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ARM: plt_size functions need to read instructions in right byte order

Message ID 1413868578-6761-2-git-send-email-victor.kamensky@linaro.org
State New
Headers show

Commit Message

vkamensky Oct. 21, 2014, 5:16 a.m. UTC 
elf32_arm_plt0_size and elf32_arm_plt_size read instructions
to determine what is size of PLT entry. However it does not
read instruction correctly in case of ARM big endian V7 case.
In this case instructions are still kept in little endian
order (BE8).

Because of that in armv7b case gdb.base/dprintf-pending.exp
test is failing - It cannot find 'pendfunc@plt' symbol.
And that symbol is not created because elf32_arm_get_synthetic_symtab
function does not create 'pendfunc@plt' symbol for symbols
from PLT after elf32_arm_plt0_size returns -1.

Fix is to introduce code reading functions read_code32,
read_code16 which would read code content in little endian
mode when it is armv7b executabe (i.e e_flags has EF_ARM_BE8)
set. elf32_arm_plt0_size and elf32_arm_plt_size to use these
functions in place where H_GET_32, H_GET_16 were used before.
---
 bfd/ChangeLog   |  9 +++++++++
 bfd/elf32-arm.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 4 deletions(-)

Comments

Alan Modra Oct. 21, 2014, 8:01 a.m. UTC | #1 
On Mon, Oct 20, 2014 at 10:16:18PM -0700, Victor Kamensky wrote:
>	* elf32-arm.c (read_code32): New function to read 32 bit
>	arm instruction.
>	(read_code16): New function to read 16 bit thumb instrution.
>	(elf32_arm_plt0_size, elf32_arm_plt_size) change code to use
>	read_code32, read_code16 to read instruction to deal with
>	BE8 arm case.

OK, with a few minor nits fixed:

> +  if ((elf_elfheader(abfd)->e_flags) & EF_ARM_BE8)
> +    {
> +       /*
> +	* V7 BE8 code is always little endian
> +	*/
> +       retval = bfd_getl32(addr);
> +    }
> +  else
> +    {
> +       retval = H_GET_32(abfd, addr);
> +    }
> +  return retval;

Please write this as:

  if ((elf_elfheader (abfd)->e_flags & EF_ARM_BE8) != 0)
    /* V7 BE8 code is always little endian.  */
    retval = bfd_getl32 (addr);
  else
    retval = bfd_get_32 (abfd, addr);
  return retval;

Note: space before open parens in function/macro call, comment
formatting, no braces for single line block, and H_GET_32 is
technically wrong.  I know you didn't introduce the use of H_GET_32,
but that function is supposed to be for reading headers or other
metadata.  bfd_get_32 is the correct function for section data.

Similarly for read_code16.
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Patch

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index e4445dc..8b183ac 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@ 
+2014-10-13  Victor Kamensky  <victor.kamensky@linaro.org>
+
+	* elf32-arm.c (read_code32): New function to read 32 bit
+	arm instruction.
+	(read_code16): New function to read 16 bit thumb instrution.
+	(elf32_arm_plt0_size, elf32_arm_plt_size) change code to use
+	read_code32, read_code16 to read instruction to deal with
+	BE8 arm case.
+
 2014-09-29  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/17440
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index 08aa3f9..89e4f35 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -15953,6 +15953,46 @@  const struct elf_size_info elf32_arm_size_info =
   bfd_elf32_swap_reloca_out
 };
 
+static bfd_vma
+read_code32 (const bfd *abfd, const bfd_byte *addr)
+{
+  bfd_vma retval;
+
+  if ((elf_elfheader(abfd)->e_flags) & EF_ARM_BE8)
+    {
+       /*
+	* V7 BE8 code is always little endian
+	*/
+       retval = bfd_getl32(addr);
+    }
+  else
+    {
+       retval = H_GET_32(abfd, addr);
+    }
+  return retval;
+}
+
+
+static bfd_vma
+read_code16 (const bfd *abfd, const bfd_byte *addr)
+{
+  bfd_vma retval;
+
+  if ((elf_elfheader(abfd)->e_flags) & EF_ARM_BE8)
+    {
+       /*
+	* V7 BE8 code is always little endian
+	*/
+       retval = bfd_getl16(addr);
+    }
+  else
+    {
+       retval = H_GET_16(abfd, addr);
+    }
+  return retval;
+}
+
+
 /* Return size of plt0 entry starting at ADDR
    or (bfd_vma) -1 if size can not be determined.  */
 
@@ -15962,7 +16002,7 @@  elf32_arm_plt0_size (const bfd *abfd, const bfd_byte *addr)
   bfd_vma first_word;
   bfd_vma plt0_size;
 
-  first_word = H_GET_32 (abfd, addr);
+  first_word = read_code32 (abfd, addr);
 
   if (first_word == elf32_arm_plt0_entry[0])
     plt0_size = 4 * ARRAY_SIZE (elf32_arm_plt0_entry);
@@ -15987,17 +16027,17 @@  elf32_arm_plt_size (const bfd *abfd, const bfd_byte *start, bfd_vma offset)
   const bfd_byte *addr = start + offset;
 
   /* PLT entry size if fixed on Thumb-only platforms.  */
-  if (H_GET_32(abfd, start) == elf32_thumb2_plt0_entry[0])
+  if (read_code32(abfd, start) == elf32_thumb2_plt0_entry[0])
       return 4 * ARRAY_SIZE (elf32_thumb2_plt_entry);
 
   /* Respect Thumb stub if necessary.  */
-  if (H_GET_16(abfd, addr) == elf32_arm_plt_thumb_stub[0])
+  if (read_code16(abfd, addr) == elf32_arm_plt_thumb_stub[0])
     {
       plt_size += 2 * ARRAY_SIZE(elf32_arm_plt_thumb_stub);
     }
 
   /* Strip immediate from first add.  */
-  first_insn = H_GET_32(abfd, addr + plt_size) & 0xffffff00;
+  first_insn = read_code32(abfd, addr + plt_size) & 0xffffff00;
 
 #ifdef FOUR_WORD_PLT
   if (first_insn == elf32_arm_plt_entry[0])