2 files changed, 34 insertions, 12 deletions

diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
index 03a0773ac2b2..366eedf949c0 100644
--- a/kernel/hw_breakpoint.c
+++ b/kernel/hw_breakpoint.c
@@ -320,18 +320,40 @@ EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
  * @triggered: callback to trigger when we hit the breakpoint
  * @tsk: pointer to 'task_struct' of the process to which the address belongs
  */
-struct perf_event *
-modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
 {
-        /*
-         * FIXME: do it without unregistering
-         * - We don't want to lose our slot
-         * - If the new bp is incorrect, don't lose the older one
-         */
-        unregister_hw_breakpoint(bp);
+        u64 old_addr = bp->attr.bp_addr;
+        int old_type = bp->attr.bp_type;
+        int old_len = bp->attr.bp_len;
+        int err = 0;
+
+        perf_event_disable(bp);
+
+        bp->attr.bp_addr = attr->bp_addr;
+        bp->attr.bp_type = attr->bp_type;
+        bp->attr.bp_len = attr->bp_len;
+
+        if (attr->disabled)
+                goto end;
 
-        return perf_event_create_kernel_counter(attr, -1, bp->ctx->task->pid,
-                                                bp->overflow_handler);
+        err = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+        if (!err)
+                perf_event_enable(bp);
+
+        if (err) {
+                bp->attr.bp_addr = old_addr;
+                bp->attr.bp_type = old_type;
+                bp->attr.bp_len = old_len;
+                if (!bp->attr.disabled)
+                        perf_event_enable(bp);
+
+                return err;
+        }
+
+end:
+        bp->attr.disabled = attr->disabled;
+
+        return 0;
 }
 EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
 
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index fd43ff4ac860..3b0cf86eee84 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -567,7 +567,7 @@ static void __perf_event_disable(void *info)
  * is the current context on this CPU and preemption is disabled,
  * hence we can't get into perf_event_task_sched_out for this context.
  */
-static void perf_event_disable(struct perf_event *event)
+void perf_event_disable(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
         struct task_struct *task = ctx->task;
@@ -971,7 +971,7 @@ static void __perf_event_enable(void *info)
  * perf_event_for_each_child or perf_event_for_each as described
  * for perf_event_disable.
  */
-static void perf_event_enable(struct perf_event *event)
+void perf_event_enable(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
         struct task_struct *task = ctx->task;