x86: Use enum instead of literals for trap values

The traps are referred to by their numbers and it can be difficult to
understand them while reading the code without context. This patch adds
enumeration of the trap numbers and replaces the numbers with the correct
enum for x86.

Signed-off-by: Kees Cook <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/include/asm/traps.h

···
 asmlinkage void mce_threshold_interrupt(void);
 #endif
 
+/* Interrupts/Exceptions */
+enum {
+	X86_TRAP_DE = 0,	/*  0, Divide-by-zero */
+	X86_TRAP_DB,		/*  1, Debug */
+	X86_TRAP_NMI,		/*  2, Non-maskable Interrupt */
+	X86_TRAP_BP,		/*  3, Breakpoint */
+	X86_TRAP_OF,		/*  4, Overflow */
+	X86_TRAP_BR,		/*  5, Bound Range Exceeded */
+	X86_TRAP_UD,		/*  6, Invalid Opcode */
+	X86_TRAP_NM,		/*  7, Device Not Available */
+	X86_TRAP_DF,		/*  8, Double Fault */
+	X86_TRAP_OLD_MF,	/*  9, Coprocessor Segment Overrun */
+	X86_TRAP_TS,		/* 10, Invalid TSS */
+	X86_TRAP_NP,		/* 11, Segment Not Present */
+	X86_TRAP_SS,		/* 12, Stack Segment Fault */
+	X86_TRAP_GP,		/* 13, General Protection Fault */
+	X86_TRAP_PF,		/* 14, Page Fault */
+	X86_TRAP_SPURIOUS,	/* 15, Spurious Interrupt */
+	X86_TRAP_MF,		/* 16, x87 Floating-Point Exception */
+	X86_TRAP_AC,		/* 17, Alignment Check */
+	X86_TRAP_MC,		/* 18, Machine Check */
+	X86_TRAP_XF,		/* 19, SIMD Floating-Point Exception */
+	X86_TRAP_IRET = 32,	/* 32, IRET Exception */
+};
+
 #endif /* _ASM_X86_TRAPS_H */

arch/x86/kernel/irqinit.c

···
 	outb(0, 0xF0);
 	if (ignore_fpu_irq || !boot_cpu_data.hard_math)
 		return IRQ_NONE;
-	math_error(get_irq_regs(), 0, 16);
+	math_error(get_irq_regs(), 0, X86_TRAP_MF);
 	return IRQ_HANDLED;
 }
 

arch/x86/kernel/traps.c

···
 		 * traps 0, 1, 3, 4, and 5 should be forwarded to vm86.
 		 * On nmi (interrupt 2), do_trap should not be called.
 		 */
-		if (trapnr < 6)
+		if (trapnr < X86_TRAP_UD)
 			goto vm86_trap;
 		goto trap_signal;
 	}
···
 	do_trap(trapnr, signr, str, regs, error_code, &info);		\
 }
 
-DO_ERROR_INFO(0, SIGFPE, "divide error", divide_error, FPE_INTDIV, regs->ip)
-DO_ERROR(4, SIGSEGV, "overflow", overflow)
-DO_ERROR(5, SIGSEGV, "bounds", bounds)
-DO_ERROR_INFO(6, SIGILL, "invalid opcode", invalid_op, ILL_ILLOPN, regs->ip)
-DO_ERROR(9, SIGFPE, "coprocessor segment overrun", coprocessor_segment_overrun)
-DO_ERROR(10, SIGSEGV, "invalid TSS", invalid_TSS)
-DO_ERROR(11, SIGBUS, "segment not present", segment_not_present)
+DO_ERROR_INFO(X86_TRAP_DE, SIGFPE, "divide error", divide_error, FPE_INTDIV,
+		regs->ip)
+DO_ERROR(X86_TRAP_OF, SIGSEGV, "overflow", overflow)
+DO_ERROR(X86_TRAP_BR, SIGSEGV, "bounds", bounds)
+DO_ERROR_INFO(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op, ILL_ILLOPN,
+		regs->ip)
+DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun",
+		coprocessor_segment_overrun)
+DO_ERROR(X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS)
+DO_ERROR(X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present)
 #ifdef CONFIG_X86_32
-DO_ERROR(12, SIGBUS, "stack segment", stack_segment)
+DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment)
 #endif
-DO_ERROR_INFO(17, SIGBUS, "alignment check", alignment_check, BUS_ADRALN, 0)
+DO_ERROR_INFO(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check,
+		BUS_ADRALN, 0)
 
 #ifdef CONFIG_X86_64
 /* Runs on IST stack */
 dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code)
 {
 	if (notify_die(DIE_TRAP, "stack segment", regs, error_code,
-			12, SIGBUS) == NOTIFY_STOP)
+			X86_TRAP_SS, SIGBUS) == NOTIFY_STOP)
 		return;
 	preempt_conditional_sti(regs);
-	do_trap(12, SIGBUS, "stack segment", regs, error_code, NULL);
+	do_trap(X86_TRAP_SS, SIGBUS, "stack segment", regs, error_code, NULL);
 	preempt_conditional_cli(regs);
 }
 
···
 	struct task_struct *tsk = current;
 
 	/* Return not checked because double check cannot be ignored */
-	notify_die(DIE_TRAP, str, regs, error_code, 8, SIGSEGV);
+	notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
 
 	tsk->thread.error_code = error_code;
-	tsk->thread.trap_no = 8;
+	tsk->thread.trap_no = X86_TRAP_DF;
 
 	/*
 	 * This is always a kernel trap and never fixable (and thus must
···
 		goto gp_in_kernel;
 
 	tsk->thread.error_code = error_code;
-	tsk->thread.trap_no = 13;
+	tsk->thread.trap_no = X86_TRAP_GP;
 
 	if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 			printk_ratelimit()) {
···
 		return;
 
 	tsk->thread.error_code = error_code;
-	tsk->thread.trap_no = 13;
-	if (notify_die(DIE_GPF, "general protection fault", regs,
-				error_code, 13, SIGSEGV) == NOTIFY_STOP)
+	tsk->thread.trap_no = X86_TRAP_GP;
+	if (notify_die(DIE_GPF, "general protection fault", regs, error_code,
+			X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP)
 		return;
 	die("general protection fault", regs, error_code);
 }
···
 dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
 {
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
-	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
-			== NOTIFY_STOP)
+	if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
+				SIGTRAP) == NOTIFY_STOP)
 		return;
 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
 
-	if (notify_die(DIE_INT3, "int3", regs, error_code, 3, SIGTRAP)
-			== NOTIFY_STOP)
+	if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
+			SIGTRAP) == NOTIFY_STOP)
 		return;
 
 	/*
···
 	 */
 	debug_stack_usage_inc();
 	preempt_conditional_sti(regs);
-	do_trap(3, SIGTRAP, "int3", regs, error_code, NULL);
+	do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
 	preempt_conditional_cli(regs);
 	debug_stack_usage_dec();
 }
···
 	preempt_conditional_sti(regs);
 
 	if (regs->flags & X86_VM_MASK) {
-		handle_vm86_trap((struct kernel_vm86_regs *) regs,
-				error_code, 1);
+		handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code,
+					X86_TRAP_DB);
 		preempt_conditional_cli(regs);
 		debug_stack_usage_dec();
 		return;
···
 	struct task_struct *task = current;
 	siginfo_t info;
 	unsigned short err;
-	char *str = (trapnr == 16) ? "fpu exception" : "simd exception";
+	char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" :
+						"simd exception";
 
 	if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP)
 		return;
···
 	info.si_signo = SIGFPE;
 	info.si_errno = 0;
 	info.si_addr = (void __user *)regs->ip;
-	if (trapnr == 16) {
+	if (trapnr == X86_TRAP_MF) {
 		unsigned short cwd, swd;
 		/*
 		 * (~cwd & swd) will mask out exceptions that are not set to unmasked
···
 		info.si_code = FPE_FLTRES;
 	} else {
 		/*
-		 * If we're using IRQ 13, or supposedly even some trap 16
-		 * implementations, it's possible we get a spurious trap...
+		 * If we're using IRQ 13, or supposedly even some trap
+		 * X86_TRAP_MF implementations, it's possible
+		 * we get a spurious trap, which is not an error.
 		 */
-		return;		/* Spurious trap, no error */
+		return;
 	}
 	force_sig_info(SIGFPE, &info, task);
 }
···
 	ignore_fpu_irq = 1;
 #endif
 
-	math_error(regs, error_code, 16);
+	math_error(regs, error_code, X86_TRAP_MF);
 }
 
 dotraplinkage void
 do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
 {
-	math_error(regs, error_code, 19);
+	math_error(regs, error_code, X86_TRAP_XF);
 }
 
 dotraplinkage void
···
 	info.si_errno = 0;
 	info.si_code = ILL_BADSTK;
 	info.si_addr = NULL;
-	if (notify_die(DIE_TRAP, "iret exception",
-			regs, error_code, 32, SIGILL) == NOTIFY_STOP)
+	if (notify_die(DIE_TRAP, "iret exception", regs, error_code,
+			X86_TRAP_IRET, SIGILL) == NOTIFY_STOP)
 		return;
-	do_trap(32, SIGILL, "iret exception", regs, error_code, &info);
+	do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
+		&info);
 }
 #endif
 
 /* Set of traps needed for early debugging. */
 void __init early_trap_init(void)
 {
-	set_intr_gate_ist(1, &debug, DEBUG_STACK);
+	set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
 	/* int3 can be called from all */
-	set_system_intr_gate_ist(3, &int3, DEBUG_STACK);
-	set_intr_gate(14, &page_fault);
+	set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
+	set_intr_gate(X86_TRAP_PF, &page_fault);
 	load_idt(&idt_descr);
 }
 
···
 	early_iounmap(p, 4);
 #endif
 
-	set_intr_gate(0, &divide_error);
-	set_intr_gate_ist(2, &nmi, NMI_STACK);
+	set_intr_gate(X86_TRAP_DE, &divide_error);
+	set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK);
 	/* int4 can be called from all */
-	set_system_intr_gate(4, &overflow);
-	set_intr_gate(5, &bounds);
-	set_intr_gate(6, &invalid_op);
-	set_intr_gate(7, &device_not_available);
+	set_system_intr_gate(X86_TRAP_OF, &overflow);
+	set_intr_gate(X86_TRAP_BR, &bounds);
+	set_intr_gate(X86_TRAP_UD, &invalid_op);
+	set_intr_gate(X86_TRAP_NM, &device_not_available);
 #ifdef CONFIG_X86_32
-	set_task_gate(8, GDT_ENTRY_DOUBLEFAULT_TSS);
+	set_task_gate(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS);
 #else
-	set_intr_gate_ist(8, &double_fault, DOUBLEFAULT_STACK);
+	set_intr_gate_ist(X86_TRAP_DF, &double_fault, DOUBLEFAULT_STACK);
 #endif
-	set_intr_gate(9, &coprocessor_segment_overrun);
-	set_intr_gate(10, &invalid_TSS);
-	set_intr_gate(11, &segment_not_present);
-	set_intr_gate_ist(12, &stack_segment, STACKFAULT_STACK);
-	set_intr_gate(13, &general_protection);
-	set_intr_gate(15, &spurious_interrupt_bug);
-	set_intr_gate(16, &coprocessor_error);
-	set_intr_gate(17, &alignment_check);
+	set_intr_gate(X86_TRAP_OLD_MF, &coprocessor_segment_overrun);
+	set_intr_gate(X86_TRAP_TS, &invalid_TSS);
+	set_intr_gate(X86_TRAP_NP, &segment_not_present);
+	set_intr_gate_ist(X86_TRAP_SS, &stack_segment, STACKFAULT_STACK);
+	set_intr_gate(X86_TRAP_GP, &general_protection);
+	set_intr_gate(X86_TRAP_SPURIOUS, &spurious_interrupt_bug);
+	set_intr_gate(X86_TRAP_MF, &coprocessor_error);
+	set_intr_gate(X86_TRAP_AC, &alignment_check);
 #ifdef CONFIG_X86_MCE
-	set_intr_gate_ist(18, &machine_check, MCE_STACK);
+	set_intr_gate_ist(X86_TRAP_MC, &machine_check, MCE_STACK);
 #endif
-	set_intr_gate(19, &simd_coprocessor_error);
+	set_intr_gate(X86_TRAP_XF, &simd_coprocessor_error);
 
 	/* Reserve all the builtin and the syscall vector: */
 	for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)
···
 
 #ifdef CONFIG_X86_64
 	memcpy(&nmi_idt_table, &idt_table, IDT_ENTRIES * 16);
-	set_nmi_gate(1, &debug);
-	set_nmi_gate(3, &int3);
+	set_nmi_gate(X86_TRAP_DB, &debug);
+	set_nmi_gate(X86_TRAP_BP, &int3);
 #endif
 }