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>
10 * entry.S contains the system-call and fault low-level handling routines.
12 * Some of this is documented in Documentation/x86/entry_64.txt
14 * NOTE: This code handles signal-recognition, which happens every time
15 * after an interrupt and after each system call.
17 * Normal syscalls and interrupts don't save a full stack frame, this is
18 * only done for syscall tracing, signals or fork/exec et.al.
20 * A note on terminology:
21 * - top of stack: Architecture defined interrupt frame from SS to RIP
22 * at the top of the kernel process stack.
23 * - partial stack frame: partially saved registers up to R11.
24 * - full stack frame: Like partial stack frame, but all register saved.
27 * - CFI macros are used to generate dwarf2 unwind information for better
28 * backtraces. They don't change any code.
29 * - SAVE_ALL/RESTORE_ALL - Save/restore all registers
30 * - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify.
31 * There are unfortunately lots of special cases where some registers
32 * not touched. The macro is a big mess that should be cleaned up.
33 * - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS.
34 * Gives a full stack frame.
35 * - ENTRY/END Define functions in the symbol table.
36 * - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
37 * frame that is otherwise undefined after a SYSCALL
38 * - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
39 * - errorentry/paranoidentry/zeroentry - Define exception entry points.
42 #include <linux/linkage.h>
43 #include <asm/segment.h>
44 #include <asm/cache.h>
45 #include <asm/errno.h>
46 #include <asm/dwarf2.h>
47 #include <asm/calling.h>
48 #include <asm/asm-offsets.h>
50 #include <asm/unistd.h>
51 #include <asm/thread_info.h>
52 #include <asm/hw_irq.h>
53 #include <asm/page_types.h>
54 #include <asm/irqflags.h>
55 #include <asm/paravirt.h>
56 #include <asm/ftrace.h>
57 #include <asm/percpu.h>
61 #include <linux/err.h>
63 /* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
64 #include <linux/elf-em.h>
65 #define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
66 #define __AUDIT_ARCH_64BIT 0x80000000
67 #define __AUDIT_ARCH_LE 0x40000000
70 .section .entry.text, "ax"
72 #ifdef CONFIG_FUNCTION_TRACER
74 #ifdef CC_USING_FENTRY
75 # define function_hook __fentry__
77 # define function_hook mcount
80 #ifdef CONFIG_DYNAMIC_FTRACE
86 /* skip is set if stack has been adjusted */
87 .macro ftrace_caller_setup skip=0
88 MCOUNT_SAVE_FRAME \skip
90 /* Load the ftrace_ops into the 3rd parameter */
91 leaq function_trace_op, %rdx
93 /* Load ip into the first parameter */
95 subq $MCOUNT_INSN_SIZE, %rdi
96 /* Load the parent_ip into the second parameter */
97 #ifdef CC_USING_FENTRY
98 movq SS+16(%rsp), %rsi
105 /* Check if tracing was disabled (quick check) */
106 cmpl $0, function_trace_stop
110 /* regs go into 4th parameter (but make it NULL) */
119 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
120 GLOBAL(ftrace_graph_call)
128 ENTRY(ftrace_regs_caller)
129 /* Save the current flags before compare (in SS location)*/
132 /* Check if tracing was disabled (quick check) */
133 cmpl $0, function_trace_stop
134 jne ftrace_restore_flags
136 /* skip=8 to skip flags saved in SS */
137 ftrace_caller_setup 8
139 /* Save the rest of pt_regs */
148 /* Copy saved flags */
150 movq %rcx, EFLAGS(%rsp)
151 /* Kernel segments */
152 movq $__KERNEL_DS, %rcx
154 movq $__KERNEL_CS, %rcx
156 /* Stack - skipping return address */
157 leaq SS+16(%rsp), %rcx
160 /* regs go into 4th parameter */
163 GLOBAL(ftrace_regs_call)
166 /* Copy flags back to SS, to restore them */
167 movq EFLAGS(%rsp), %rax
170 /* Handlers can change the RIP */
172 movq %rax, SS+8(%rsp)
174 /* restore the rest of pt_regs */
183 /* skip=8 to skip flags saved in SS */
184 MCOUNT_RESTORE_FRAME 8
190 ftrace_restore_flags:
194 END(ftrace_regs_caller)
197 #else /* ! CONFIG_DYNAMIC_FTRACE */
200 cmpl $0, function_trace_stop
203 cmpq $ftrace_stub, ftrace_trace_function
206 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
207 cmpq $ftrace_stub, ftrace_graph_return
208 jnz ftrace_graph_caller
210 cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
211 jnz ftrace_graph_caller
221 #ifdef CC_USING_FENTRY
222 movq SS+16(%rsp), %rsi
226 subq $MCOUNT_INSN_SIZE, %rdi
228 call *ftrace_trace_function
234 #endif /* CONFIG_DYNAMIC_FTRACE */
235 #endif /* CONFIG_FUNCTION_TRACER */
237 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
238 ENTRY(ftrace_graph_caller)
241 #ifdef CC_USING_FENTRY
242 leaq SS+16(%rsp), %rdi
243 movq $0, %rdx /* No framepointers needed */
249 subq $MCOUNT_INSN_SIZE, %rsi
251 call prepare_ftrace_return
256 END(ftrace_graph_caller)
258 GLOBAL(return_to_handler)
261 /* Save the return values */
266 call ftrace_return_to_handler
276 #ifndef CONFIG_PREEMPT
277 #define retint_kernel retint_restore_args
280 #ifdef CONFIG_PARAVIRT
281 ENTRY(native_usergs_sysret64)
284 ENDPROC(native_usergs_sysret64)
285 #endif /* CONFIG_PARAVIRT */
288 .macro TRACE_IRQS_IRETQ offset=ARGOFFSET
289 #ifdef CONFIG_TRACE_IRQFLAGS
290 bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */
298 * When dynamic function tracer is enabled it will add a breakpoint
299 * to all locations that it is about to modify, sync CPUs, update
300 * all the code, sync CPUs, then remove the breakpoints. In this time
301 * if lockdep is enabled, it might jump back into the debug handler
302 * outside the updating of the IST protection. (TRACE_IRQS_ON/OFF).
304 * We need to change the IDT table before calling TRACE_IRQS_ON/OFF to
305 * make sure the stack pointer does not get reset back to the top
306 * of the debug stack, and instead just reuses the current stack.
308 #if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS)
310 .macro TRACE_IRQS_OFF_DEBUG
311 call debug_stack_set_zero
313 call debug_stack_reset
316 .macro TRACE_IRQS_ON_DEBUG
317 call debug_stack_set_zero
319 call debug_stack_reset
322 .macro TRACE_IRQS_IRETQ_DEBUG offset=ARGOFFSET
323 bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */
330 # define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF
331 # define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON
332 # define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ
336 * C code is not supposed to know about undefined top of stack. Every time
337 * a C function with an pt_regs argument is called from the SYSCALL based
338 * fast path FIXUP_TOP_OF_STACK is needed.
339 * RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
343 /* %rsp:at FRAMEEND */
344 .macro FIXUP_TOP_OF_STACK tmp offset=0
345 movq PER_CPU_VAR(old_rsp),\tmp
346 movq \tmp,RSP+\offset(%rsp)
347 movq $__USER_DS,SS+\offset(%rsp)
348 movq $__USER_CS,CS+\offset(%rsp)
349 movq $-1,RCX+\offset(%rsp)
350 movq R11+\offset(%rsp),\tmp /* get eflags */
351 movq \tmp,EFLAGS+\offset(%rsp)
354 .macro RESTORE_TOP_OF_STACK tmp offset=0
355 movq RSP+\offset(%rsp),\tmp
356 movq \tmp,PER_CPU_VAR(old_rsp)
357 movq EFLAGS+\offset(%rsp),\tmp
358 movq \tmp,R11+\offset(%rsp)
361 .macro FAKE_STACK_FRAME child_rip
362 /* push in order ss, rsp, eflags, cs, rip */
364 pushq_cfi $__KERNEL_DS /* ss */
365 /*CFI_REL_OFFSET ss,0*/
366 pushq_cfi %rax /* rsp */
368 pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_BIT1) /* eflags - interrupts on */
369 /*CFI_REL_OFFSET rflags,0*/
370 pushq_cfi $__KERNEL_CS /* cs */
371 /*CFI_REL_OFFSET cs,0*/
372 pushq_cfi \child_rip /* rip */
374 pushq_cfi %rax /* orig rax */
377 .macro UNFAKE_STACK_FRAME
379 CFI_ADJUST_CFA_OFFSET -(6*8)
383 * initial frame state for interrupts (and exceptions without error code)
385 .macro EMPTY_FRAME start=1 offset=0
389 CFI_DEF_CFA rsp,8+\offset
391 CFI_DEF_CFA_OFFSET 8+\offset
396 * initial frame state for interrupts (and exceptions without error code)
398 .macro INTR_FRAME start=1 offset=0
399 EMPTY_FRAME \start, SS+8+\offset-RIP
400 /*CFI_REL_OFFSET ss, SS+\offset-RIP*/
401 CFI_REL_OFFSET rsp, RSP+\offset-RIP
402 /*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/
403 /*CFI_REL_OFFSET cs, CS+\offset-RIP*/
404 CFI_REL_OFFSET rip, RIP+\offset-RIP
408 * initial frame state for exceptions with error code (and interrupts
409 * with vector already pushed)
411 .macro XCPT_FRAME start=1 offset=0
412 INTR_FRAME \start, RIP+\offset-ORIG_RAX
413 /*CFI_REL_OFFSET orig_rax, ORIG_RAX-ORIG_RAX*/
417 * frame that enables calling into C.
419 .macro PARTIAL_FRAME start=1 offset=0
420 XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET
421 CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET
422 CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET
423 CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET
424 CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET
425 CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET
426 CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET
427 CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET
428 CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET
429 CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET
433 * frame that enables passing a complete pt_regs to a C function.
435 .macro DEFAULT_FRAME start=1 offset=0
436 PARTIAL_FRAME \start, R11+\offset-R15
437 CFI_REL_OFFSET rbx, RBX+\offset
438 CFI_REL_OFFSET rbp, RBP+\offset
439 CFI_REL_OFFSET r12, R12+\offset
440 CFI_REL_OFFSET r13, R13+\offset
441 CFI_REL_OFFSET r14, R14+\offset
442 CFI_REL_OFFSET r15, R15+\offset
445 /* save partial stack frame */
448 /* start from rbp in pt_regs and jump over */
449 movq_cfi rdi, (RDI-RBP)
450 movq_cfi rsi, (RSI-RBP)
451 movq_cfi rdx, (RDX-RBP)
452 movq_cfi rcx, (RCX-RBP)
453 movq_cfi rax, (RAX-RBP)
454 movq_cfi r8, (R8-RBP)
455 movq_cfi r9, (R9-RBP)
456 movq_cfi r10, (R10-RBP)
457 movq_cfi r11, (R11-RBP)
459 /* Save rbp so that we can unwind from get_irq_regs() */
462 /* Save previous stack value */
465 leaq -RBP(%rsp),%rdi /* arg1 for handler */
466 testl $3, CS-RBP(%rsi)
470 * irq_count is used to check if a CPU is already on an interrupt stack
471 * or not. While this is essentially redundant with preempt_count it is
472 * a little cheaper to use a separate counter in the PDA (short of
473 * moving irq_enter into assembly, which would be too much work)
475 1: incl PER_CPU_VAR(irq_count)
476 cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
477 CFI_DEF_CFA_REGISTER rsi
479 /* Store previous stack value */
481 CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \
482 0x77 /* DW_OP_breg7 */, 0, \
483 0x06 /* DW_OP_deref */, \
484 0x08 /* DW_OP_const1u */, SS+8-RBP, \
485 0x22 /* DW_OP_plus */
486 /* We entered an interrupt context - irqs are off: */
491 PARTIAL_FRAME 1 (REST_SKIP+8)
492 movq 5*8+16(%rsp), %r11 /* save return address */
499 movq %r11, 8(%rsp) /* return address */
500 FIXUP_TOP_OF_STACK %r11, 16
505 /* save complete stack frame */
506 .pushsection .kprobes.text, "ax"
526 movl $MSR_GS_BASE,%ecx
529 js 1f /* negative -> in kernel */
538 * A newly forked process directly context switches into this address.
540 * rdi: prev task we switched from
545 LOCK ; btr $TIF_FORK,TI_flags(%r8)
548 popfq_cfi # reset kernel eflags
550 call schedule_tail # rdi: 'prev' task parameter
552 GET_THREAD_INFO(%rcx)
556 testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread?
559 testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET
560 jnz int_ret_from_sys_call
562 RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
563 jmp ret_from_sys_call # go to the SYSRET fastpath
566 subq $REST_SKIP, %rsp # move the stack pointer back
567 CFI_ADJUST_CFA_OFFSET REST_SKIP
573 ud2 # padding for call trace
579 * System call entry. Up to 6 arguments in registers are supported.
581 * SYSCALL does not save anything on the stack and does not change the
582 * stack pointer. However, it does mask the flags register for us, so
583 * CLD and CLAC are not needed.
588 * rax system call number
590 * rcx return address for syscall/sysret, C arg3
593 * r10 arg3 (--> moved to rcx for C)
596 * r11 eflags for syscall/sysret, temporary for C
597 * r12-r15,rbp,rbx saved by C code, not touched.
599 * Interrupts are off on entry.
600 * Only called from user space.
602 * XXX if we had a free scratch register we could save the RSP into the stack frame
603 * and report it properly in ps. Unfortunately we haven't.
605 * When user can change the frames always force IRET. That is because
606 * it deals with uncanonical addresses better. SYSRET has trouble
607 * with them due to bugs in both AMD and Intel CPUs.
613 CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET
615 /*CFI_REGISTER rflags,r11*/
618 * A hypervisor implementation might want to use a label
619 * after the swapgs, so that it can do the swapgs
620 * for the guest and jump here on syscall.
622 GLOBAL(system_call_after_swapgs)
624 movq %rsp,PER_CPU_VAR(old_rsp)
625 movq PER_CPU_VAR(kernel_stack),%rsp
627 * No need to follow this irqs off/on section - it's straight
630 ENABLE_INTERRUPTS(CLBR_NONE)
632 movq %rax,ORIG_RAX-ARGOFFSET(%rsp)
633 movq %rcx,RIP-ARGOFFSET(%rsp)
634 CFI_REL_OFFSET rip,RIP-ARGOFFSET
635 testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
637 system_call_fastpath:
638 #if __SYSCALL_MASK == ~0
639 cmpq $__NR_syscall_max,%rax
641 andl $__SYSCALL_MASK,%eax
642 cmpl $__NR_syscall_max,%eax
646 call *sys_call_table(,%rax,8) # XXX: rip relative
647 movq %rax,RAX-ARGOFFSET(%rsp)
649 * Syscall return path ending with SYSRET (fast path)
650 * Has incomplete stack frame and undefined top of stack.
653 movl $_TIF_ALLWORK_MASK,%edi
657 DISABLE_INTERRUPTS(CLBR_NONE)
659 movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx
664 * sysretq will re-enable interrupts:
667 movq RIP-ARGOFFSET(%rsp),%rcx
669 RESTORE_ARGS 1,-ARG_SKIP,0
670 /*CFI_REGISTER rflags,r11*/
671 movq PER_CPU_VAR(old_rsp), %rsp
675 /* Handle reschedules */
676 /* edx: work, edi: workmask */
678 bt $TIF_NEED_RESCHED,%edx
681 ENABLE_INTERRUPTS(CLBR_NONE)
687 /* Handle a signal */
690 ENABLE_INTERRUPTS(CLBR_NONE)
691 #ifdef CONFIG_AUDITSYSCALL
692 bt $TIF_SYSCALL_AUDIT,%edx
696 * We have a signal, or exit tracing or single-step.
697 * These all wind up with the iret return path anyway,
698 * so just join that path right now.
700 FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
701 jmp int_check_syscall_exit_work
704 movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
705 jmp ret_from_sys_call
707 #ifdef CONFIG_AUDITSYSCALL
709 * Fast path for syscall audit without full syscall trace.
710 * We just call __audit_syscall_entry() directly, and then
711 * jump back to the normal fast path.
714 movq %r10,%r9 /* 6th arg: 4th syscall arg */
715 movq %rdx,%r8 /* 5th arg: 3rd syscall arg */
716 movq %rsi,%rcx /* 4th arg: 2nd syscall arg */
717 movq %rdi,%rdx /* 3rd arg: 1st syscall arg */
718 movq %rax,%rsi /* 2nd arg: syscall number */
719 movl $AUDIT_ARCH_X86_64,%edi /* 1st arg: audit arch */
720 call __audit_syscall_entry
721 LOAD_ARGS 0 /* reload call-clobbered registers */
722 jmp system_call_fastpath
725 * Return fast path for syscall audit. Call __audit_syscall_exit()
726 * directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
730 movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */
731 cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */
732 setbe %al /* 1 if so, 0 if not */
733 movzbl %al,%edi /* zero-extend that into %edi */
734 call __audit_syscall_exit
735 movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
737 #endif /* CONFIG_AUDITSYSCALL */
739 /* Do syscall tracing */
741 #ifdef CONFIG_AUDITSYSCALL
742 testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
746 movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
747 FIXUP_TOP_OF_STACK %rdi
749 call syscall_trace_enter
751 * Reload arg registers from stack in case ptrace changed them.
752 * We don't reload %rax because syscall_trace_enter() returned
753 * the value it wants us to use in the table lookup.
755 LOAD_ARGS ARGOFFSET, 1
757 #if __SYSCALL_MASK == ~0
758 cmpq $__NR_syscall_max,%rax
760 andl $__SYSCALL_MASK,%eax
761 cmpl $__NR_syscall_max,%eax
763 ja int_ret_from_sys_call /* RAX(%rsp) set to -ENOSYS above */
764 movq %r10,%rcx /* fixup for C */
765 call *sys_call_table(,%rax,8)
766 movq %rax,RAX-ARGOFFSET(%rsp)
767 /* Use IRET because user could have changed frame */
770 * Syscall return path ending with IRET.
771 * Has correct top of stack, but partial stack frame.
773 GLOBAL(int_ret_from_sys_call)
774 DISABLE_INTERRUPTS(CLBR_NONE)
776 movl $_TIF_ALLWORK_MASK,%edi
777 /* edi: mask to check */
778 GLOBAL(int_with_check)
780 GET_THREAD_INFO(%rcx)
781 movl TI_flags(%rcx),%edx
784 andl $~TS_COMPAT,TI_status(%rcx)
787 /* Either reschedule or signal or syscall exit tracking needed. */
788 /* First do a reschedule test. */
789 /* edx: work, edi: workmask */
791 bt $TIF_NEED_RESCHED,%edx
794 ENABLE_INTERRUPTS(CLBR_NONE)
798 DISABLE_INTERRUPTS(CLBR_NONE)
802 /* handle signals and tracing -- both require a full stack frame */
805 ENABLE_INTERRUPTS(CLBR_NONE)
806 int_check_syscall_exit_work:
808 /* Check for syscall exit trace */
809 testl $_TIF_WORK_SYSCALL_EXIT,%edx
812 leaq 8(%rsp),%rdi # &ptregs -> arg1
813 call syscall_trace_leave
815 andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
819 testl $_TIF_DO_NOTIFY_MASK,%edx
821 movq %rsp,%rdi # &ptregs -> arg1
822 xorl %esi,%esi # oldset -> arg2
823 call do_notify_resume
824 1: movl $_TIF_WORK_MASK,%edi
827 DISABLE_INTERRUPTS(CLBR_NONE)
834 * Certain special system calls that need to save a complete full stack frame.
836 .macro PTREGSCALL label,func,arg
838 PARTIAL_FRAME 1 8 /* offset 8: return address */
839 subq $REST_SKIP, %rsp
840 CFI_ADJUST_CFA_OFFSET REST_SKIP
842 DEFAULT_FRAME 0 8 /* offset 8: return address */
843 leaq 8(%rsp), \arg /* pt_regs pointer */
845 jmp ptregscall_common
850 PTREGSCALL stub_clone, sys_clone, %r8
851 PTREGSCALL stub_fork, sys_fork, %rdi
852 PTREGSCALL stub_vfork, sys_vfork, %rdi
853 PTREGSCALL stub_sigaltstack, sys_sigaltstack, %rdx
854 PTREGSCALL stub_iopl, sys_iopl, %rsi
856 ENTRY(ptregscall_common)
857 DEFAULT_FRAME 1 8 /* offset 8: return address */
858 RESTORE_TOP_OF_STACK %r11, 8
859 movq_cfi_restore R15+8, r15
860 movq_cfi_restore R14+8, r14
861 movq_cfi_restore R13+8, r13
862 movq_cfi_restore R12+8, r12
863 movq_cfi_restore RBP+8, rbp
864 movq_cfi_restore RBX+8, rbx
865 ret $REST_SKIP /* pop extended registers */
867 END(ptregscall_common)
874 FIXUP_TOP_OF_STACK %r11
876 RESTORE_TOP_OF_STACK %r11
879 jmp int_ret_from_sys_call
884 * sigreturn is special because it needs to restore all registers on return.
885 * This cannot be done with SYSRET, so use the IRET return path instead.
887 ENTRY(stub_rt_sigreturn)
893 FIXUP_TOP_OF_STACK %r11
894 call sys_rt_sigreturn
895 movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
897 jmp int_ret_from_sys_call
899 END(stub_rt_sigreturn)
901 #ifdef CONFIG_X86_X32_ABI
902 PTREGSCALL stub_x32_sigaltstack, sys32_sigaltstack, %rdx
904 ENTRY(stub_x32_rt_sigreturn)
910 FIXUP_TOP_OF_STACK %r11
911 call sys32_x32_rt_sigreturn
912 movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
914 jmp int_ret_from_sys_call
916 END(stub_x32_rt_sigreturn)
918 ENTRY(stub_x32_execve)
923 FIXUP_TOP_OF_STACK %r11
924 call compat_sys_execve
925 RESTORE_TOP_OF_STACK %r11
928 jmp int_ret_from_sys_call
935 * Build the entry stubs and pointer table with some assembler magic.
936 * We pack 7 stubs into a single 32-byte chunk, which will fit in a
937 * single cache line on all modern x86 implementations.
939 .section .init.rodata,"a"
943 .p2align CONFIG_X86_L1_CACHE_SHIFT
944 ENTRY(irq_entries_start)
946 vector=FIRST_EXTERNAL_VECTOR
947 .rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7
950 .if vector < NR_VECTORS
951 .if vector <> FIRST_EXTERNAL_VECTOR
952 CFI_ADJUST_CFA_OFFSET -8
954 1: pushq_cfi $(~vector+0x80) /* Note: always in signed byte range */
955 .if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6
964 2: jmp common_interrupt
967 END(irq_entries_start)
974 * Interrupt entry/exit.
976 * Interrupt entry points save only callee clobbered registers in fast path.
978 * Entry runs with interrupts off.
981 /* 0(%rsp): ~(interrupt number) */
982 .macro interrupt func
983 /* reserve pt_regs for scratch regs and rbp */
984 subq $ORIG_RAX-RBP, %rsp
985 CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
991 * Interrupt entry/exit should be protected against kprobes
993 .pushsection .kprobes.text, "ax"
995 * The interrupt stubs push (~vector+0x80) onto the stack and
996 * then jump to common_interrupt.
998 .p2align CONFIG_X86_L1_CACHE_SHIFT
1002 addq $-0x80,(%rsp) /* Adjust vector to [-256,-1] range */
1004 /* 0(%rsp): old_rsp-ARGOFFSET */
1006 DISABLE_INTERRUPTS(CLBR_NONE)
1008 decl PER_CPU_VAR(irq_count)
1010 /* Restore saved previous stack */
1012 CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */
1013 leaq ARGOFFSET-RBP(%rsi), %rsp
1014 CFI_DEF_CFA_REGISTER rsp
1015 CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET
1018 GET_THREAD_INFO(%rcx)
1019 testl $3,CS-ARGOFFSET(%rsp)
1022 /* Interrupt came from user space */
1024 * Has a correct top of stack, but a partial stack frame
1025 * %rcx: thread info. Interrupts off.
1027 retint_with_reschedule:
1028 movl $_TIF_WORK_MASK,%edi
1030 LOCKDEP_SYS_EXIT_IRQ
1031 movl TI_flags(%rcx),%edx
1036 retint_swapgs: /* return to user-space */
1038 * The iretq could re-enable interrupts:
1040 DISABLE_INTERRUPTS(CLBR_ANY)
1045 retint_restore_args: /* return to kernel space */
1046 DISABLE_INTERRUPTS(CLBR_ANY)
1048 * The iretq could re-enable interrupts:
1056 _ASM_EXTABLE(irq_return, bad_iret)
1058 #ifdef CONFIG_PARAVIRT
1061 _ASM_EXTABLE(native_iret, bad_iret)
1064 .section .fixup,"ax"
1067 * The iret traps when the %cs or %ss being restored is bogus.
1068 * We've lost the original trap vector and error code.
1069 * #GPF is the most likely one to get for an invalid selector.
1070 * So pretend we completed the iret and took the #GPF in user mode.
1072 * We are now running with the kernel GS after exception recovery.
1073 * But error_entry expects us to have user GS to match the user %cs,
1079 jmp general_protection
1083 /* edi: workmask, edx: work */
1086 bt $TIF_NEED_RESCHED,%edx
1089 ENABLE_INTERRUPTS(CLBR_NONE)
1093 GET_THREAD_INFO(%rcx)
1094 DISABLE_INTERRUPTS(CLBR_NONE)
1099 testl $_TIF_DO_NOTIFY_MASK,%edx
1102 ENABLE_INTERRUPTS(CLBR_NONE)
1104 movq $-1,ORIG_RAX(%rsp)
1105 xorl %esi,%esi # oldset
1106 movq %rsp,%rdi # &pt_regs
1107 call do_notify_resume
1109 DISABLE_INTERRUPTS(CLBR_NONE)
1111 GET_THREAD_INFO(%rcx)
1112 jmp retint_with_reschedule
1114 #ifdef CONFIG_PREEMPT
1115 /* Returning to kernel space. Check if we need preemption */
1116 /* rcx: threadinfo. interrupts off. */
1117 ENTRY(retint_kernel)
1118 cmpl $0,TI_preempt_count(%rcx)
1119 jnz retint_restore_args
1120 bt $TIF_NEED_RESCHED,TI_flags(%rcx)
1121 jnc retint_restore_args
1122 bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */
1123 jnc retint_restore_args
1124 call preempt_schedule_irq
1129 END(common_interrupt)
1131 * End of kprobes section
1138 .macro apicinterrupt num sym do_sym
1151 apicinterrupt IRQ_MOVE_CLEANUP_VECTOR \
1152 irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
1153 apicinterrupt REBOOT_VECTOR \
1154 reboot_interrupt smp_reboot_interrupt
1157 #ifdef CONFIG_X86_UV
1158 apicinterrupt UV_BAU_MESSAGE \
1159 uv_bau_message_intr1 uv_bau_message_interrupt
1161 apicinterrupt LOCAL_TIMER_VECTOR \
1162 apic_timer_interrupt smp_apic_timer_interrupt
1163 apicinterrupt X86_PLATFORM_IPI_VECTOR \
1164 x86_platform_ipi smp_x86_platform_ipi
1166 apicinterrupt THRESHOLD_APIC_VECTOR \
1167 threshold_interrupt smp_threshold_interrupt
1168 apicinterrupt THERMAL_APIC_VECTOR \
1169 thermal_interrupt smp_thermal_interrupt
1172 apicinterrupt CALL_FUNCTION_SINGLE_VECTOR \
1173 call_function_single_interrupt smp_call_function_single_interrupt
1174 apicinterrupt CALL_FUNCTION_VECTOR \
1175 call_function_interrupt smp_call_function_interrupt
1176 apicinterrupt RESCHEDULE_VECTOR \
1177 reschedule_interrupt smp_reschedule_interrupt
1180 apicinterrupt ERROR_APIC_VECTOR \
1181 error_interrupt smp_error_interrupt
1182 apicinterrupt SPURIOUS_APIC_VECTOR \
1183 spurious_interrupt smp_spurious_interrupt
1185 #ifdef CONFIG_IRQ_WORK
1186 apicinterrupt IRQ_WORK_VECTOR \
1187 irq_work_interrupt smp_irq_work_interrupt
1191 * Exception entry points.
1193 .macro zeroentry sym do_sym
1197 PARAVIRT_ADJUST_EXCEPTION_FRAME
1198 pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
1199 subq $ORIG_RAX-R15, %rsp
1200 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1203 movq %rsp,%rdi /* pt_regs pointer */
1204 xorl %esi,%esi /* no error code */
1206 jmp error_exit /* %ebx: no swapgs flag */
1211 .macro paranoidzeroentry sym do_sym
1215 PARAVIRT_ADJUST_EXCEPTION_FRAME
1216 pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
1217 subq $ORIG_RAX-R15, %rsp
1218 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1221 movq %rsp,%rdi /* pt_regs pointer */
1222 xorl %esi,%esi /* no error code */
1224 jmp paranoid_exit /* %ebx: no swapgs flag */
1229 #define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8)
1230 .macro paranoidzeroentry_ist sym do_sym ist
1234 PARAVIRT_ADJUST_EXCEPTION_FRAME
1235 pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
1236 subq $ORIG_RAX-R15, %rsp
1237 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1239 TRACE_IRQS_OFF_DEBUG
1240 movq %rsp,%rdi /* pt_regs pointer */
1241 xorl %esi,%esi /* no error code */
1242 subq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
1244 addq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
1245 jmp paranoid_exit /* %ebx: no swapgs flag */
1250 .macro errorentry sym do_sym
1254 PARAVIRT_ADJUST_EXCEPTION_FRAME
1255 subq $ORIG_RAX-R15, %rsp
1256 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1259 movq %rsp,%rdi /* pt_regs pointer */
1260 movq ORIG_RAX(%rsp),%rsi /* get error code */
1261 movq $-1,ORIG_RAX(%rsp) /* no syscall to restart */
1263 jmp error_exit /* %ebx: no swapgs flag */
1268 /* error code is on the stack already */
1269 .macro paranoiderrorentry sym do_sym
1273 PARAVIRT_ADJUST_EXCEPTION_FRAME
1274 subq $ORIG_RAX-R15, %rsp
1275 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1279 movq %rsp,%rdi /* pt_regs pointer */
1280 movq ORIG_RAX(%rsp),%rsi /* get error code */
1281 movq $-1,ORIG_RAX(%rsp) /* no syscall to restart */
1283 jmp paranoid_exit /* %ebx: no swapgs flag */
1288 zeroentry divide_error do_divide_error
1289 zeroentry overflow do_overflow
1290 zeroentry bounds do_bounds
1291 zeroentry invalid_op do_invalid_op
1292 zeroentry device_not_available do_device_not_available
1293 paranoiderrorentry double_fault do_double_fault
1294 zeroentry coprocessor_segment_overrun do_coprocessor_segment_overrun
1295 errorentry invalid_TSS do_invalid_TSS
1296 errorentry segment_not_present do_segment_not_present
1297 zeroentry spurious_interrupt_bug do_spurious_interrupt_bug
1298 zeroentry coprocessor_error do_coprocessor_error
1299 errorentry alignment_check do_alignment_check
1300 zeroentry simd_coprocessor_error do_simd_coprocessor_error
1303 /* Reload gs selector with exception handling */
1304 /* edi: new selector */
1305 ENTRY(native_load_gs_index)
1308 DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
1312 2: mfence /* workaround */
1317 END(native_load_gs_index)
1319 _ASM_EXTABLE(gs_change,bad_gs)
1320 .section .fixup,"ax"
1321 /* running with kernelgs */
1323 SWAPGS /* switch back to user gs */
1329 ENTRY(ret_from_kernel_execve)
1333 movq 0*8(%rsp), %r15
1334 movq 1*8(%rsp), %r14
1335 movq 2*8(%rsp), %r13
1336 movq 3*8(%rsp), %r12
1337 movq 4*8(%rsp), %rbp
1338 movq 5*8(%rsp), %rbx
1340 jmp int_ret_from_sys_call
1341 END(ret_from_kernel_execve)
1343 /* Call softirq on interrupt stack. Interrupts are off. */
1347 CFI_REL_OFFSET rbp,0
1349 CFI_DEF_CFA_REGISTER rbp
1350 incl PER_CPU_VAR(irq_count)
1351 cmove PER_CPU_VAR(irq_stack_ptr),%rsp
1352 push %rbp # backlink for old unwinder
1356 CFI_DEF_CFA_REGISTER rsp
1357 CFI_ADJUST_CFA_OFFSET -8
1358 decl PER_CPU_VAR(irq_count)
1364 zeroentry xen_hypervisor_callback xen_do_hypervisor_callback
1367 * A note on the "critical region" in our callback handler.
1368 * We want to avoid stacking callback handlers due to events occurring
1369 * during handling of the last event. To do this, we keep events disabled
1370 * until we've done all processing. HOWEVER, we must enable events before
1371 * popping the stack frame (can't be done atomically) and so it would still
1372 * be possible to get enough handler activations to overflow the stack.
1373 * Although unlikely, bugs of that kind are hard to track down, so we'd
1374 * like to avoid the possibility.
1375 * So, on entry to the handler we detect whether we interrupted an
1376 * existing activation in its critical region -- if so, we pop the current
1377 * activation and restart the handler using the previous one.
1379 ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs)
1382 * Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
1383 * see the correct pointer to the pt_regs
1385 movq %rdi, %rsp # we don't return, adjust the stack frame
1388 11: incl PER_CPU_VAR(irq_count)
1390 CFI_DEF_CFA_REGISTER rbp
1391 cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
1392 pushq %rbp # backlink for old unwinder
1393 call xen_evtchn_do_upcall
1395 CFI_DEF_CFA_REGISTER rsp
1396 decl PER_CPU_VAR(irq_count)
1399 END(xen_do_hypervisor_callback)
1402 * Hypervisor uses this for application faults while it executes.
1403 * We get here for two reasons:
1404 * 1. Fault while reloading DS, ES, FS or GS
1405 * 2. Fault while executing IRET
1406 * Category 1 we do not need to fix up as Xen has already reloaded all segment
1407 * registers that could be reloaded and zeroed the others.
1408 * Category 2 we fix up by killing the current process. We cannot use the
1409 * normal Linux return path in this case because if we use the IRET hypercall
1410 * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
1411 * We distinguish between categories by comparing each saved segment register
1412 * with its current contents: any discrepancy means we in category 1.
1414 ENTRY(xen_failsafe_callback)
1416 /*CFI_REL_OFFSET gs,GS*/
1417 /*CFI_REL_OFFSET fs,FS*/
1418 /*CFI_REL_OFFSET es,ES*/
1419 /*CFI_REL_OFFSET ds,DS*/
1420 CFI_REL_OFFSET r11,8
1421 CFI_REL_OFFSET rcx,0
1435 /* All segments match their saved values => Category 2 (Bad IRET). */
1441 CFI_ADJUST_CFA_OFFSET -0x30
1442 pushq_cfi $0 /* RIP */
1445 jmp general_protection
1447 1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
1453 CFI_ADJUST_CFA_OFFSET -0x30
1458 END(xen_failsafe_callback)
1460 apicinterrupt XEN_HVM_EVTCHN_CALLBACK \
1461 xen_hvm_callback_vector xen_evtchn_do_upcall
1463 #endif /* CONFIG_XEN */
1466 * Some functions should be protected against kprobes
1468 .pushsection .kprobes.text, "ax"
1470 paranoidzeroentry_ist debug do_debug DEBUG_STACK
1471 paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
1472 paranoiderrorentry stack_segment do_stack_segment
1474 zeroentry xen_debug do_debug
1475 zeroentry xen_int3 do_int3
1476 errorentry xen_stack_segment do_stack_segment
1478 errorentry general_protection do_general_protection
1479 errorentry page_fault do_page_fault
1480 #ifdef CONFIG_KVM_GUEST
1481 errorentry async_page_fault do_async_page_fault
1483 #ifdef CONFIG_X86_MCE
1484 paranoidzeroentry machine_check *machine_check_vector(%rip)
1488 * "Paranoid" exit path from exception stack.
1489 * Paranoid because this is used by NMIs and cannot take
1490 * any kernel state for granted.
1491 * We don't do kernel preemption checks here, because only
1492 * NMI should be common and it does not enable IRQs and
1493 * cannot get reschedule ticks.
1495 * "trace" is 0 for the NMI handler only, because irq-tracing
1496 * is fundamentally NMI-unsafe. (we cannot change the soft and
1497 * hard flags at once, atomically)
1500 /* ebx: no swapgs flag */
1501 ENTRY(paranoid_exit)
1503 DISABLE_INTERRUPTS(CLBR_NONE)
1504 TRACE_IRQS_OFF_DEBUG
1505 testl %ebx,%ebx /* swapgs needed? */
1506 jnz paranoid_restore
1508 jnz paranoid_userspace
1515 TRACE_IRQS_IRETQ_DEBUG 0
1519 GET_THREAD_INFO(%rcx)
1520 movl TI_flags(%rcx),%ebx
1521 andl $_TIF_WORK_MASK,%ebx
1523 movq %rsp,%rdi /* &pt_regs */
1525 movq %rax,%rsp /* switch stack for scheduling */
1526 testl $_TIF_NEED_RESCHED,%ebx
1527 jnz paranoid_schedule
1528 movl %ebx,%edx /* arg3: thread flags */
1530 ENABLE_INTERRUPTS(CLBR_NONE)
1531 xorl %esi,%esi /* arg2: oldset */
1532 movq %rsp,%rdi /* arg1: &pt_regs */
1533 call do_notify_resume
1534 DISABLE_INTERRUPTS(CLBR_NONE)
1536 jmp paranoid_userspace
1539 ENABLE_INTERRUPTS(CLBR_ANY)
1541 DISABLE_INTERRUPTS(CLBR_ANY)
1543 jmp paranoid_userspace
1548 * Exception entry point. This expects an error code/orig_rax on the stack.
1549 * returns in "no swapgs flag" in %ebx.
1553 CFI_ADJUST_CFA_OFFSET 15*8
1554 /* oldrax contains error code */
1573 je error_kernelspace
1581 * There are two places in the kernel that can potentially fault with
1582 * usergs. Handle them here. The exception handlers after iret run with
1583 * kernel gs again, so don't set the user space flag. B stepping K8s
1584 * sometimes report an truncated RIP for IRET exceptions returning to
1585 * compat mode. Check for these here too.
1589 leaq irq_return(%rip),%rcx
1590 cmpq %rcx,RIP+8(%rsp)
1592 movl %ecx,%eax /* zero extend */
1593 cmpq %rax,RIP+8(%rsp)
1595 cmpq $gs_change,RIP+8(%rsp)
1600 /* Fix truncated RIP */
1601 movq %rcx,RIP+8(%rsp)
1607 /* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */
1612 DISABLE_INTERRUPTS(CLBR_NONE)
1614 GET_THREAD_INFO(%rcx)
1617 LOCKDEP_SYS_EXIT_IRQ
1618 movl TI_flags(%rcx),%edx
1619 movl $_TIF_WORK_MASK,%edi
1627 * Test if a given stack is an NMI stack or not.
1629 .macro test_in_nmi reg stack nmi_ret normal_ret
1632 subq $EXCEPTION_STKSZ, %\reg
1638 /* runs on exception stack */
1641 PARAVIRT_ADJUST_EXCEPTION_FRAME
1643 * We allow breakpoints in NMIs. If a breakpoint occurs, then
1644 * the iretq it performs will take us out of NMI context.
1645 * This means that we can have nested NMIs where the next
1646 * NMI is using the top of the stack of the previous NMI. We
1647 * can't let it execute because the nested NMI will corrupt the
1648 * stack of the previous NMI. NMI handlers are not re-entrant
1651 * To handle this case we do the following:
1652 * Check the a special location on the stack that contains
1653 * a variable that is set when NMIs are executing.
1654 * The interrupted task's stack is also checked to see if it
1656 * If the variable is not set and the stack is not the NMI
1658 * o Set the special variable on the stack
1659 * o Copy the interrupt frame into a "saved" location on the stack
1660 * o Copy the interrupt frame into a "copy" location on the stack
1661 * o Continue processing the NMI
1662 * If the variable is set or the previous stack is the NMI stack:
1663 * o Modify the "copy" location to jump to the repeate_nmi
1664 * o return back to the first NMI
1666 * Now on exit of the first NMI, we first clear the stack variable
1667 * The NMI stack will tell any nested NMIs at that point that it is
1668 * nested. Then we pop the stack normally with iret, and if there was
1669 * a nested NMI that updated the copy interrupt stack frame, a
1670 * jump will be made to the repeat_nmi code that will handle the second
1674 /* Use %rdx as out temp variable throughout */
1676 CFI_REL_OFFSET rdx, 0
1679 * If %cs was not the kernel segment, then the NMI triggered in user
1680 * space, which means it is definitely not nested.
1682 cmpl $__KERNEL_CS, 16(%rsp)
1686 * Check the special variable on the stack to see if NMIs are
1693 * Now test if the previous stack was an NMI stack.
1694 * We need the double check. We check the NMI stack to satisfy the
1695 * race when the first NMI clears the variable before returning.
1696 * We check the variable because the first NMI could be in a
1697 * breakpoint routine using a breakpoint stack.
1700 test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
1705 * Do nothing if we interrupted the fixup in repeat_nmi.
1706 * It's about to repeat the NMI handler, so we are fine
1707 * with ignoring this one.
1709 movq $repeat_nmi, %rdx
1712 movq $end_repeat_nmi, %rdx
1717 /* Set up the interrupted NMIs stack to jump to repeat_nmi */
1718 leaq -6*8(%rsp), %rdx
1720 CFI_ADJUST_CFA_OFFSET 6*8
1721 pushq_cfi $__KERNEL_DS
1724 pushq_cfi $__KERNEL_CS
1725 pushq_cfi $repeat_nmi
1727 /* Put stack back */
1729 CFI_ADJUST_CFA_OFFSET -11*8
1735 /* No need to check faults here */
1741 * Because nested NMIs will use the pushed location that we
1742 * stored in rdx, we must keep that space available.
1743 * Here's what our stack frame will look like:
1744 * +-------------------------+
1746 * | original Return RSP |
1747 * | original RFLAGS |
1750 * +-------------------------+
1751 * | temp storage for rdx |
1752 * +-------------------------+
1753 * | NMI executing variable |
1754 * +-------------------------+
1756 * | Saved Return RSP |
1760 * +-------------------------+
1762 * | copied Return RSP |
1766 * +-------------------------+
1768 * +-------------------------+
1770 * The saved stack frame is used to fix up the copied stack frame
1771 * that a nested NMI may change to make the interrupted NMI iret jump
1772 * to the repeat_nmi. The original stack frame and the temp storage
1773 * is also used by nested NMIs and can not be trusted on exit.
1775 /* Do not pop rdx, nested NMIs will corrupt that part of the stack */
1779 /* Set the NMI executing variable on the stack. */
1782 /* Copy the stack frame to the Saved frame */
1786 CFI_DEF_CFA_OFFSET SS+8-RIP
1788 /* Everything up to here is safe from nested NMIs */
1791 * If there was a nested NMI, the first NMI's iret will return
1792 * here. But NMIs are still enabled and we can take another
1793 * nested NMI. The nested NMI checks the interrupted RIP to see
1794 * if it is between repeat_nmi and end_repeat_nmi, and if so
1795 * it will just return, as we are about to repeat an NMI anyway.
1796 * This makes it safe to copy to the stack frame that a nested
1801 * Update the stack variable to say we are still in NMI (the update
1802 * is benign for the non-repeat case, where 1 was pushed just above
1803 * to this very stack slot).
1807 /* Make another copy, this one may be modified by nested NMIs */
1811 CFI_DEF_CFA_OFFSET SS+8-RIP
1815 * Everything below this point can be preempted by a nested
1816 * NMI if the first NMI took an exception and reset our iret stack
1817 * so that we repeat another NMI.
1819 pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
1820 subq $ORIG_RAX-R15, %rsp
1821 CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
1823 * Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit
1824 * as we should not be calling schedule in NMI context.
1825 * Even with normal interrupts enabled. An NMI should not be
1826 * setting NEED_RESCHED or anything that normal interrupts and
1827 * exceptions might do.
1833 * Save off the CR2 register. If we take a page fault in the NMI then
1834 * it could corrupt the CR2 value. If the NMI preempts a page fault
1835 * handler before it was able to read the CR2 register, and then the
1836 * NMI itself takes a page fault, the page fault that was preempted
1837 * will read the information from the NMI page fault and not the
1838 * origin fault. Save it off and restore it if it changes.
1839 * Use the r12 callee-saved register.
1843 /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
1848 /* Did the NMI take a page fault? Restore cr2 if it did */
1855 testl %ebx,%ebx /* swapgs needed? */
1861 /* Clear the NMI executing stack variable */
1867 ENTRY(ignore_sysret)
1875 * End of kprobes section