On Wed, Jan 09, 2013 at 10:08:42PM -0800, Ian Lance Taylor wrote:
> On Wed, Jan 9, 2013 at 10:19 AM, horseriver <horserivers@xxxxxxxxx> wrote:
> >
> > here is the disassembly code ,
> >
> > 629: 0f 84 0e 01 00 00 je 73d <acpi_ec_add+0x125>
> > 62f: 68 d0 00 00 00 push $0xd0
> > 634: ff 35 10 00 00 00 pushl 0x10
> > 63a: e8 fc ff ff ff call 63b <acpi_ec_add+0x23>
> > 63f: 89 c3 mov %eax,%ebx
> > 641: 5f pop %edi
> > 642: 58 pop %eax
> > 643: b8 f4 ff ff ff mov $0xfffffff4,%eax
> >
> >
> > look at the code at 63a address :
> >
> > 63a: e8 fc ff ff ff call 63b <acpi_ec_add+0x23>
> >
> > e8 is a CALL instruction , but , obviously , 63b is not a subroutin address ,so how does this "call 63b " generate?
> >
> > amd what does it do ?
>
> You are looking at an object file, not an executable. There is a
> relocation associated with that address. The linker will use the
> relocation to fill in the final address when you link the object file
> into an executable.
>
> If you are using "objdump -d" to get the above disassembly, use
> "objdump -dr" to also see the relocation information.
Thanks!
I use -dr options ,and this is part of optput :
676: e8 fc ff ff ff call 677 <acpi_ec_add+0x5f>
677: R_386_PC32 strcpy
67b: 68 19 00 00 00 push $0x19
67c: R_386_32 .rodata.str1.1
680: 8d 46 75 lea 0x75(%esi),%eax
683: 50 push %eax
I have understanded what you say , here are my new question :
1. why use "fc ff ff ff " in call instruction?
2. In my .c source file ,I have not used strcpy function , so why it is disassembly out here ?
after research , I find this call instruction is corresponding to this line :
sprintf(acpi_device_name(device), "%s", ACPI_EC_DEVICE_NAME);
sprintf is a externel implemented function .
but why in disassebly code it is strcpy ?
whether something wrong with relocation data?
>
> Ian
