[ALPHA] Streamline opDEC_check and the actual fixup bits in do_entIF.

arch/alpha/kernel/traps.c

@@ -15,6 +15,7 @@
 #include <linux/delay.h>
 #include <linux/smp_lock.h>
 #include <linux/module.h>
+#include <linux/init.h>
 
 #include <asm/gentrap.h>
 #include <asm/uaccess.h>
@@ -25,35 +26,37 @@
 
 #include "proto.h"
 
-/* data/code implementing a work-around for some SRMs which
-   mishandle opDEC faults
-*/
-static int opDEC_testing = 0;
-static int opDEC_fix = 0;
-static int opDEC_checked = 0;
-static unsigned long opDEC_test_pc = 0;
+/* Work-around for some SRMs which mishandle opDEC faults.  */
 
-static void
+static int opDEC_fix;
+
+static void __init
 opDEC_check(void)
 {
-	unsigned long test_pc;
-
-	if (opDEC_checked) return;
-
-	lock_kernel();
-	opDEC_testing = 1;
-
-	__asm__ __volatile__(
-		"       br      %0,1f\n"
-		"1:     addq    %0,8,%0\n"
-		"       stq     %0,%1\n"
-		"       cvttq/svm $f31,$f31\n"
-		: "=&r"(test_pc), "=m"(opDEC_test_pc)
-		: );
-
-	opDEC_testing = 0;
-	opDEC_checked = 1;
-	unlock_kernel();
+	__asm__ __volatile__ (
+	/* Load the address of... */
+	"	br	$16, 1f\n"
+	/* A stub instruction fault handler.  Just add 4 to the
+	   pc and continue.  */
+	"	ldq	$16, 8($sp)\n"
+	"	addq	$16, 4, $16\n"
+	"	stq	$16, 8($sp)\n"
+	"	call_pal %[rti]\n"
+	/* Install the instruction fault handler.  */
+	"1:	lda	$17, 3\n"
+	"	call_pal %[wrent]\n"
+	/* With that in place, the fault from the round-to-minf fp
+	   insn will arrive either at the "lda 4" insn (bad) or one
+	   past that (good).  This places the correct fixup in %0.  */
+	"	lda %[fix], 0\n"
+	"	cvttq/svm $f31,$f31\n"
+	"	lda %[fix], 4"
+	: [fix] "=r" (opDEC_fix)
+	: [rti] "n" (PAL_rti), [wrent] "n" (PAL_wrent)
+	: "$0", "$1", "$16", "$17", "$22", "$23", "$24", "$25");
+
+	if (opDEC_fix)
+		printk("opDEC fixup enabled.\n");
 }
 
 void
@@ -244,7 +247,7 @@ do_entIF(unsigned long type, struct pt_regs *regs)
 	siginfo_t info;
 	int signo, code;
 
-	if (!opDEC_testing || type != 4) {
+	if (regs->ps == 0) {
 		if (type == 1) {
 			const unsigned int *data
 			  = (const unsigned int *) regs->pc;
@@ -359,14 +362,6 @@ do_entIF(unsigned long type, struct pt_regs *regs)
 			   fault during the boot sequence and testing if
 			   we get the correct PC.  If not, we set a flag
 			   to correct it every time through.  */
-			if (opDEC_testing) {
-				if (regs->pc == opDEC_test_pc) {
-					opDEC_fix = 4;
-					regs->pc += 4;
-					printk("opDEC fixup enabled.\n");
-				}
-				return;
-			}
 			regs->pc += opDEC_fix; 
 			
 			/* EV4 does not implement anything except normal
@@ -1083,22 +1078,22 @@ do_entUnaUser(void * va, unsigned long opcode,
 	return;
 }
 
-void
+void __init
 trap_init(void)
 {
 	/* Tell PAL-code what global pointer we want in the kernel.  */
 	register unsigned long gptr __asm__("$29");
 	wrkgp(gptr);
 
+	/* Hack for Multia (UDB) and JENSEN: some of their SRMs have
+	   a bug in the handling of the opDEC fault.  Fix it up if so.  */
+	if (implver() == IMPLVER_EV4)
+		opDEC_check();
+
 	wrent(entArith, 1);
 	wrent(entMM, 2);
 	wrent(entIF, 3);
 	wrent(entUna, 4);
 	wrent(entSys, 5);
 	wrent(entDbg, 6);
-
-	/* Hack for Multia (UDB) and JENSEN: some of their SRMs have
-	   a bug in the handling of the opDEC fault.  Fix it up if so.  */
-	if (implver() == IMPLVER_EV4)
-		opDEC_check();
 }