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Re: [PATCH/AARCH64] Fix 32bit reloc for ILP32

Hi Andrew,

Thanks for the patch.

On 07/23/13 23:31, Andrew Pinski wrote:
Index: bfd/elfnn-aarch64.c
RCS file: /cvs/src/src/bfd/elfnn-aarch64.c,v
retrieving revision 1.7
diff -u -p -r1.7 elfnn-aarch64.c
--- bfd/elfnn-aarch64.c	3 Jul 2013 17:23:24 -0000	1.7
+++ bfd/elfnn-aarch64.c	23 Jul 2013 22:18:07 -0000
@@ -344,7 +344,11 @@ static reloc_howto_type elfNN_aarch64_ho
  	 32,			/* bitsize */
  	 FALSE,			/* pc_relative */
  	 0,			/* bitpos */
+#if ARCH_SIZE == 64
  	 complain_overflow_unsigned,	/* complain_on_overflow */
+	 complain_overflow_signed,	/* complain_on_overflow */

complain_overflow_unsigned is wrong to use regardless of ELF64 or ELF32, but complain_overflow_signed is not the right choice either. According to AAELF64 4.6.5, the 32-bit relocs shall have the overflow check of [-2^31, 2^32), and a following note explains that "these overflow ranges permit either signed or unsigned narrow values to be created from the intermediate result viewed as a 64-bit signed integer. ...". In other words, the 32-bit relocs are only overflowed when the check fails in both cases of complain_overflow_unsigned complain_overflow_signed. FYI, there is another checking type - complain_overflow_bitfield, but it is not suitable either as it allows some extra negative values.

I suggest to introduce a new check type which checks the range of [-2^(N-1), 2^N) for 32-bit and 16-bit relocs (including ABS and PREL). For 64-bit relocs, their howto entries should really have complain_overflow_dont instead.

The issue doesn't seem to be ILP32-specific.


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