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