On Mon, Jul 27, 2009 at 05:48:27AM +0530, K.Prasad wrote:
> Modify the ptrace code to use the hardware breakpoint interfaces for
> user-space.
>
> Signed-off-by: K.Prasad <pra...@linux.vnet.ibm.com>
> ---
> arch/powerpc/kernel/ptrace.c | 43
> +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 43 insertions(+)
>
> Index: linux-2.6-tip.hbkpt/arch/powerpc/kernel/ptrace.c
> ===================================================================
> --- linux-2.6-tip.hbkpt.orig/arch/powerpc/kernel/ptrace.c
> +++ linux-2.6-tip.hbkpt/arch/powerpc/kernel/ptrace.c
> @@ -37,6 +37,7 @@
> #include <asm/page.h>
> #include <asm/pgtable.h>
> #include <asm/system.h>
> +#include <asm/hw_breakpoint.h>
>
> /*
> * does not yet catch signals sent when the child dies.
> @@ -757,11 +758,24 @@ void user_disable_single_step(struct tas
>
> void ptrace_triggered(struct hw_breakpoint *bp, struct pt_regs *regs)
> {
> + /*
> + * Unregister the breakpoint request here since ptrace has defined a
> + * one-shot behaviour for breakpoint exceptions in PPC64.
> + * The SIGTRAP signal is generated automatically for us in do_dabr().
> + * We don't have to do anything here
> + */
> + unregister_user_hw_breakpoint(current, bp);
> + kfree(bp);
This unregisters the breakpoint, but doesn't actually abort the
current breakpoint handling sequence it's invoked from. So, if your
breakpoint handler was invoked at all, which as previously mentioned,
I don't think it is, wouldn't this result in *two* SIGTRAPs from a
ptrace breakpoint: one issued before the trapping instruction from
do_dabr() and another afterwards from your step-over code.
> }
>
> int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
> unsigned long data)
> {
> +#ifdef CONFIG_PPC64
> + struct thread_struct *thread = &(task->thread);
> + struct hw_breakpoint *bp;
> + int ret;
> +#endif
> /* For ppc64 we support one DABR and no IABR's at the moment (ppc64).
> * For embedded processors we support one DAC and no IAC's at the
> * moment.
> @@ -791,6 +805,35 @@ int ptrace_set_debugreg(struct task_stru
> if (data && !(data & DABR_TRANSLATION))
> return -EIO;
>
> +#ifdef CONFIG_PPC64
> + bp = thread->hbp[0];
> + if (data == 0) {
> + if (bp) {
> + unregister_user_hw_breakpoint(task, bp);
> + kfree(bp);
> + }
> + return 0;
> + }
> +
> + if (bp) {
> + bp->info.type = data & HW_BREAKPOINT_RW;
> + task->thread.dabr = bp->info.address = data;
> + return modify_user_hw_breakpoint(task, bp);
> + }
> + bp = kzalloc(sizeof(struct hw_breakpoint), GFP_KERNEL);
> + if (!bp)
> + return -ENOMEM;
> +
> + /* Store the type of breakpoint */
> + bp->info.type = data & HW_BREAKPOINT_RW;
> + bp->triggered = ptrace_triggered;
> + task->thread.dabr = bp->info.address = data;
> +
> + ret = register_user_hw_breakpoint(task, bp);
> + if (ret)
> + return ret;
> +#endif /* CONFIG_PPC64 */
> +
> /* Move contents to the DABR register */
> task->thread.dabr = data;
>
>
> _______________________________________________
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> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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