2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
5 * Pentium III FXSR, SSE support
6 * Gareth Hughes <gareth@valinux.com>, May 2000
10 * Handle hardware traps and faults.
13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15 #include <linux/context_tracking.h>
16 #include <linux/interrupt.h>
17 #include <linux/kallsyms.h>
18 #include <linux/spinlock.h>
19 #include <linux/kprobes.h>
20 #include <linux/uaccess.h>
21 #include <linux/kdebug.h>
22 #include <linux/kgdb.h>
23 #include <linux/kernel.h>
24 #include <linux/module.h>
25 #include <linux/ptrace.h>
26 #include <linux/uprobes.h>
27 #include <linux/string.h>
28 #include <linux/delay.h>
29 #include <linux/errno.h>
30 #include <linux/kexec.h>
31 #include <linux/sched.h>
32 #include <linux/timer.h>
33 #include <linux/init.h>
34 #include <linux/bug.h>
35 #include <linux/nmi.h>
37 #include <linux/smp.h>
41 #include <linux/ioport.h>
42 #include <linux/eisa.h>
45 #if defined(CONFIG_EDAC)
46 #include <linux/edac.h>
49 #include <asm/kmemcheck.h>
50 #include <asm/stacktrace.h>
51 #include <asm/processor.h>
52 #include <asm/debugreg.h>
53 #include <linux/atomic.h>
54 #include <asm/ftrace.h>
55 #include <asm/traps.h>
58 #include <asm/fpu-internal.h>
60 #include <asm/fixmap.h>
61 #include <asm/mach_traps.h>
62 #include <asm/alternative.h>
65 #include <asm/x86_init.h>
66 #include <asm/pgalloc.h>
67 #include <asm/proto.h>
69 /* No need to be aligned, but done to keep all IDTs defined the same way. */
70 gate_desc debug_idt_table[NR_VECTORS] __page_aligned_bss;
72 #include <asm/processor-flags.h>
73 #include <asm/setup.h>
75 asmlinkage int system_call(void);
78 /* Must be page-aligned because the real IDT is used in a fixmap. */
79 gate_desc idt_table[NR_VECTORS] __page_aligned_bss;
81 DECLARE_BITMAP(used_vectors, NR_VECTORS);
82 EXPORT_SYMBOL_GPL(used_vectors);
84 static inline void conditional_sti(struct pt_regs *regs)
86 if (regs->flags & X86_EFLAGS_IF)
90 static inline void preempt_conditional_sti(struct pt_regs *regs)
93 if (regs->flags & X86_EFLAGS_IF)
97 static inline void conditional_cli(struct pt_regs *regs)
99 if (regs->flags & X86_EFLAGS_IF)
103 static inline void preempt_conditional_cli(struct pt_regs *regs)
105 if (regs->flags & X86_EFLAGS_IF)
110 static nokprobe_inline int
111 do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
112 struct pt_regs *regs, long error_code)
115 if (regs->flags & X86_VM_MASK) {
117 * Traps 0, 1, 3, 4, and 5 should be forwarded to vm86.
118 * On nmi (interrupt 2), do_trap should not be called.
120 if (trapnr < X86_TRAP_UD) {
121 if (!handle_vm86_trap((struct kernel_vm86_regs *) regs,
128 if (!user_mode(regs)) {
129 if (!fixup_exception(regs)) {
130 tsk->thread.error_code = error_code;
131 tsk->thread.trap_nr = trapnr;
132 die(str, regs, error_code);
140 static siginfo_t *fill_trap_info(struct pt_regs *regs, int signr, int trapnr,
143 unsigned long siaddr;
148 return SEND_SIG_PRIV;
152 siaddr = uprobe_get_trap_addr(regs);
156 siaddr = uprobe_get_trap_addr(regs);
164 info->si_signo = signr;
166 info->si_code = sicode;
167 info->si_addr = (void __user *)siaddr;
172 do_trap(int trapnr, int signr, char *str, struct pt_regs *regs,
173 long error_code, siginfo_t *info)
175 struct task_struct *tsk = current;
178 if (!do_trap_no_signal(tsk, trapnr, str, regs, error_code))
181 * We want error_code and trap_nr set for userspace faults and
182 * kernelspace faults which result in die(), but not
183 * kernelspace faults which are fixed up. die() gives the
184 * process no chance to handle the signal and notice the
185 * kernel fault information, so that won't result in polluting
186 * the information about previously queued, but not yet
187 * delivered, faults. See also do_general_protection below.
189 tsk->thread.error_code = error_code;
190 tsk->thread.trap_nr = trapnr;
193 if (show_unhandled_signals && unhandled_signal(tsk, signr) &&
194 printk_ratelimit()) {
195 pr_info("%s[%d] trap %s ip:%lx sp:%lx error:%lx",
196 tsk->comm, tsk->pid, str,
197 regs->ip, regs->sp, error_code);
198 print_vma_addr(" in ", regs->ip);
203 force_sig_info(signr, info ?: SEND_SIG_PRIV, tsk);
205 NOKPROBE_SYMBOL(do_trap);
207 static void do_error_trap(struct pt_regs *regs, long error_code, char *str,
208 unsigned long trapnr, int signr)
210 enum ctx_state prev_state = exception_enter();
213 if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, signr) !=
215 conditional_sti(regs);
216 do_trap(trapnr, signr, str, regs, error_code,
217 fill_trap_info(regs, signr, trapnr, &info));
220 exception_exit(prev_state);
223 #define DO_ERROR(trapnr, signr, str, name) \
224 dotraplinkage void do_##name(struct pt_regs *regs, long error_code) \
226 do_error_trap(regs, error_code, str, trapnr, signr); \
229 DO_ERROR(X86_TRAP_DE, SIGFPE, "divide error", divide_error)
230 DO_ERROR(X86_TRAP_OF, SIGSEGV, "overflow", overflow)
231 DO_ERROR(X86_TRAP_BR, SIGSEGV, "bounds", bounds)
232 DO_ERROR(X86_TRAP_UD, SIGILL, "invalid opcode", invalid_op)
233 DO_ERROR(X86_TRAP_OLD_MF, SIGFPE, "coprocessor segment overrun",coprocessor_segment_overrun)
234 DO_ERROR(X86_TRAP_TS, SIGSEGV, "invalid TSS", invalid_TSS)
235 DO_ERROR(X86_TRAP_NP, SIGBUS, "segment not present", segment_not_present)
236 DO_ERROR(X86_TRAP_SS, SIGBUS, "stack segment", stack_segment)
237 DO_ERROR(X86_TRAP_AC, SIGBUS, "alignment check", alignment_check)
240 /* Runs on IST stack */
241 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
243 static const char str[] = "double fault";
244 struct task_struct *tsk = current;
246 #ifdef CONFIG_X86_ESPFIX64
247 extern unsigned char native_irq_return_iret[];
250 * If IRET takes a non-IST fault on the espfix64 stack, then we
251 * end up promoting it to a doublefault. In that case, modify
252 * the stack to make it look like we just entered the #GP
253 * handler from user space, similar to bad_iret.
255 if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
256 regs->cs == __KERNEL_CS &&
257 regs->ip == (unsigned long)native_irq_return_iret)
259 struct pt_regs *normal_regs = task_pt_regs(current);
261 /* Fake a #GP(0) from userspace. */
262 memmove(&normal_regs->ip, (void *)regs->sp, 5*8);
263 normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */
264 regs->ip = (unsigned long)general_protection;
265 regs->sp = (unsigned long)&normal_regs->orig_ax;
271 /* Return not checked because double check cannot be ignored */
272 notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
274 tsk->thread.error_code = error_code;
275 tsk->thread.trap_nr = X86_TRAP_DF;
277 #ifdef CONFIG_DOUBLEFAULT
278 df_debug(regs, error_code);
281 * This is always a kernel trap and never fixable (and thus must
285 die(str, regs, error_code);
290 do_general_protection(struct pt_regs *regs, long error_code)
292 struct task_struct *tsk;
293 enum ctx_state prev_state;
295 prev_state = exception_enter();
296 conditional_sti(regs);
299 if (regs->flags & X86_VM_MASK) {
301 handle_vm86_fault((struct kernel_vm86_regs *) regs, error_code);
307 if (!user_mode(regs)) {
308 if (fixup_exception(regs))
311 tsk->thread.error_code = error_code;
312 tsk->thread.trap_nr = X86_TRAP_GP;
313 if (notify_die(DIE_GPF, "general protection fault", regs, error_code,
314 X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP)
315 die("general protection fault", regs, error_code);
319 tsk->thread.error_code = error_code;
320 tsk->thread.trap_nr = X86_TRAP_GP;
322 if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
323 printk_ratelimit()) {
324 pr_info("%s[%d] general protection ip:%lx sp:%lx error:%lx",
325 tsk->comm, task_pid_nr(tsk),
326 regs->ip, regs->sp, error_code);
327 print_vma_addr(" in ", regs->ip);
331 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
333 exception_exit(prev_state);
335 NOKPROBE_SYMBOL(do_general_protection);
337 /* May run on IST stack. */
338 dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
340 enum ctx_state prev_state;
342 #ifdef CONFIG_DYNAMIC_FTRACE
344 * ftrace must be first, everything else may cause a recursive crash.
345 * See note by declaration of modifying_ftrace_code in ftrace.c
347 if (unlikely(atomic_read(&modifying_ftrace_code)) &&
348 ftrace_int3_handler(regs))
351 if (poke_int3_handler(regs))
354 prev_state = exception_enter();
355 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
356 if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
357 SIGTRAP) == NOTIFY_STOP)
359 #endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
361 #ifdef CONFIG_KPROBES
362 if (kprobe_int3_handler(regs))
366 if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
367 SIGTRAP) == NOTIFY_STOP)
371 * Let others (NMI) know that the debug stack is in use
372 * as we may switch to the interrupt stack.
374 debug_stack_usage_inc();
375 preempt_conditional_sti(regs);
376 do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
377 preempt_conditional_cli(regs);
378 debug_stack_usage_dec();
380 exception_exit(prev_state);
382 NOKPROBE_SYMBOL(do_int3);
386 * Help handler running on IST stack to switch back to user stack
387 * for scheduling or signal handling. The actual stack switch is done in
390 asmlinkage __visible struct pt_regs *sync_regs(struct pt_regs *eregs)
392 struct pt_regs *regs = eregs;
393 /* Did already sync */
394 if (eregs == (struct pt_regs *)eregs->sp)
396 /* Exception from user space */
397 else if (user_mode(eregs))
398 regs = task_pt_regs(current);
400 * Exception from kernel and interrupts are enabled. Move to
401 * kernel process stack.
403 else if (eregs->flags & X86_EFLAGS_IF)
404 regs = (struct pt_regs *)(eregs->sp -= sizeof(struct pt_regs));
409 NOKPROBE_SYMBOL(sync_regs);
411 struct bad_iret_stack {
412 void *error_entry_ret;
417 struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)
420 * This is called from entry_64.S early in handling a fault
421 * caused by a bad iret to user mode. To handle the fault
422 * correctly, we want move our stack frame to task_pt_regs
423 * and we want to pretend that the exception came from the
426 struct bad_iret_stack *new_stack =
427 container_of(task_pt_regs(current),
428 struct bad_iret_stack, regs);
430 /* Copy the IRET target to the new stack. */
431 memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);
433 /* Copy the remainder of the stack from the current stack. */
434 memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));
436 BUG_ON(!user_mode_vm(&new_stack->regs));
442 * Our handling of the processor debug registers is non-trivial.
443 * We do not clear them on entry and exit from the kernel. Therefore
444 * it is possible to get a watchpoint trap here from inside the kernel.
445 * However, the code in ./ptrace.c has ensured that the user can
446 * only set watchpoints on userspace addresses. Therefore the in-kernel
447 * watchpoint trap can only occur in code which is reading/writing
448 * from user space. Such code must not hold kernel locks (since it
449 * can equally take a page fault), therefore it is safe to call
450 * force_sig_info even though that claims and releases locks.
452 * Code in ./signal.c ensures that the debug control register
453 * is restored before we deliver any signal, and therefore that
454 * user code runs with the correct debug control register even though
457 * Being careful here means that we don't have to be as careful in a
458 * lot of more complicated places (task switching can be a bit lazy
459 * about restoring all the debug state, and ptrace doesn't have to
460 * find every occurrence of the TF bit that could be saved away even
463 * May run on IST stack.
465 dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
467 struct task_struct *tsk = current;
468 enum ctx_state prev_state;
473 prev_state = exception_enter();
475 get_debugreg(dr6, 6);
477 /* Filter out all the reserved bits which are preset to 1 */
478 dr6 &= ~DR6_RESERVED;
481 * If dr6 has no reason to give us about the origin of this trap,
482 * then it's very likely the result of an icebp/int01 trap.
483 * User wants a sigtrap for that.
485 if (!dr6 && user_mode(regs))
488 /* Catch kmemcheck conditions first of all! */
489 if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
492 /* DR6 may or may not be cleared by the CPU */
496 * The processor cleared BTF, so don't mark that we need it set.
498 clear_tsk_thread_flag(tsk, TIF_BLOCKSTEP);
500 /* Store the virtualized DR6 value */
501 tsk->thread.debugreg6 = dr6;
503 #ifdef CONFIG_KPROBES
504 if (kprobe_debug_handler(regs))
508 if (notify_die(DIE_DEBUG, "debug", regs, (long)&dr6, error_code,
509 SIGTRAP) == NOTIFY_STOP)
513 * Let others (NMI) know that the debug stack is in use
514 * as we may switch to the interrupt stack.
516 debug_stack_usage_inc();
518 /* It's safe to allow irq's after DR6 has been saved */
519 preempt_conditional_sti(regs);
521 if (regs->flags & X86_VM_MASK) {
522 handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code,
524 preempt_conditional_cli(regs);
525 debug_stack_usage_dec();
530 * Single-stepping through system calls: ignore any exceptions in
531 * kernel space, but re-enable TF when returning to user mode.
533 * We already checked v86 mode above, so we can check for kernel mode
534 * by just checking the CPL of CS.
536 if ((dr6 & DR_STEP) && !user_mode(regs)) {
537 tsk->thread.debugreg6 &= ~DR_STEP;
538 set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
539 regs->flags &= ~X86_EFLAGS_TF;
541 si_code = get_si_code(tsk->thread.debugreg6);
542 if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp)
543 send_sigtrap(tsk, regs, error_code, si_code);
544 preempt_conditional_cli(regs);
545 debug_stack_usage_dec();
548 exception_exit(prev_state);
550 NOKPROBE_SYMBOL(do_debug);
553 * Note that we play around with the 'TS' bit in an attempt to get
554 * the correct behaviour even in the presence of the asynchronous
557 static void math_error(struct pt_regs *regs, int error_code, int trapnr)
559 struct task_struct *task = current;
562 char *str = (trapnr == X86_TRAP_MF) ? "fpu exception" :
565 if (notify_die(DIE_TRAP, str, regs, error_code, trapnr, SIGFPE) == NOTIFY_STOP)
567 conditional_sti(regs);
569 if (!user_mode_vm(regs))
571 if (!fixup_exception(regs)) {
572 task->thread.error_code = error_code;
573 task->thread.trap_nr = trapnr;
574 die(str, regs, error_code);
580 * Save the info for the exception handler and clear the error.
583 task->thread.trap_nr = trapnr;
584 task->thread.error_code = error_code;
585 info.si_signo = SIGFPE;
587 info.si_addr = (void __user *)uprobe_get_trap_addr(regs);
588 if (trapnr == X86_TRAP_MF) {
589 unsigned short cwd, swd;
591 * (~cwd & swd) will mask out exceptions that are not set to unmasked
592 * status. 0x3f is the exception bits in these regs, 0x200 is the
593 * C1 reg you need in case of a stack fault, 0x040 is the stack
594 * fault bit. We should only be taking one exception at a time,
595 * so if this combination doesn't produce any single exception,
596 * then we have a bad program that isn't synchronizing its FPU usage
597 * and it will suffer the consequences since we won't be able to
598 * fully reproduce the context of the exception
600 cwd = get_fpu_cwd(task);
601 swd = get_fpu_swd(task);
606 * The SIMD FPU exceptions are handled a little differently, as there
607 * is only a single status/control register. Thus, to determine which
608 * unmasked exception was caught we must mask the exception mask bits
609 * at 0x1f80, and then use these to mask the exception bits at 0x3f.
611 unsigned short mxcsr = get_fpu_mxcsr(task);
612 err = ~(mxcsr >> 7) & mxcsr;
615 if (err & 0x001) { /* Invalid op */
617 * swd & 0x240 == 0x040: Stack Underflow
618 * swd & 0x240 == 0x240: Stack Overflow
619 * User must clear the SF bit (0x40) if set
621 info.si_code = FPE_FLTINV;
622 } else if (err & 0x004) { /* Divide by Zero */
623 info.si_code = FPE_FLTDIV;
624 } else if (err & 0x008) { /* Overflow */
625 info.si_code = FPE_FLTOVF;
626 } else if (err & 0x012) { /* Denormal, Underflow */
627 info.si_code = FPE_FLTUND;
628 } else if (err & 0x020) { /* Precision */
629 info.si_code = FPE_FLTRES;
632 * If we're using IRQ 13, or supposedly even some trap
633 * X86_TRAP_MF implementations, it's possible
634 * we get a spurious trap, which is not an error.
638 force_sig_info(SIGFPE, &info, task);
641 dotraplinkage void do_coprocessor_error(struct pt_regs *regs, long error_code)
643 enum ctx_state prev_state;
645 prev_state = exception_enter();
646 math_error(regs, error_code, X86_TRAP_MF);
647 exception_exit(prev_state);
651 do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
653 enum ctx_state prev_state;
655 prev_state = exception_enter();
656 math_error(regs, error_code, X86_TRAP_XF);
657 exception_exit(prev_state);
661 do_spurious_interrupt_bug(struct pt_regs *regs, long error_code)
663 conditional_sti(regs);
665 /* No need to warn about this any longer. */
666 pr_info("Ignoring P6 Local APIC Spurious Interrupt Bug...\n");
670 asmlinkage __visible void __attribute__((weak)) smp_thermal_interrupt(void)
674 asmlinkage __visible void __attribute__((weak)) smp_threshold_interrupt(void)
679 * 'math_state_restore()' saves the current math information in the
680 * old math state array, and gets the new ones from the current task
682 * Careful.. There are problems with IBM-designed IRQ13 behaviour.
683 * Don't touch unless you *really* know how it works.
685 * Must be called with kernel preemption disabled (eg with local
686 * local interrupts as in the case of do_device_not_available).
688 void math_state_restore(void)
690 struct task_struct *tsk = current;
692 if (!tsk_used_math(tsk)) {
695 * does a slab alloc which can sleep
701 do_group_exit(SIGKILL);
707 __thread_fpu_begin(tsk);
710 * Paranoid restore. send a SIGSEGV if we fail to restore the state.
712 if (unlikely(restore_fpu_checking(tsk))) {
714 force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
718 tsk->thread.fpu_counter++;
720 EXPORT_SYMBOL_GPL(math_state_restore);
723 do_device_not_available(struct pt_regs *regs, long error_code)
725 enum ctx_state prev_state;
727 prev_state = exception_enter();
728 BUG_ON(use_eager_fpu());
730 #ifdef CONFIG_MATH_EMULATION
731 if (read_cr0() & X86_CR0_EM) {
732 struct math_emu_info info = { };
734 conditional_sti(regs);
738 exception_exit(prev_state);
742 math_state_restore(); /* interrupts still off */
744 conditional_sti(regs);
746 exception_exit(prev_state);
748 NOKPROBE_SYMBOL(do_device_not_available);
751 dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
754 enum ctx_state prev_state;
756 prev_state = exception_enter();
759 info.si_signo = SIGILL;
761 info.si_code = ILL_BADSTK;
763 if (notify_die(DIE_TRAP, "iret exception", regs, error_code,
764 X86_TRAP_IRET, SIGILL) != NOTIFY_STOP) {
765 do_trap(X86_TRAP_IRET, SIGILL, "iret exception", regs, error_code,
768 exception_exit(prev_state);
772 /* Set of traps needed for early debugging. */
773 void __init early_trap_init(void)
775 set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
776 /* int3 can be called from all */
777 set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
779 set_intr_gate(X86_TRAP_PF, page_fault);
781 load_idt(&idt_descr);
784 void __init early_trap_pf_init(void)
787 set_intr_gate(X86_TRAP_PF, page_fault);
791 void __init trap_init(void)
796 void __iomem *p = early_ioremap(0x0FFFD9, 4);
798 if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))
803 set_intr_gate(X86_TRAP_DE, divide_error);
804 set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK);
805 /* int4 can be called from all */
806 set_system_intr_gate(X86_TRAP_OF, &overflow);
807 set_intr_gate(X86_TRAP_BR, bounds);
808 set_intr_gate(X86_TRAP_UD, invalid_op);
809 set_intr_gate(X86_TRAP_NM, device_not_available);
811 set_task_gate(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS);
813 set_intr_gate_ist(X86_TRAP_DF, &double_fault, DOUBLEFAULT_STACK);
815 set_intr_gate(X86_TRAP_OLD_MF, coprocessor_segment_overrun);
816 set_intr_gate(X86_TRAP_TS, invalid_TSS);
817 set_intr_gate(X86_TRAP_NP, segment_not_present);
818 set_intr_gate(X86_TRAP_SS, stack_segment);
819 set_intr_gate(X86_TRAP_GP, general_protection);
820 set_intr_gate(X86_TRAP_SPURIOUS, spurious_interrupt_bug);
821 set_intr_gate(X86_TRAP_MF, coprocessor_error);
822 set_intr_gate(X86_TRAP_AC, alignment_check);
823 #ifdef CONFIG_X86_MCE
824 set_intr_gate_ist(X86_TRAP_MC, &machine_check, MCE_STACK);
826 set_intr_gate(X86_TRAP_XF, simd_coprocessor_error);
828 /* Reserve all the builtin and the syscall vector: */
829 for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)
830 set_bit(i, used_vectors);
832 #ifdef CONFIG_IA32_EMULATION
833 set_system_intr_gate(IA32_SYSCALL_VECTOR, ia32_syscall);
834 set_bit(IA32_SYSCALL_VECTOR, used_vectors);
838 set_system_trap_gate(SYSCALL_VECTOR, &system_call);
839 set_bit(SYSCALL_VECTOR, used_vectors);
843 * Set the IDT descriptor to a fixed read-only location, so that the
844 * "sidt" instruction will not leak the location of the kernel, and
845 * to defend the IDT against arbitrary memory write vulnerabilities.
846 * It will be reloaded in cpu_init() */
847 __set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);
848 idt_descr.address = fix_to_virt(FIX_RO_IDT);
851 * Should be a barrier for any external CPU state:
855 x86_init.irqs.trap_init();
858 memcpy(&debug_idt_table, &idt_table, IDT_ENTRIES * 16);
859 set_nmi_gate(X86_TRAP_DB, &debug);
860 set_nmi_gate(X86_TRAP_BP, &int3);