BUG REPORT

[Konstantin A. Kostyukhin]

1. GDB version 6.1 and lower

2. Native platform is `i686-pc-linux-gnu',
   target platform is `mips64-*-*'

3. GDB was compiled with GCC 3.2.2

4. The debugged program was compiled with GCC 3.4

5. Options used for compilation of the debugged program: "-g -G 0 -c"

6. The debugged program (test.c):

static int test (long long param) {return param;}

int main(void)
{
     return (int) test (5);
}

Disassembler of this test (by objdump):

test.o:     file format elf32-bigmips

Disassembly of section .text:

00000000 <test>:
   0:   27bdfff8        addiu   sp,sp,-8
   4:   ffbe0000        sd      s8,0(sp)
   8:   03a0f02d        move    s8,sp
!  c:   ffc40008        sd      a0,8(s8)
  10:   dfc20008        ld      v0,8(s8)
  14:   00021000        sll     v0,v0,0x0
  18:   03c0e82d        move    sp,s8
  1c:   dfbe0000        ld      s8,0(sp)
  20:   27bd0008        addiu   sp,sp,8
  24:   03e00008        jr      ra
  28:   00000000        nop

0000002c <main>:
  2c:   27bdffd0        addiu   sp,sp,-48
  30:   ffbf0028        sd      ra,40(sp)
  34:   ffbe0020        sd      s8,32(sp)
  38:   03a0f02d        move    s8,sp
  3c:   24040005        li      a0,5
  40:   0c000000        jal     0 <test>
  44:   00000000        nop
  48:   03c0e82d        move    sp,s8
  4c:   dfbf0028        ld      ra,40(sp)
  50:   dfbe0020        ld      s8,32(sp)
  54:   27bd0030        addiu   sp,sp,48
  58:   03e00008        jr      ra
  5c:   00000000        nop

7. Look at the string below:

!  c:   ffc40008        sd      a0,8(s8)

GDB doesn't recognize this code as a part of prologue, so
we receive incorrect argument value after hitting breakpoint on the function
'test'.

8. I suppose that the cause of the problem is the following.

Current version of function mips-tdep.c::mips32_skip_prologue:

static CORE_ADDR
mips32_skip_prologue (CORE_ADDR pc)
{
...
      else if ((inst & 0xF3E00000) == 0xA3C00000 && (inst & 0x001F0000))
        /* sx reg,n($s8) */
        continue;               /* reg != $zero */
      else if (((inst & 0xFFE00000) == 0xAFA00000       /* sw reg,n($sp) */
                || (inst & 0xFFE00000) == 0xFFA00000)   /* sd reg,n($sp) */
               && (inst & 0x001F0000))  /* reg != $zero */
        continue;

      else if ((inst & 0xFFE00000) == 0xE7A00000)       /* swc1 freg,n($sp) */
        continue;
      else if ((inst & 0xF3E00000) == 0xA3C00000 && (inst & 0x001F0000))
        /* sx reg,n($s8) */
        continue;               /* reg != $zero */
...
}

My version of function mips-tdep.c::mips32_skip_prologue:

static CORE_ADDR
mips32_skip_prologue (CORE_ADDR pc)
{
...
      else if ((inst & 0xF3E00000) == 0xA3C00000 && (inst & 0x001F0000))
        /* sx reg,n($s8) */
        continue;               /* reg != $zero */
      else if (((inst & 0xFFE00000) == 0xAFA00000       /* sw reg,n($sp) */
                || (inst & 0xFFE00000) == 0xFFA00000)   /* sd reg,n($sp) */
               && (inst & 0x001F0000))  /* reg != $zero */
        continue;

      else if ((inst & 0xFFE00000) == 0xE7A00000)       /* swc1 freg,n($sp) */
        continue;

      /* Be carefull!!! We forgot command sd reg,n($s8)
         address@hidden 18-jun-04 */
      else if (((inst & 0xF3E00000) == 0xA3C00000       /* sw reg,n($s8) */
                || (inst & 0xF3E00000) == 0xF3C00000)   /* sd reg,n($s8) */
               && (inst & 0x001F0000))
          continue;                           /* reg != $zero */
...
}

9. I hope that my patch for this bug is correct.

Best regards,
Konstantin Kostyuhin