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linux/arch/x86/kernel/entry_64.S

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/*
* linux/arch/x86_64/entry.S
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
* Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
*/
/*
* entry.S contains the system-call and fault low-level handling routines.
*
* Some of this is documented in Documentation/x86/entry_64.txt
*
* NOTE: This code handles signal-recognition, which happens every time
* after an interrupt and after each system call.
*
* Normal syscalls and interrupts don't save a full stack frame, this is
* only done for syscall tracing, signals or fork/exec et.al.
*
* A note on terminology:
* - top of stack: Architecture defined interrupt frame from SS to RIP
* at the top of the kernel process stack.
* - partial stack frame: partially saved registers up to R11.
* - full stack frame: Like partial stack frame, but all register saved.
*
* Some macro usage:
* - CFI macros are used to generate dwarf2 unwind information for better
* backtraces. They don't change any code.
* - SAVE_ALL/RESTORE_ALL - Save/restore all registers
* - SAVE_ARGS/RESTORE_ARGS - Save/restore registers that C functions modify.
* There are unfortunately lots of special cases where some registers
* not touched. The macro is a big mess that should be cleaned up.
* - SAVE_REST/RESTORE_REST - Handle the registers not saved by SAVE_ARGS.
* Gives a full stack frame.
* - ENTRY/END Define functions in the symbol table.
* - FIXUP_TOP_OF_STACK/RESTORE_TOP_OF_STACK - Fix up the hardware stack
* frame that is otherwise undefined after a SYSCALL
* - TRACE_IRQ_* - Trace hard interrupt state for lock debugging.
* - idtentry - Define exception entry points.
*/
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/cache.h>
#include <asm/errno.h>
#include <asm/dwarf2.h>
#include <asm/calling.h>
#include <asm/asm-offsets.h>
#include <asm/msr.h>
#include <asm/unistd.h>
#include <asm/thread_info.h>
#include <asm/hw_irq.h>
#include <asm/page_types.h>
#include <asm/irqflags.h>
#include <asm/paravirt.h>
#include <asm/percpu.h>
#include <asm/asm.h>
#include <asm/context_tracking.h>
#include <asm/smap.h>
#include <asm/pgtable_types.h>
#include <linux/err.h>
/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
#include <linux/elf-em.h>
#define AUDIT_ARCH_X86_64 (EM_X86_64|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_64BIT 0x80000000
#define __AUDIT_ARCH_LE 0x40000000
.code64
.section .entry.text, "ax"
#ifndef CONFIG_PREEMPT
#define retint_kernel retint_restore_args
#endif
#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret64)
swapgs
sysretq
ENDPROC(native_usergs_sysret64)
#endif /* CONFIG_PARAVIRT */
.macro TRACE_IRQS_IRETQ offset=ARGOFFSET
#ifdef CONFIG_TRACE_IRQFLAGS
bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */
jnc 1f
TRACE_IRQS_ON
1:
#endif
.endm
/*
* When dynamic function tracer is enabled it will add a breakpoint
* to all locations that it is about to modify, sync CPUs, update
* all the code, sync CPUs, then remove the breakpoints. In this time
* if lockdep is enabled, it might jump back into the debug handler
* outside the updating of the IST protection. (TRACE_IRQS_ON/OFF).
*
* We need to change the IDT table before calling TRACE_IRQS_ON/OFF to
* make sure the stack pointer does not get reset back to the top
* of the debug stack, and instead just reuses the current stack.
*/
#if defined(CONFIG_DYNAMIC_FTRACE) && defined(CONFIG_TRACE_IRQFLAGS)
.macro TRACE_IRQS_OFF_DEBUG
call debug_stack_set_zero
TRACE_IRQS_OFF
call debug_stack_reset
.endm
.macro TRACE_IRQS_ON_DEBUG
call debug_stack_set_zero
TRACE_IRQS_ON
call debug_stack_reset
.endm
.macro TRACE_IRQS_IRETQ_DEBUG offset=ARGOFFSET
bt $9,EFLAGS-\offset(%rsp) /* interrupts off? */
jnc 1f
TRACE_IRQS_ON_DEBUG
1:
.endm
#else
# define TRACE_IRQS_OFF_DEBUG TRACE_IRQS_OFF
# define TRACE_IRQS_ON_DEBUG TRACE_IRQS_ON
# define TRACE_IRQS_IRETQ_DEBUG TRACE_IRQS_IRETQ
#endif
/*
* C code is not supposed to know about undefined top of stack. Every time
* a C function with an pt_regs argument is called from the SYSCALL based
* fast path FIXUP_TOP_OF_STACK is needed.
* RESTORE_TOP_OF_STACK syncs the syscall state after any possible ptregs
* manipulation.
*/
/* %rsp:at FRAMEEND */
.macro FIXUP_TOP_OF_STACK tmp offset=0
movq PER_CPU_VAR(old_rsp),\tmp
movq \tmp,RSP+\offset(%rsp)
movq $__USER_DS,SS+\offset(%rsp)
movq $__USER_CS,CS+\offset(%rsp)
movq $-1,RCX+\offset(%rsp)
movq R11+\offset(%rsp),\tmp /* get eflags */
movq \tmp,EFLAGS+\offset(%rsp)
.endm
.macro RESTORE_TOP_OF_STACK tmp offset=0
movq RSP+\offset(%rsp),\tmp
movq \tmp,PER_CPU_VAR(old_rsp)
movq EFLAGS+\offset(%rsp),\tmp
movq \tmp,R11+\offset(%rsp)
.endm
.macro FAKE_STACK_FRAME child_rip
/* push in order ss, rsp, eflags, cs, rip */
xorl %eax, %eax
pushq_cfi $__KERNEL_DS /* ss */
/*CFI_REL_OFFSET ss,0*/
pushq_cfi %rax /* rsp */
CFI_REL_OFFSET rsp,0
pushq_cfi $(X86_EFLAGS_IF|X86_EFLAGS_FIXED) /* eflags - interrupts on */
/*CFI_REL_OFFSET rflags,0*/
pushq_cfi $__KERNEL_CS /* cs */
/*CFI_REL_OFFSET cs,0*/
pushq_cfi \child_rip /* rip */
CFI_REL_OFFSET rip,0
pushq_cfi %rax /* orig rax */
.endm
.macro UNFAKE_STACK_FRAME
addq $8*6, %rsp
CFI_ADJUST_CFA_OFFSET -(6*8)
.endm
/*
* initial frame state for interrupts (and exceptions without error code)
*/
.macro EMPTY_FRAME start=1 offset=0
.if \start
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA rsp,8+\offset
.else
CFI_DEF_CFA_OFFSET 8+\offset
.endif
.endm
/*
* initial frame state for interrupts (and exceptions without error code)
*/
.macro INTR_FRAME start=1 offset=0
EMPTY_FRAME \start, SS+8+\offset-RIP
/*CFI_REL_OFFSET ss, SS+\offset-RIP*/
CFI_REL_OFFSET rsp, RSP+\offset-RIP
/*CFI_REL_OFFSET rflags, EFLAGS+\offset-RIP*/
/*CFI_REL_OFFSET cs, CS+\offset-RIP*/
CFI_REL_OFFSET rip, RIP+\offset-RIP
.endm
/*
* initial frame state for exceptions with error code (and interrupts
* with vector already pushed)
*/
.macro XCPT_FRAME start=1 offset=0
INTR_FRAME \start, RIP+\offset-ORIG_RAX
/*CFI_REL_OFFSET orig_rax, ORIG_RAX-ORIG_RAX*/
.endm
/*
* frame that enables calling into C.
*/
.macro PARTIAL_FRAME start=1 offset=0
XCPT_FRAME \start, ORIG_RAX+\offset-ARGOFFSET
CFI_REL_OFFSET rdi, RDI+\offset-ARGOFFSET
CFI_REL_OFFSET rsi, RSI+\offset-ARGOFFSET
CFI_REL_OFFSET rdx, RDX+\offset-ARGOFFSET
CFI_REL_OFFSET rcx, RCX+\offset-ARGOFFSET
CFI_REL_OFFSET rax, RAX+\offset-ARGOFFSET
CFI_REL_OFFSET r8, R8+\offset-ARGOFFSET
CFI_REL_OFFSET r9, R9+\offset-ARGOFFSET
CFI_REL_OFFSET r10, R10+\offset-ARGOFFSET
CFI_REL_OFFSET r11, R11+\offset-ARGOFFSET
.endm
/*
* frame that enables passing a complete pt_regs to a C function.
*/
.macro DEFAULT_FRAME start=1 offset=0
PARTIAL_FRAME \start, R11+\offset-R15
CFI_REL_OFFSET rbx, RBX+\offset
CFI_REL_OFFSET rbp, RBP+\offset
CFI_REL_OFFSET r12, R12+\offset
CFI_REL_OFFSET r13, R13+\offset
CFI_REL_OFFSET r14, R14+\offset
CFI_REL_OFFSET r15, R15+\offset
.endm
/* save partial stack frame */
.macro SAVE_ARGS_IRQ
cld
/* start from rbp in pt_regs and jump over */
movq_cfi rdi, (RDI-RBP)
movq_cfi rsi, (RSI-RBP)
movq_cfi rdx, (RDX-RBP)
movq_cfi rcx, (RCX-RBP)
movq_cfi rax, (RAX-RBP)
movq_cfi r8, (R8-RBP)
movq_cfi r9, (R9-RBP)
movq_cfi r10, (R10-RBP)
movq_cfi r11, (R11-RBP)
/* Save rbp so that we can unwind from get_irq_regs() */
movq_cfi rbp, 0
/* Save previous stack value */
movq %rsp, %rsi
leaq -RBP(%rsp),%rdi /* arg1 for handler */
testl $3, CS-RBP(%rsi)
je 1f
SWAPGS
/*
* irq_count is used to check if a CPU is already on an interrupt stack
* or not. While this is essentially redundant with preempt_count it is
* a little cheaper to use a separate counter in the PDA (short of
* moving irq_enter into assembly, which would be too much work)
*/
1: incl PER_CPU_VAR(irq_count)
cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
CFI_DEF_CFA_REGISTER rsi
/* Store previous stack value */
pushq %rsi
CFI_ESCAPE 0x0f /* DW_CFA_def_cfa_expression */, 6, \
0x77 /* DW_OP_breg7 */, 0, \
0x06 /* DW_OP_deref */, \
0x08 /* DW_OP_const1u */, SS+8-RBP, \
0x22 /* DW_OP_plus */
/* We entered an interrupt context - irqs are off: */
TRACE_IRQS_OFF
.endm
ENTRY(save_paranoid)
XCPT_FRAME 1 RDI+8
cld
movq_cfi rdi, RDI+8
movq_cfi rsi, RSI+8
movq_cfi rdx, RDX+8
movq_cfi rcx, RCX+8
movq_cfi rax, RAX+8
movq_cfi r8, R8+8
movq_cfi r9, R9+8
movq_cfi r10, R10+8
movq_cfi r11, R11+8
movq_cfi rbx, RBX+8
movq_cfi rbp, RBP+8
movq_cfi r12, R12+8
movq_cfi r13, R13+8
movq_cfi r14, R14+8
movq_cfi r15, R15+8
movl $1,%ebx
movl $MSR_GS_BASE,%ecx
rdmsr
testl %edx,%edx
js 1f /* negative -> in kernel */
SWAPGS
xorl %ebx,%ebx
1: ret
CFI_ENDPROC
END(save_paranoid)
/*
* A newly forked process directly context switches into this address.
*
* rdi: prev task we switched from
*/
ENTRY(ret_from_fork)
DEFAULT_FRAME
LOCK ; btr $TIF_FORK,TI_flags(%r8)
pushq_cfi $0x0002
popfq_cfi # reset kernel eflags
call schedule_tail # rdi: 'prev' task parameter
GET_THREAD_INFO(%rcx)
RESTORE_REST
testl $3, CS-ARGOFFSET(%rsp) # from kernel_thread?
jz 1f
testl $_TIF_IA32, TI_flags(%rcx) # 32-bit compat task needs IRET
jnz int_ret_from_sys_call
RESTORE_TOP_OF_STACK %rdi, -ARGOFFSET
jmp ret_from_sys_call # go to the SYSRET fastpath
1:
subq $REST_SKIP, %rsp # leave space for volatiles
CFI_ADJUST_CFA_OFFSET REST_SKIP
movq %rbp, %rdi
call *%rbx
movl $0, RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(ret_from_fork)
/*
* System call entry. Up to 6 arguments in registers are supported.
*
* SYSCALL does not save anything on the stack and does not change the
* stack pointer. However, it does mask the flags register for us, so
* CLD and CLAC are not needed.
*/
/*
* Register setup:
* rax system call number
* rdi arg0
* rcx return address for syscall/sysret, C arg3
* rsi arg1
* rdx arg2
* r10 arg3 (--> moved to rcx for C)
* r8 arg4
* r9 arg5
* r11 eflags for syscall/sysret, temporary for C
* r12-r15,rbp,rbx saved by C code, not touched.
*
* Interrupts are off on entry.
* Only called from user space.
*
* XXX if we had a free scratch register we could save the RSP into the stack frame
* and report it properly in ps. Unfortunately we haven't.
*
* When user can change the frames always force IRET. That is because
* it deals with uncanonical addresses better. SYSRET has trouble
* with them due to bugs in both AMD and Intel CPUs.
*/
ENTRY(system_call)
CFI_STARTPROC simple
CFI_SIGNAL_FRAME
CFI_DEF_CFA rsp,KERNEL_STACK_OFFSET
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
SWAPGS_UNSAFE_STACK
/*
* A hypervisor implementation might want to use a label
* after the swapgs, so that it can do the swapgs
* for the guest and jump here on syscall.
*/
GLOBAL(system_call_after_swapgs)
movq %rsp,PER_CPU_VAR(old_rsp)
movq PER_CPU_VAR(kernel_stack),%rsp
/*
* No need to follow this irqs off/on section - it's straight
* and short:
*/
ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_ARGS 8,0
movq %rax,ORIG_RAX-ARGOFFSET(%rsp)
movq %rcx,RIP-ARGOFFSET(%rsp)
CFI_REL_OFFSET rip,RIP-ARGOFFSET
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jnz tracesys
system_call_fastpath:
#if __SYSCALL_MASK == ~0
cmpq $__NR_syscall_max,%rax
#else
andl $__SYSCALL_MASK,%eax
cmpl $__NR_syscall_max,%eax
#endif
ja badsys
movq %r10,%rcx
call *sys_call_table(,%rax,8) # XXX: rip relative
movq %rax,RAX-ARGOFFSET(%rsp)
/*
* Syscall return path ending with SYSRET (fast path)
* Has incomplete stack frame and undefined top of stack.
*/
ret_from_sys_call:
movl $_TIF_ALLWORK_MASK,%edi
/* edi: flagmask */
sysret_check:
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
movl TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET),%edx
andl %edi,%edx
jnz sysret_careful
CFI_REMEMBER_STATE
/*
* sysretq will re-enable interrupts:
*/
TRACE_IRQS_ON
movq RIP-ARGOFFSET(%rsp),%rcx
CFI_REGISTER rip,rcx
RESTORE_ARGS 1,-ARG_SKIP,0
/*CFI_REGISTER rflags,r11*/
movq PER_CPU_VAR(old_rsp), %rsp
USERGS_SYSRET64
CFI_RESTORE_STATE
/* Handle reschedules */
/* edx: work, edi: workmask */
sysret_careful:
bt $TIF_NEED_RESCHED,%edx
jnc sysret_signal
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
SCHEDULE_USER
popq_cfi %rdi
jmp sysret_check
/* Handle a signal */
sysret_signal:
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
#ifdef CONFIG_AUDITSYSCALL
bt $TIF_SYSCALL_AUDIT,%edx
jc sysret_audit
#endif
/*
* We have a signal, or exit tracing or single-step.
* These all wind up with the iret return path anyway,
* so just join that path right now.
*/
FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
jmp int_check_syscall_exit_work
badsys:
movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
jmp ret_from_sys_call
#ifdef CONFIG_AUDITSYSCALL
/*
* Fast path for syscall audit without full syscall trace.
* We just call __audit_syscall_entry() directly, and then
* jump back to the normal fast path.
*/
auditsys:
movq %r10,%r9 /* 6th arg: 4th syscall arg */
movq %rdx,%r8 /* 5th arg: 3rd syscall arg */
movq %rsi,%rcx /* 4th arg: 2nd syscall arg */
movq %rdi,%rdx /* 3rd arg: 1st syscall arg */
movq %rax,%rsi /* 2nd arg: syscall number */
movl $AUDIT_ARCH_X86_64,%edi /* 1st arg: audit arch */
call __audit_syscall_entry
LOAD_ARGS 0 /* reload call-clobbered registers */
jmp system_call_fastpath
/*
* Return fast path for syscall audit. Call __audit_syscall_exit()
* directly and then jump back to the fast path with TIF_SYSCALL_AUDIT
* masked off.
*/
sysret_audit:
movq RAX-ARGOFFSET(%rsp),%rsi /* second arg, syscall return value */
cmpq $-MAX_ERRNO,%rsi /* is it < -MAX_ERRNO? */
setbe %al /* 1 if so, 0 if not */
movzbl %al,%edi /* zero-extend that into %edi */
call __audit_syscall_exit
movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT),%edi
jmp sysret_check
#endif /* CONFIG_AUDITSYSCALL */
/* Do syscall tracing */
tracesys:
#ifdef CONFIG_AUDITSYSCALL
testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT),TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jz auditsys
#endif
SAVE_REST
movq $-ENOSYS,RAX(%rsp) /* ptrace can change this for a bad syscall */
FIXUP_TOP_OF_STACK %rdi
movq %rsp,%rdi
call syscall_trace_enter
/*
* Reload arg registers from stack in case ptrace changed them.
* We don't reload %rax because syscall_trace_enter() returned
* the value it wants us to use in the table lookup.
*/
LOAD_ARGS ARGOFFSET, 1
RESTORE_REST
#if __SYSCALL_MASK == ~0
cmpq $__NR_syscall_max,%rax
#else
andl $__SYSCALL_MASK,%eax
cmpl $__NR_syscall_max,%eax
#endif
ja int_ret_from_sys_call /* RAX(%rsp) set to -ENOSYS above */
movq %r10,%rcx /* fixup for C */
call *sys_call_table(,%rax,8)
movq %rax,RAX-ARGOFFSET(%rsp)
/* Use IRET because user could have changed frame */
/*
* Syscall return path ending with IRET.
* Has correct top of stack, but partial stack frame.
*/
GLOBAL(int_ret_from_sys_call)
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
movl $_TIF_ALLWORK_MASK,%edi
/* edi: mask to check */
GLOBAL(int_with_check)
LOCKDEP_SYS_EXIT_IRQ
GET_THREAD_INFO(%rcx)
movl TI_flags(%rcx),%edx
andl %edi,%edx
jnz int_careful
andl $~TS_COMPAT,TI_status(%rcx)
jmp retint_swapgs
/* Either reschedule or signal or syscall exit tracking needed. */
/* First do a reschedule test. */
/* edx: work, edi: workmask */
int_careful:
bt $TIF_NEED_RESCHED,%edx
jnc int_very_careful
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
SCHEDULE_USER
popq_cfi %rdi
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp int_with_check
/* handle signals and tracing -- both require a full stack frame */
int_very_careful:
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
int_check_syscall_exit_work:
SAVE_REST
/* Check for syscall exit trace */
testl $_TIF_WORK_SYSCALL_EXIT,%edx
jz int_signal
pushq_cfi %rdi
leaq 8(%rsp),%rdi # &ptregs -> arg1
call syscall_trace_leave
popq_cfi %rdi
andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
jmp int_restore_rest
int_signal:
testl $_TIF_DO_NOTIFY_MASK,%edx
jz 1f
movq %rsp,%rdi # &ptregs -> arg1
xorl %esi,%esi # oldset -> arg2
call do_notify_resume
1: movl $_TIF_WORK_MASK,%edi
int_restore_rest:
RESTORE_REST
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp int_with_check
CFI_ENDPROC
END(system_call)
.macro FORK_LIKE func
ENTRY(stub_\func)
CFI_STARTPROC
popq %r11 /* save return address */
PARTIAL_FRAME 0
SAVE_REST
pushq %r11 /* put it back on stack */
FIXUP_TOP_OF_STACK %r11, 8
DEFAULT_FRAME 0 8 /* offset 8: return address */
call sys_\func
RESTORE_TOP_OF_STACK %r11, 8
ret $REST_SKIP /* pop extended registers */
CFI_ENDPROC
END(stub_\func)
.endm
.macro FIXED_FRAME label,func
ENTRY(\label)
CFI_STARTPROC
PARTIAL_FRAME 0 8 /* offset 8: return address */
FIXUP_TOP_OF_STACK %r11, 8-ARGOFFSET
call \func
RESTORE_TOP_OF_STACK %r11, 8-ARGOFFSET
ret
CFI_ENDPROC
END(\label)
.endm
FORK_LIKE clone
FORK_LIKE fork
FORK_LIKE vfork
FIXED_FRAME stub_iopl, sys_iopl
ENTRY(ptregscall_common)
DEFAULT_FRAME 1 8 /* offset 8: return address */
RESTORE_TOP_OF_STACK %r11, 8
movq_cfi_restore R15+8, r15
movq_cfi_restore R14+8, r14
movq_cfi_restore R13+8, r13
movq_cfi_restore R12+8, r12
movq_cfi_restore RBP+8, rbp
movq_cfi_restore RBX+8, rbx
ret $REST_SKIP /* pop extended registers */
CFI_ENDPROC
END(ptregscall_common)
ENTRY(stub_execve)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call sys_execve
movq %rax,RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_execve)
/*
* sigreturn is special because it needs to restore all registers on return.
* This cannot be done with SYSRET, so use the IRET return path instead.
*/
ENTRY(stub_rt_sigreturn)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call sys_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_rt_sigreturn)
#ifdef CONFIG_X86_X32_ABI
ENTRY(stub_x32_rt_sigreturn)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call sys32_x32_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_x32_rt_sigreturn)
ENTRY(stub_x32_execve)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call compat_sys_execve
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_x32_execve)
#endif
/*
* Build the entry stubs and pointer table with some assembler magic.
* We pack 7 stubs into a single 32-byte chunk, which will fit in a
* single cache line on all modern x86 implementations.
*/
.section .init.rodata,"a"
ENTRY(interrupt)
.section .entry.text
.p2align 5
.p2align CONFIG_X86_L1_CACHE_SHIFT
ENTRY(irq_entries_start)
INTR_FRAME
vector=FIRST_EXTERNAL_VECTOR
.rept (NR_VECTORS-FIRST_EXTERNAL_VECTOR+6)/7
.balign 32
.rept 7
.if vector < NR_VECTORS
.if vector <> FIRST_EXTERNAL_VECTOR
CFI_ADJUST_CFA_OFFSET -8
.endif
1: pushq_cfi $(~vector+0x80) /* Note: always in signed byte range */
.if ((vector-FIRST_EXTERNAL_VECTOR)%7) <> 6
jmp 2f
.endif
.previous
.quad 1b
.section .entry.text
vector=vector+1
.endif
.endr
2: jmp common_interrupt
.endr
CFI_ENDPROC
END(irq_entries_start)
.previous
END(interrupt)
.previous
/*
* Interrupt entry/exit.
*
* Interrupt entry points save only callee clobbered registers in fast path.
*
* Entry runs with interrupts off.
*/
/* 0(%rsp): ~(interrupt number) */
.macro interrupt func
/* reserve pt_regs for scratch regs and rbp */
subq $ORIG_RAX-RBP, %rsp
CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP
SAVE_ARGS_IRQ
call \func
.endm
/*
* The interrupt stubs push (~vector+0x80) onto the stack and
* then jump to common_interrupt.
*/
.p2align CONFIG_X86_L1_CACHE_SHIFT
common_interrupt:
XCPT_FRAME
ASM_CLAC
addq $-0x80,(%rsp) /* Adjust vector to [-256,-1] range */
interrupt do_IRQ
/* 0(%rsp): old_rsp-ARGOFFSET */
ret_from_intr:
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
decl PER_CPU_VAR(irq_count)
/* Restore saved previous stack */
popq %rsi
CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */
leaq ARGOFFSET-RBP(%rsi), %rsp
CFI_DEF_CFA_REGISTER rsp
CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET
exit_intr:
GET_THREAD_INFO(%rcx)
testl $3,CS-ARGOFFSET(%rsp)
je retint_kernel
/* Interrupt came from user space */
/*
* Has a correct top of stack, but a partial stack frame
* %rcx: thread info. Interrupts off.
*/
retint_with_reschedule:
movl $_TIF_WORK_MASK,%edi
retint_check:
LOCKDEP_SYS_EXIT_IRQ
movl TI_flags(%rcx),%edx
andl %edi,%edx
CFI_REMEMBER_STATE
jnz retint_careful
retint_swapgs: /* return to user-space */
/*
* The iretq could re-enable interrupts:
*/
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_IRETQ
SWAPGS
jmp restore_args
retint_restore_args: /* return to kernel space */
DISABLE_INTERRUPTS(CLBR_ANY)
/*
* The iretq could re-enable interrupts:
*/
TRACE_IRQS_IRETQ
restore_args:
RESTORE_ARGS 1,8,1
irq_return:
/*
* Are we returning to a stack segment from the LDT? Note: in
* 64-bit mode SS:RSP on the exception stack is always valid.
*/
#ifdef CONFIG_X86_ESPFIX64
testb $4,(SS-RIP)(%rsp)
jnz irq_return_ldt
#endif
irq_return_iret:
INTERRUPT_RETURN
_ASM_EXTABLE(irq_return_iret, bad_iret)
#ifdef CONFIG_PARAVIRT
ENTRY(native_iret)
iretq
_ASM_EXTABLE(native_iret, bad_iret)
#endif
#ifdef CONFIG_X86_ESPFIX64
irq_return_ldt:
pushq_cfi %rax
pushq_cfi %rdi
SWAPGS
movq PER_CPU_VAR(espfix_waddr),%rdi
movq %rax,(0*8)(%rdi) /* RAX */
movq (2*8)(%rsp),%rax /* RIP */
movq %rax,(1*8)(%rdi)
movq (3*8)(%rsp),%rax /* CS */
movq %rax,(2*8)(%rdi)
movq (4*8)(%rsp),%rax /* RFLAGS */
movq %rax,(3*8)(%rdi)
movq (6*8)(%rsp),%rax /* SS */
movq %rax,(5*8)(%rdi)
movq (5*8)(%rsp),%rax /* RSP */
movq %rax,(4*8)(%rdi)
andl $0xffff0000,%eax
popq_cfi %rdi
orq PER_CPU_VAR(espfix_stack),%rax
SWAPGS
movq %rax,%rsp
popq_cfi %rax
jmp irq_return_iret
#endif
.section .fixup,"ax"
bad_iret:
/*
* The iret traps when the %cs or %ss being restored is bogus.
* We've lost the original trap vector and error code.
* #GPF is the most likely one to get for an invalid selector.
* So pretend we completed the iret and took the #GPF in user mode.
*
* We are now running with the kernel GS after exception recovery.
* But error_entry expects us to have user GS to match the user %cs,
* so swap back.
*/
pushq $0
SWAPGS
jmp general_protection
.previous
/* edi: workmask, edx: work */
retint_careful:
CFI_RESTORE_STATE
bt $TIF_NEED_RESCHED,%edx
jnc retint_signal
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
pushq_cfi %rdi
SCHEDULE_USER
popq_cfi %rdi
GET_THREAD_INFO(%rcx)
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp retint_check
retint_signal:
testl $_TIF_DO_NOTIFY_MASK,%edx
jz retint_swapgs
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_REST
movq $-1,ORIG_RAX(%rsp)
xorl %esi,%esi # oldset
movq %rsp,%rdi # &pt_regs
call do_notify_resume
RESTORE_REST
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
GET_THREAD_INFO(%rcx)
jmp retint_with_reschedule
#ifdef CONFIG_PREEMPT
/* Returning to kernel space. Check if we need preemption */
/* rcx: threadinfo. interrupts off. */
ENTRY(retint_kernel)
cmpl $0,PER_CPU_VAR(__preempt_count)
jnz retint_restore_args
bt $9,EFLAGS-ARGOFFSET(%rsp) /* interrupts off? */
jnc retint_restore_args
call preempt_schedule_irq
jmp exit_intr
#endif
CFI_ENDPROC
END(common_interrupt)
/*
* If IRET takes a fault on the espfix stack, then we
* end up promoting it to a doublefault. In that case,
* modify the stack to make it look like we just entered
* the #GP handler from user space, similar to bad_iret.
*/
#ifdef CONFIG_X86_ESPFIX64
ALIGN
__do_double_fault:
XCPT_FRAME 1 RDI+8
movq RSP(%rdi),%rax /* Trap on the espfix stack? */
sarq $PGDIR_SHIFT,%rax
cmpl $ESPFIX_PGD_ENTRY,%eax
jne do_double_fault /* No, just deliver the fault */
cmpl $__KERNEL_CS,CS(%rdi)
jne do_double_fault
movq RIP(%rdi),%rax
cmpq $irq_return_iret,%rax
#ifdef CONFIG_PARAVIRT
je 1f
cmpq $native_iret,%rax
#endif
jne do_double_fault /* This shouldn't happen... */
1:
movq PER_CPU_VAR(kernel_stack),%rax
subq $(6*8-KERNEL_STACK_OFFSET),%rax /* Reset to original stack */
movq %rax,RSP(%rdi)
movq $0,(%rax) /* Missing (lost) #GP error code */
movq $general_protection,RIP(%rdi)
retq
CFI_ENDPROC
END(__do_double_fault)
#else
# define __do_double_fault do_double_fault
#endif
/*
* APIC interrupts.
*/
.macro apicinterrupt3 num sym do_sym
ENTRY(\sym)
INTR_FRAME
ASM_CLAC
pushq_cfi $~(\num)
.Lcommon_\sym:
interrupt \do_sym
jmp ret_from_intr
CFI_ENDPROC
END(\sym)
.endm
#ifdef CONFIG_TRACING
#define trace(sym) trace_##sym
#define smp_trace(sym) smp_trace_##sym
.macro trace_apicinterrupt num sym
apicinterrupt3 \num trace(\sym) smp_trace(\sym)
.endm
#else
.macro trace_apicinterrupt num sym do_sym
.endm
#endif
.macro apicinterrupt num sym do_sym
apicinterrupt3 \num \sym \do_sym
trace_apicinterrupt \num \sym
.endm
#ifdef CONFIG_SMP
apicinterrupt3 IRQ_MOVE_CLEANUP_VECTOR \
irq_move_cleanup_interrupt smp_irq_move_cleanup_interrupt
apicinterrupt3 REBOOT_VECTOR \
reboot_interrupt smp_reboot_interrupt
#endif
#ifdef CONFIG_X86_UV
apicinterrupt3 UV_BAU_MESSAGE \
uv_bau_message_intr1 uv_bau_message_interrupt
#endif
apicinterrupt LOCAL_TIMER_VECTOR \
apic_timer_interrupt smp_apic_timer_interrupt
apicinterrupt X86_PLATFORM_IPI_VECTOR \
x86_platform_ipi smp_x86_platform_ipi
#ifdef CONFIG_HAVE_KVM
apicinterrupt3 POSTED_INTR_VECTOR \
kvm_posted_intr_ipi smp_kvm_posted_intr_ipi
#endif
#ifdef CONFIG_X86_MCE_THRESHOLD
apicinterrupt THRESHOLD_APIC_VECTOR \
threshold_interrupt smp_threshold_interrupt
#endif
#ifdef CONFIG_X86_THERMAL_VECTOR
apicinterrupt THERMAL_APIC_VECTOR \
thermal_interrupt smp_thermal_interrupt
#endif
#ifdef CONFIG_SMP
apicinterrupt CALL_FUNCTION_SINGLE_VECTOR \
call_function_single_interrupt smp_call_function_single_interrupt
apicinterrupt CALL_FUNCTION_VECTOR \
call_function_interrupt smp_call_function_interrupt
apicinterrupt RESCHEDULE_VECTOR \
reschedule_interrupt smp_reschedule_interrupt
#endif
apicinterrupt ERROR_APIC_VECTOR \
error_interrupt smp_error_interrupt
apicinterrupt SPURIOUS_APIC_VECTOR \
spurious_interrupt smp_spurious_interrupt
#ifdef CONFIG_IRQ_WORK
apicinterrupt IRQ_WORK_VECTOR \
irq_work_interrupt smp_irq_work_interrupt
#endif
/*
* Exception entry points.
*/
#define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8)
.macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
ENTRY(\sym)
/* Sanity check */
.if \shift_ist != -1 && \paranoid == 0
.error "using shift_ist requires paranoid=1"
.endif
.if \has_error_code
XCPT_FRAME
.else
INTR_FRAME
.endif
ASM_CLAC
PARAVIRT_ADJUST_EXCEPTION_FRAME
.ifeq \has_error_code
pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
.endif
subq $ORIG_RAX-R15, %rsp
CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
.if \paranoid
call save_paranoid
.else
call error_entry
.endif
DEFAULT_FRAME 0
.if \paranoid
.if \shift_ist != -1
TRACE_IRQS_OFF_DEBUG /* reload IDT in case of recursion */
.else
TRACE_IRQS_OFF
.endif
.endif
movq %rsp,%rdi /* pt_regs pointer */
.if \has_error_code
movq ORIG_RAX(%rsp),%rsi /* get error code */
movq $-1,ORIG_RAX(%rsp) /* no syscall to restart */
.else
xorl %esi,%esi /* no error code */
.endif
.if \shift_ist != -1
subq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist)
.endif
call \do_sym
.if \shift_ist != -1
addq $EXCEPTION_STKSZ, INIT_TSS_IST(\shift_ist)
.endif
.if \paranoid
jmp paranoid_exit /* %ebx: no swapgs flag */
.else
jmp error_exit /* %ebx: no swapgs flag */
.endif
CFI_ENDPROC
END(\sym)
.endm
#ifdef CONFIG_TRACING
.macro trace_idtentry sym do_sym has_error_code:req
idtentry trace(\sym) trace(\do_sym) has_error_code=\has_error_code
idtentry \sym \do_sym has_error_code=\has_error_code
.endm
#else
.macro trace_idtentry sym do_sym has_error_code:req
idtentry \sym \do_sym has_error_code=\has_error_code
.endm
#endif
idtentry divide_error do_divide_error has_error_code=0
idtentry overflow do_overflow has_error_code=0
idtentry bounds do_bounds has_error_code=0
idtentry invalid_op do_invalid_op has_error_code=0
idtentry device_not_available do_device_not_available has_error_code=0
idtentry double_fault __do_double_fault has_error_code=1 paranoid=1
idtentry coprocessor_segment_overrun do_coprocessor_segment_overrun has_error_code=0
idtentry invalid_TSS do_invalid_TSS has_error_code=1
idtentry segment_not_present do_segment_not_present has_error_code=1
idtentry spurious_interrupt_bug do_spurious_interrupt_bug has_error_code=0
idtentry coprocessor_error do_coprocessor_error has_error_code=0
idtentry alignment_check do_alignment_check has_error_code=1
idtentry simd_coprocessor_error do_simd_coprocessor_error has_error_code=0
/* Reload gs selector with exception handling */
/* edi: new selector */
ENTRY(native_load_gs_index)
CFI_STARTPROC
pushfq_cfi
DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
SWAPGS
gs_change:
movl %edi,%gs
2: mfence /* workaround */
SWAPGS
popfq_cfi
ret
CFI_ENDPROC
END(native_load_gs_index)
_ASM_EXTABLE(gs_change,bad_gs)
.section .fixup,"ax"
/* running with kernelgs */
bad_gs:
SWAPGS /* switch back to user gs */
xorl %eax,%eax
movl %eax,%gs
jmp 2b
.previous
/* Call softirq on interrupt stack. Interrupts are off. */
ENTRY(do_softirq_own_stack)
CFI_STARTPROC
pushq_cfi %rbp
CFI_REL_OFFSET rbp,0
mov %rsp,%rbp
CFI_DEF_CFA_REGISTER rbp
incl PER_CPU_VAR(irq_count)
cmove PER_CPU_VAR(irq_stack_ptr),%rsp
push %rbp # backlink for old unwinder
call __do_softirq
leaveq
CFI_RESTORE rbp
CFI_DEF_CFA_REGISTER rsp
CFI_ADJUST_CFA_OFFSET -8
decl PER_CPU_VAR(irq_count)
ret
CFI_ENDPROC
END(do_softirq_own_stack)
#ifdef CONFIG_XEN
idtentry xen_hypervisor_callback xen_do_hypervisor_callback has_error_code=0
/*
* A note on the "critical region" in our callback handler.
* We want to avoid stacking callback handlers due to events occurring
* during handling of the last event. To do this, we keep events disabled
* until we've done all processing. HOWEVER, we must enable events before
* popping the stack frame (can't be done atomically) and so it would still
* be possible to get enough handler activations to overflow the stack.
* Although unlikely, bugs of that kind are hard to track down, so we'd
* like to avoid the possibility.
* So, on entry to the handler we detect whether we interrupted an
* existing activation in its critical region -- if so, we pop the current
* activation and restart the handler using the previous one.
*/
ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs)
CFI_STARTPROC
/*
* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
* see the correct pointer to the pt_regs
*/
movq %rdi, %rsp # we don't return, adjust the stack frame
CFI_ENDPROC
DEFAULT_FRAME
11: incl PER_CPU_VAR(irq_count)
movq %rsp,%rbp
CFI_DEF_CFA_REGISTER rbp
cmovzq PER_CPU_VAR(irq_stack_ptr),%rsp
pushq %rbp # backlink for old unwinder
call xen_evtchn_do_upcall
popq %rsp
CFI_DEF_CFA_REGISTER rsp
decl PER_CPU_VAR(irq_count)
jmp error_exit
CFI_ENDPROC
END(xen_do_hypervisor_callback)
/*
* Hypervisor uses this for application faults while it executes.
* We get here for two reasons:
* 1. Fault while reloading DS, ES, FS or GS
* 2. Fault while executing IRET
* Category 1 we do not need to fix up as Xen has already reloaded all segment
* registers that could be reloaded and zeroed the others.
* Category 2 we fix up by killing the current process. We cannot use the
* normal Linux return path in this case because if we use the IRET hypercall
* to pop the stack frame we end up in an infinite loop of failsafe callbacks.
* We distinguish between categories by comparing each saved segment register
* with its current contents: any discrepancy means we in category 1.
*/
ENTRY(xen_failsafe_callback)
INTR_FRAME 1 (6*8)
/*CFI_REL_OFFSET gs,GS*/
/*CFI_REL_OFFSET fs,FS*/
/*CFI_REL_OFFSET es,ES*/
/*CFI_REL_OFFSET ds,DS*/
CFI_REL_OFFSET r11,8
CFI_REL_OFFSET rcx,0
movw %ds,%cx
cmpw %cx,0x10(%rsp)
CFI_REMEMBER_STATE
jne 1f
movw %es,%cx
cmpw %cx,0x18(%rsp)
jne 1f
movw %fs,%cx
cmpw %cx,0x20(%rsp)
jne 1f
movw %gs,%cx
cmpw %cx,0x28(%rsp)
jne 1f
/* All segments match their saved values => Category 2 (Bad IRET). */
movq (%rsp),%rcx
CFI_RESTORE rcx
movq 8(%rsp),%r11
CFI_RESTORE r11
addq $0x30,%rsp
CFI_ADJUST_CFA_OFFSET -0x30
pushq_cfi $0 /* RIP */
pushq_cfi %r11
pushq_cfi %rcx
jmp general_protection
CFI_RESTORE_STATE
1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
movq (%rsp),%rcx
CFI_RESTORE rcx
movq 8(%rsp),%r11
CFI_RESTORE r11
addq $0x30,%rsp
CFI_ADJUST_CFA_OFFSET -0x30
pushq_cfi $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
jmp error_exit
CFI_ENDPROC
END(xen_failsafe_callback)
apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
xen_hvm_callback_vector xen_evtchn_do_upcall
#endif /* CONFIG_XEN */
#if IS_ENABLED(CONFIG_HYPERV)
apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \
hyperv_callback_vector hyperv_vector_handler
#endif /* CONFIG_HYPERV */
idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
idtentry int3 do_int3 has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK
idtentry stack_segment do_stack_segment has_error_code=1 paranoid=1
#ifdef CONFIG_XEN
idtentry xen_debug do_debug has_error_code=0
idtentry xen_int3 do_int3 has_error_code=0
idtentry xen_stack_segment do_stack_segment has_error_code=1
#endif
idtentry general_protection do_general_protection has_error_code=1
trace_idtentry page_fault do_page_fault has_error_code=1
#ifdef CONFIG_KVM_GUEST
idtentry async_page_fault do_async_page_fault has_error_code=1
#endif
#ifdef CONFIG_X86_MCE
idtentry machine_check has_error_code=0 paranoid=1 do_sym=*machine_check_vector(%rip)
#endif
/*
* "Paranoid" exit path from exception stack.
* Paranoid because this is used by NMIs and cannot take
* any kernel state for granted.
* We don't do kernel preemption checks here, because only
* NMI should be common and it does not enable IRQs and
* cannot get reschedule ticks.
*
* "trace" is 0 for the NMI handler only, because irq-tracing
* is fundamentally NMI-unsafe. (we cannot change the soft and
* hard flags at once, atomically)
*/
/* ebx: no swapgs flag */
ENTRY(paranoid_exit)
DEFAULT_FRAME
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF_DEBUG
testl %ebx,%ebx /* swapgs needed? */
jnz paranoid_restore
testl $3,CS(%rsp)
jnz paranoid_userspace
paranoid_swapgs:
TRACE_IRQS_IRETQ 0
SWAPGS_UNSAFE_STACK
RESTORE_ALL 8
jmp irq_return
paranoid_restore:
TRACE_IRQS_IRETQ_DEBUG 0
RESTORE_ALL 8
jmp irq_return
paranoid_userspace:
GET_THREAD_INFO(%rcx)
movl TI_flags(%rcx),%ebx
andl $_TIF_WORK_MASK,%ebx
jz paranoid_swapgs
movq %rsp,%rdi /* &pt_regs */
call sync_regs
movq %rax,%rsp /* switch stack for scheduling */
testl $_TIF_NEED_RESCHED,%ebx
jnz paranoid_schedule
movl %ebx,%edx /* arg3: thread flags */
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
xorl %esi,%esi /* arg2: oldset */
movq %rsp,%rdi /* arg1: &pt_regs */
call do_notify_resume
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
jmp paranoid_userspace
paranoid_schedule:
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_ANY)
SCHEDULE_USER
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
jmp paranoid_userspace
CFI_ENDPROC
END(paranoid_exit)
/*
* Exception entry point. This expects an error code/orig_rax on the stack.
* returns in "no swapgs flag" in %ebx.
*/
ENTRY(error_entry)
XCPT_FRAME
CFI_ADJUST_CFA_OFFSET 15*8
/* oldrax contains error code */
cld
movq_cfi rdi, RDI+8
movq_cfi rsi, RSI+8
movq_cfi rdx, RDX+8
movq_cfi rcx, RCX+8
movq_cfi rax, RAX+8
movq_cfi r8, R8+8
movq_cfi r9, R9+8
movq_cfi r10, R10+8
movq_cfi r11, R11+8
movq_cfi rbx, RBX+8
movq_cfi rbp, RBP+8
movq_cfi r12, R12+8
movq_cfi r13, R13+8
movq_cfi r14, R14+8
movq_cfi r15, R15+8
xorl %ebx,%ebx
testl $3,CS+8(%rsp)
je error_kernelspace
error_swapgs:
SWAPGS
error_sti:
TRACE_IRQS_OFF
ret
/*
* There are two places in the kernel that can potentially fault with
* usergs. Handle them here. The exception handlers after iret run with
* kernel gs again, so don't set the user space flag. B stepping K8s
* sometimes report an truncated RIP for IRET exceptions returning to
* compat mode. Check for these here too.
*/
error_kernelspace:
incl %ebx
leaq irq_return_iret(%rip),%rcx
cmpq %rcx,RIP+8(%rsp)
je error_swapgs
movl %ecx,%eax /* zero extend */
cmpq %rax,RIP+8(%rsp)
je bstep_iret
cmpq $gs_change,RIP+8(%rsp)
je error_swapgs
jmp error_sti
bstep_iret:
/* Fix truncated RIP */
movq %rcx,RIP+8(%rsp)
jmp error_swapgs
CFI_ENDPROC
END(error_entry)
/* ebx: no swapgs flag (1: don't need swapgs, 0: need it) */
ENTRY(error_exit)
DEFAULT_FRAME
movl %ebx,%eax
RESTORE_REST
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
GET_THREAD_INFO(%rcx)
testl %eax,%eax
jne retint_kernel
LOCKDEP_SYS_EXIT_IRQ
movl TI_flags(%rcx),%edx
movl $_TIF_WORK_MASK,%edi
andl %edi,%edx
jnz retint_careful
jmp retint_swapgs
CFI_ENDPROC
END(error_exit)
/*
* Test if a given stack is an NMI stack or not.
*/
.macro test_in_nmi reg stack nmi_ret normal_ret
cmpq %\reg, \stack
ja \normal_ret
subq $EXCEPTION_STKSZ, %\reg
cmpq %\reg, \stack
jb \normal_ret
jmp \nmi_ret
.endm
/* runs on exception stack */
ENTRY(nmi)
INTR_FRAME
PARAVIRT_ADJUST_EXCEPTION_FRAME
/*
* We allow breakpoints in NMIs. If a breakpoint occurs, then
* the iretq it performs will take us out of NMI context.
* This means that we can have nested NMIs where the next
* NMI is using the top of the stack of the previous NMI. We
* can't let it execute because the nested NMI will corrupt the
* stack of the previous NMI. NMI handlers are not re-entrant
* anyway.
*
* To handle this case we do the following:
* Check the a special location on the stack that contains
* a variable that is set when NMIs are executing.
* The interrupted task's stack is also checked to see if it
* is an NMI stack.
* If the variable is not set and the stack is not the NMI
* stack then:
* o Set the special variable on the stack
* o Copy the interrupt frame into a "saved" location on the stack
* o Copy the interrupt frame into a "copy" location on the stack
* o Continue processing the NMI
* If the variable is set or the previous stack is the NMI stack:
* o Modify the "copy" location to jump to the repeate_nmi
* o return back to the first NMI
*
* Now on exit of the first NMI, we first clear the stack variable
* The NMI stack will tell any nested NMIs at that point that it is
* nested. Then we pop the stack normally with iret, and if there was
* a nested NMI that updated the copy interrupt stack frame, a
* jump will be made to the repeat_nmi code that will handle the second
* NMI.
*/
/* Use %rdx as out temp variable throughout */
pushq_cfi %rdx
CFI_REL_OFFSET rdx, 0
/*
* If %cs was not the kernel segment, then the NMI triggered in user
* space, which means it is definitely not nested.
*/
cmpl $__KERNEL_CS, 16(%rsp)
jne first_nmi
/*
* Check the special variable on the stack to see if NMIs are
* executing.
*/
cmpl $1, -8(%rsp)
je nested_nmi
/*
* Now test if the previous stack was an NMI stack.
* We need the double check. We check the NMI stack to satisfy the
* race when the first NMI clears the variable before returning.
* We check the variable because the first NMI could be in a
* breakpoint routine using a breakpoint stack.
*/
lea 6*8(%rsp), %rdx
test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
CFI_REMEMBER_STATE
nested_nmi:
/*
* Do nothing if we interrupted the fixup in repeat_nmi.
* It's about to repeat the NMI handler, so we are fine
* with ignoring this one.
*/
movq $repeat_nmi, %rdx
cmpq 8(%rsp), %rdx
ja 1f
movq $end_repeat_nmi, %rdx
cmpq 8(%rsp), %rdx
ja nested_nmi_out
1:
/* Set up the interrupted NMIs stack to jump to repeat_nmi */
leaq -1*8(%rsp), %rdx
movq %rdx, %rsp
CFI_ADJUST_CFA_OFFSET 1*8
leaq -10*8(%rsp), %rdx
pushq_cfi $__KERNEL_DS
pushq_cfi %rdx
pushfq_cfi
pushq_cfi $__KERNEL_CS
pushq_cfi $repeat_nmi
/* Put stack back */
addq $(6*8), %rsp
CFI_ADJUST_CFA_OFFSET -6*8
nested_nmi_out:
popq_cfi %rdx
CFI_RESTORE rdx
/* No need to check faults here */
INTERRUPT_RETURN
CFI_RESTORE_STATE
first_nmi:
/*
* Because nested NMIs will use the pushed location that we
* stored in rdx, we must keep that space available.
* Here's what our stack frame will look like:
* +-------------------------+
* | original SS |
* | original Return RSP |
* | original RFLAGS |
* | original CS |
* | original RIP |
* +-------------------------+
* | temp storage for rdx |
* +-------------------------+
* | NMI executing variable |
* +-------------------------+
* | copied SS |
* | copied Return RSP |
* | copied RFLAGS |
* | copied CS |
* | copied RIP |
* +-------------------------+
* | Saved SS |
* | Saved Return RSP |
* | Saved RFLAGS |
* | Saved CS |
* | Saved RIP |
* +-------------------------+
* | pt_regs |
* +-------------------------+
*
* The saved stack frame is used to fix up the copied stack frame
* that a nested NMI may change to make the interrupted NMI iret jump
* to the repeat_nmi. The original stack frame and the temp storage
* is also used by nested NMIs and can not be trusted on exit.
*/
/* Do not pop rdx, nested NMIs will corrupt that part of the stack */
movq (%rsp), %rdx
CFI_RESTORE rdx
/* Set the NMI executing variable on the stack. */
pushq_cfi $1
/*
* Leave room for the "copied" frame
*/
subq $(5*8), %rsp
CFI_ADJUST_CFA_OFFSET 5*8
/* Copy the stack frame to the Saved frame */
.rept 5
pushq_cfi 11*8(%rsp)
.endr
CFI_DEF_CFA_OFFSET SS+8-RIP
/* Everything up to here is safe from nested NMIs */
/*
* If there was a nested NMI, the first NMI's iret will return
* here. But NMIs are still enabled and we can take another
* nested NMI. The nested NMI checks the interrupted RIP to see
* if it is between repeat_nmi and end_repeat_nmi, and if so
* it will just return, as we are about to repeat an NMI anyway.
* This makes it safe to copy to the stack frame that a nested
* NMI will update.
*/
repeat_nmi:
/*
* Update the stack variable to say we are still in NMI (the update
* is benign for the non-repeat case, where 1 was pushed just above
* to this very stack slot).
*/
movq $1, 10*8(%rsp)
/* Make another copy, this one may be modified by nested NMIs */
addq $(10*8), %rsp
CFI_ADJUST_CFA_OFFSET -10*8
.rept 5
pushq_cfi -6*8(%rsp)
.endr
subq $(5*8), %rsp
CFI_DEF_CFA_OFFSET SS+8-RIP
end_repeat_nmi:
/*
* Everything below this point can be preempted by a nested
* NMI if the first NMI took an exception and reset our iret stack
* so that we repeat another NMI.
*/
pushq_cfi $-1 /* ORIG_RAX: no syscall to restart */
subq $ORIG_RAX-R15, %rsp
CFI_ADJUST_CFA_OFFSET ORIG_RAX-R15
/*
* Use save_paranoid to handle SWAPGS, but no need to use paranoid_exit
* as we should not be calling schedule in NMI context.
* Even with normal interrupts enabled. An NMI should not be
* setting NEED_RESCHED or anything that normal interrupts and
* exceptions might do.
*/
call save_paranoid
DEFAULT_FRAME 0
/*
* Save off the CR2 register. If we take a page fault in the NMI then
* it could corrupt the CR2 value. If the NMI preempts a page fault
* handler before it was able to read the CR2 register, and then the
* NMI itself takes a page fault, the page fault that was preempted
* will read the information from the NMI page fault and not the
* origin fault. Save it off and restore it if it changes.
* Use the r12 callee-saved register.
*/
movq %cr2, %r12
/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
movq %rsp,%rdi
movq $-1,%rsi
call do_nmi
/* Did the NMI take a page fault? Restore cr2 if it did */
movq %cr2, %rcx
cmpq %rcx, %r12
je 1f
movq %r12, %cr2
1:
testl %ebx,%ebx /* swapgs needed? */
jnz nmi_restore
nmi_swapgs:
SWAPGS_UNSAFE_STACK
nmi_restore:
/* Pop the extra iret frame at once */
RESTORE_ALL 6*8
/* Clear the NMI executing stack variable */
movq $0, 5*8(%rsp)
jmp irq_return
CFI_ENDPROC
END(nmi)
ENTRY(ignore_sysret)
CFI_STARTPROC
mov $-ENOSYS,%eax
sysret
CFI_ENDPROC
END(ignore_sysret)
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