2 * linux/arch/x86_64/entry.S
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 * Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
6 * Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
8 * entry.S contains the system-call and fault low-level handling routines.
10 * Some of this is documented in Documentation/x86/entry_64.txt
12 * A note on terminology:
13 * - iret frame: Architecture defined interrupt frame from SS to RIP
14 * at the top of the kernel process stack.
17 * - ENTRY/END: Define functions in the symbol table.
18 * - TRACE_IRQ_*: Trace hardirq state for lock debugging.
19 * - idtentry: Define exception entry points.
21 #include <linux/linkage.h>
22 #include <asm/segment.h>
23 #include <asm/cache.h>
24 #include <asm/errno.h>
26 #include <asm/asm-offsets.h>
28 #include <asm/unistd.h>
29 #include <asm/thread_info.h>
30 #include <asm/hw_irq.h>
31 #include <asm/page_types.h>
32 #include <asm/irqflags.h>
33 #include <asm/paravirt.h>
34 #include <asm/percpu.h>
37 #include <asm/pgtable_types.h>
38 #include <linux/err.h>
40 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
41 #include <linux/elf-em.h>
42 #define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
43 #define __AUDIT_ARCH_64BIT 0x80000000
44 #define __AUDIT_ARCH_LE 0x40000000
47 .section .entry.text, "ax"
49 #ifdef CONFIG_PARAVIRT
50 ENTRY(native_usergs_sysret64)
53 ENDPROC(native_usergs_sysret64)
54 #endif /* CONFIG_PARAVIRT */
56 .macro TRACE_IRQS_IRETQ
57 #ifdef CONFIG_TRACE_IRQFLAGS
58 bt $9, EFLAGS(%rsp) /* interrupts off? */
66 * When dynamic function tracer is enabled it will add a breakpoint
67 * to all locations that it is about to modify, sync CPUs, update
68 * all the code, sync CPUs, then remove the breakpoints. In this time
69 * if lockdep is enabled, it might jump back into the debug handler
70 * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF).
72 * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to
73 * make sure the stack pointer does not get reset back to the top
74 * of the debug stack, and instead just reuses the current stack.
76 #if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS)
78 .macro TRACE_IRQS_OFF_DEBUG
79 call debug_stack_set_zero
81 call debug_stack_reset
84 .macro TRACE_IRQS_ON_DEBUG
85 call debug_stack_set_zero
87 call debug_stack_reset
90 .macro TRACE_IRQS_IRETQ_DEBUG
91 bt $9, EFLAGS(%rsp) /* interrupts off? */
98 # define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF
99 # define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON
100 # define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ
104 * 64-bit SYSCALL instruction entry. Up to 6 arguments in registers.
106 * 64-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
107 * then loads new ss, cs, and rip from previously programmed MSRs.
108 * rflags gets masked by a value from another MSR (so CLD and CLAC
109 * are not needed). SYSCALL does not save anything on the stack
110 * and does not change rsp.
112 * Registers on entry:
113 * rax system call number
115 * r11 saved rflags (note: r11 is callee-clobbered register in C ABI)
119 * r10 arg3 (needs to be moved to rcx to conform to C ABI)
122 * (note: r12-r15, rbp, rbx are callee-preserved in C ABI)
124 * Only called from user space.
126 * When user can change pt_regs->foo always force IRET. That is because
127 * it deals with uncanonical addresses better. SYSRET has trouble
128 * with them due to bugs in both AMD and Intel CPUs.
131 ENTRY(entry_SYSCALL_64)
133 * Interrupts are off on entry.
134 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
135 * it is too small to ever cause noticeable irq latency.
139 * A hypervisor implementation might want to use a label
140 * after the swapgs, so that it can do the swapgs
141 * for the guest and jump here on syscall.
143 GLOBAL(entry_SYSCALL_64_after_swapgs)
145 movq %rsp, PER_CPU_VAR(rsp_scratch)
146 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
148 /* Construct struct pt_regs on stack */
149 pushq $__USER_DS /* pt_regs->ss */
150 pushq PER_CPU_VAR(rsp_scratch) /* pt_regs->sp */
152 * Re-enable interrupts.
153 * We use 'rsp_scratch' as a scratch space, hence irq-off block above
154 * must execute atomically in the face of possible interrupt-driven
155 * task preemption. We must enable interrupts only after we're done
156 * with using rsp_scratch:
158 ENABLE_INTERRUPTS(CLBR_NONE)
159 pushq %r11 /* pt_regs->flags */
160 pushq $__USER_CS /* pt_regs->cs */
161 pushq %rcx /* pt_regs->ip */
162 pushq %rax /* pt_regs->orig_ax */
163 pushq %rdi /* pt_regs->di */
164 pushq %rsi /* pt_regs->si */
165 pushq %rdx /* pt_regs->dx */
166 pushq %rcx /* pt_regs->cx */
167 pushq $-ENOSYS /* pt_regs->ax */
168 pushq %r8 /* pt_regs->r8 */
169 pushq %r9 /* pt_regs->r9 */
170 pushq %r10 /* pt_regs->r10 */
171 pushq %r11 /* pt_regs->r11 */
172 sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */
174 testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
176 entry_SYSCALL_64_fastpath:
177 #if __SYSCALL_MASK == ~0
178 cmpq $__NR_syscall_max, %rax
180 andl $__SYSCALL_MASK, %eax
181 cmpl $__NR_syscall_max, %eax
183 ja 1f /* return -ENOSYS (already in pt_regs->ax) */
185 call *sys_call_table(, %rax, 8)
189 * Syscall return path ending with SYSRET (fast path).
190 * Has incompletely filled pt_regs.
194 * We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
195 * it is too small to ever cause noticeable irq latency.
197 DISABLE_INTERRUPTS(CLBR_NONE)
200 * We must check ti flags with interrupts (or at least preemption)
201 * off because we must *never* return to userspace without
202 * processing exit work that is enqueued if we're preempted here.
203 * In particular, returning to userspace with any of the one-shot
204 * flags (TIF_NOTIFY_RESUME, TIF_USER_RETURN_NOTIFY, etc) set is
207 testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
208 jnz int_ret_from_sys_call_irqs_off /* Go to the slow path */
210 RESTORE_C_REGS_EXCEPT_RCX_R11
212 movq EFLAGS(%rsp), %r11
215 * 64-bit SYSRET restores rip from rcx,
216 * rflags from r11 (but RF and VM bits are forced to 0),
217 * cs and ss are loaded from MSRs.
218 * Restoration of rflags re-enables interrupts.
220 * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
221 * descriptor is not reinitialized. This means that we should
222 * avoid SYSRET with SS == NULL, which could happen if we schedule,
223 * exit the kernel, and re-enter using an interrupt vector. (All
224 * interrupt entries on x86_64 set SS to NULL.) We prevent that
225 * from happening by reloading SS in __switch_to. (Actually
226 * detecting the failure in 64-bit userspace is tricky but can be
231 GLOBAL(int_ret_from_sys_call_irqs_off)
233 ENABLE_INTERRUPTS(CLBR_NONE)
234 jmp int_ret_from_sys_call
236 /* Do syscall entry tracing */
239 movl $AUDIT_ARCH_X86_64, %esi
240 call syscall_trace_enter_phase1
242 jnz tracesys_phase2 /* if needed, run the slow path */
243 RESTORE_C_REGS_EXCEPT_RAX /* else restore clobbered regs */
244 movq ORIG_RAX(%rsp), %rax
245 jmp entry_SYSCALL_64_fastpath /* and return to the fast path */
250 movl $AUDIT_ARCH_X86_64, %esi
252 call syscall_trace_enter_phase2
255 * Reload registers from stack in case ptrace changed them.
256 * We don't reload %rax because syscall_trace_entry_phase2() returned
257 * the value it wants us to use in the table lookup.
259 RESTORE_C_REGS_EXCEPT_RAX
261 #if __SYSCALL_MASK == ~0
262 cmpq $__NR_syscall_max, %rax
264 andl $__SYSCALL_MASK, %eax
265 cmpl $__NR_syscall_max, %eax
267 ja 1f /* return -ENOSYS (already in pt_regs->ax) */
268 movq %r10, %rcx /* fixup for C */
269 call *sys_call_table(, %rax, 8)
272 /* Use IRET because user could have changed pt_regs->foo */
275 * Syscall return path ending with IRET.
276 * Has correct iret frame.
278 GLOBAL(int_ret_from_sys_call)
281 call syscall_return_slowpath /* returns with IRQs disabled */
283 TRACE_IRQS_IRETQ /* we're about to change IF */
286 * Try to use SYSRET instead of IRET if we're returning to
287 * a completely clean 64-bit userspace context.
291 cmpq %rcx, %r11 /* RCX == RIP */
292 jne opportunistic_sysret_failed
295 * On Intel CPUs, SYSRET with non-canonical RCX/RIP will #GP
296 * in kernel space. This essentially lets the user take over
297 * the kernel, since userspace controls RSP.
299 * If width of "canonical tail" ever becomes variable, this will need
300 * to be updated to remain correct on both old and new CPUs.
302 .ifne __VIRTUAL_MASK_SHIFT - 47
303 .error "virtual address width changed -- SYSRET checks need update"
306 /* Change top 16 bits to be the sign-extension of 47th bit */
307 shl $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
308 sar $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
310 /* If this changed %rcx, it was not canonical */
312 jne opportunistic_sysret_failed
314 cmpq $__USER_CS, CS(%rsp) /* CS must match SYSRET */
315 jne opportunistic_sysret_failed
318 cmpq %r11, EFLAGS(%rsp) /* R11 == RFLAGS */
319 jne opportunistic_sysret_failed
322 * SYSRET can't restore RF. SYSRET can restore TF, but unlike IRET,
323 * restoring TF results in a trap from userspace immediately after
324 * SYSRET. This would cause an infinite loop whenever #DB happens
325 * with register state that satisfies the opportunistic SYSRET
326 * conditions. For example, single-stepping this user code:
328 * movq $stuck_here, %rcx
333 * would never get past 'stuck_here'.
335 testq $(X86_EFLAGS_RF|X86_EFLAGS_TF), %r11
336 jnz opportunistic_sysret_failed
338 /* nothing to check for RSP */
340 cmpq $__USER_DS, SS(%rsp) /* SS must match SYSRET */
341 jne opportunistic_sysret_failed
344 * We win! This label is here just for ease of understanding
345 * perf profiles. Nothing jumps here.
347 syscall_return_via_sysret:
348 /* rcx and r11 are already restored (see code above) */
349 RESTORE_C_REGS_EXCEPT_RCX_R11
353 opportunistic_sysret_failed:
355 jmp restore_c_regs_and_iret
356 END(entry_SYSCALL_64)
359 .macro FORK_LIKE func
375 /* exec failed, can use fast SYSRET code path in this case */
378 /* must use IRET code path (pt_regs->cs may have changed) */
382 jmp int_ret_from_sys_call
385 * Remaining execve stubs are only 7 bytes long.
386 * ENTRY() often aligns to 16 bytes, which in this case has no benefits.
389 GLOBAL(stub_execveat)
391 jmp return_from_execve
394 #if defined(CONFIG_X86_X32_ABI)
396 GLOBAL(stub_x32_execve)
397 call compat_sys_execve
398 jmp return_from_execve
401 GLOBAL(stub_x32_execveat)
402 call compat_sys_execveat
403 jmp return_from_execve
404 END(stub_x32_execveat)
408 * sigreturn is special because it needs to restore all registers on return.
409 * This cannot be done with SYSRET, so use the IRET return path instead.
411 ENTRY(stub_rt_sigreturn)
413 * SAVE_EXTRA_REGS result is not normally needed:
414 * sigreturn overwrites all pt_regs->GPREGS.
415 * But sigreturn can fail (!), and there is no easy way to detect that.
416 * To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
417 * we SAVE_EXTRA_REGS here.
420 call sys_rt_sigreturn
425 jmp int_ret_from_sys_call
426 END(stub_rt_sigreturn)
428 #ifdef CONFIG_X86_X32_ABI
429 ENTRY(stub_x32_rt_sigreturn)
431 call sys32_x32_rt_sigreturn
433 END(stub_x32_rt_sigreturn)
437 * A newly forked process directly context switches into this address.
439 * rdi: prev task we switched from
443 LOCK ; btr $TIF_FORK, TI_flags(%r8)
446 popfq /* reset kernel eflags */
448 call schedule_tail /* rdi: 'prev' task parameter */
452 testb $3, CS(%rsp) /* from kernel_thread? */
455 * By the time we get here, we have no idea whether our pt_regs,
456 * ti flags, and ti status came from the 64-bit SYSCALL fast path,
457 * the slow path, or one of the 32-bit compat paths.
458 * Use IRET code path to return, since it can safely handle
461 jnz int_ret_from_sys_call
464 * We came from kernel_thread
465 * nb: we depend on RESTORE_EXTRA_REGS above
471 jmp int_ret_from_sys_call
475 * Build the entry stubs with some assembler magic.
476 * We pack 1 stub into every 8-byte block.
479 ENTRY(irq_entries_start)
480 vector=FIRST_EXTERNAL_VECTOR
481 .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
482 pushq $(~vector+0x80) /* Note: always in signed byte range */
487 END(irq_entries_start)
490 * Interrupt entry/exit.
492 * Interrupt entry points save only callee clobbered registers in fast path.
494 * Entry runs with interrupts off.
497 /* 0(%rsp): ~(interrupt number) */
498 .macro interrupt func
500 ALLOC_PT_GPREGS_ON_STACK
508 * IRQ from user mode. Switch to kernel gsbase and inform context
509 * tracking that we're in kernel mode.
514 * We need to tell lockdep that IRQs are off. We can't do this until
515 * we fix gsbase, and we should do it before enter_from_user_mode
516 * (which can take locks). Since TRACE_IRQS_OFF idempotent,
517 * the simplest way to handle it is to just call it twice if
518 * we enter from user mode. There's no reason to optimize this since
519 * TRACE_IRQS_OFF is a no-op if lockdep is off.
523 #ifdef CONFIG_CONTEXT_TRACKING
524 call enter_from_user_mode
529 * Save previous stack pointer, optionally switch to interrupt stack.
530 * irq_count is used to check if a CPU is already on an interrupt stack
531 * or not. While this is essentially redundant with preempt_count it is
532 * a little cheaper to use a separate counter in the PDA (short of
533 * moving irq_enter into assembly, which would be too much work)
536 incl PER_CPU_VAR(irq_count)
537 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp
539 /* We entered an interrupt context - irqs are off: */
542 call \func /* rdi points to pt_regs */
546 * The interrupt stubs push (~vector+0x80) onto the stack and
547 * then jump to common_interrupt.
549 .p2align CONFIG_X86_L1_CACHE_SHIFT
552 addq $-0x80, (%rsp) /* Adjust vector to [-256, -1] range */
554 /* 0(%rsp): old RSP */
556 DISABLE_INTERRUPTS(CLBR_NONE)
558 decl PER_CPU_VAR(irq_count)
560 /* Restore saved previous stack */
566 /* Interrupt came from user space */
569 call prepare_exit_to_usermode
572 jmp restore_regs_and_iret
574 /* Returning to kernel space */
576 #ifdef CONFIG_PREEMPT
577 /* Interrupts are off */
578 /* Check if we need preemption */
579 bt $9, EFLAGS(%rsp) /* were interrupts off? */
581 0: cmpl $0, PER_CPU_VAR(__preempt_count)
583 call preempt_schedule_irq
588 * The iretq could re-enable interrupts:
593 * At this label, code paths which return to kernel and to user,
594 * which come from interrupts/exception and from syscalls, merge.
596 GLOBAL(restore_regs_and_iret)
598 restore_c_regs_and_iret:
600 REMOVE_PT_GPREGS_FROM_STACK 8
605 * Are we returning to a stack segment from the LDT? Note: in
606 * 64-bit mode SS:RSP on the exception stack is always valid.
608 #ifdef CONFIG_X86_ESPFIX64
609 testb $4, (SS-RIP)(%rsp)
610 jnz native_irq_return_ldt
613 .global native_irq_return_iret
614 native_irq_return_iret:
616 * This may fault. Non-paranoid faults on return to userspace are
617 * handled by fixup_bad_iret. These include #SS, #GP, and #NP.
618 * Double-faults due to espfix64 are handled in do_double_fault.
619 * Other faults here are fatal.
623 #ifdef CONFIG_X86_ESPFIX64
624 native_irq_return_ldt:
628 movq PER_CPU_VAR(espfix_waddr), %rdi
629 movq %rax, (0*8)(%rdi) /* RAX */
630 movq (2*8)(%rsp), %rax /* RIP */
631 movq %rax, (1*8)(%rdi)
632 movq (3*8)(%rsp), %rax /* CS */
633 movq %rax, (2*8)(%rdi)
634 movq (4*8)(%rsp), %rax /* RFLAGS */
635 movq %rax, (3*8)(%rdi)
636 movq (6*8)(%rsp), %rax /* SS */
637 movq %rax, (5*8)(%rdi)
638 movq (5*8)(%rsp), %rax /* RSP */
639 movq %rax, (4*8)(%rdi)
640 andl $0xffff0000, %eax
642 orq PER_CPU_VAR(espfix_stack), %rax
646 jmp native_irq_return_iret
648 END(common_interrupt)
653 .macro apicinterrupt3 num sym do_sym
663 #ifdef CONFIG_TRACING
664 #define trace(sym) trace_##sym
665 #define smp_trace(sym) smp_trace_##sym
667 .macro trace_apicinterrupt num sym
668 apicinterrupt3 \num trace(\sym) smp_trace(\sym)
671 .macro trace_apicinterrupt num sym do_sym
675 .macro apicinterrupt num sym do_sym
676 apicinterrupt3 \num \sym \do_sym
677 trace_apicinterrupt \num \sym
681 apicinterrupt3 IRQ_MOVE_CLEANUP_VECTOR irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
682 apicinterrupt3 REBOOT_VECTOR reboot_interrupt smp_reboot_interrupt
686 apicinterrupt3 UV_BAU_MESSAGE uv_bau_message_intr1 uv_bau_message_interrupt
689 apicinterrupt LOCAL_TIMER_VECTOR apic_timer_interrupt smp_apic_timer_interrupt
690 apicinterrupt X86_PLATFORM_IPI_VECTOR x86_platform_ipi smp_x86_platform_ipi
692 #ifdef CONFIG_HAVE_KVM
693 apicinterrupt3 POSTED_INTR_VECTOR kvm_posted_intr_ipi smp_kvm_posted_intr_ipi
694 apicinterrupt3 POSTED_INTR_WAKEUP_VECTOR kvm_posted_intr_wakeup_ipi smp_kvm_posted_intr_wakeup_ipi
697 #ifdef CONFIG_X86_MCE_THRESHOLD
698 apicinterrupt THRESHOLD_APIC_VECTOR threshold_interrupt smp_threshold_interrupt
701 #ifdef CONFIG_X86_MCE_AMD
702 apicinterrupt DEFERRED_ERROR_VECTOR deferred_error_interrupt smp_deferred_error_interrupt
705 #ifdef CONFIG_X86_THERMAL_VECTOR
706 apicinterrupt THERMAL_APIC_VECTOR thermal_interrupt smp_thermal_interrupt
710 apicinterrupt CALL_FUNCTION_SINGLE_VECTOR call_function_single_interrupt smp_call_function_single_interrupt
711 apicinterrupt CALL_FUNCTION_VECTOR call_function_interrupt smp_call_function_interrupt
712 apicinterrupt RESCHEDULE_VECTOR reschedule_interrupt smp_reschedule_interrupt
715 apicinterrupt ERROR_APIC_VECTOR error_interrupt smp_error_interrupt
716 apicinterrupt SPURIOUS_APIC_VECTOR spurious_interrupt smp_spurious_interrupt
718 #ifdef CONFIG_IRQ_WORK
719 apicinterrupt IRQ_WORK_VECTOR irq_work_interrupt smp_irq_work_interrupt
723 * Exception entry points.
725 #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8)
727 .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
730 .if \shift_ist != -1 && \paranoid == 0
731 .error "using shift_ist requires paranoid=1"
735 PARAVIRT_ADJUST_EXCEPTION_FRAME
737 .ifeq \has_error_code
738 pushq $-1 /* ORIG_RAX: no syscall to restart */
741 ALLOC_PT_GPREGS_ON_STACK
745 testb $3, CS(%rsp) /* If coming from userspace, switch stacks */
752 /* returned flag: ebx=0: need swapgs on exit, ebx=1: don't need it */
756 TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */
762 movq %rsp, %rdi /* pt_regs pointer */
765 movq ORIG_RAX(%rsp), %rsi /* get error code */
766 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
768 xorl %esi, %esi /* no error code */
772 subq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
778 addq $EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
781 /* these procedures expect "no swapgs" flag in ebx */
790 * Paranoid entry from userspace. Switch stacks and treat it
791 * as a normal entry. This means that paranoid handlers
792 * run in real process context if user_mode(regs).
798 movq %rsp, %rdi /* pt_regs pointer */
800 movq %rax, %rsp /* switch stack */
802 movq %rsp, %rdi /* pt_regs pointer */
805 movq ORIG_RAX(%rsp), %rsi /* get error code */
806 movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
808 xorl %esi, %esi /* no error code */
813 jmp error_exit /* %ebx: no swapgs flag */
818 #ifdef CONFIG_TRACING
819 .macro trace_idtentry sym do_sym has_error_code:req
820 idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code
821 idtentry \sym \do_sym has_error_code=\has_error_code
824 .macro trace_idtentry sym do_sym has_error_code:req
825 idtentry \sym \do_sym has_error_code=\has_error_code
829 idtentry divide_error do_divide_error has_error_code=0
830 idtentry overflow do_overflow has_error_code=0
831 idtentry bounds do_bounds has_error_code=0
832 idtentry invalid_op do_invalid_op has_error_code=0
833 idtentry device_not_available do_device_not_available has_error_code=0
834 idtentry double_fault do_double_fault has_error_code=1 paranoid=2
835 idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0
836 idtentry invalid_TSS do_invalid_TSS has_error_code=1
837 idtentry segment_not_present do_segment_not_present has_error_code=1
838 idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0
839 idtentry coprocessor_error do_coprocessor_error has_error_code=0
840 idtentry alignment_check do_alignment_check has_error_code=1
841 idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0
845 * Reload gs selector with exception handling
848 ENTRY(native_load_gs_index)
850 DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
854 2: mfence /* workaround */
858 END(native_load_gs_index)
860 _ASM_EXTABLE(gs_change, bad_gs)
861 .section .fixup, "ax"
862 /* running with kernelgs */
864 SWAPGS /* switch back to user gs */
870 /* Call softirq on interrupt stack. Interrupts are off. */
871 ENTRY(do_softirq_own_stack)
874 incl PER_CPU_VAR(irq_count)
875 cmove PER_CPU_VAR(irq_stack_ptr), %rsp
876 push %rbp /* frame pointer backlink */
879 decl PER_CPU_VAR(irq_count)
881 END(do_softirq_own_stack)
884 idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0
887 * A note on the "critical region" in our callback handler.
888 * We want to avoid stacking callback handlers due to events occurring
889 * during handling of the last event. To do this, we keep events disabled
890 * until we've done all processing. HOWEVER, we must enable events before
891 * popping the stack frame (can't be done atomically) and so it would still
892 * be possible to get enough handler activations to overflow the stack.
893 * Although unlikely, bugs of that kind are hard to track down, so we'd
894 * like to avoid the possibility.
895 * So, on entry to the handler we detect whether we interrupted an
896 * existing activation in its critical region -- if so, we pop the current
897 * activation and restart the handler using the previous one.
899 ENTRY(xen_do_hypervisor_callback) /* do_hypervisor_callback(struct *pt_regs) */
902 * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
903 * see the correct pointer to the pt_regs
905 movq %rdi, %rsp /* we don't return, adjust the stack frame */
906 11: incl PER_CPU_VAR(irq_count)
908 cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp
909 pushq %rbp /* frame pointer backlink */
910 call xen_evtchn_do_upcall
912 decl PER_CPU_VAR(irq_count)
913 #ifndef CONFIG_PREEMPT
914 call xen_maybe_preempt_hcall
917 END(xen_do_hypervisor_callback)
920 * Hypervisor uses this for application faults while it executes.
921 * We get here for two reasons:
922 * 1. Fault while reloading DS, ES, FS or GS
923 * 2. Fault while executing IRET
924 * Category 1 we do not need to fix up as Xen has already reloaded all segment
925 * registers that could be reloaded and zeroed the others.
926 * Category 2 we fix up by killing the current process. We cannot use the
927 * normal Linux return path in this case because if we use the IRET hypercall
928 * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
929 * We distinguish between categories by comparing each saved segment register
930 * with its current contents: any discrepancy means we in category 1.
932 ENTRY(xen_failsafe_callback)
945 /* All segments match their saved values => Category 2 (Bad IRET). */
952 jmp general_protection
953 1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
957 pushq $-1 /* orig_ax = -1 => not a system call */
958 ALLOC_PT_GPREGS_ON_STACK
962 END(xen_failsafe_callback)
964 apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
965 xen_hvm_callback_vector xen_evtchn_do_upcall
967 #endif /* CONFIG_XEN */
969 #if IS_ENABLED(CONFIG_HYPERV)
970 apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
971 hyperv_callback_vector hyperv_vector_handler
972 #endif /* CONFIG_HYPERV */
974 idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
975 idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
976 idtentry stack_segment do_stack_segment has_error_code=1
979 idtentry xen_debug do_debug has_error_code=0
980 idtentry xen_int3 do_int3 has_error_code=0
981 idtentry xen_stack_segment do_stack_segment has_error_code=1
984 idtentry general_protection do_general_protection has_error_code=1
985 trace_idtentry page_fault do_page_fault has_error_code=1
987 #ifdef CONFIG_KVM_GUEST
988 idtentry async_page_fault do_async_page_fault has_error_code=1
991 #ifdef CONFIG_X86_MCE
992 idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
996 * Save all registers in pt_regs, and switch gs if needed.
997 * Use slow, but surefire "are we in kernel?" check.
998 * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
1000 ENTRY(paranoid_entry)
1005 movl $MSR_GS_BASE, %ecx
1008 js 1f /* negative -> in kernel */
1015 * "Paranoid" exit path from exception stack. This is invoked
1016 * only on return from non-NMI IST interrupts that came
1017 * from kernel space.
1019 * We may be returning to very strange contexts (e.g. very early
1020 * in syscall entry), so checking for preemption here would
1021 * be complicated. Fortunately, we there's no good reason
1022 * to try to handle preemption here.
1024 * On entry, ebx is "no swapgs" flag (1: don't need swapgs, 0: need it)
1026 ENTRY(paranoid_exit)
1027 DISABLE_INTERRUPTS(CLBR_NONE)
1028 TRACE_IRQS_OFF_DEBUG
1029 testl %ebx, %ebx /* swapgs needed? */
1030 jnz paranoid_exit_no_swapgs
1033 jmp paranoid_exit_restore
1034 paranoid_exit_no_swapgs:
1035 TRACE_IRQS_IRETQ_DEBUG
1036 paranoid_exit_restore:
1039 REMOVE_PT_GPREGS_FROM_STACK 8
1044 * Save all registers in pt_regs, and switch gs if needed.
1045 * Return: EBX=0: came from user mode; EBX=1: otherwise
1052 testb $3, CS+8(%rsp)
1053 jz .Lerror_kernelspace
1055 .Lerror_entry_from_usermode_swapgs:
1057 * We entered from user mode or we're pretending to have entered
1058 * from user mode due to an IRET fault.
1062 .Lerror_entry_from_usermode_after_swapgs:
1064 * We need to tell lockdep that IRQs are off. We can't do this until
1065 * we fix gsbase, and we should do it before enter_from_user_mode
1066 * (which can take locks).
1069 #ifdef CONFIG_CONTEXT_TRACKING
1070 call enter_from_user_mode
1079 * There are two places in the kernel that can potentially fault with
1080 * usergs. Handle them here. B stepping K8s sometimes report a
1081 * truncated RIP for IRET exceptions returning to compat mode. Check
1082 * for these here too.
1084 .Lerror_kernelspace:
1086 leaq native_irq_return_iret(%rip), %rcx
1087 cmpq %rcx, RIP+8(%rsp)
1089 movl %ecx, %eax /* zero extend */
1090 cmpq %rax, RIP+8(%rsp)
1092 cmpq $gs_change, RIP+8(%rsp)
1093 jne .Lerror_entry_done
1096 * hack: gs_change can fail with user gsbase. If this happens, fix up
1097 * gsbase and proceed. We'll fix up the exception and land in
1098 * gs_change's error handler with kernel gsbase.
1100 jmp .Lerror_entry_from_usermode_swapgs
1103 /* Fix truncated RIP */
1104 movq %rcx, RIP+8(%rsp)
1109 * We came from an IRET to user mode, so we have user gsbase.
1110 * Switch to kernel gsbase:
1115 * Pretend that the exception came from user mode: set up pt_regs
1116 * as if we faulted immediately after IRET and clear EBX so that
1117 * error_exit knows that we will be returning to user mode.
1123 jmp .Lerror_entry_from_usermode_after_swapgs
1128 * On entry, EBS is a "return to kernel mode" flag:
1129 * 1: already in kernel mode, don't need SWAPGS
1130 * 0: user gsbase is loaded, we need SWAPGS and standard preparation for return to usermode
1134 DISABLE_INTERRUPTS(CLBR_NONE)
1141 /* Runs on exception stack */
1144 * Fix up the exception frame if we're on Xen.
1145 * PARAVIRT_ADJUST_EXCEPTION_FRAME is guaranteed to push at most
1146 * one value to the stack on native, so it may clobber the rdx
1147 * scratch slot, but it won't clobber any of the important
1150 * Xen is a different story, because the Xen frame itself overlaps
1151 * the "NMI executing" variable.
1153 PARAVIRT_ADJUST_EXCEPTION_FRAME
1156 * We allow breakpoints in NMIs. If a breakpoint occurs, then
1157 * the iretq it performs will take us out of NMI context.
1158 * This means that we can have nested NMIs where the next
1159 * NMI is using the top of the stack of the previous NMI. We
1160 * can't let it execute because the nested NMI will corrupt the
1161 * stack of the previous NMI. NMI handlers are not re-entrant
1164 * To handle this case we do the following:
1165 * Check the a special location on the stack that contains
1166 * a variable that is set when NMIs are executing.
1167 * The interrupted task's stack is also checked to see if it
1169 * If the variable is not set and the stack is not the NMI
1171 * o Set the special variable on the stack
1172 * o Copy the interrupt frame into an "outermost" location on the
1174 * o Copy the interrupt frame into an "iret" location on the stack
1175 * o Continue processing the NMI
1176 * If the variable is set or the previous stack is the NMI stack:
1177 * o Modify the "iret" location to jump to the repeat_nmi
1178 * o return back to the first NMI
1180 * Now on exit of the first NMI, we first clear the stack variable
1181 * The NMI stack will tell any nested NMIs at that point that it is
1182 * nested. Then we pop the stack normally with iret, and if there was
1183 * a nested NMI that updated the copy interrupt stack frame, a
1184 * jump will be made to the repeat_nmi code that will handle the second
1187 * However, espfix prevents us from directly returning to userspace
1188 * with a single IRET instruction. Similarly, IRET to user mode
1189 * can fault. We therefore handle NMIs from user space like
1190 * other IST entries.
1193 /* Use %rdx as our temp variable throughout */
1196 testb $3, CS-RIP+8(%rsp)
1197 jz .Lnmi_from_kernel
1200 * NMI from user mode. We need to run on the thread stack, but we
1201 * can't go through the normal entry paths: NMIs are masked, and
1202 * we don't want to enable interrupts, because then we'll end
1203 * up in an awkward situation in which IRQs are on but NMIs
1206 * We also must not push anything to the stack before switching
1207 * stacks lest we corrupt the "NMI executing" variable.
1213 movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
1214 pushq 5*8(%rdx) /* pt_regs->ss */
1215 pushq 4*8(%rdx) /* pt_regs->rsp */
1216 pushq 3*8(%rdx) /* pt_regs->flags */
1217 pushq 2*8(%rdx) /* pt_regs->cs */
1218 pushq 1*8(%rdx) /* pt_regs->rip */
1219 pushq $-1 /* pt_regs->orig_ax */
1220 pushq %rdi /* pt_regs->di */
1221 pushq %rsi /* pt_regs->si */
1222 pushq (%rdx) /* pt_regs->dx */
1223 pushq %rcx /* pt_regs->cx */
1224 pushq %rax /* pt_regs->ax */
1225 pushq %r8 /* pt_regs->r8 */
1226 pushq %r9 /* pt_regs->r9 */
1227 pushq %r10 /* pt_regs->r10 */
1228 pushq %r11 /* pt_regs->r11 */
1229 pushq %rbx /* pt_regs->rbx */
1230 pushq %rbp /* pt_regs->rbp */
1231 pushq %r12 /* pt_regs->r12 */
1232 pushq %r13 /* pt_regs->r13 */
1233 pushq %r14 /* pt_regs->r14 */
1234 pushq %r15 /* pt_regs->r15 */
1237 * At this point we no longer need to worry about stack damage
1238 * due to nesting -- we're on the normal thread stack and we're
1239 * done with the NMI stack.
1247 * Return back to user mode. We must *not* do the normal exit
1248 * work, because we don't want to enable interrupts. Fortunately,
1249 * do_nmi doesn't modify pt_regs.
1252 jmp restore_c_regs_and_iret
1256 * Here's what our stack frame will look like:
1257 * +---------------------------------------------------------+
1259 * | original Return RSP |
1260 * | original RFLAGS |
1263 * +---------------------------------------------------------+
1264 * | temp storage for rdx |
1265 * +---------------------------------------------------------+
1266 * | "NMI executing" variable |
1267 * +---------------------------------------------------------+
1268 * | iret SS } Copied from "outermost" frame |
1269 * | iret Return RSP } on each loop iteration; overwritten |
1270 * | iret RFLAGS } by a nested NMI to force another |
1271 * | iret CS } iteration if needed. |
1273 * +---------------------------------------------------------+
1274 * | outermost SS } initialized in first_nmi; |
1275 * | outermost Return RSP } will not be changed before |
1276 * | outermost RFLAGS } NMI processing is done. |
1277 * | outermost CS } Copied to "iret" frame on each |
1278 * | outermost RIP } iteration. |
1279 * +---------------------------------------------------------+
1281 * +---------------------------------------------------------+
1283 * The "original" frame is used by hardware. Before re-enabling
1284 * NMIs, we need to be done with it, and we need to leave enough
1285 * space for the asm code here.
1287 * We return by executing IRET while RSP points to the "iret" frame.
1288 * That will either return for real or it will loop back into NMI
1291 * The "outermost" frame is copied to the "iret" frame on each
1292 * iteration of the loop, so each iteration starts with the "iret"
1293 * frame pointing to the final return target.
1297 * Determine whether we're a nested NMI.
1299 * If we interrupted kernel code between repeat_nmi and
1300 * end_repeat_nmi, then we are a nested NMI. We must not
1301 * modify the "iret" frame because it's being written by
1302 * the outer NMI. That's okay; the outer NMI handler is
1303 * about to about to call do_nmi anyway, so we can just
1304 * resume the outer NMI.
1307 movq $repeat_nmi, %rdx
1310 movq $end_repeat_nmi, %rdx
1316 * Now check "NMI executing". If it's set, then we're nested.
1317 * This will not detect if we interrupted an outer NMI just
1324 * Now test if the previous stack was an NMI stack. This covers
1325 * the case where we interrupt an outer NMI after it clears
1326 * "NMI executing" but before IRET. We need to be careful, though:
1327 * there is one case in which RSP could point to the NMI stack
1328 * despite there being no NMI active: naughty userspace controls
1329 * RSP at the very beginning of the SYSCALL targets. We can
1330 * pull a fast one on naughty userspace, though: we program
1331 * SYSCALL to mask DF, so userspace cannot cause DF to be set
1332 * if it controls the kernel's RSP. We set DF before we clear
1336 /* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */
1337 cmpq %rdx, 4*8(%rsp)
1338 /* If the stack pointer is above the NMI stack, this is a normal NMI */
1341 subq $EXCEPTION_STKSZ, %rdx
1342 cmpq %rdx, 4*8(%rsp)
1343 /* If it is below the NMI stack, it is a normal NMI */
1346 /* Ah, it is within the NMI stack. */
1348 testb $(X86_EFLAGS_DF >> 8), (3*8 + 1)(%rsp)
1349 jz first_nmi /* RSP was user controlled. */
1351 /* This is a nested NMI. */
1355 * Modify the "iret" frame to point to repeat_nmi, forcing another
1356 * iteration of NMI handling.
1359 leaq -10*8(%rsp), %rdx
1366 /* Put stack back */
1372 /* We are returning to kernel mode, so this cannot result in a fault. */
1379 /* Make room for "NMI executing". */
1382 /* Leave room for the "iret" frame */
1385 /* Copy the "original" frame to the "outermost" frame */
1390 /* Everything up to here is safe from nested NMIs */
1392 #ifdef CONFIG_DEBUG_ENTRY
1394 * For ease of testing, unmask NMIs right away. Disabled by
1395 * default because IRET is very expensive.
1398 pushq %rsp /* RSP (minus 8 because of the previous push) */
1399 addq $8, (%rsp) /* Fix up RSP */
1401 pushq $__KERNEL_CS /* CS */
1403 INTERRUPT_RETURN /* continues at repeat_nmi below */
1409 * If there was a nested NMI, the first NMI's iret will return
1410 * here. But NMIs are still enabled and we can take another
1411 * nested NMI. The nested NMI checks the interrupted RIP to see
1412 * if it is between repeat_nmi and end_repeat_nmi, and if so
1413 * it will just return, as we are about to repeat an NMI anyway.
1414 * This makes it safe to copy to the stack frame that a nested
1417 * RSP is pointing to "outermost RIP". gsbase is unknown, but, if
1418 * we're repeating an NMI, gsbase has the same value that it had on
1419 * the first iteration. paranoid_entry will load the kernel
1420 * gsbase if needed before we call do_nmi. "NMI executing"
1423 movq $1, 10*8(%rsp) /* Set "NMI executing". */
1426 * Copy the "outermost" frame to the "iret" frame. NMIs that nest
1427 * here must not modify the "iret" frame while we're writing to
1428 * it or it will end up containing garbage.
1438 * Everything below this point can be preempted by a nested NMI.
1439 * If this happens, then the inner NMI will change the "iret"
1440 * frame to point back to repeat_nmi.
1442 pushq $-1 /* ORIG_RAX: no syscall to restart */
1443 ALLOC_PT_GPREGS_ON_STACK
1446 * Use paranoid_entry to handle SWAPGS, but no need to use paranoid_exit
1447 * as we should not be calling schedule in NMI context.
1448 * Even with normal interrupts enabled. An NMI should not be
1449 * setting NEED_RESCHED or anything that normal interrupts and
1450 * exceptions might do.
1454 /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
1459 testl %ebx, %ebx /* swapgs needed? */
1467 /* Point RSP at the "iret" frame. */
1468 REMOVE_PT_GPREGS_FROM_STACK 6*8
1471 * Clear "NMI executing". Set DF first so that we can easily
1472 * distinguish the remaining code between here and IRET from
1473 * the SYSCALL entry and exit paths. On a native kernel, we
1474 * could just inspect RIP, but, on paravirt kernels,
1475 * INTERRUPT_RETURN can translate into a jump into a
1479 movq $0, 5*8(%rsp) /* clear "NMI executing" */
1482 * INTERRUPT_RETURN reads the "iret" frame and exits the NMI
1483 * stack in a single instruction. We are returning to kernel
1484 * mode, so this cannot result in a fault.
1489 ENTRY(ignore_sysret)