[Patch 5/6] ARM attributes: attribute ordering

[Andrew Stubbs <ams at codesourcery dot com>]

The ARM ABI specifies that Tag_conformance must always comes first (in
order to aid human readability of the binary), and that Tag_nodefaults
should come next (because it may influence the way the rest of the
attributes are read), in the output binary file. The rest of the
attributes may be in any order, I think, but they are always emitted in
numerical order (known attributes first, then unrecognised ones).

This patch does the reordering, and adds a test to the gas testsuite. It
is intended to be layered on top of my default values patch already posted.

OK?

Andrew


2009-01-12  Andrew Stubbs  <ams@codesourcery.com>

	bfd/
	* elf-attrs.c (vendor_set_obj_attr_contents): Support tag ordering.
	* elf-bfd.h (elf_backend_data): Add obj_attrs_order.
	* elf32-arm.c (elf32_arm_obj_attrs_order): New function.
	(elf_backend_obj_attrs_order): New define.
	* elfxx-target.h (elf_backend_obj_attrs_order): New define.
	(elfNN_bed): Add elf_backend_obj_attrs_order.

	gas/testsuite/
	* gas/arm/attr-order.d: New file.
	* gas/arm/attr-order.s: New file.

---
 bfd/elf-attrs.c                    |    7 ++++++-
 bfd/elf-bfd.h                      |    6 ++++++
 bfd/elf32-arm.c                    |   19 +++++++++++++++++++
 bfd/elfxx-target.h                 |    4 ++++
 gas/testsuite/gas/arm/attr-order.d |   15 +++++++++++++++
 gas/testsuite/gas/arm/attr-order.s |    9 +++++++++
 6 files changed, 59 insertions(+), 1 deletion(-)

Index: bfd/elf-attrs.c
===================================================================
--- bfd/elf-attrs.c.orig
+++ bfd/elf-attrs.c
@@ -189,7 +189,12 @@ vendor_set_obj_attr_contents (bfd *abfd,
 
   attr = elf_known_obj_attributes (abfd)[vendor];
   for (i = 4; i < NUM_KNOWN_OBJ_ATTRIBUTES; i++)
-    p = write_obj_attribute (p, i, &attr[i]);
+    {
+      int tag = i;
+      if (get_elf_backend_data (abfd)->obj_attrs_order)
+	tag = get_elf_backend_data (abfd)->obj_attrs_order (i);
+      p = write_obj_attribute (p, tag, &attr[tag]);
+    }
 
   for (list = elf_other_obj_attributes (abfd)[vendor];
        list;
Index: bfd/elf-bfd.h
===================================================================
--- bfd/elf-bfd.h.orig
+++ bfd/elf-bfd.h
@@ -1166,6 +1166,12 @@ struct elf_backend_data
   /* The section type to use for an attributes section.  */
   unsigned int obj_attrs_section_type;
 
+  /* This function determines the order in which any attributes are written.
+     It must be defined for input in the range 4..NUM_KNOWN_OBJ_ATTRIBUTES-1
+     (this range is used in order to make unity easy).  The returned value is
+     the actual tag number to place in the input position.  */
+  int (*obj_attrs_order) (int);
+
   /* This is TRUE if the linker should act like collect and gather
      global constructors and destructors by name.  This is TRUE for
      MIPS ELF because the Irix 5 tools can not handle the .init
Index: bfd/elf32-arm.c
===================================================================
--- bfd/elf32-arm.c.orig
+++ bfd/elf32-arm.c
@@ -8145,6 +8145,24 @@ elf32_arm_obj_attrs_arg_type (int tag)
     return (tag & 1) != 0 ? 2 : 1;
 }
 
+/* The ABI defines that Tag_conformance should be emitted first, and that
+   Tag_nodefaults should be second (if either is defined).  This sets those
+   two positions, and bumps up the position of all the remaining tags to
+   compensate.  */
+static int
+elf32_arm_obj_attrs_order (int num)
+{
+  if (num == 4)
+    return Tag_conformance;
+  if (num == 5)
+    return Tag_nodefaults;
+  if ((num - 2) < Tag_nodefaults)
+    return num - 2;
+  if ((num - 1) < Tag_conformance)
+    return num - 1;
+  return num;
+}
+
 /* Read the architecture from the Tag_also_compatible_with attribute, if any.
    Returns -1 if no architecture could be read.  */
 
@@ -12290,6 +12308,7 @@ const struct elf_size_info elf32_arm_siz
 #define elf_backend_obj_attrs_arg_type		elf32_arm_obj_attrs_arg_type
 #undef  elf_backend_obj_attrs_section_type
 #define elf_backend_obj_attrs_section_type	SHT_ARM_ATTRIBUTES
+#define elf_backend_obj_attrs_order	elf32_arm_obj_attrs_order
 
 #include "elf32-target.h"
 
Index: bfd/elfxx-target.h
===================================================================
--- bfd/elfxx-target.h.orig
+++ bfd/elfxx-target.h
@@ -461,6 +461,9 @@
 #ifndef elf_backend_obj_attrs_section_type
 #define elf_backend_obj_attrs_section_type		SHT_GNU_ATTRIBUTES
 #endif
+#ifndef elf_backend_obj_attrs_order
+#define elf_backend_obj_attrs_order		NULL
+#endif
 #ifndef elf_backend_post_process_headers
 #define elf_backend_post_process_headers	NULL
 #endif
@@ -720,6 +723,7 @@ static struct elf_backend_data elfNN_bed
   elf_backend_obj_attrs_section,
   elf_backend_obj_attrs_arg_type,
   elf_backend_obj_attrs_section_type,
+  elf_backend_obj_attrs_order,
   elf_backend_collect,
   elf_backend_type_change_ok,
   elf_backend_may_use_rel_p,
Index: gas/testsuite/gas/arm/attr-order.d
===================================================================
--- /dev/null
+++ gas/testsuite/gas/arm/attr-order.d
@@ -0,0 +1,15 @@
+# name: EABI attribute ordering
+# source: attr-order.s
+# as:
+# readelf: -A
+
+Attribute Section: aeabi
+File Attributes
+  Tag_conformance: "2.07"
+  Tag_nodefaults: True
+  Tag_CPU_name: "ARM7TDMI"
+  Tag_CPU_arch: v4T
+  Tag_unknown_63: "val"
+  Tag_also_compatible_with: v6-M
+  Tag_T2EE_use: Allowed
+  Tag_Virtualization_use: Allowed
Index: gas/testsuite/gas/arm/attr-order.s
===================================================================
--- /dev/null
+++ gas/testsuite/gas/arm/attr-order.s
@@ -0,0 +1,9 @@
+@ This test ensures that the following attributes
+@ are emitted in the proper order.
+	.cpu arm7tdmi
+	.eabi_attribute 63, "val"
+	.eabi_attribute Tag_nodefaults, 0
+	.eabi_attribute Tag_also_compatible_with, "\006\013"
+	.eabi_attribute Tag_T2EE_use, 1
+	.eabi_attribute Tag_conformance, "2.07"
+	.eabi_attribute Tag_Virtualization_use, 1