Jeremy Fitzhardinge wrote:
For example, say we wanted to put a general call for sti into entry.S,
where its expected it won't touch any registers. In that case, we'd
have a sequence like:
push %eax
push %ecx
push %edx
call paravirt_cli
pop %edx
pop %ecx
pop %eax
If we parse the relocs, then we'd find the reference to paravirt_cli.
If we look at the byte before and see 0xe8, then we can see if its a
call. If we then work out in each direction and see matched push/pops,
then we know what registers can be trashed in the call. This also
allows us to determine the callsite size, and therefore how much space
we need for inlining.
No, that is a very dangerous suggestion. You absolutely *cannot* do
this safely without explicitly marking the start EIP of this code. You
*must* use metadata to do that. It is never safe to disassemble
backwards or "rewind" EIP for x86 code.
Zach
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
