[Patch 3/6] Modify ptrace code to use Hardware Breakpoint interfaces

["K.Prasad" <prasad@linux.vnet.ibm.com>]

Modify the ptrace code to use the hardware breakpoint interfaces for user-space.

Signed-off-by: K.Prasad <prasad@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.
@@ -737,11 +738,24 @@ 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);
 }
 
 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.
@@ -771,6 +785,35 @@ 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;