Disassembly with odd sized section

["Subhash Verma" <subhash dot verma at wipro dot com>]

Hi all,
I found some problem with disassembler for Thumb(ARM) processor. Here
 I am giving the input file and its disassembed output.

 

contents of input file (trail_zero.s)is:
----------------------------------------------------------
.text
   lsl r6, r0, #4     ;some instruction
   lsl r5, r0, #6     ;some instruction
   .byte 0x08
.data
   .byte 0x00
   .byte 0x00
   .byte 0x00
-------------------------------------------------------------
output (trail_zero.out) is assembled with ./arm-elf-as.exe -mthumb -a trail_zero.s -o trail_zero.out
output of disassembler is:
(./arm-elf-objdump.exe -D -disassembler-options=force-thumb trail_zero.out)
--------------------------------------------------------------
trail_zero.out:     file format elf32-littlearm

 

Disassembly of section .text:

 

00000000 <.text>:
   0:   0106            lsl     r6, r0, #4
   2:   0185            lsl     r5, r0, #6
   4:   Address 0x4 is out of bounds.

 

Disassembly of section .data:

 

00000000 <.data>:
   0:   0000            lsl     r0, r0, #0
        ...
--------------------------------------------------------------

 

There is a problem in disassembler in handling the trailing byte for an odd sized section.
If it is non-zero ( as in text section )it gives "Address 0x4 is out of bounds" message.
and if it zero (like in data section) it simply replaces it with "...", instead of displaying it as '0x00'.

 

Another example:
input file:
------------------------------------------------------------------
  .text
     lsl r6, r0, #4       ;some instruction
     lsl r7, r0, #5       ;some instruction
     lsl r0, r0, #0
  .data
     .byte 0x00
     .byte 0x00
     .byte 0x00
--------------------------------------------------------------------
trail_zero.out:     file format elf32-littlearm

 

Disassembly of section .text:

 

00000000 <.text>:
   0:   0601            lsl     r6, r0, #4
   2:   4701            lsl     r7, r0, #5
        ...
Disassembly of section .data:

 

00000000 <.data>:
   0:   0000            lsl     r0, r0, #0
        ...
----------------------------------------------------------------------
Here instead of disassembling the last instruction in text section it is replaced with "...",
because its opcode is "0x0000".
I think it is a bug in disassembler (objdump.c) for thumb(arm).
Could anybody please verify this. If it is a bug,please suggest any probable solution.

 

 Thanks in advance.
 Regards,
 Subhash Verma

 

 

 

 

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