Re: LinuxAsmTools Announcement
Brian Raiter <[email protected]> Thu, 18 Dec 2008 20:36:24 -0800
| Newsgroups | org.kernel.vger.linux-assembly |
|---|---|
| Message-ID | <[email protected]> |
> when i disassemble *.o object file on x86 machine and find > instruction "call 0xFCFFFFFF",because not link,but why this address > 0xFCFFFFFF not 0xFFFFFFFF or others? First of all, the value is not 0xFCFFFFFF, it's 0xFFFFFFFC (little-endian), which is the 32-bit equivalent of -4. And the reason for the -4 is that it's an offset. When the linker fills in the real address, it will subtract the subroutine's absolute address from the address of the -4 value to get a relative address, which it will then add to the existing -4 to get the correct relative address for the call instruction. And, the reason that 4 needs to be subtracted is that when the call is executed, it will actually jump from the end of the call instruction, which is 4 bytes ahead of where the relative address is stored. b