[PATCH] [RFC] PR target/52813 and target/11807

Dimitar Dimitrov dimitar@dinux.eu
Wed Dec 19 06:40:00 GMT 2018


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



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