x86/irq/64: Sanitize the top/bottom confusion

On x86, stacks go top to bottom, but the stack overflow check uses it
the other way round, which is just confusing. Clean it up and sanitize
the warning string a bit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190414160143.961241397@linutronix.de

arch/x86/kernel/irq_64.c

@@ -42,7 +42,7 @@ int sysctl_panic_on_stackoverflow;
 static inline void stack_overflow_check(struct pt_regs *regs)
 {
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
-#define STACK_TOP_MARGIN	128
+#define STACK_MARGIN	128
 	struct orig_ist *oist;
 	u64 irq_stack_top, irq_stack_bottom;
 	u64 estack_top, estack_bottom;
@@ -51,25 +51,25 @@ static inline void stack_overflow_check(struct pt_regs *regs)
 	if (user_mode(regs))
 		return;
 
-	if (regs->sp >= curbase + sizeof(struct pt_regs) + STACK_TOP_MARGIN &&
+	if (regs->sp >= curbase + sizeof(struct pt_regs) + STACK_MARGIN &&
 	    regs->sp <= curbase + THREAD_SIZE)
 		return;
 
-	irq_stack_bottom = (u64)__this_cpu_read(irq_stack_ptr);
-	irq_stack_top = irq_stack_bottom - IRQ_STACK_SIZE + STACK_TOP_MARGIN;
-	if (regs->sp >= irq_stack_top && regs->sp <= irq_stack_bottom)
+	irq_stack_top = (u64)__this_cpu_read(irq_stack_ptr);
+	irq_stack_bottom = irq_stack_top - IRQ_STACK_SIZE + STACK_MARGIN;
+	if (regs->sp >= irq_stack_bottom && regs->sp <= irq_stack_top)
 		return;
 
 	oist = this_cpu_ptr(&orig_ist);
-	estack_bottom = (u64)oist->ist[DEBUG_STACK];
-	estack_top = estack_bottom - DEBUG_STKSZ + STACK_TOP_MARGIN;
-	if (regs->sp >= estack_top && regs->sp <= estack_bottom)
+	estack_top = (u64)oist->ist[DEBUG_STACK];
+	estack_bottom = estack_top - DEBUG_STKSZ + STACK_MARGIN;
+	if (regs->sp >= estack_bottom && regs->sp <= estack_top)
 		return;
 
-	WARN_ONCE(1, "do_IRQ(): %s has overflown the kernel stack (cur:%Lx,sp:%lx,irq stk top-bottom:%Lx-%Lx,exception stk top-bottom:%Lx-%Lx,ip:%pF)\n",
+	WARN_ONCE(1, "do_IRQ(): %s has overflown the kernel stack (cur:%Lx,sp:%lx, irq stack:%Lx-%Lx, exception stack: %Lx-%Lx, ip:%pF)\n",
 		current->comm, curbase, regs->sp,
-		irq_stack_top, irq_stack_bottom,
-		estack_top, estack_bottom, (void *)regs->ip);
+		irq_stack_bottom, irq_stack_top,
+		estack_bottom, estack_top, (void *)regs->ip);
 
 	if (sysctl_panic_on_stackoverflow)
 		panic("low stack detected by irq handler - check messages\n");