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Re: [PATCH v3 2.6.39-rc1-tip 14/26] 14: x86: x86 specific probe handling
- From: Peter Zijlstra <peterz at infradead dot org>
- To: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Christoph Hellwig <hch at infradead dot org>, Andi Kleen <andi at firstfloor dot org>, Thomas Gleixner <tglx at linutronix dot de>, Jonathan Corbet <corbet at lwn dot net>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Roland McGrath <roland at hack dot frob dot com>, SystemTap <systemtap at sources dot redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>
- Date: Mon, 18 Apr 2011 18:57:56 +0200
- Subject: Re: [PATCH v3 2.6.39-rc1-tip 14/26] 14: x86: x86 specific probe handling
- References: <20110401143223.15455.19844.sendpatchset@localhost6.localdomain6> <20110401143517.15455.88373.sendpatchset@localhost6.localdomain6>
On Fri, 2011-04-01 at 20:05 +0530, Srikar Dronamraju wrote:
> +void arch_uprobe_enable_sstep(struct pt_regs *regs)
> +{
> + /*
> + * Enable single-stepping by
> + * - Set TF on stack
> + * - Set TIF_SINGLESTEP: Guarantees that TF is set when
> + * returning to user mode.
> + * - Indicate that TF is set by us.
> + */
> + regs->flags |= X86_EFLAGS_TF;
> + set_thread_flag(TIF_SINGLESTEP);
> + set_thread_flag(TIF_FORCED_TF);
> +}
> +
> +void arch_uprobe_disable_sstep(struct pt_regs *regs)
> +{
> + /* Disable single-stepping by clearing what we set */
> + clear_thread_flag(TIF_SINGLESTEP);
> + clear_thread_flag(TIF_FORCED_TF);
> + regs->flags &= ~X86_EFLAGS_TF;
> +}
Don't you loose the single step flag if userspace was already
single-stepping when it hit your breakpoint? Also, you don't seem to
touch the blockstep settings.