Don't forget to reset the hardware debug registers when a process that

was using them exits.

Don't allow a user process to cause the kernel to take a TRCTRAP on a
user space address.

Reviewed by:	jlemon, sef
Approved by:	jkh

1 files changed, 19 insertions, 1 deletions

diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index 4199346..a8b73cf 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/trap.c
@@ -519,8 +519,26 @@ kernel_trap:
 				frame.tf_eflags &= ~PSL_T;
 				return;
 			}
+                        /*
+                         * Ignore debug register trace traps due to
+                         * accesses in the user's address space, which
+                         * can happen under several conditions such as
+                         * if a user sets a watchpoint on a buffer and
+                         * then passes that buffer to a system call.
+                         * We still want to get TRCTRAPS for addresses
+                         * in kernel space because that is useful when
+                         * debugging the kernel.
+                         */
+                        if (user_dbreg_trap()) {
+                                /*
+                                 * Reset breakpoint bits because the
+                                 * processor doesn't
+                                 */
+                                load_dr6(rdr6() & 0xfffffff0);
+                                return;
+                        }
 			/*
-			 * Fall through.
+			 * Fall through (TRCTRAP kernel mode, kernel address)
 			 */
 		case T_BPTFLT:
 			/*