This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC 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]

Re: RFC: stack/heap collision vulnerability and mitigation with GCC


On 06/19/2017 08:02 PM, Richard Biener wrote:
> Oh, and using push intelligently with first bumping to SP & 4096-1 + 4095 would solve the signal atomicity as well. Might be larger and somewhat interfere with CPUs stack engine.  Who knows...

On x86-64, PUSH REG is just a single byte, so for sequences that have to
move SP and probe, it's the shortest possible sequence AFAIK.  NEG/NOT
can take an offsettable memory operand, but it's three bytes.

(I believe the use of ORQ in the current -fstack-check probes might be
an oversight.  For a start, the REX prefix seems completely unnecessary.)

Thanks,
Florian


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]