[Qemu-devel] Trace all instrucdtions in loop

[vanson . dang]

Dear All.

Currently, QEMU doesn't trace all  instructions in loop

for example:

main.c
------------------------------
main()
{
      int a = 1,b = 2,c = 3, i;
      int sum,sub,mul;
      for(i = 0; i < 3; i++) {
            sum = b+c;
            sub = b-c;
            mul = b*c;
      }
      return 0;
}
------------------------------

I compile it to main.bin


I modify QEMU to trace all instructions in loop

exec.c

in function TranslationBlock *tb_gen_code(CPUState *env,
                                    target_ulong pc, target_ulong cs_base,
                                    int flags, int cflags)
Comment this line
------------------------------
//tb_link_phys(tb, phys_pc, phys_page2);
------------------------------



cpu-exec.c

in function static TranslationBlock *tb_find_slow(target_ulong pc,
                                            target_ulong cs_base,
                                            uint64_t flags)

Insert this line
......
 not_found:
   /* if no translated code available, then translate it now */
    tb = tb_gen_code(env, pc, cs_base, flags, 0);
------------------------------
    return tb;
------------------------------
 found:
    /* we add the TB in the virtual pc hash table */
    env->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
    return tb;
......

and run it following command;

qemu-system-arm -M realview-pbx-a9 -kernel /QEMU/main.bin -d in_asm

And I open file /tmp/qemu.log. Please see below

All instructions traced in loop.

But When I trace with the number of loop is bigger. for example 500 times.
main()
{
      int a = 1,b = 2,c = 3, i;
      int sum,sub,mul;
      for(i = 0; i < 500; i++) {
            sum = b+c;
            sub = b-c;
            mul = b*c;
      }
      return 0;
}
QEMU log incorrectly. some time it log 515 time. sometime it log 512 ...

So why does it log incorrectly?

----------------
IN:
0x00000000:  mov  r0, #0      ; 0x0
0x00000004:  mov  r1, #109    ; 0x6d
0x00000008:  orr  r1, r1, #1792     ; 0x700
0x0000000c:  ldr  r2, [pc, #0]      ; 0x14
0x00000010:  ldr  pc, [pc, #0]      ; 0x18

----------------
IN:
0x70010000:  ldr  sp, [pc, #4]      ; 0x7001000c
0x70010004:  bl   0x700100f0

----------------
IN:
0x700100f0:  push {fp}        ; (str fp, [sp, #-4]!)
0x700100f4:  add  fp, sp, #0  ; 0x0
0x700100f8:  sub  sp, sp, #36 ; 0x24
0x700100fc:  mov  r3, #1      ; 0x1
0x70010100:  str  r3, [fp, #-32]
0x70010104:  mov  r3, #2      ; 0x2
0x70010108:  str  r3, [fp, #-28]
0x7001010c:  mov  r3, #3      ; 0x3
0x70010110:  str  r3, [fp, #-24]
0x70010114:  mov  r3, #0      ; 0x0
0x70010118:  str  r3, [fp, #-20]
0x7001011c:  b    0x7001015c

----------------
IN:
0x7001015c:  ldr  r3, [fp, #-20]
0x70010160:  cmp  r3, #2      ; 0x2
0x70010164:  ble  0x70010120

----------------
IN:
0x70010120:  ldr  r2, [fp, #-28]
0x70010124:  ldr  r3, [fp, #-24]
0x70010128:  add  r3, r2, r3
0x7001012c:  str  r3, [fp, #-16]
0x70010130:  ldr  r2, [fp, #-28]
0x70010134:  ldr  r3, [fp, #-24]
0x70010138:  rsb  r3, r3, r2
0x7001013c:  str  r3, [fp, #-12]
0x70010140:  ldr  r3, [fp, #-28]
0x70010144:  ldr  r2, [fp, #-24]
0x70010148:  mul  r3, r2, r3
0x7001014c:  str  r3, [fp, #-8]
0x70010150:  ldr  r3, [fp, #-20]
0x70010154:  add  r3, r3, #1  ; 0x1
0x70010158:  str  r3, [fp, #-20]
0x7001015c:  ldr  r3, [fp, #-20]
0x70010160:  cmp  r3, #2      ; 0x2
0x70010164:  ble  0x70010120

----------------
IN:
0x70010120:  ldr  r2, [fp, #-28]
0x70010124:  ldr  r3, [fp, #-24]
0x70010128:  add  r3, r2, r3
0x7001012c:  str  r3, [fp, #-16]
0x70010130:  ldr  r2, [fp, #-28]
0x70010134:  ldr  r3, [fp, #-24]
0x70010138:  rsb  r3, r3, r2
0x7001013c:  str  r3, [fp, #-12]
0x70010140:  ldr  r3, [fp, #-28]
0x70010144:  ldr  r2, [fp, #-24]
0x70010148:  mul  r3, r2, r3
0x7001014c:  str  r3, [fp, #-8]
0x70010150:  ldr  r3, [fp, #-20]
0x70010154:  add  r3, r3, #1  ; 0x1
0x70010158:  str  r3, [fp, #-20]
0x7001015c:  ldr  r3, [fp, #-20]
0x70010160:  cmp  r3, #2      ; 0x2
0x70010164:  ble  0x70010120

----------------
IN:
0x70010120:  ldr  r2, [fp, #-28]
0x70010124:  ldr  r3, [fp, #-24]
0x70010128:  add  r3, r2, r3
0x7001012c:  str  r3, [fp, #-16]
0x70010130:  ldr  r2, [fp, #-28]
0x70010134:  ldr  r3, [fp, #-24]
0x70010138:  rsb  r3, r3, r2
0x7001013c:  str  r3, [fp, #-12]
0x70010140:  ldr  r3, [fp, #-28]
0x70010144:  ldr  r2, [fp, #-24]
0x70010148:  mul  r3, r2, r3
0x7001014c:  str  r3, [fp, #-8]
0x70010150:  ldr  r3, [fp, #-20]
0x70010154:  add  r3, r3, #1  ; 0x1
0x70010158:  str  r3, [fp, #-20]
0x7001015c:  ldr  r3, [fp, #-20]
0x70010160:  cmp  r3, #2      ; 0x2
0x70010164:  ble  0x70010120

----------------
IN:
0x70010168:  mov  r3, #0      ; 0x0
0x7001016c:  mov  r0, r3
0x70010170:  add  sp, fp, #0  ; 0x0
0x70010174:  pop  {fp}        ; (ldr fp, [sp], #4)
0x70010178:  bx   lr

----------------
IN:
0x70010008:  b    0x70010008


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