m68k: Fix assembler constraint to prevent overeager gcc optimisation

Passing the address of a variable as an operand to an asm statement
doesn't mark the value of this variable as used, so gcc may optimize its
initialisation away.  Fix this by using the "m" constraint instead.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org

arch/m68k/kernel/process_mm.c

@@ -189,8 +189,8 @@ void flush_thread(void)
 	current->thread.fs = __USER_DS;
 	if (!FPU_IS_EMU)
 		asm volatile (".chip 68k/68881\n\t"
-			      "frestore %0@\n\t"
-			      ".chip 68k" : : "a" (&zero));
+			      "frestore %0\n\t"
+			      ".chip 68k" : : "m" (zero));
 }
 
 /*

arch/m68k/kernel/process_no.c

@@ -163,8 +163,8 @@ void flush_thread(void)
 #ifdef CONFIG_FPU
 	if (!FPU_IS_EMU)
 		asm volatile (".chip 68k/68881\n\t"
-			      "frestore %0@\n\t"
-			      ".chip 68k" : : "a" (&zero));
+			      "frestore %0\n\t"
+			      ".chip 68k" : : "m" (zero));
 #endif
 }
 

arch/m68k/kernel/traps.c

@@ -552,13 +552,13 @@ static inline void bus_error030 (struct frame *fp)
 
 #ifdef DEBUG
 		asm volatile ("ptestr %3,%2@,#7,%0\n\t"
-			      "pmove %%psr,%1@"
-			      : "=a&" (desc)
-			      : "a" (&temp), "a" (addr), "d" (ssw));
+			      "pmove %%psr,%1"
+			      : "=a&" (desc), "=m" (temp)
+			      : "a" (addr), "d" (ssw));
 #else
 		asm volatile ("ptestr %2,%1@,#7\n\t"
-			      "pmove %%psr,%0@"
-			      : : "a" (&temp), "a" (addr), "d" (ssw));
+			      "pmove %%psr,%0"
+			      : "=m" (temp) : "a" (addr), "d" (ssw));
 #endif
 		mmusr = temp;
 
@@ -605,20 +605,18 @@ static inline void bus_error030 (struct frame *fp)
 			       !(ssw & RW) ? "write" : "read", addr,
 			       fp->ptregs.pc, ssw);
 			asm volatile ("ptestr #1,%1@,#0\n\t"
-				      "pmove %%psr,%0@"
-				      : /* no outputs */
-				      : "a" (&temp), "a" (addr));
+				      "pmove %%psr,%0"
+				      : "=m" (temp)
+				      : "a" (addr));
 			mmusr = temp;
 
 			printk ("level 0 mmusr is %#x\n", mmusr);
 #if 0
-			asm volatile ("pmove %%tt0,%0@"
-				      : /* no outputs */
-				      : "a" (&tlong));
+			asm volatile ("pmove %%tt0,%0"
+				      : "=m" (tlong));
 			printk("tt0 is %#lx, ", tlong);
-			asm volatile ("pmove %%tt1,%0@"
-				      : /* no outputs */
-				      : "a" (&tlong));
+			asm volatile ("pmove %%tt1,%0"
+				      : "=m" (tlong));
 			printk("tt1 is %#lx\n", tlong);
 #endif
 #ifdef DEBUG
@@ -668,13 +666,13 @@ static inline void bus_error030 (struct frame *fp)
 
 #ifdef DEBUG
 	asm volatile ("ptestr #1,%2@,#7,%0\n\t"
-		      "pmove %%psr,%1@"
-		      : "=a&" (desc)
-		      : "a" (&temp), "a" (addr));
+		      "pmove %%psr,%1"
+		      : "=a&" (desc), "=m" (temp)
+		      : "a" (addr));
 #else
 	asm volatile ("ptestr #1,%1@,#7\n\t"
-		      "pmove %%psr,%0@"
-		      : : "a" (&temp), "a" (addr));
+		      "pmove %%psr,%0"
+		      : "=m" (temp) : "a" (addr));
 #endif
 	mmusr = temp;