This is the mail archive of the gdb-patches@sourceware.org mailing list for the GDB project.
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |
Other format: | [Raw text] |
Hi. I took a crack at implementing displaced stepping support for amd64.Ooh nice! And fortuitous timing, I was supposed to write this very code next week...
Using the disassembler to compute instruction lengths is awkward, I know.My kneejerk would be to borrow libopcodes.
It's needed in order to compute the address of rip-relative addressing.
The address is %rip + address-of-next-insn + displacement,
and the displacement is only 32 bits so it's not guaranteed to be enough
to cover the distance between the original instruction and its copy.
To compensate I compute an unused integer reg, set it to
%rip + address-of-next-insn, and rewrite the insn to use base+disp addressing.
I think the GNU tools need a general-purpose library of ISA-related tools.
Until then, I went with the disassembler. The code is laid out such that
when a better implementation of computing insn lengths comes along, it
can be easily dropped in.
I read it and it seems sensible, I'm the not the displaced stepping maven though.This also includes a testcase! :-) Plus I added a testcase for the i386 case.
Ok to check in?
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |