[patch 2.6.12-rc5] Extract correct break number for break.b

[Keith Owens <kaos@sgi.com>]

break.b does not store the break number in cr.iim, instead it stores 0,
which makes all break.b instructions look like BUG().  Extract the
break number from the instruction itself.

Signed-off-by: Keith Owens <kaos@sgi.com>

Index: linux/arch/ia64/kernel/traps.c
=================================--- linux.orig/arch/ia64/kernel/traps.c	2005-05-28 14:37:42.648499458 +1000
+++ linux/arch/ia64/kernel/traps.c	2005-05-28 14:39:52.436651847 +1000
@@ -111,6 +111,24 @@ ia64_bad_break (unsigned long break_num,
 	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;