hw-breakpoints: Fix broken a.out format dump

Fix the broken a.out format dump. For now we only dump the ptrace
breakpoints.

TODO: Dump every perf breakpoints for the current thread, not only
ptrace based ones.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "K. Prasad" <prasad@linux.vnet.ibm.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index e622620790bd..57dcee5fa958 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -376,6 +376,41 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp,
 }
 
 /*
+ * Dump the debug register contents to the user.
+ * We can't dump our per cpu values because it
+ * may contain cpu wide breakpoint, something that
+ * doesn't belong to the current task.
+ *
+ * TODO: include non-ptrace user breakpoints (perf)
+ */
+void aout_dump_debugregs(struct user *dump)
+{
+        int i;
+        int dr7 = 0;
+        struct perf_event *bp;
+        struct arch_hw_breakpoint *info;
+        struct thread_struct *thread = &current->thread;
+
+        for (i = 0; i < HBP_NUM; i++) {
+                bp = thread->ptrace_bps[i];
+
+                if (bp && !bp->attr.disabled) {
+                        dump->u_debugreg[i] = bp->attr.bp_addr;
+                        info = counter_arch_bp(bp);
+                        dr7 |= encode_dr7(i, info->len, info->type);
+                } else {
+                        dump->u_debugreg[i] = 0;
+                }
+        }
+
+        dump->u_debugreg[4] = 0;
+        dump->u_debugreg[5] = 0;
+        dump->u_debugreg[6] = current->thread.debugreg6;
+
+        dump->u_debugreg[7] = dr7;
+}
+
+/*
  * Release the user breakpoints used by ptrace
  */
 void flush_ptrace_hw_breakpoint(struct task_struct *tsk)