Re: Disassembler disagrees with translator over instruction decoding

[Alex Bennée]

Станислав Юдин <CityAceE@reext.ru> writes:

> Hello,
>
> I've just got this message, when I dubugging my code:
>
> Disassembler disagrees with translator over instruction decoding
> Please report this to qemu-devel@nongnu.org
>
> *
>
> Binary code is in the attachment.

The binary seems to reconfigure itself as it executes as I can't find
the instructions in the objdump. However via gdbstub we get to:

  (gdb) x/4i $pc
  => 0x60011ab8:  pop     {r0, r1, r2, r3, r4, r5, r6, pc}
     0x60011aba:  push    {lr}
     0x60011abc:  mov.w   r11, #4
     0x60011ac0:  ldrb.w  r7, [r0, r10]
  (gdb) x/10i 0x60010168
     0x60010168:  ldrb    r6, [r0, r1]
     0x6001016a:  addw    r7, pc, #6
     0x6001016e:  ldr.w   pc, [r7]
     0x60010172:  lsls    r2, r6, #21
     0x60010174:  str     r1, [r0, #0]
     0x60010176:  lsls    r2, r7, #21
     0x60010178:  str     r1, [r0, #0]
     0x6001017a:  lsls    r6, r3, #22
     0x6001017c:  str     r1, [r0, #0]
     0x6001017e:  lsls    r6, r5, #22
  (gdb) hbreak *0x6001016e
  Hardware assisted breakpoint 2 at 0x6001016e
  (gdb) c
  Continuing.

  Breakpoint 2, 0x6001016e in ?? ()
  (gdb) i
  0x60010572 in ?? ()
  => 0x60010572:  streq   pc, [r4, #-421] @ 0xfffffe5b
     0x60010576:  ldmiblt r7, {r0, r12, sp, lr, pc}^
     0x6001057a:  tsteq   r1, r1, lsl #2  @ <UNPREDICTABLE>
  (gdb) x/5i $pc
  => 0x60010572:  streq   pc, [r4, #-421] @ 0xfffffe5b
     0x60010576:  ldmiblt r7, {r0, r12, sp, lr, pc}^
     0x6001057a:  tsteq   r1, r1, lsl #2  @ <UNPREDICTABLE>
     0x6001057e:  smlabteq        r0, r0, r2, pc  @ <UNPREDICTABLE>
     0x60010582:  blt     0x61da66a2
  (gdb) x/10w $pc
  0x60010572:     0x0504f1a5      0xb9d7f001      0x0101f101      0x0100f2c0
  0x60010582:     0xba765846      0x0300f2c0      0x0436bfe1      0x31024333
  0x60010592:     0x0100f2c0      0x050af1a5
  (gdb) 

Which seems to agree with the disassembler from the console:

  (qemu) x/5i 0x60010572
  0x60010572:  0504f1a5  streq    pc, [r4, #-0x1a5]
  0x60010576:  b9d7f001  ldmiblt  r7, {r0, ip, sp, lr, pc} ^
  0x6001057a:  0101f101  mrseq    pc, apsr
  0x6001057e:  0100f2c0  smlabteq r0, r0, r2, pc
  0x60010582:  ba765846  blt      #0x61da66a2

>
> It launches by this command:
>
> "c:\Program Files\qemu\qemu-system-arm.exe" -M vexpress-a9 -serial stdio -m 
> 512M -kernel speciarmlist.bin -d
> in_asm
>
>
> qemu-system-arm.exe -version
> QEMU emulator version 8.0.94 (v8.1.0-rc4-12032-g74a4cbee04)
> Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project developers


-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro