[IA64] Remove getting break_num by decoding instruction

break.b always sets cr.iim to 0 and the current code tries to
get the break_num by decoding instruction. However, their
seems to be a race condition while reading the regs->cr_iip,
as on other cpu the break.b at regs->cr_iip might have been
replaced with the original instruction as a result of
unregister_kprobe() and hence decoding instruction to
obtain break_num will result in wrong value in this case.

Also includes changes to kprobes.c which now has to handle
break number zero.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

2 files changed, 1 insertions, 19 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 801eeaeaf3de..2895d6e6062f 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -740,7 +740,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         switch(val) {
         case DIE_BREAK:
                 /* err is break number from ia64_bad_break() */
-                if (args->err == 0x80200 || args->err == 0x80300)
+                if (args->err == 0x80200 || args->err == 0x80300 || args->err == 0)
                         if (pre_kprobes_handler(args))
                                 ret = NOTIFY_STOP;
                 break;
diff --git a/arch/ia64/kernel/traps.c b/arch/ia64/kernel/traps.c
index fba5fdd1f968..d3e0ecb56d62 100644
--- a/arch/ia64/kernel/traps.c
+++ b/arch/ia64/kernel/traps.c
@@ -132,24 +132,6 @@ __kprobes 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;