Hi Nathan:
#define VOS_OK (0)
typedef unsigned long VOS_UINT32;
VOS_UINT32 VOS_ShowDopraInfoEx( VOS_UINT32 ulFlag )
{
int x = ulFlag;
switch(x){
case 1:
vos_printf("para is 1\n");
break;
case 2:
vos_printf("para is 2\n");
break;
case 3:
vos_printf("para is 3\n");
break;
case 4:
vos_printf("para is 4\n");
break;
case 5:
vos_printf("para is 5\n");
break;
case 6:
vos_printf("para is 6\n");
break;
default:
vos_printf("para is default.\n");
break;
}
return VOS_OK;
}
I use MIPS GCC 2.96 in Tornado2.2 to compile it, following is disassemble code with ?dr, please note red part(can't highligh, please note 18,20 in bracket) .
addiu $a0,$a0,-1
addiu $sp,$sp,-40
sltiu $v0,$a0,6
beqz $v0,c0 <testFunc+0xc0>
sd $ra,32($sp)
sll $v0,$a0,0x2
lui $v1,0x0
(18: R_MIPS_HI16 .rodata+0x78)
daddu $v1,$v1,$v0
lw $v1,120($v1)
(20: R_MIPS_LO16 .rodata+0x78)
jr $v1
lui $a0,0x0
30: R_MIPS_HI16 .rodata
jal 0 <testFunc>
34: R_MIPS_26 vos_printf
daddiu $a0,$a0,0
38: R_MIPS_LO16 .rodata
j d0 <testFunc+0xd0>
3c: R_MIPS_26 .text+0xd0
ld $ra,32($sp)
….
Following is rodata section of obj:
80180000: 7061 7261 2069 7320 310a 0000 0000 0000 *para is 1.......*
80180010: 7061 7261 2069 7320 320a 0000 0000 0000 *para is 2.......*
80180020: 7061 7261 2069 7320 330a 0000 0000 0000 *para is 3.......*
80180030: 7061 7261 2069 7320 340a 0000 0000 0000 *para is 4.......*
80180040: 7061 7261 2069 7320 350a 0000 0000 0000 *para is 5.......*
80180050: 7061 7261 2069 7320 360a 0000 0000 0000 *para is 6.......*
80180060: 7061 7261 2069 7320 6465 6661 756c 740a *para is default.*
80180070: 0000 0000 0000 0000 0000 0030 0000 0048 *...........0...H*
80180080: 0000 0060 0000 0078 0000 0090 0000 00a8 *...`...x........*
please note offset 0x78 in .rodata.
value: 0000 0030 0000 0048 0000 0060 0000 0078 0000 0090 0000 00a8
Following is rodata section of executable program,
8123a7c0: 7061 7261 2069 7320 310a 0000 0000 0000 *para is 1.......*
8123a7d0: 7061 7261 2069 7320 320a 0000 0000 0000 *para is 2.......*
8123a7e0: 7061 7261 2069 7320 330a 0000 0000 0000 *para is 3.......*
8123a7f0: 7061 7261 2069 7320 340a 0000 0000 0000 *para is 4.......*
8123a800: 7061 7261 2069 7320 350a 0000 0000 0000 *para is 5.......*
8123a810: 7061 7261 2069 7320 360a 0000 0000 0000 *para is 6.......*
8123a820: 7061 7261 2069 7320 6465 6661 756c 740a *para is default.*
8123a830: 0000 0000 0000 0000 80e1 38a0 80e1 38b8 *..........8...8.*
8123a840: 80e1 38d0 80e1 38e8 80e1 3900 80e1 3918 *..8...8...9...9.*
Compare rodata section:
value: 0000 0030 0000 0048 0000 0060 0000 0078 0000 0090 0000 00a8
vlaue: 80e1 38a0 80e1 38b8 80e1 38d0 80e1 38e8 80e1 3900 80e1 3918
we know rodata section have been relocated.
There have 24 bytes (6*4) modified.
But as we know, relocation doesn’t tell how much byte will be modified,
why linker know six words will be relocated,
this is my question.
