Commit 7effaa88 authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds
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[PATCH] x86-64: Fix CFI information



Being the foundation for reliable stack unwinding, this fixes CFI unwind
annotations in many low-level x86_64 routines, plus a config option
(available to all architectures, and also present in the previously sent
patch adding such annotations to i386 code) to enable them separatly
rather than only along with adding full debug information.
Signed-off-by: default avatarJan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b3ab8382
......@@ -55,20 +55,34 @@
* with the int 0x80 path.
*/
ENTRY(ia32_sysenter_target)
CFI_STARTPROC
CFI_STARTPROC simple
CFI_DEF_CFA rsp,0
CFI_REGISTER rsp,rbp
swapgs
movq %gs:pda_kernelstack, %rsp
addq $(PDA_STACKOFFSET),%rsp
sti
movl %ebp,%ebp /* zero extension */
pushq $__USER32_DS
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET ss,0*/
pushq %rbp
CFI_ADJUST_CFA_OFFSET 8
CFI_REL_OFFSET rsp,0
pushfq
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET rflags,0*/
movl $VSYSCALL32_SYSEXIT, %r10d
CFI_REGISTER rip,r10
pushq $__USER32_CS
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET cs,0*/
movl %eax, %eax
pushq %r10
CFI_ADJUST_CFA_OFFSET 8
CFI_REL_OFFSET rip,0
pushq %rax
CFI_ADJUST_CFA_OFFSET 8
cld
SAVE_ARGS 0,0,1
/* no need to do an access_ok check here because rbp has been
......@@ -79,6 +93,7 @@ ENTRY(ia32_sysenter_target)
.previous
GET_THREAD_INFO(%r10)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
CFI_REMEMBER_STATE
jnz sysenter_tracesys
sysenter_do_call:
cmpl $(IA32_NR_syscalls),%eax
......@@ -94,14 +109,20 @@ sysenter_do_call:
andl $~0x200,EFLAGS-R11(%rsp)
RESTORE_ARGS 1,24,1,1,1,1
popfq
CFI_ADJUST_CFA_OFFSET -8
/*CFI_RESTORE rflags*/
popq %rcx /* User %esp */
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rsp,rcx
movl $VSYSCALL32_SYSEXIT,%edx /* User %eip */
CFI_REGISTER rip,rdx
swapgs
sti /* sti only takes effect after the next instruction */
/* sysexit */
.byte 0xf, 0x35
sysenter_tracesys:
CFI_RESTORE_STATE
SAVE_REST
CLEAR_RREGS
movq $-ENOSYS,RAX(%rsp) /* really needed? */
......@@ -140,21 +161,28 @@ sysenter_tracesys:
* with the int 0x80 path.
*/
ENTRY(ia32_cstar_target)
CFI_STARTPROC
CFI_STARTPROC simple
CFI_DEF_CFA rsp,0
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
swapgs
movl %esp,%r8d
CFI_REGISTER rsp,r8
movq %gs:pda_kernelstack,%rsp
sti
SAVE_ARGS 8,1,1
movl %eax,%eax /* zero extension */
movq %rax,ORIG_RAX-ARGOFFSET(%rsp)
movq %rcx,RIP-ARGOFFSET(%rsp)
CFI_REL_OFFSET rip,RIP-ARGOFFSET
movq %rbp,RCX-ARGOFFSET(%rsp) /* this lies slightly to ptrace */
movl %ebp,%ecx
movq $__USER32_CS,CS-ARGOFFSET(%rsp)
movq $__USER32_DS,SS-ARGOFFSET(%rsp)
movq %r11,EFLAGS-ARGOFFSET(%rsp)
/*CFI_REL_OFFSET rflags,EFLAGS-ARGOFFSET*/
movq %r8,RSP-ARGOFFSET(%rsp)
CFI_REL_OFFSET rsp,RSP-ARGOFFSET
/* no need to do an access_ok check here because r8 has been
32bit zero extended */
/* hardware stack frame is complete now */
......@@ -164,6 +192,7 @@ ENTRY(ia32_cstar_target)
.previous
GET_THREAD_INFO(%r10)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%r10)
CFI_REMEMBER_STATE
jnz cstar_tracesys
cstar_do_call:
cmpl $IA32_NR_syscalls,%eax
......@@ -177,12 +206,16 @@ cstar_do_call:
jnz int_ret_from_sys_call
RESTORE_ARGS 1,-ARG_SKIP,1,1,1
movl RIP-ARGOFFSET(%rsp),%ecx
CFI_REGISTER rip,rcx
movl EFLAGS-ARGOFFSET(%rsp),%r11d
/*CFI_REGISTER rflags,r11*/
movl RSP-ARGOFFSET(%rsp),%esp
CFI_RESTORE rsp
swapgs
sysretl
cstar_tracesys:
CFI_RESTORE_STATE
SAVE_REST
CLEAR_RREGS
movq $-ENOSYS,RAX(%rsp) /* really needed? */
......@@ -226,11 +259,18 @@ ia32_badarg:
*/
ENTRY(ia32_syscall)
CFI_STARTPROC
CFI_STARTPROC simple
CFI_DEF_CFA rsp,SS+8-RIP
/*CFI_REL_OFFSET ss,SS-RIP*/
CFI_REL_OFFSET rsp,RSP-RIP
/*CFI_REL_OFFSET rflags,EFLAGS-RIP*/
/*CFI_REL_OFFSET cs,CS-RIP*/
CFI_REL_OFFSET rip,RIP-RIP
swapgs
sti
movl %eax,%eax
pushq %rax
CFI_ADJUST_CFA_OFFSET 8
cld
/* note the registers are not zero extended to the sf.
this could be a problem. */
......@@ -278,6 +318,8 @@ quiet_ni_syscall:
jmp ia32_ptregs_common
.endm
CFI_STARTPROC
PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn, %rdi
PTREGSCALL stub32_sigreturn, sys32_sigreturn, %rdi
PTREGSCALL stub32_sigaltstack, sys32_sigaltstack, %rdx
......@@ -290,8 +332,9 @@ quiet_ni_syscall:
PTREGSCALL stub32_rt_sigsuspend, sys_rt_sigsuspend, %rdx
ENTRY(ia32_ptregs_common)
CFI_STARTPROC
popq %r11
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rip, r11
SAVE_REST
call *%rax
RESTORE_REST
......
......@@ -79,16 +79,19 @@
xorl %eax, %eax
pushq %rax /* ss */
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET ss,0*/
pushq %rax /* rsp */
CFI_ADJUST_CFA_OFFSET 8
CFI_OFFSET rip,0
CFI_REL_OFFSET rsp,0
pushq $(1<<9) /* eflags - interrupts on */
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET rflags,0*/
pushq $__KERNEL_CS /* cs */
CFI_ADJUST_CFA_OFFSET 8
/*CFI_REL_OFFSET cs,0*/
pushq \child_rip /* rip */
CFI_ADJUST_CFA_OFFSET 8
CFI_OFFSET rip,0
CFI_REL_OFFSET rip,0
pushq %rax /* orig rax */
CFI_ADJUST_CFA_OFFSET 8
.endm
......@@ -98,32 +101,39 @@
CFI_ADJUST_CFA_OFFSET -(6*8)
.endm
.macro CFI_DEFAULT_STACK
CFI_ADJUST_CFA_OFFSET (SS)
CFI_OFFSET r15,R15-SS
CFI_OFFSET r14,R14-SS
CFI_OFFSET r13,R13-SS
CFI_OFFSET r12,R12-SS
CFI_OFFSET rbp,RBP-SS
CFI_OFFSET rbx,RBX-SS
CFI_OFFSET r11,R11-SS
CFI_OFFSET r10,R10-SS
CFI_OFFSET r9,R9-SS
CFI_OFFSET r8,R8-SS
CFI_OFFSET rax,RAX-SS
CFI_OFFSET rcx,RCX-SS
CFI_OFFSET rdx,RDX-SS
CFI_OFFSET rsi,RSI-SS
CFI_OFFSET rdi,RDI-SS
CFI_OFFSET rsp,RSP-SS
CFI_OFFSET rip,RIP-SS
.macro CFI_DEFAULT_STACK start=1
.if \start
CFI_STARTPROC simple
CFI_DEF_CFA rsp,SS+8
.else
CFI_DEF_CFA_OFFSET SS+8
.endif
CFI_REL_OFFSET r15,R15
CFI_REL_OFFSET r14,R14
CFI_REL_OFFSET r13,R13
CFI_REL_OFFSET r12,R12
CFI_REL_OFFSET rbp,RBP
CFI_REL_OFFSET rbx,RBX
CFI_REL_OFFSET r11,R11
CFI_REL_OFFSET r10,R10
CFI_REL_OFFSET r9,R9
CFI_REL_OFFSET r8,R8
CFI_REL_OFFSET rax,RAX
CFI_REL_OFFSET rcx,RCX
CFI_REL_OFFSET rdx,RDX
CFI_REL_OFFSET rsi,RSI
CFI_REL_OFFSET rdi,RDI
CFI_REL_OFFSET rip,RIP
/*CFI_REL_OFFSET cs,CS*/
/*CFI_REL_OFFSET rflags,EFLAGS*/
CFI_REL_OFFSET rsp,RSP
/*CFI_REL_OFFSET ss,SS*/
.endm
/*
* A newly forked process directly context switches into this.
*/
/* rdi: prev */
ENTRY(ret_from_fork)
CFI_STARTPROC
CFI_DEFAULT_STACK
call schedule_tail
GET_THREAD_INFO(%rcx)
......@@ -172,16 +182,21 @@ rff_trace:
*/
ENTRY(system_call)
CFI_STARTPROC
CFI_STARTPROC simple
CFI_DEF_CFA rsp,0
CFI_REGISTER rip,rcx
/*CFI_REGISTER rflags,r11*/
swapgs
movq %rsp,%gs:pda_oldrsp
movq %gs:pda_kernelstack,%rsp
sti
SAVE_ARGS 8,1
movq %rax,ORIG_RAX-ARGOFFSET(%rsp)
movq %rcx,RIP-ARGOFFSET(%rsp)
movq %rcx,RIP-ARGOFFSET(%rsp)
CFI_REL_OFFSET rip,RIP-ARGOFFSET
GET_THREAD_INFO(%rcx)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP),threadinfo_flags(%rcx)
CFI_REMEMBER_STATE
jnz tracesys
cmpq $__NR_syscall_max,%rax
ja badsys
......@@ -201,9 +216,12 @@ sysret_check:
cli
movl threadinfo_flags(%rcx),%edx
andl %edi,%edx
CFI_REMEMBER_STATE
jnz sysret_careful
movq RIP-ARGOFFSET(%rsp),%rcx
CFI_REGISTER rip,rcx
RESTORE_ARGS 0,-ARG_SKIP,1
/*CFI_REGISTER rflags,r11*/
movq %gs:pda_oldrsp,%rsp
swapgs
sysretq
......@@ -211,12 +229,15 @@ sysret_check:
/* Handle reschedules */
/* edx: work, edi: workmask */
sysret_careful:
CFI_RESTORE_STATE
bt $TIF_NEED_RESCHED,%edx
jnc sysret_signal
sti
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
jmp sysret_check
/* Handle a signal */
......@@ -234,8 +255,13 @@ sysret_signal:
1: movl $_TIF_NEED_RESCHED,%edi
jmp sysret_check
badsys:
movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
jmp ret_from_sys_call
/* Do syscall tracing */
tracesys:
CFI_RESTORE_STATE
SAVE_REST
movq $-ENOSYS,RAX(%rsp)
FIXUP_TOP_OF_STACK %rdi
......@@ -254,16 +280,29 @@ tracesys:
RESTORE_TOP_OF_STACK %rbx
RESTORE_REST
jmp ret_from_sys_call
CFI_ENDPROC
badsys:
movq $-ENOSYS,RAX-ARGOFFSET(%rsp)
jmp ret_from_sys_call
/*
* Syscall return path ending with IRET.
* Has correct top of stack, but partial stack frame.
*/
ENTRY(int_ret_from_sys_call)
ENTRY(int_ret_from_sys_call)
CFI_STARTPROC simple
CFI_DEF_CFA rsp,SS+8-ARGOFFSET
/*CFI_REL_OFFSET ss,SS-ARGOFFSET*/
CFI_REL_OFFSET rsp,RSP-ARGOFFSET
/*CFI_REL_OFFSET rflags,EFLAGS-ARGOFFSET*/
/*CFI_REL_OFFSET cs,CS-ARGOFFSET*/
CFI_REL_OFFSET rip,RIP-ARGOFFSET
CFI_REL_OFFSET rdx,RDX-ARGOFFSET
CFI_REL_OFFSET rcx,RCX-ARGOFFSET
CFI_REL_OFFSET rax,RAX-ARGOFFSET
CFI_REL_OFFSET rdi,RDI-ARGOFFSET
CFI_REL_OFFSET rsi,RSI-ARGOFFSET
CFI_REL_OFFSET r8,R8-ARGOFFSET
CFI_REL_OFFSET r9,R9-ARGOFFSET
CFI_REL_OFFSET r10,R10-ARGOFFSET
CFI_REL_OFFSET r11,R11-ARGOFFSET
cli
testl $3,CS-ARGOFFSET(%rsp)
je retint_restore_args
......@@ -284,8 +323,10 @@ int_careful:
jnc int_very_careful
sti
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
cli
jmp int_with_check
......@@ -297,9 +338,11 @@ int_very_careful:
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edx
jz int_signal
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
leaq 8(%rsp),%rdi # &ptregs -> arg1
call syscall_trace_leave
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
andl $~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edi
cli
jmp int_restore_rest
......@@ -329,6 +372,8 @@ int_restore_rest:
jmp ptregscall_common
.endm
CFI_STARTPROC
PTREGSCALL stub_clone, sys_clone, %r8
PTREGSCALL stub_fork, sys_fork, %rdi
PTREGSCALL stub_vfork, sys_vfork, %rdi
......@@ -337,40 +382,49 @@ int_restore_rest:
PTREGSCALL stub_iopl, sys_iopl, %rsi
ENTRY(ptregscall_common)
CFI_STARTPROC
popq %r11
CFI_ADJUST_CFA_OFFSET -8
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rip, r11
SAVE_REST
movq %r11, %r15
CFI_REGISTER rip, r15
FIXUP_TOP_OF_STACK %r11
call *%rax
RESTORE_TOP_OF_STACK %r11
movq %r15, %r11
CFI_REGISTER rip, r11
RESTORE_REST
pushq %r11
CFI_ADJUST_CFA_OFFSET 8
CFI_ADJUST_CFA_OFFSET 8
CFI_REL_OFFSET rip, 0
ret
CFI_ENDPROC
ENTRY(stub_execve)
CFI_STARTPROC
popq %r11
CFI_ADJUST_CFA_OFFSET -8
CFI_ADJUST_CFA_OFFSET -8
CFI_REGISTER rip, r11
SAVE_REST
movq %r11, %r15
CFI_REGISTER rip, r15
FIXUP_TOP_OF_STACK %r11
call sys_execve
GET_THREAD_INFO(%rcx)
bt $TIF_IA32,threadinfo_flags(%rcx)
CFI_REMEMBER_STATE
jc exec_32bit
RESTORE_TOP_OF_STACK %r11
movq %r15, %r11
CFI_REGISTER rip, r11
RESTORE_REST
push %r11
pushq %r11
CFI_ADJUST_CFA_OFFSET 8
CFI_REL_OFFSET rip, 0
ret
exec_32bit:
CFI_ADJUST_CFA_OFFSET REST_SKIP
CFI_RESTORE_STATE
movq %rax,RAX(%rsp)
RESTORE_REST
jmp int_ret_from_sys_call
......@@ -382,7 +436,8 @@ exec_32bit:
*/
ENTRY(stub_rt_sigreturn)
CFI_STARTPROC
addq $8, %rsp
addq $8, %rsp
CFI_ADJUST_CFA_OFFSET -8
SAVE_REST
movq %rsp,%rdi
FIXUP_TOP_OF_STACK %r11
......@@ -392,6 +447,25 @@ ENTRY(stub_rt_sigreturn)
jmp int_ret_from_sys_call
CFI_ENDPROC
/*
* initial frame state for interrupts and exceptions
*/
.macro _frame ref
CFI_STARTPROC simple
CFI_DEF_CFA rsp,SS+8-\ref
/*CFI_REL_OFFSET ss,SS-\ref*/
CFI_REL_OFFSET rsp,RSP-\ref
/*CFI_REL_OFFSET rflags,EFLAGS-\ref*/
/*CFI_REL_OFFSET cs,CS-\ref*/
CFI_REL_OFFSET rip,RIP-\ref
.endm
/* initial frame state for interrupts (and exceptions without error code) */
#define INTR_FRAME _frame RIP
/* initial frame state for exceptions with error code (and interrupts with
vector already pushed) */
#define XCPT_FRAME _frame ORIG_RAX
/*
* Interrupt entry/exit.
*
......@@ -402,10 +476,6 @@ ENTRY(stub_rt_sigreturn)
/* 0(%rsp): interrupt number */
.macro interrupt func
CFI_STARTPROC simple
CFI_DEF_CFA rsp,(SS-RDI)
CFI_REL_OFFSET rsp,(RSP-ORIG_RAX)
CFI_REL_OFFSET rip,(RIP-ORIG_RAX)
cld
#ifdef CONFIG_DEBUG_INFO
SAVE_ALL
......@@ -425,23 +495,27 @@ ENTRY(stub_rt_sigreturn)
swapgs
1: incl %gs:pda_irqcount # RED-PEN should check preempt count
movq %gs:pda_irqstackptr,%rax
cmoveq %rax,%rsp
cmoveq %rax,%rsp /*todo This needs CFI annotation! */
pushq %rdi # save old stack
CFI_ADJUST_CFA_OFFSET 8
call \func
.endm
ENTRY(common_interrupt)
XCPT_FRAME
interrupt do_IRQ
/* 0(%rsp): oldrsp-ARGOFFSET */
ret_from_intr:
ret_from_intr:
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
cli
decl %gs:pda_irqcount
#ifdef CONFIG_DEBUG_INFO
movq RBP(%rdi),%rbp
CFI_DEF_CFA_REGISTER rsp
#endif
leaq ARGOFFSET(%rdi),%rsp
exit_intr:
leaq ARGOFFSET(%rdi),%rsp /*todo This needs CFI annotation! */
exit_intr:
GET_THREAD_INFO(%rcx)
testl $3,CS-ARGOFFSET(%rsp)
je retint_kernel
......@@ -453,9 +527,10 @@ exit_intr:
*/
retint_with_reschedule:
movl $_TIF_WORK_MASK,%edi
retint_check:
retint_check:
movl threadinfo_flags(%rcx),%edx
andl %edi,%edx
CFI_REMEMBER_STATE
jnz retint_careful
retint_swapgs:
swapgs
......@@ -476,14 +551,17 @@ bad_iret:
jmp do_exit
.previous
/* edi: workmask, edx: work */
/* edi: workmask, edx: work */
retint_careful:
CFI_RESTORE_STATE
bt $TIF_NEED_RESCHED,%edx
jnc retint_signal
sti
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
call schedule
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
GET_THREAD_INFO(%rcx)
cli
jmp retint_check
......@@ -523,7 +601,9 @@ retint_kernel:
* APIC interrupts.
*/
.macro apicinterrupt num,func
INTR_FRAME
pushq $\num-256
CFI_ADJUST_CFA_OFFSET 8
interrupt \func
jmp ret_from_intr
CFI_ENDPROC
......@@ -569,16 +649,23 @@ ENTRY(spurious_interrupt)
* Exception entry points.
*/
.macro zeroentry sym
INTR_FRAME
pushq $0 /* push error code/oldrax */
CFI_ADJUST_CFA_OFFSET 8
pushq %rax /* push real oldrax to the rdi slot */
CFI_ADJUST_CFA_OFFSET 8
leaq \sym(%rip),%rax
jmp error_entry
CFI_ENDPROC
.endm
.macro errorentry sym
XCPT_FRAME
pushq %rax
CFI_ADJUST_CFA_OFFSET 8
leaq \sym(%rip),%rax
jmp error_entry
CFI_ENDPROC
.endm
/* error code is on the stack already */
......@@ -605,10 +692,7 @@ ENTRY(spurious_interrupt)
* and the exception handler in %rax.
*/
ENTRY(error_entry)
CFI_STARTPROC simple
CFI_DEF_CFA rsp,(SS-RDI)
CFI_REL_OFFSET rsp,(RSP-RDI)
CFI_REL_OFFSET rip,(RIP-RDI)
_frame RDI
/* rdi slot contains rax, oldrax contains error code */
cld
subq $14*8,%rsp
......@@ -690,7 +774,9 @@ error_kernelspace:
/* Reload gs selector with exception handling */
/* edi: new selector */
ENTRY(load_gs_index)
CFI_STARTPROC
pushf
CFI_ADJUST_CFA_OFFSET 8
cli
swapgs
gs_change:
......@@ -698,7 +784,9 @@ gs_change:
2: mfence /* workaround */
swapgs
popf
CFI_ADJUST_CFA_OFFSET -8
ret
CFI_ENDPROC
.section __ex_table,"a"
.align 8
......@@ -810,7 +898,7 @@ ENTRY(device_not_available)
/* runs on exception stack */
KPROBE_ENTRY(debug)
CFI_STARTPROC
INTR_FRAME
pushq $0
CFI_ADJUST_CFA_OFFSET 8
paranoidentry do_debug
......@@ -820,9 +908,9 @@ KPROBE_ENTRY(debug)
/* runs on exception stack */
ENTRY(nmi)
CFI_STARTPROC
INTR_FRAME
pushq $-1
CFI_ADJUST_CFA_OFFSET 8
CFI_ADJUST_CFA_OFFSET 8
paranoidentry do_nmi
/*
* "Paranoid" exit path from exception stack.
......@@ -888,7 +976,7 @@ ENTRY(reserved)
/* runs on exception stack */
ENTRY(double_fault)
CFI_STARTPROC
XCPT_FRAME
paranoidentry do_double_fault
jmp paranoid_exit
CFI_ENDPROC
......@@ -901,7 +989,7 @@ ENTRY(segment_not_present)
/* runs on exception stack */
ENTRY(stack_segment)
CFI_STARTPROC
XCPT_FRAME
paranoidentry do_stack_segment
jmp paranoid_exit
CFI_ENDPROC
......@@ -922,7 +1010,7 @@ ENTRY(spurious_interrupt_bug)
#ifdef CONFIG_X86_MCE
/* runs on exception stack */
ENTRY(machine_check)