[PATCH] Remove most of the special cases for the debug IST stack

Remove most of the special cases for the debug IST stack.  This is a
follow on clean up patch, it requires the bug fix patch that adds
orig_ist.

Signed-off-by: Keith Owens <kaos@ocs.com.au>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/x86_64/kernel/setup64.c

@@ -237,28 +237,17 @@ void __cpuinit cpu_init (void)
 	 * set up and load the per-CPU TSS
 	 */
 	for (v = 0; v < N_EXCEPTION_STACKS; v++) {
+		static const unsigned int order[N_EXCEPTION_STACKS] = {
+			[0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
+			[DEBUG_STACK - 1] = DEBUG_STACK_ORDER
+		};
 		if (cpu) {
-			static const unsigned int order[N_EXCEPTION_STACKS] = {
-				[0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STACK_ORDER,
-				[DEBUG_STACK - 1] = DEBUG_STACK_ORDER
-			};
-
 			estacks = (char *)__get_free_pages(GFP_ATOMIC, order[v]);
 			if (!estacks)
 				panic("Cannot allocate exception stack %ld %d\n",
 				      v, cpu); 
 		}
-		switch (v + 1) {
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-		case DEBUG_STACK:
-			cpu_pda(cpu)->debugstack = (unsigned long)estacks;
-			estacks += DEBUG_STKSZ;
-			break;
-#endif
-		default:
-			estacks += EXCEPTION_STKSZ;
-			break;
-		}
+		estacks += PAGE_SIZE << order[v];
 		orig_ist->ist[v] = t->ist[v] = (unsigned long)estacks;
 	}
 

arch/x86_64/kernel/traps.c

@@ -162,26 +162,7 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 	 * 'stack' is in one of them:
 	 */
 	for (k = 0; k < N_EXCEPTION_STACKS; k++) {
-		unsigned long end;
-
-		/*
-		 * set 'end' to the end of the exception stack.
-		 */
-		switch (k + 1) {
-		/*
-		 * TODO: this block is not needed i think, because
-		 * setup64.c:cpu_init() sets up t->ist[DEBUG_STACK]
-		 * properly too.
-		 */
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-		case DEBUG_STACK:
-			end = cpu_pda(cpu)->debugstack + DEBUG_STKSZ;
-			break;
-#endif
-		default:
-			end = per_cpu(orig_ist, cpu).ist[k];
-			break;
-		}
+		unsigned long end = per_cpu(orig_ist, cpu).ist[k];
 		/*
 		 * Is 'stack' above this exception frame's end?
 		 * If yes then skip to the next frame.

include/asm-x86_64/pda.h

@@ -13,9 +13,6 @@ struct x8664_pda {
 	unsigned long data_offset;	/* Per cpu data offset from linker address */
 	unsigned long kernelstack;  /* top of kernel stack for current */ 
 	unsigned long oldrsp; 	    /* user rsp for system call */
-#if DEBUG_STKSZ > EXCEPTION_STKSZ
-	unsigned long debugstack;   /* #DB/#BP stack. */
-#endif
         int irqcount;		    /* Irq nesting counter. Starts with -1 */  	
 	int cpunumber;		    /* Logical CPU number */
 	char *irqstackptr;	/* top of irqstack */