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 <keescook@chromium.org>
Link: http://lkml.kernel.org/r/20120310000710.GA32667@www.outflux.net
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/traps.h

@@ -89,4 +89,29 @@ asmlinkage void smp_thermal_interrupt(void);
 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

@@ -61,7 +61,7 @@ static irqreturn_t math_error_irq(int cpl, void *dev_id)
 	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

@@ -119,7 +119,7 @@ do_trap(int trapnr, int signr, char *str, struct pt_regs *regs,
 		 * 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;
 	}
@@ -203,27 +203,31 @@ dotraplinkage void do_##name(struct pt_regs *regs, long error_code)	\
 	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);
 }
 
@@ -233,10 +237,10 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
 	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
@@ -264,7 +268,7 @@ do_general_protection(struct pt_regs *regs, long error_code)
 		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()) {
@@ -291,9 +295,9 @@ do_general_protection(struct pt_regs *regs, long error_code)
 		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);
 }
@@ -302,13 +306,13 @@ do_general_protection(struct pt_regs *regs, long 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;
 
 	/*
@@ -317,7 +321,7 @@ dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
 	 */
 	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();
 }
@@ -422,8 +426,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 	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;
@@ -460,7 +464,8 @@ void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	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;
@@ -485,7 +490,7 @@ void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	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
@@ -529,10 +534,11 @@ void math_error(struct pt_regs *regs, int error_code, int trapnr)
 		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);
 }
@@ -543,13 +549,13 @@ dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
 	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
@@ -643,20 +649,21 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 	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);
 }
 
@@ -672,30 +679,30 @@ void __init trap_init(void)
 	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++)
@@ -720,7 +727,7 @@ void __init trap_init(void)
 
 #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
 }