     {
-      sec->contents = uncompressed_buffer;
-      sec->compress_status = COMPRESS_SECTION_NONE;
+      bfd_size_type size = uncompressed_size;
+      int header_size = 12 + compression_header_size;
+      if (compress ((Bytef*) buffer + header_size,
+		    &compressed_size,
+		    (const Bytef*) uncompressed_buffer,
+		    uncompressed_size) != Z_OK)
+	{
+	  free (buffer);
+	  bfd_set_error (bfd_error_bad_value);
+	  return 0;
+	}
+
+      compressed_size += header_size;
+      /* PR binutils/18087: If compression didn't make the section smaller,
+	 just keep it uncompressed.  */
+      if (compressed_size < uncompressed_size)
+	{
+	  bfd_update_compression_header (abfd, buffer, sec);
+
+	  /* Write the zlib header.  In this case, it should be "ZLIB"
+	     followed by the uncompressed section size, 8 bytes in
+	     big-endian order.  */
+	  memcpy (buffer + compression_header_size, "ZLIB", 4);
+	  bfd_putb64 (size, buffer + compression_header_size + 4);
+	}
+      else
+	{
+	  sec->contents = uncompressed_buffer;
+	  sec->compress_status = COMPRESS_SECTION_NONE;
+	  return uncompressed_size;
+	}
     }
 
-  return TRUE;
+  free (uncompressed_buffer);
+  sec->contents = buffer;
+  sec->size = compressed_size;
+  sec->compress_status = COMPRESS_SECTION_DONE;
+
+  return uncompressed_size;
 }
 
 /*
@@ -143,6 +226,7 @@ bfd_get_full_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **ptr)
   bfd_size_type save_size;
   bfd_size_type save_rawsize;
   bfd_byte *compressed_buffer;
+  unsigned int compression_header_size;
 
   if (abfd->direction != write_direction && sec->rawsize != 0)
     sz = sec->rawsize;
@@ -200,7 +284,9 @@ bfd_get_full_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **ptr)
       if (p == NULL)
 	goto fail_compressed;
 
-      if (!decompress_contents (compressed_buffer, sec->compressed_size, p, sz))
+      compression_header_size = bfd_get_compression_header_size (abfd, sec);
+      if (!decompress_contents (compressed_buffer + compression_header_size,
+				sec->compressed_size, p, sz))
 	{
 	  bfd_set_error (bfd_error_bad_value);
 	  if (p != *ptr)
@@ -256,50 +342,96 @@ bfd_cache_section_contents (asection *sec, void *contents)
   sec->flags |= SEC_IN_MEMORY;
 }
 
-
 /*
 FUNCTION
-	bfd_is_section_compressed
+	bfd_is_section_compressed_with_header
 
 SYNOPSIS
-	bfd_boolean bfd_is_section_compressed
-	  (bfd *abfd, asection *section);
+	bfd_boolean bfd_is_section_compressed_with_header
+	  (bfd *abfd, asection *section,
+	  int *compression_header_size_p);
 
 DESCRIPTION
-	Return @code{TRUE} if @var{section} is compressed.
+	Return @code{TRUE} if @var{section} is compressed.  Compression
+	header size is returned in @var{compression_header_size_p}.  If
+	compression is unsupported, compression header size is returned
+	with -1.
 */
 
 bfd_boolean
-bfd_is_section_compressed (bfd *abfd, sec_ptr sec)
+bfd_is_section_compressed_with_header (bfd *abfd, sec_ptr sec,
+				       int *compression_header_size_p)
 {
-  bfd_byte compressed_buffer [12];
+  bfd_byte header[MAX_COMPRESSION_HEADER_SIZE + 12];
+  int compression_header_size;
+  int header_size = 12;
   unsigned int saved = sec->compress_status;
   bfd_boolean compressed;
 
+  compression_header_size = bfd_get_compression_header_size (abfd, sec);
+  if (compression_header_size > MAX_COMPRESSION_HEADER_SIZE)
+    abort ();
+  header_size += compression_header_size;
+
   /* Don't decompress the section.  */
   sec->compress_status = COMPRESS_SECTION_NONE;
 
   /* Read the zlib header.  In this case, it should be "ZLIB" followed
      by the uncompressed section size, 8 bytes in big-endian order.  */
-  compressed = (bfd_get_section_contents (abfd, sec, compressed_buffer, 0, 12)
-		&& CONST_STRNEQ ((char*) compressed_buffer, "ZLIB"));
+  compressed = bfd_get_section_contents (abfd, sec, header, 0,
+					 header_size)
+		&& CONST_STRNEQ ((char*) header + compression_header_size,
+				 "ZLIB");
 
-  /* Check for the pathalogical case of a debug string section that
-     contains the string ZLIB.... as the first entry.  We assume that
-     no uncompressed .debug_str section would ever be big enough to
-     have the first byte of its (big-endian) size be non-zero.  */
-  if (compressed
-      && strcmp (sec->name, ".debug_str") == 0
-      && ISPRINT (compressed_buffer[4]))
-    compressed = FALSE;
+  if (compressed)
+    {
+      if (compression_header_size != 0)
+	{
+	  bfd_size_type uncompressed_size
+	    = bfd_getb64 ((bfd_byte *) header
+			  + compression_header_size + 4);
+	  if (!bfd_check_compression_header (abfd, header, sec,
+					     uncompressed_size))
+	    compression_header_size = -1;
+	}
+      /* Check for the pathalogical case of a debug string section that
+	 contains the string ZLIB.... as the first entry.  We assume that
+	 no uncompressed .debug_str section would ever be big enough to
+	 have the first byte of its (big-endian) size be non-zero.  */
+      else if (strcmp (sec->name, ".debug_str") == 0
+	       && ISPRINT (header[compression_header_size + 4]))
+	compressed = FALSE;
+    }
 
   /* Restore compress_status.  */
   sec->compress_status = saved;
+  *compression_header_size_p = compression_header_size;
   return compressed;
 }
 
 /*
 FUNCTION
+	bfd_is_section_compressed
+
+SYNOPSIS
+	bfd_boolean bfd_is_section_compressed
+	  (bfd *abfd, asection *section);
+
+DESCRIPTION
+	Return @code{TRUE} if @var{section} is compressed.
+*/
+
+bfd_boolean
+bfd_is_section_compressed (bfd *abfd, sec_ptr sec)
+{
+  int compression_header_size;
+  return (bfd_is_section_compressed_with_header (abfd, sec,
+						 &compression_header_size)
+	  && compression_header_size >= 0);
+}
+
+/*
+FUNCTION
 	bfd_init_section_decompress_status
 
 SYNOPSIS
@@ -319,13 +451,20 @@ DESCRIPTION
 bfd_boolean
 bfd_init_section_decompress_status (bfd *abfd, sec_ptr sec)
 {
-  bfd_byte compressed_buffer [12];
+  bfd_byte header[MAX_COMPRESSION_HEADER_SIZE + 12];
+  int compression_header_size;
+  int header_size = 12;
   bfd_size_type uncompressed_size;
 
+  compression_header_size = bfd_get_compression_header_size (abfd, sec);
+  if (compression_header_size > MAX_COMPRESSION_HEADER_SIZE)
+    abort ();
+  header_size += compression_header_size;
+
   if (sec->rawsize != 0
       || sec->contents != NULL
       || sec->compress_status != COMPRESS_SECTION_NONE
-      || !bfd_get_section_contents (abfd, sec, compressed_buffer, 0, 12))
+      || !bfd_get_section_contents (abfd, sec, header, 0, header_size))
     {
       bfd_set_error (bfd_error_invalid_operation);
       return FALSE;
@@ -333,13 +472,20 @@ bfd_init_section_decompress_status (bfd *abfd, sec_ptr sec)
 
   /* Read the zlib header.  In this case, it should be "ZLIB" followed
      by the uncompressed section size, 8 bytes in big-endian order.  */
-  if (! CONST_STRNEQ ((char*) compressed_buffer, "ZLIB"))
+  if (! CONST_STRNEQ ((char*) header + compression_header_size, "ZLIB"))
     {
       bfd_set_error (bfd_error_wrong_format);
       return FALSE;
     }
 
-  uncompressed_size = bfd_getb64 (compressed_buffer + 4);
+  uncompressed_size = bfd_getb64 (header + compression_header_size + 4);
+  if (compression_header_size != 0
+      && !bfd_check_compression_header (abfd, header, sec,
+					uncompressed_size))
+    {
+      bfd_set_error (bfd_error_wrong_format);
+      return FALSE;
+    }
   sec->compressed_size = sec->size;
   sec->size = uncompressed_size;
   sec->compress_status = DECOMPRESS_SECTION_SIZED;
@@ -389,9 +535,12 @@ bfd_init_section_compress_status (bfd *abfd, sec_ptr sec)
 				 0, uncompressed_size))
     ret = FALSE;
   else
-    ret = bfd_compress_section_contents (abfd, sec,
-					 uncompressed_buffer,
-					 uncompressed_size);
+    {
+      uncompressed_size = bfd_compress_section_contents (abfd, sec,
+							 uncompressed_buffer,
+							 uncompressed_size);
+      ret = uncompressed_size != 0;
+    }
 
   return ret;
 }
diff --git a/bfd/elf.c b/bfd/elf.c
index 5fad4f1..a031b9e 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -1042,26 +1042,35 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
     {
       enum { nothing, compress, decompress } action = nothing;
       char *new_name;
+      int compression_header_size;
+      bfd_boolean compressed
+	= bfd_is_section_compressed_with_header (abfd, newsect,
+						 &compression_header_size);
 
-      if (bfd_is_section_compressed (abfd, newsect))
+      if (compressed)
 	{
 	  /* Compressed section.  Check if we should decompress.  */
 	  if ((abfd->flags & BFD_DECOMPRESS))
 	    action = decompress;
 	}
-      else
+
+      /* Compress the uncompressed section or convert from/to .zdebug*
+	 section.  Check if we should compress.  */
+      if (action == nothing)
 	{
-	  /* Normal section.  Check if we should compress.  */
-	  if ((abfd->flags & BFD_COMPRESS) && newsect->size != 0)
+	  if (newsect->size != 0
+	      && (abfd->flags & BFD_COMPRESS)
+	      && compression_header_size >= 0
+	      && (!compressed
+		  || ((compression_header_size > 0)
+		      != ((abfd->flags & BFD_COMPRESS_GABI) != 0))))
 	    action = compress;
+	  else
+	    return TRUE;
 	}
 
-      new_name = NULL;
-      switch (action)
+      if (action == compress)
 	{
-	case nothing:
-	  break;
-	case compress:
 	  if (!bfd_init_section_compress_status (abfd, newsect))
 	    {
 	      (*_bfd_error_handler)
@@ -1069,25 +1078,9 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 		 abfd, name);
 	      return FALSE;
 	    }
-	  /* PR binutils/18087: Compression does not always make a section
-	     smaller.  So only rename the section when compression has
-	     actually taken place.  */
-	  if (newsect->compress_status == COMPRESS_SECTION_DONE)
-	    {
-	      if (name[1] != 'z')
-		{
-		  unsigned int len = strlen (name);
-
-		  new_name = bfd_alloc (abfd, len + 2);
-		  if (new_name == NULL)
-		    return FALSE;
-		  new_name[0] = '.';
-		  new_name[1] = 'z';
-		  memcpy (new_name + 2, name + 1, len);
-		}
-	    }
-	  break;
-	case decompress:
+	}
+      else
+	{
 	  if (!bfd_init_section_decompress_status (abfd, newsect))
 	    {
 	      (*_bfd_error_handler)
@@ -1095,6 +1088,13 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 		 abfd, name);
 	      return FALSE;
 	    }
+	}
+
+      new_name = NULL;
+      if (action == decompress
+	   || (action == compress
+	       && (abfd->flags & BFD_COMPRESS_GABI) != 0))
+	{
 	  if (name[1] == 'z')
 	    {
 	      unsigned int len = strlen (name);
@@ -1105,7 +1105,24 @@ _bfd_elf_make_section_from_shdr (bfd *abfd,
 	      new_name[0] = '.';
 	      memcpy (new_name + 1, name + 2, len - 1);
 	    }
-	  break;
+	}
+      else if (action == compress
+	       && newsect->compress_status == COMPRESS_SECTION_DONE)
+	{
+	  /* PR binutils/18087: Compression does not always make a section
+	     smaller.  So only rename the section when compression has
+	     actually taken place.  */
+	  if (name[1] != 'z')
+	    {
+	      unsigned int len = strlen (name);
+
+	      new_name = bfd_alloc (abfd, len + 2);
+	      if (new_name == NULL)
+		return FALSE;
+	      new_name[0] = '.';
+	      new_name[1] = 'z';
+	      memcpy (new_name + 2, name + 1, len);
+	    }
 	}
       if (new_name != NULL)
 	bfd_rename_section (abfd, newsect, new_name);