powerpc: BookE hardware watchpoint support

This patch implements support for HW based watchpoint via the
DBSR_DAC (Data Address Compare) facility of the BookE processors.

It does so by interfacing with the existing DABR breakpoint code
and adding the necessary bits and pieces for the new bits to
be properly set or cleared

Signed-off-by: Luis Machado <luisgpm@br.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 878fbddb6ae..81ccb8dd1a5 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1067,6 +1067,22 @@ void __kprobes DebugException(struct pt_regs *regs, unsigned long debug_status)
                 }
 
                 _exception(SIGTRAP, regs, TRAP_TRACE, regs->nip);
+        } else if (debug_status & (DBSR_DAC1R | DBSR_DAC1W)) {
+                regs->msr &= ~MSR_DE;
+
+                if (user_mode(regs)) {
+                        current->thread.dbcr0 &= ~(DBSR_DAC1R | DBSR_DAC1W |
+                                                                DBCR0_IDM);
+                } else {
+                        /* Disable DAC interupts */
+                        mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) & ~(DBSR_DAC1R |
+                                                DBSR_DAC1W | DBCR0_IDM));
+
+                        /* Clear the DAC event */
+                        mtspr(SPRN_DBSR, (DBSR_DAC1R | DBSR_DAC1W));
+                }
+                /* Setup and send the trap to the handler */
+                do_dabr(regs, mfspr(SPRN_DAC1), debug_status);
         }
 }
 #endif /* CONFIG_4xx || CONFIG_BOOKE */