1 files changed, 18 insertions, 0 deletions

diff --git a/arch/ia64/kernel/traps.c b/arch/ia64/kernel/traps.c
index e82ad78081b3..9bad6652d531 100644
--- a/arch/ia64/kernel/traps.c
+++ b/arch/ia64/kernel/traps.c
@@ -111,6 +111,24 @@ ia64_bad_break (unsigned long break_num, struct pt_regs *regs)
         siginfo_t siginfo;
         int sig, code;
 
+        /* break.b always sets cr.iim to 0, which causes problems for
+         * debuggers.  Get the real break number from the original instruction,
+         * but only for kernel code.  User space break.b is left alone, to
+         * preserve the existing behaviour.  All break codings have the same
+         * format, so there is no need to check the slot type.
+         */
+        if (break_num == 0 && !user_mode(regs)) {
+                struct ia64_psr *ipsr = ia64_psr(regs);
+                unsigned long *bundle = (unsigned long *)regs->cr_iip;
+                unsigned long slot;
+                switch (ipsr->ri) {
+                      case 0:  slot = (bundle[0] >>  5); break;
+                      case 1:  slot = (bundle[0] >> 46) | (bundle[1] << 18); break;
+                      default: slot = (bundle[1] >> 23); break;
+                }
+                break_num = ((slot >> 36 & 1) << 20) | (slot >> 6 & 0xfffff);
+        }
+
         /* SIGILL, SIGFPE, SIGSEGV, and SIGBUS want these field initialized: */
         siginfo.si_addr = (void __user *) (regs->cr_iip + ia64_psr(regs)->ri);
         siginfo.si_imm = break_num;