1 files changed, 40 insertions, 15 deletions

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index ba386bd94107..18d39ea4c02f 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -159,6 +159,12 @@ static int debug_arch_supported(void)
                 arch >= ARM_DEBUG_ARCH_V7_1;
 }
 
+/* Can we determine the watchpoint access type from the fsr? */
+static int debug_exception_updates_fsr(void)
+{
+        return 0;
+}
+
 /* Determine number of WRP registers available. */
 static int get_num_wrp_resources(void)
 {
@@ -619,18 +625,35 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
         info->address &= ~alignment_mask;
         info->ctrl.len <<= offset;
 
-        /*
-         * Currently we rely on an overflow handler to take
-         * care of single-stepping the breakpoint when it fires.
-         * In the case of userspace breakpoints on a core with V7 debug,
-         * we can use the mismatch feature as a poor-man's hardware
-         * single-step, but this only works for per-task breakpoints.
-         */
-        if (!bp->overflow_handler && (arch_check_bp_in_kernelspace(bp) ||
-            !core_has_mismatch_brps() || !bp->hw.bp_target)) {
-                pr_warning("overflow handler required but none found\n");
-                ret = -EINVAL;
+        if (!bp->overflow_handler) {
+                /*
+                 * Mismatch breakpoints are required for single-stepping
+                 * breakpoints.
+                 */
+                if (!core_has_mismatch_brps())
+                        return -EINVAL;
+
+                /* We don't allow mismatch breakpoints in kernel space. */
+                if (arch_check_bp_in_kernelspace(bp))
+                        return -EPERM;
+
+                /*
+                 * Per-cpu breakpoints are not supported by our stepping
+                 * mechanism.
+                 */
+                if (!bp->hw.bp_target)
+                        return -EINVAL;
+
+                /*
+                 * We only support specific access types if the fsr
+                 * reports them.
+                 */
+                if (!debug_exception_updates_fsr() &&
+                    (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
+                     info->ctrl.type == ARM_BREAKPOINT_STORE))
+                        return -EINVAL;
         }
+
 out:
         return ret;
 }
@@ -706,10 +729,12 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr,
                                 goto unlock;
 
                         /* Check that the access type matches. */
-                        access = (fsr & ARM_FSR_ACCESS_MASK) ? HW_BREAKPOINT_W :
-                                 HW_BREAKPOINT_R;
-                        if (!(access & hw_breakpoint_type(wp)))
-                                goto unlock;
+                        if (debug_exception_updates_fsr()) {
+                                access = (fsr & ARM_FSR_ACCESS_MASK) ?
+                                          HW_BREAKPOINT_W : HW_BREAKPOINT_R;
+                                if (!(access & hw_breakpoint_type(wp)))
+                                        goto unlock;
+                        }
 
                         /* We have a winner. */
                         info->trigger = addr;