2 files changed, 22 insertions, 8 deletions

diff --git a/arch/ia64/kernel/traps.c b/arch/ia64/kernel/traps.c
index d3e0ecb56d62..55391901b013 100644
--- a/arch/ia64/kernel/traps.c
+++ b/arch/ia64/kernel/traps.c
@@ -530,12 +530,15 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
                 if (fsys_mode(current, &regs)) {
                         extern char __kernel_syscall_via_break[];
                         /*
-                         * Got a trap in fsys-mode: Taken Branch Trap and Single Step trap
-                         * need special handling; Debug trap is not supposed to happen.
+                         * Got a trap in fsys-mode: Taken Branch Trap
+                         * and Single Step trap need special handling;
+                         * Debug trap is ignored (we disable it here
+                         * and re-enable it in the lower-privilege trap).
                          */
                         if (unlikely(vector == 29)) {
-                                die("Got debug trap in fsys-mode---not supposed to happen!",
-                                    &regs, 0);
+                                set_thread_flag(TIF_DB_DISABLED);
+                                ia64_psr(&regs)->db = 0;
+                                ia64_psr(&regs)->lp = 1;
                                 return;
                         }
                         /* re-do the system call via break 0x100000: */
@@ -589,10 +592,19 @@ ia64_fault (unsigned long vector, unsigned long isr, unsigned long ifa,
               case 34:
                 if (isr & 0x2) {
                         /* Lower-Privilege Transfer Trap */
+
+                        /* If we disabled debug traps during an fsyscall,
+                         * re-enable them here.
+                         */
+                        if (test_thread_flag(TIF_DB_DISABLED)) {
+                                clear_thread_flag(TIF_DB_DISABLED);
+                                ia64_psr(&regs)->db = 1;
+                        }
+
                         /*
-                         * Just clear PSR.lp and then return immediately: all the
-                         * interesting work (e.g., signal delivery is done in the kernel
-                         * exit path).
+                         * Just clear PSR.lp and then return immediately:
+                         * all the interesting work (e.g., signal delivery)
+                         * is done in the kernel exit path.
                          */
                         ia64_psr(&regs)->lp = 0;
                         return;
diff --git a/include/asm-ia64/thread_info.h b/include/asm-ia64/thread_info.h
index 653bb7f9a753..1d6518fe1f02 100644
--- a/include/asm-ia64/thread_info.h
+++ b/include/asm-ia64/thread_info.h
@@ -93,6 +93,7 @@ struct thread_info {
 #define TIF_POLLING_NRFLAG      16      /* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_MEMDIE              17
 #define TIF_MCA_INIT            18      /* this task is processing MCA or INIT */
+#define TIF_DB_DISABLED         19      /* debug trap disabled for fsyscall */
 
 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 #define _TIF_SYSCALL_AUDIT      (1 << TIF_SYSCALL_AUDIT)
@@ -100,9 +101,10 @@ struct thread_info {
 #define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
 #define _TIF_SIGPENDING         (1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED       (1 << TIF_NEED_RESCHED)
-#define _TIF_SIGDELAYED (1 << TIF_SIGDELAYED)
+#define _TIF_SIGDELAYED         (1 << TIF_SIGDELAYED)
 #define _TIF_POLLING_NRFLAG     (1 << TIF_POLLING_NRFLAG)
 #define _TIF_MCA_INIT           (1 << TIF_MCA_INIT)
+#define _TIF_DB_DISABLED        (1 << TIF_DB_DISABLED)
 
 /* "work to do on user-return" bits */
 #define TIF_ALLWORK_MASK        (_TIF_NOTIFY_RESUME|_TIF_SIGPENDING|_TIF_NEED_RESCHED|_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SIGDELAYED)