powerpc/ptrace: Enable hardware breakpoint upon re-registering

On powerpc, ptrace will disable hardware breakpoint request once the
breakpoint is hit. It is the responsibility of the caller to set it
again. However, when the caller sets the hardware breakpoint again
using ptrace(PTRACE_SET_DEBUGREG, child_pid, 0, addr), the hardware
breakpoint is not enabled.

While gdb's approach is to unregister and re-register the hardware
breakpoint every time the breakpoint is hit - which is working fine,
this could affect other programs trying to re-register hardware
breakpoint without unregistering.

This patch enables hardware breakpoint if the caller is re-registering.

Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index 817b4116e5bbb1dda824cb1d6cc6dc9af5bd251f..c4970004d44d2cfa0e190cf6d7be973b5f4b03ec 100644 (file)
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -952,6 +952,10 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
                arch_bp_generic_fields(data &
                                        (DABR_DATA_WRITE | DABR_DATA_READ),
                                                        &attr.bp_type);
+
+               /* Enable breakpoint */
+               attr.disabled = false;
+
                ret =  modify_user_hw_breakpoint(bp, &attr);
                if (ret) {
                        ptrace_put_breakpoints(task);