[arm-gnu] undefined instruction

[Carlos O'Donell]

On 5/16/2012 3:43 PM, Carlo Caione wrote:
> On Wed, May 16, 2012 at 1:04 AM, Carlos O'Donell
> <carlos_odonell at mentor.com> wrote:
> 
>> What did you use to get this disassembly?
> 
> arm-none-aebi-gdb in eclipse. Without eclipse is (obviously :) the same:
> 
> (gdb) disassemble
> Dump of assembler code for function strlen:
> => 0x40205c84 <+0>:    beq    0x40205d18 <memcpy>
>    0x40205c88 <+4>:            ; <UNDEFINED> instruction: 0xf03fe03a
>    0x40205c8c <+8>:    andeq    r0, r0, r6
>    0x40205c90 <+12>:    andeq    r0, r0, r4
>    0x40205c94 <+16>:    andeq    r0, r0, r7
>    0x40205c98 <+20>:    andeq    r0, r0, sp, lsl r0
>    0x40205c9c <+24>:    ldrdmi    r0, [r0], -r3
>    0x40205ca0 <+28>:            ; <UNDEFINED> instruction: 0xffffffff
> End of assembler dump.

Either gdb thinks this is wrong architecture/endian, or you didn't load anything and it's disassembling garbage from memory, or the probe is returning garbage for that memory location. You need to rule these out one at a time.

Switch to the gdb console and issue `show architecture', then issue `show endian', what does it show?

>> When you compile with -save-temps what does the output assembly look like before being assembled?

That looks good.

> This is the disassebly of the object file:

This looks good.

>> It might be that the mapping symbols are missing and your disassembling constant pool data.
>>
>> What are the .gnu_attribute flags for the object file?
> 
> I don't have any flags (If I have correctly understood what you mean).

Run `*-readelf -Wa` on your file (there is an run external tool for this in the IDE), and provide the output of the "Attribute section"

e.g.

Attribute Section: aeabi
File Attributes
  Tag_CPU_name: "ARM7TDMI"
  Tag_CPU_arch: v4T
  Tag_ARM_ISA_use: Yes
  Tag_THUMB_ISA_use: Thumb-1
  Tag_FP_arch: VFPv2
  Tag_ABI_PCS_wchar_t: 4
  Tag_ABI_FP_denormal: Needed
  Tag_ABI_FP_exceptions: Needed
  Tag_ABI_FP_number_model: IEEE 754
  Tag_ABI_align_needed: 8-byte
  Tag_ABI_enum_size: small
  Tag_DIV_use: Not allowed


Cheers,
Carlos.
-- 
Carlos O'Donell
Mentor Graphics / CodeSourcery
carlos_odonell at mentor.com
carlos at codesourcery.com
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