Re: utrace comments

From: Christoph Hellwig
Date: Mon Apr 30 2007 - 06:34:02 EST

On Mon, Apr 30, 2007 at 10:45:10AM +0100, Russell King wrote:
> For the sake of avoiding too much rehash, here's Roland's reply to my
> initial forrey into utrace:

In that mail Roland suggests keeping the singlestep code entirely
in the arm ptrace code. After a brief look at the arm code this
looks easily possible. From a brief look the arm software singlestep
consist of the following pieces:

- PTRACE_SINGLESTEP implementation. Sets the PT_SINGLESTEP flag,
clears TIF_SYSCALL_TRACE, sets ->exit_code in the traced code
to the singlestepping signal and wakes the traced process up.

This can easily be implemented by putting alsmost equivalent code
into arch_ptrace.
- clearing PT_SINGLESTEP and cancelling the breakpoint in ptrace_disable.

Equivalent code can go into tracehook_disable_single_step.

- Various places in signal.c that check PT_SINGLESTEP to set/clear
the special singlestep breakpoint. This can stay, it just needs
a different place to store the singlestep flag.

Do I miss something?

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