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Re: how GDB use ptrace to return from a function

From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
To: Joel Brobecker <brobecker at adacore dot com>
Cc: Yubin Ruan <ablacktshirt at gmail dot com>, gdb at sourceware dot org
Date: Sat, 18 Nov 2017 08:58:41 +0100
Subject: Re: how GDB use ptrace to return from a function
Authentication-results: sourceware.org; auth=none
References: <CAJYFCiMqA1NO-32g7_vrwpU-h7dmyPaqUe=UZzey1gfFz7ax3g@mail.gmail.com> <20171117161059.3oxfgipkgknfymrm@adacore.com> <CAJYFCiPOOcEv+QMaJMQsgaoDp7Hwn_g2+DT7D-355EOFHy70Rg@mail.gmail.com> <20171118040311.tri7yn4alqxzc3gt@adacore.com>

On Sat, 18 Nov 2017 05:03:11 +0100, Joel Brobecker wrote:
> > what break point events are common for X86?
> 
> IIRC, the breakpoint instruction on x86 is the int3 instruction.
> It should generate a SIGTRAP upon execution, just like any user-
> inserted breakpoints.

A toy debugger should have available also a hardware breakpoint (hbreak) using
the hardware registers commonly used only for hardware watchpoints.

Then the return address can be arbitrary as the debugger does not have to
write anything into that address.

Jan

References:
- how GDB use ptrace to return from a function
  - From: Yubin Ruan
- Re: how GDB use ptrace to return from a function
  - From: Joel Brobecker
- Re: how GDB use ptrace to return from a function
  - From: Yubin Ruan
- Re: how GDB use ptrace to return from a function
  - From: Joel Brobecker

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