On Mon, Dec 17 2018 20:15:02 EET Bernd Edlinger wrote:
> out of curiosity I looked at the clobber statement in
> gdb/nat/linux-ptrace.c:
>
> asm volatile ("pushq %0;"
> ".globl linux_ptrace_test_ret_to_nx_instr;"
> "linux_ptrace_test_ret_to_nx_instr:"
> "ret"
> : : "r" ((uint64_t) (uintptr_t) return_address)
> : "%rsp", "memory");
>
> it turns out to be a far jump, instruction.
GDB functionality should not be affected if SP clobber is removed, even if the
generated code is slightly different. Please see this comment:
http://sourceware.org/ml/gdb-patches/2018-12/msg00204.html
As I understand it, this particular code is never meant to return. It should
either stop due to the NX mapping of return_address/%0, or hit the breakpoint
placed at return_address/%0.
Regards,
Dimitar
