linux-kernel - Re: [PATCH 2/14] alpha: use generic ptrace

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Message-ID: <b4198de61002022035s3111a07ctf6aa94bbf2088c08@mail.gmail.com>
Date:	Tue, 2 Feb 2010 23:35:42 -0500
From:	Matt Turner <mattst88@...il.com>
To:	Christoph Hellwig <hch@....de>
Cc:	roland@...hat.com, oleg@...hat.com, akpm@...ux-foundation.org,
	ink@...assic.park.msu.ru, rth@...ddle.net,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 2/14] alpha: use generic ptrace_resume code

On Tue, Feb 2, 2010 at 1:58 PM, Christoph Hellwig <hch@....de> wrote:
> Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT,
> PTRACE_KILL and PTRACE_SINGLESTEP.  This implies defining
> arch_has_single_step in <asm/ptrace.h> and implementing the
> user_enable_single_step and user_disable_single_step functions, which
> also causes the breakpoint information to be cleared on fork, which
> could be considered a bug fix.
>
> Also the TIF_SYSCALL_TRACE thread flag is now cleared on PTRACE_KILL
> which it previously wasn't, which is consistent with all architectures
> using the modern ptrace code.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
>
> Index: linux-2.6/arch/alpha/kernel/ptrace.c
> ===================================================================
> --- linux-2.6.orig/arch/alpha/kernel/ptrace.c   2010-02-02 11:05:03.197004058 +0100
> +++ linux-2.6/arch/alpha/kernel/ptrace.c        2010-02-02 11:07:04.091006019 +0100
> @@ -249,6 +249,17 @@ ptrace_cancel_bpt(struct task_struct * c
>        return (nsaved != 0);
>  }
>
> +void user_enable_single_step(struct task_struct *child)
> +{
> +       /* Mark single stepping.  */
> +       task_thread_info(child)->bpt_nsaved = -1;
> +}
> +
> +void user_disable_single_step(struct task_struct *child)
> +{
> +       ptrace_cancel_bpt(child);
> +}
> +
>  /*
>  * Called by kernel/ptrace.c when detaching..
>  *
> @@ -256,7 +267,7 @@ ptrace_cancel_bpt(struct task_struct * c
>  */
>  void ptrace_disable(struct task_struct *child)
>  {
> -       ptrace_cancel_bpt(child);
> +       user_disable_single_step(child);
>  }
>
>  long arch_ptrace(struct task_struct *child, long request, long addr, long data)
> @@ -289,52 +300,6 @@ long arch_ptrace(struct task_struct *chi
>                DBG(DBG_MEM, ("poke $%ld<-%#lx\n", addr, data));
>                ret = put_reg(child, addr, data);
>                break;
> -
> -       case PTRACE_SYSCALL:
> -               /* continue and stop at next (return from) syscall */
> -       case PTRACE_CONT:    /* restart after signal. */
> -               ret = -EIO;
> -               if (!valid_signal(data))
> -                       break;
> -               if (request == PTRACE_SYSCALL)
> -                       set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
> -               else
> -                       clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
> -               child->exit_code = data;
> -               /* make sure single-step breakpoint is gone. */
> -               ptrace_cancel_bpt(child);
> -               wake_up_process(child);
> -               ret = 0;
> -               break;
> -
> -       /*
> -        * Make the child exit.  Best I can do is send it a sigkill.
> -        * perhaps it should be put in the status that it wants to
> -        * exit.
> -        */
> -       case PTRACE_KILL:
> -               ret = 0;
> -               if (child->exit_state == EXIT_ZOMBIE)
> -                       break;
> -               child->exit_code = SIGKILL;
> -               /* make sure single-step breakpoint is gone. */
> -               ptrace_cancel_bpt(child);
> -               wake_up_process(child);
> -               break;
> -
> -       case PTRACE_SINGLESTEP:  /* execute single instruction. */
> -               ret = -EIO;
> -               if (!valid_signal(data))
> -                       break;
> -               /* Mark single stepping.  */
> -               task_thread_info(child)->bpt_nsaved = -1;
> -               clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
> -               child->exit_code = data;
> -               wake_up_process(child);
> -               /* give it a chance to run. */
> -               ret = 0;
> -               break;
> -
>        default:
>                ret = ptrace_request(child, request, addr, data);
>                break;
> Index: linux-2.6/arch/alpha/include/asm/ptrace.h
> ===================================================================
> --- linux-2.6.orig/arch/alpha/include/asm/ptrace.h      2010-02-02 11:07:29.091023600 +0100
> +++ linux-2.6/arch/alpha/include/asm/ptrace.h   2010-02-02 11:07:38.645007248 +0100
> @@ -68,6 +68,7 @@ struct switch_stack {
>
>  #ifdef __KERNEL__
>
> +#define arch_has_single_step()         (1)
>  #define user_mode(regs) (((regs)->ps & 8) != 0)
>  #define instruction_pointer(regs) ((regs)->pc)
>  #define profile_pc(regs) instruction_pointer(regs)
>

Acked-by: Matt Turner <mattst88@...il.com>
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