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I think I'm really brain-dead and am not really sure what to do next, but I am trying to manually convert assembly code to a C program. It's not really working, but I'm not sure what is wrong. I would be glad for any help. The code consists of two .c files and one header file for the subroutine. In the header file, I only declared the extern int b variable, so I'm not posting it here.

program code


build/program-mips:     file format elf32-tradbigmips


Disassembly of section my_text:

00405060 <subroutine_fnc>:
  405060:   27bdfff8    addiu   sp,sp,-8
  405064:   afbe0004    sw  s8,4(sp)
  405068:   03a0f025    move    s8,sp
  40506c:   afc40008    sw  a0,8(s8)
  405070:   8fc20008    lw  v0,8(s8)
  405074:   00000000    nop
  405078:   2842005b    slti    v0,v0,91
  40507c:   10400006    beqz    v0,405098 <subroutine_fnc+0x38>
  405080:   00000000    nop
  405084:   8fc20008    lw  v0,8(s8)
  405088:   00000000    nop
  40508c:   28420041    slti    v0,v0,65
  405090:   10400004    beqz    v0,4050a4 <subroutine_fnc+0x44>
  405094:   00000000    nop
  405098:   8fc20008    lw  v0,8(s8)
  40509c:   1000000c    b   4050d0 <subroutine_fnc+0x70>
  4050a0:   00000000    nop
  4050a4:   3c020041    lui v0,0x41
  4050a8:   8c4260d0    lw  v0,24784(v0)
  4050ac:   00000000    nop
  4050b0:   24430001    addiu   v1,v0,1
  4050b4:   3c020041    lui v0,0x41
  4050b8:   ac4360d0    sw  v1,24784(v0)
  4050bc:   8fc20008    lw  v0,8(s8)
  4050c0:   00000000    nop
  4050c4:   24420020    addiu   v0,v0,32
  4050c8:   afc20008    sw  v0,8(s8)
  4050cc:   8fc20008    lw  v0,8(s8)
  4050d0:   03c0e825    move    sp,s8
  4050d4:   8fbe0004    lw  s8,4(sp)
  4050d8:   27bd0008    addiu   sp,sp,8
  4050dc:   03e00008    jr  ra
  4050e0:   00000000    nop

004050e4 <toplevel_fnc>:
  4050e4:   27bdffc8    addiu   sp,sp,-56
  4050e8:   afbf0034    sw  ra,52(sp)
  4050ec:   afbe0030    sw  s8,48(sp)
  4050f0:   03a0f025    move    s8,sp
  4050f4:   1000001e    b   405170 <toplevel_fnc+0x8c>
  4050f8:   00000000    nop
  4050fc:   83c20028    lb  v0,40(s8)
  405100:   00000000    nop
  405104:   00402025    move    a0,v0
  405108:   0c101418    jal 405060 <subroutine_fnc>
  40510c:   00000000    nop
  405110:   00021600    sll v0,v0,0x18
  405114:   00021603    sra v0,v0,0x18
  405118:   a3c20028    sb  v0,40(s8)
  40511c:   24040001    li  a0,1
  405120:   27c20028    addiu   v0,s8,40
  405124:   00402825    move    a1,v0
  405128:   24060001    li  a2,1
  40512c:   24020fa4    li  v0,4004
  405130:   0000000c    syscall
  405134:   afc70018    sw  a3,24(s8)
  405138:   afc20024    sw  v0,36(s8)
  40513c:   8fc20018    lw  v0,24(s8)
  405140:   00000000    nop
  405144:   14400004    bnez    v0,405158 <toplevel_fnc+0x74>
  405148:   00000000    nop
  40514c:   8fc20024    lw  v0,36(s8)
  405150:   10000002    b   40515c <toplevel_fnc+0x78>
  405154:   00000000    nop
  405158:   2402ffff    li  v0,-1
  40515c:   afc20020    sw  v0,32(s8)
  405160:   8fc20020    lw  v0,32(s8)
  405164:   00000000    nop
  405168:   04400018    bltz    v0,4051cc <toplevel_fnc+0xe8>
  40516c:   00000000    nop
  405170:   00002025    move    a0,zero
  405174:   27c20028    addiu   v0,s8,40
  405178:   00402825    move    a1,v0
  40517c:   24060001    li  a2,1
  405180:   24020fa3    li  v0,4003
  405184:   0000000c    syscall
  405188:   afc70018    sw  a3,24(s8)
  40518c:   afc2001c    sw  v0,28(s8)
  405190:   8fc20018    lw  v0,24(s8)
  405194:   00000000    nop
  405198:   14400004    bnez    v0,4051ac <toplevel_fnc+0xc8>
  40519c:   00000000    nop
  4051a0:   8fc2001c    lw  v0,28(s8)
  4051a4:   10000002    b   4051b0 <toplevel_fnc+0xcc>
  4051a8:   00000000    nop
  4051ac:   2402ffff    li  v0,-1
  4051b0:   afc20020    sw  v0,32(s8)
  4051b4:   8fc30020    lw  v1,32(s8)
  4051b8:   24020001    li  v0,1
  4051bc:   1062ffcf    beq v1,v0,4050fc <toplevel_fnc+0x18>
  4051c0:   00000000    nop
  4051c4:   10000002    b   4051d0 <toplevel_fnc+0xec>
  4051c8:   00000000    nop
  4051cc:   00000000    nop
  4051d0:   3c020041    lui v0,0x41
  4051d4:   8c4260d0    lw  v0,24784(v0)
  4051d8:   03c0e825    move    sp,s8
  4051dc:   8fbf0034    lw  ra,52(sp)
  4051e0:   8fbe0030    lw  s8,48(sp)
  4051e4:   27bd0038    addiu   sp,sp,56
  4051e8:   03e00008    jr  ra
  4051ec:   00000000    nop

program data


build/program-mips:     file format elf32-tradbigmips

Contents of section my_data:
 4160d0 00000000                             ....      

Here is the code I retrieved so far:

Toplevel

#include <stdio.h>
#include "subroutine.h"


int b = 0;
int toplevel_fnc(void)
{
  char a = 0;
  while (b < 0)
  {
    read(0, a, 1);
    a = 3;
    if (a != 1)
    {
      (long)b;
      a = subroutine_fnc(b);
      write(1,a,1);
      b += 4;
    }
  }
  return b;
}

Subroutine

/* Implementation of the subroutine subroutine_fnc */

#include "subroutine.h"



int subroutine_fnc(int a)
{
  if (90 < a)
  {
    return a;
  }
  if (64 < a)
  {
    b += 1;
    a += 32;
    return a;
  }
}
2
  • 1
    IDA PRO 7.5 then press F5 and problem should be solved.
    – SSpoke
    Jul 3 at 3:48
  • Or in Ghidra ctrl+e Jul 13 at 8:17
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Generating Pseudo-Code

You should try to use specialized programs to generate pseudo-code in C. Writing code in C from raw asm is pain and it's strongly not recommended.

Tools

  1. Ghidra (Free)
  2. IDA PRO (Paid)

If you realy need to write it manually for some reasons I sugesst to use dissasemblers which will display asm in nice looking graph what should really help you. For example:

  1. Ghidra
  2. IDA FREE
  3. Cutter

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