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alistair23-linux/arch/x86/kernel/entry_64.S
Andy Lutomirski 96b6352c12 x86_64, entry: Remove the syscall exit audit and schedule optimizations 
We used to optimize rescheduling and audit on syscall exit.  Now
that the full slow path is reasonably fast, remove these
optimizations.  Syscall exit auditing is now handled exclusively by
syscall_trace_leave.

This adds something like 10ns to the previously optimized paths on
my computer, presumably due mostly to SAVE_REST / RESTORE_REST.

I think that we should eventually replace both the syscall and
non-paranoid interrupt exit slow paths with a pair of C functions
along the lines of the syscall entry hooks.

Link: http://lkml.kernel.org/r/22f2aa4a0361707a5cfb1de9d45260b39965dead.1421453410.git.luto@amacapital.net
Acked-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
2015-02-01 04:03:02 -08:00

1677 lines
42 KiB
ArmAsm
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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 RIP+\offset(%rsp),\tmp /* get rip */
movq \tmp,RCX+\offset(%rsp) /* copy it to rcx as sysret would do */
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
/*
* 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
.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
ENTRY(save_paranoid)
XCPT_FRAME 1 RDI+8
cld
movq %rdi, RDI+8(%rsp)
movq %rsi, RSI+8(%rsp)
movq_cfi rdx, RDX+8
movq_cfi rcx, RCX+8
movq_cfi rax, RAX+8
movq %r8, R8+8(%rsp)
movq %r9, R9+8(%rsp)
movq %r10, R10+8(%rsp)
movq %r11, R11+8(%rsp)
movq_cfi rbx, RBX+8
movq %rbp, RBP+8(%rsp)
movq %r12, R12+8(%rsp)
movq %r13, R13+8(%rsp)
movq %r14, R14+8(%rsp)
movq %r15, R15+8(%rsp)
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, rax_enosys=1
movq_cfi rax,(ORIG_RAX-ARGOFFSET)
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 ret_from_sys_call /* and return regs->ax */
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:
testl $_TIF_ALLWORK_MASK,TI_flags+THREAD_INFO(%rsp,RIP-ARGOFFSET)
jnz int_ret_from_sys_call_fixup /* Go the the slow path */
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
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
int_ret_from_sys_call_fixup:
FIXUP_TOP_OF_STACK %r11, -ARGOFFSET
jmp int_ret_from_sys_call
/* Do syscall tracing */
tracesys:
leaq -REST_SKIP(%rsp), %rdi
movq $AUDIT_ARCH_X86_64, %rsi
call syscall_trace_enter_phase1
test %rax, %rax
jnz tracesys_phase2 /* if needed, run the slow path */
LOAD_ARGS 0 /* else restore clobbered regs */
jmp system_call_fastpath /* and return to the fast path */
tracesys_phase2:
SAVE_REST
FIXUP_TOP_OF_STACK %rdi
movq %rsp, %rdi
movq $AUDIT_ARCH_X86_64, %rsi
movq %rax,%rdx
call syscall_trace_enter_phase2
/*
* Reload arg registers from stack in case ptrace changed them.
* We don't reload %rax because syscall_trace_entry_phase2() 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) is already set */
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(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)
ENTRY(stub_execveat)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call sys_execveat
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_execveat)
/*
* 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)
ENTRY(stub_x32_execveat)
CFI_STARTPROC
addq $8, %rsp
PARTIAL_FRAME 0
SAVE_REST
FIXUP_TOP_OF_STACK %r11
call compat_sys_execveat
RESTORE_TOP_OF_STACK %r11
movq %rax,RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_x32_execveat)
#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 (FIRST_SYSTEM_VECTOR-FIRST_EXTERNAL_VECTOR+6)/7
.balign 32
.rept 7
.if vector < FIRST_SYSTEM_VECTOR
.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
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
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
/*
* Try to use SYSRET instead of IRET if we're returning to
* a completely clean 64-bit userspace context.
*/
movq (RCX-R11)(%rsp), %rcx
cmpq %rcx,(RIP-R11)(%rsp) /* RCX == RIP */
jne opportunistic_sysret_failed
/*
* On Intel CPUs, sysret with non-canonical RCX/RIP will #GP
* in kernel space. This essentially lets the user take over
* the kernel, since userspace controls RSP. It's not worth
* testing for canonicalness exactly -- this check detects any
* of the 17 high bits set, which is true for non-canonical
* or kernel addresses. (This will pessimize vsyscall=native.
* Big deal.)
*
* If virtual addresses ever become wider, this will need
* to be updated to remain correct on both old and new CPUs.
*/
.ifne __VIRTUAL_MASK_SHIFT - 47
.error "virtual address width changed -- sysret checks need update"
.endif
shr $__VIRTUAL_MASK_SHIFT, %rcx
jnz opportunistic_sysret_failed
cmpq $__USER_CS,(CS-R11)(%rsp) /* CS must match SYSRET */
jne opportunistic_sysret_failed
movq (R11-ARGOFFSET)(%rsp), %r11
cmpq %r11,(EFLAGS-ARGOFFSET)(%rsp) /* R11 == RFLAGS */
jne opportunistic_sysret_failed
testq $X86_EFLAGS_RF,%r11 /* sysret can't restore RF */
jnz opportunistic_sysret_failed
/* nothing to check for RSP */
cmpq $__USER_DS,(SS-ARGOFFSET)(%rsp) /* SS must match SYSRET */
jne opportunistic_sysret_failed
/*
* We win! This label is here just for ease of understanding
* perf profiles. Nothing jumps here.
*/
irq_return_via_sysret:
CFI_REMEMBER_STATE
RESTORE_ARGS 1,8,1
movq (RSP-RIP)(%rsp),%rsp
USERGS_SYSRET64
CFI_RESTORE_STATE
opportunistic_sysret_failed:
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:
INTERRUPT_RETURN
ENTRY(native_iret)
/*
* 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 native_irq_return_ldt
#endif
.global native_irq_return_iret
native_irq_return_iret:
/*
* This may fault. Non-paranoid faults on return to userspace are
* handled by fixup_bad_iret. These include #SS, #GP, and #NP.
* Double-faults due to espfix64 are handled in do_double_fault.
* Other faults here are fatal.
*/
iretq
#ifdef CONFIG_X86_ESPFIX64
native_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 native_irq_return_iret
#endif
/* 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)
/*
* 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
.if \paranoid == 1
CFI_REMEMBER_STATE
testl $3, CS(%rsp) /* If coming from userspace, switch */
jnz 1f /* stacks. */
.endif
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
.if \paranoid == 1
CFI_RESTORE_STATE
/*
* Paranoid entry from userspace. Switch stacks and treat it
* as a normal entry. This means that paranoid handlers
* run in real process context if user_mode(regs).
*/
1:
call error_entry
DEFAULT_FRAME 0
movq %rsp,%rdi /* pt_regs pointer */
call sync_regs
movq %rax,%rsp /* switch stack */
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
call \do_sym
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=2
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
#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. This is invoked
* only on return from non-NMI IST interrupts that came
* from kernel space.
*
* We may be returning to very strange contexts (e.g. very early
* in syscall entry), so checking for preemption here would
* be complicated. Fortunately, we there's no good reason
* to try to handle preemption here.
*/
/* 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
TRACE_IRQS_IRETQ 0
SWAPGS_UNSAFE_STACK
RESTORE_ALL 8
INTERRUPT_RETURN
paranoid_restore:
TRACE_IRQS_IRETQ_DEBUG 0
RESTORE_ALL 8
INTERRUPT_RETURN
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 %rdi, RDI+8(%rsp)
movq %rsi, RSI+8(%rsp)
movq %rdx, RDX+8(%rsp)
movq %rcx, RCX+8(%rsp)
movq %rax, RAX+8(%rsp)
movq %r8, R8+8(%rsp)
movq %r9, R9+8(%rsp)
movq %r10, R10+8(%rsp)
movq %r11, R11+8(%rsp)
movq_cfi rbx, RBX+8
movq %rbp, RBP+8(%rsp)
movq %r12, R12+8(%rsp)
movq %r13, R13+8(%rsp)
movq %r14, R14+8(%rsp)
movq %r15, R15+8(%rsp)
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. B stepping K8s sometimes report a
* truncated RIP for IRET exceptions returning to compat mode. Check
* for these here too.
*/
error_kernelspace:
CFI_REL_OFFSET rcx, RCX+8
incl %ebx
leaq native_irq_return_iret(%rip),%rcx
cmpq %rcx,RIP+8(%rsp)
je error_bad_iret
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)
/* fall through */
error_bad_iret:
SWAPGS
mov %rsp,%rdi
call fixup_bad_iret
mov %rax,%rsp
decl %ebx /* Return to usergs */
jmp error_sti
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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