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linux-stable/arch/x86/kernel/head_64.S

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* linux/arch/x86/kernel/head_64.S -- start in 32bit and switch to 64bit
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
* Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
* Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
* Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/export.h>
#include <linux/linkage.h>
#include <linux/threads.h>
#include <linux/init.h>
#include <linux/pgtable.h>
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/cache.h>
#include <asm/processor-flags.h>
#include <asm/percpu.h>
#include <asm/nops.h>
#include "../entry/calling.h"
#include <asm/nospec-branch.h>
#include <asm/apicdef.h>
#include <asm/fixmap.h>
#include <asm/smp.h>
#include <asm/thread_info.h>
/*
* We are not able to switch in one step to the final KERNEL ADDRESS SPACE
* because we need identity-mapped pages.
*/
#define l4_index(x) (((x) >> 39) & 511)
#define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
L4_PAGE_OFFSET = l4_index(__PAGE_OFFSET_BASE_L4)
L4_START_KERNEL = l4_index(__START_KERNEL_map)
L3_START_KERNEL = pud_index(__START_KERNEL_map)
__HEAD
.code64
SYM_CODE_START_NOALIGN(startup_64)
UNWIND_HINT_END_OF_STACK
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded an identity mapped page table
* for us. These identity mapped page tables map all of the
* kernel pages and possibly all of memory.
*
* %RSI holds the physical address of the boot_params structure
* provided by the bootloader. Preserve it in %R15 so C function calls
* will not clobber it.
*
* We come here either directly from a 64bit bootloader, or from
* arch/x86/boot/compressed/head_64.S.
*
* We only come here initially at boot nothing else comes here.
*
* Since we may be loaded at an address different from what we were
* compiled to run at we first fixup the physical addresses in our page
* tables and then reload them.
*/
mov %rsi, %r15
/* Set up the stack for verify_cpu() */
leaq __top_init_kernel_stack(%rip), %rsp
/* Setup GSBASE to allow stack canary access for C code */
movl $MSR_GS_BASE, %ecx
leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
movl %edx, %eax
shrq $32, %rdx
wrmsr
call startup_64_setup_gdt_idt
/* Now switch to __KERNEL_CS so IRET works reliably */
pushq $__KERNEL_CS
leaq .Lon_kernel_cs(%rip), %rax
pushq %rax
lretq
.Lon_kernel_cs:
UNWIND_HINT_END_OF_STACK
#ifdef CONFIG_AMD_MEM_ENCRYPT
/*
* Activate SEV/SME memory encryption if supported/enabled. This needs to
* be done now, since this also includes setup of the SEV-SNP CPUID table,
* which needs to be done before any CPUID instructions are executed in
* subsequent code. Pass the boot_params pointer as the first argument.
*/
movq %r15, %rdi
call sme_enable
#endif
/* Sanitize CPU configuration */
call verify_cpu
/*
* Perform pagetable fixups. Additionally, if SME is active, encrypt
* the kernel and retrieve the modifier (SME encryption mask if SME
* is active) to be added to the initial pgdir entry that will be
* programmed into CR3.
*/
leaq _text(%rip), %rdi
movq %r15, %rsi
call __startup_64
/* Form the CR3 value being sure to include the CR3 modifier */
leaq early_top_pgt(%rip), %rcx
addq %rcx, %rax
#ifdef CONFIG_AMD_MEM_ENCRYPT
mov %rax, %rdi
/*
* For SEV guests: Verify that the C-bit is correct. A malicious
* hypervisor could lie about the C-bit position to perform a ROP
* attack on the guest by writing to the unencrypted stack and wait for
* the next RET instruction.
*/
call sev_verify_cbit
#endif
/*
* Switch to early_top_pgt which still has the identity mappings
* present.
*/
movq %rax, %cr3
/* Branch to the common startup code at its kernel virtual address */
ANNOTATE_RETPOLINE_SAFE
jmp *0f(%rip)
SYM_CODE_END(startup_64)
__INITRODATA
0: .quad common_startup_64
.text
SYM_CODE_START(secondary_startup_64)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded a mapped page table.
*
* We come here either from startup_64 (using physical addresses)
* or from trampoline.S (using virtual addresses).
*
* Using virtual addresses from trampoline.S removes the need
* to have any identity mapped pages in the kernel page table
* after the boot processor executes this code.
*/
/* Sanitize CPU configuration */
call verify_cpu
/*
* The secondary_startup_64_no_verify entry point is only used by
* SEV-ES guests. In those guests the call to verify_cpu() would cause
* #VC exceptions which can not be handled at this stage of secondary
* CPU bringup.
*
* All non SEV-ES systems, especially Intel systems, need to execute
* verify_cpu() above to make sure NX is enabled.
*/
SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR
/* Clear %R15 which holds the boot_params pointer on the boot CPU */
xorl %r15d, %r15d
/* Derive the runtime physical address of init_top_pgt[] */
movq phys_base(%rip), %rax
addq $(init_top_pgt - __START_KERNEL_map), %rax
/*
* Retrieve the modifier (SME encryption mask if SME is active) to be
* added to the initial pgdir entry that will be programmed into CR3.
*/
#ifdef CONFIG_AMD_MEM_ENCRYPT
addq sme_me_mask(%rip), %rax
#endif
/*
* Switch to the init_top_pgt here, away from the trampoline_pgd and
* unmap the identity mapped ranges.
*/
movq %rax, %cr3
SYM_INNER_LABEL(common_startup_64, SYM_L_LOCAL)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR
/*
* Create a mask of CR4 bits to preserve. Omit PGE in order to flush
* global 1:1 translations from the TLBs.
*
* From the SDM:
* "If CR4.PGE is changing from 0 to 1, there were no global TLB
* entries before the execution; if CR4.PGE is changing from 1 to 0,
* there will be no global TLB entries after the execution."
*/
movl $(X86_CR4_PAE | X86_CR4_LA57), %edx
#ifdef CONFIG_X86_MCE
/*
* Preserve CR4.MCE if the kernel will enable #MC support.
* Clearing MCE may fault in some environments (that also force #MC
* support). Any machine check that occurs before #MC support is fully
* configured will crash the system regardless of the CR4.MCE value set
* here.
*/
orl $X86_CR4_MCE, %edx
#endif
movq %cr4, %rcx
andl %edx, %ecx
/* Even if ignored in long mode, set PSE uniformly on all logical CPUs. */
btsl $X86_CR4_PSE_BIT, %ecx
movq %rcx, %cr4
/*
* Set CR4.PGE to re-enable global translations.
*/
btsl $X86_CR4_PGE_BIT, %ecx
movq %rcx, %cr4
#ifdef CONFIG_SMP
/*
* For parallel boot, the APIC ID is read from the APIC, and then
* used to look up the CPU number. For booting a single CPU, the
* CPU number is encoded in smpboot_control.
*
* Bit 31 STARTUP_READ_APICID (Read APICID from APIC)
* Bit 0-23 CPU# if STARTUP_xx flags are not set
*/
movl smpboot_control(%rip), %ecx
testl $STARTUP_READ_APICID, %ecx
jnz .Lread_apicid
/*
* No control bit set, single CPU bringup. CPU number is provided
* in bit 0-23. This is also the boot CPU case (CPU number 0).
*/
andl $(~STARTUP_PARALLEL_MASK), %ecx
jmp .Lsetup_cpu
.Lread_apicid:
/* Check whether X2APIC mode is already enabled */
mov $MSR_IA32_APICBASE, %ecx
rdmsr
testl $X2APIC_ENABLE, %eax
jnz .Lread_apicid_msr
#ifdef CONFIG_X86_X2APIC
/*
* If system is in X2APIC mode then MMIO base might not be
* mapped causing the MMIO read below to fault. Faults can't
* be handled at that point.
*/
cmpl $0, x2apic_mode(%rip)
jz .Lread_apicid_mmio
/* Force the AP into X2APIC mode. */
orl $X2APIC_ENABLE, %eax
wrmsr
jmp .Lread_apicid_msr
#endif
.Lread_apicid_mmio:
/* Read the APIC ID from the fix-mapped MMIO space. */
movq apic_mmio_base(%rip), %rcx
addq $APIC_ID, %rcx
movl (%rcx), %eax
shr $24, %eax
jmp .Llookup_AP
.Lread_apicid_msr:
mov $APIC_X2APIC_ID_MSR, %ecx
rdmsr
.Llookup_AP:
/* EAX contains the APIC ID of the current CPU */
xorl %ecx, %ecx
leaq cpuid_to_apicid(%rip), %rbx
.Lfind_cpunr:
cmpl (%rbx,%rcx,4), %eax
jz .Lsetup_cpu
inc %ecx
#ifdef CONFIG_FORCE_NR_CPUS
cmpl $NR_CPUS, %ecx
#else
cmpl nr_cpu_ids(%rip), %ecx
#endif
jb .Lfind_cpunr
/* APIC ID not found in the table. Drop the trampoline lock and bail. */
movq trampoline_lock(%rip), %rax
movl $0, (%rax)
1: cli
hlt
jmp 1b
.Lsetup_cpu:
/* Get the per cpu offset for the given CPU# which is in ECX */
movq __per_cpu_offset(,%rcx,8), %rdx
#else
xorl %edx, %edx /* zero-extended to clear all of RDX */
#endif /* CONFIG_SMP */
/*
* Setup a boot time stack - Any secondary CPU will have lost its stack
* by now because the cr3-switch above unmaps the real-mode stack.
*
* RDX contains the per-cpu offset
*/
movq pcpu_hot + X86_current_task(%rdx), %rax
movq TASK_threadsp(%rax), %rsp
/*
* Now that this CPU is running on its own stack, drop the realmode
* protection. For the boot CPU the pointer is NULL!
*/
movq trampoline_lock(%rip), %rax
testq %rax, %rax
jz .Lsetup_gdt
movl $0, (%rax)
.Lsetup_gdt:
/*
* We must switch to a new descriptor in kernel space for the GDT
* because soon the kernel won't have access anymore to the userspace
* addresses where we're currently running on. We have to do that here
* because in 32bit we couldn't load a 64bit linear address.
*/
subq $16, %rsp
movw $(GDT_SIZE-1), (%rsp)
leaq gdt_page(%rdx), %rax
movq %rax, 2(%rsp)
lgdt (%rsp)
addq $16, %rsp
/* set up data segments */
xorl %eax,%eax
movl %eax,%ds
movl %eax,%ss
movl %eax,%es
/*
* We don't really need to load %fs or %gs, but load them anyway
* to kill any stale realmode selectors. This allows execution
* under VT hardware.
*/
movl %eax,%fs
movl %eax,%gs
/* Set up %gs.
*
* The base of %gs always points to fixed_percpu_data. If the
* stack protector canary is enabled, it is located at %gs:40.
* Note that, on SMP, the boot cpu uses init data section until
* the per cpu areas are set up.
*/
movl $MSR_GS_BASE,%ecx
#ifndef CONFIG_SMP
leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
#endif
movl %edx, %eax
shrq $32, %rdx
wrmsr
/* Setup and Load IDT */
call early_setup_idt
/* Check if nx is implemented */
movl $0x80000001, %eax
cpuid
movl %edx,%edi
/* Setup EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
/*
* Preserve current value of EFER for comparison and to skip
* EFER writes if no change was made (for TDX guest)
*/
movl %eax, %edx
btsl $_EFER_SCE, %eax /* Enable System Call */
btl $20,%edi /* No Execute supported? */
jnc 1f
btsl $_EFER_NX, %eax
btsq $_PAGE_BIT_NX,early_pmd_flags(%rip)
/* Avoid writing EFER if no change was made (for TDX guest) */
1: cmpl %edx, %eax
je 1f
xor %edx, %edx
wrmsr /* Make changes effective */
1:
/* Setup cr0 */
movl $CR0_STATE, %eax
/* Make changes effective */
movq %rax, %cr0
/* zero EFLAGS after setting rsp */
pushq $0
popfq
/* Pass the boot_params pointer as first argument */
movq %r15, %rdi
.Ljump_to_C_code:
xorl %ebp, %ebp # clear frame pointer
ANNOTATE_RETPOLINE_SAFE
callq *initial_code(%rip)
ud2
SYM_CODE_END(secondary_startup_64)
#include "verify_cpu.S"
#include "sev_verify_cbit.S"
#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_AMD_MEM_ENCRYPT)
/*
* Entry point for soft restart of a CPU. Invoked from xxx_play_dead() for
* restarting the boot CPU or for restarting SEV guest CPUs after CPU hot
* unplug. Everything is set up already except the stack.
*/
SYM_CODE_START(soft_restart_cpu)
ANNOTATE_NOENDBR
UNWIND_HINT_END_OF_STACK
/* Find the idle task stack */
movq PER_CPU_VAR(pcpu_hot + X86_current_task), %rcx
movq TASK_threadsp(%rcx), %rsp
jmp .Ljump_to_C_code
SYM_CODE_END(soft_restart_cpu)
#endif
#ifdef CONFIG_AMD_MEM_ENCRYPT
/*
* VC Exception handler used during early boot when running on kernel
* addresses, but before the switch to the idt_table can be made.
* The early_idt_handler_array can't be used here because it calls into a lot
* of __init code and this handler is also used during CPU offlining/onlining.
* Therefore this handler ends up in the .text section so that it stays around
* when .init.text is freed.
*/
SYM_CODE_START_NOALIGN(vc_boot_ghcb)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
/* Build pt_regs */
PUSH_AND_CLEAR_REGS
/* Call C handler */
movq %rsp, %rdi
movq ORIG_RAX(%rsp), %rsi
movq initial_vc_handler(%rip), %rax
ANNOTATE_RETPOLINE_SAFE
call *%rax
/* Unwind pt_regs */
POP_REGS
/* Remove Error Code */
addq $8, %rsp
iretq
SYM_CODE_END(vc_boot_ghcb)
#endif
/* Both SMP bootup and ACPI suspend change these variables */
__REFDATA
.balign 8
SYM_DATA(initial_code, .quad x86_64_start_kernel)
#ifdef CONFIG_AMD_MEM_ENCRYPT
SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb)
#endif
SYM_DATA(trampoline_lock, .quad 0);
__FINITDATA
__INIT
SYM_CODE_START(early_idt_handler_array)
i = 0
.rept NUM_EXCEPTION_VECTORS
.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
UNWIND_HINT_IRET_REGS
ENDBR
pushq $0 # Dummy error code, to make stack frame uniform
.else
UNWIND_HINT_IRET_REGS offset=8
ENDBR
.endif
pushq $i # 72(%rsp) Vector number
jmp early_idt_handler_common
UNWIND_HINT_IRET_REGS
i = i + 1
.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
.endr
SYM_CODE_END(early_idt_handler_array)
ANNOTATE_NOENDBR // early_idt_handler_array[NUM_EXCEPTION_VECTORS]
SYM_CODE_START_LOCAL(early_idt_handler_common)
UNWIND_HINT_IRET_REGS offset=16
/*
* The stack is the hardware frame, an error code or zero, and the
* vector number.
*/
cld
incl early_recursion_flag(%rip)
/* The vector number is currently in the pt_regs->di slot. */
pushq %rsi /* pt_regs->si */
movq 8(%rsp), %rsi /* RSI = vector number */
movq %rdi, 8(%rsp) /* pt_regs->di = RDI */
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq %rax /* pt_regs->ax */
pushq %r8 /* pt_regs->r8 */
pushq %r9 /* pt_regs->r9 */
pushq %r10 /* pt_regs->r10 */
pushq %r11 /* pt_regs->r11 */
pushq %rbx /* pt_regs->bx */
pushq %rbp /* pt_regs->bp */
pushq %r12 /* pt_regs->r12 */
pushq %r13 /* pt_regs->r13 */
pushq %r14 /* pt_regs->r14 */
pushq %r15 /* pt_regs->r15 */
UNWIND_HINT_REGS
movq %rsp,%rdi /* RDI = pt_regs; RSI is already trapnr */
call do_early_exception
decl early_recursion_flag(%rip)
jmp restore_regs_and_return_to_kernel
SYM_CODE_END(early_idt_handler_common)
#ifdef CONFIG_AMD_MEM_ENCRYPT
/*
* VC Exception handler used during very early boot. The
* early_idt_handler_array can't be used because it returns via the
* paravirtualized INTERRUPT_RETURN and pv-ops don't work that early.
*
* XXX it does, fix this.
*
* This handler will end up in the .init.text section and not be
* available to boot secondary CPUs.
*/
SYM_CODE_START_NOALIGN(vc_no_ghcb)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
/* Build pt_regs */
PUSH_AND_CLEAR_REGS
/* Call C handler */
movq %rsp, %rdi
movq ORIG_RAX(%rsp), %rsi
call do_vc_no_ghcb
/* Unwind pt_regs */
POP_REGS
/* Remove Error Code */
addq $8, %rsp
/* Pure iret required here - don't use INTERRUPT_RETURN */
iretq
SYM_CODE_END(vc_no_ghcb)
#endif
#define SYM_DATA_START_PAGE_ALIGNED(name) \
SYM_START(name, SYM_L_GLOBAL, .balign PAGE_SIZE)
#ifdef CONFIG_MITIGATION_PAGE_TABLE_ISOLATION
/*
* Each PGD needs to be 8k long and 8k aligned. We do not
* ever go out to userspace with these, so we do not
* strictly *need* the second page, but this allows us to
* have a single set_pgd() implementation that does not
* need to worry about whether it has 4k or 8k to work
* with.
*
* This ensures PGDs are 8k long:
*/
#define PTI_USER_PGD_FILL 512
/* This ensures they are 8k-aligned: */
#define SYM_DATA_START_PTI_ALIGNED(name) \
SYM_START(name, SYM_L_GLOBAL, .balign 2 * PAGE_SIZE)
#else
#define SYM_DATA_START_PTI_ALIGNED(name) \
SYM_DATA_START_PAGE_ALIGNED(name)
#define PTI_USER_PGD_FILL 0
#endif
/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT) \
i = 0 ; \
.rept (COUNT) ; \
.quad (START) + (i << PMD_SHIFT) + (PERM) ; \
i = i + 1 ; \
.endr
__INITDATA
.balign 4
SYM_DATA_START_PTI_ALIGNED(early_top_pgt)
.fill 511,8,0
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
.fill PTI_USER_PGD_FILL,8,0
SYM_DATA_END(early_top_pgt)
SYM_DATA_START_PAGE_ALIGNED(early_dynamic_pgts)
.fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0
SYM_DATA_END(early_dynamic_pgts)
SYM_DATA(early_recursion_flag, .long 0)
.data
#if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH)
SYM_DATA_START_PTI_ALIGNED(init_top_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.org init_top_pgt + L4_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.org init_top_pgt + L4_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
.fill PTI_USER_PGD_FILL,8,0
SYM_DATA_END(init_top_pgt)
SYM_DATA_START_PAGE_ALIGNED(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.fill 511, 8, 0
SYM_DATA_END(level3_ident_pgt)
SYM_DATA_START_PAGE_ALIGNED(level2_ident_pgt)
/*
* Since I easily can, map the first 1G.
* Don't set NX because code runs from these pages.
*
* Note: This sets _PAGE_GLOBAL despite whether
* the CPU supports it or it is enabled. But,
* the CPU should ignore the bit.
*/
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
SYM_DATA_END(level2_ident_pgt)
#else
SYM_DATA_START_PTI_ALIGNED(init_top_pgt)
.fill 512,8,0
.fill PTI_USER_PGD_FILL,8,0
SYM_DATA_END(init_top_pgt)
#endif
#ifdef CONFIG_X86_5LEVEL
SYM_DATA_START_PAGE_ALIGNED(level4_kernel_pgt)
.fill 511,8,0
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
SYM_DATA_END(level4_kernel_pgt)
#endif
SYM_DATA_START_PAGE_ALIGNED(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
.quad level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC
SYM_DATA_END(level3_kernel_pgt)
SYM_DATA_START_PAGE_ALIGNED(level2_kernel_pgt)
/*
* Kernel high mapping.
*
* The kernel code+data+bss must be located below KERNEL_IMAGE_SIZE in
* virtual address space, which is 1 GiB if RANDOMIZE_BASE is enabled,
* 512 MiB otherwise.
*
* (NOTE: after that starts the module area, see MODULES_VADDR.)
*
* This table is eventually used by the kernel during normal runtime.
* Care must be taken to clear out undesired bits later, like _PAGE_RW
* or _PAGE_GLOBAL in some cases.
*/
PMDS(0, __PAGE_KERNEL_LARGE_EXEC, KERNEL_IMAGE_SIZE/PMD_SIZE)
SYM_DATA_END(level2_kernel_pgt)
SYM_DATA_START_PAGE_ALIGNED(level2_fixmap_pgt)
.fill (512 - 4 - FIXMAP_PMD_NUM),8,0
pgtno = 0
.rept (FIXMAP_PMD_NUM)
.quad level1_fixmap_pgt + (pgtno << PAGE_SHIFT) - __START_KERNEL_map \
+ _PAGE_TABLE_NOENC;
pgtno = pgtno + 1
.endr
/* 6 MB reserved space + a 2MB hole */
.fill 4,8,0
SYM_DATA_END(level2_fixmap_pgt)
SYM_DATA_START_PAGE_ALIGNED(level1_fixmap_pgt)
.rept (FIXMAP_PMD_NUM)
.fill 512,8,0
.endr
SYM_DATA_END(level1_fixmap_pgt)
#undef PMDS
.data
.align 16
SYM_DATA(smpboot_control, .long 0)
.align 16
/* This must match the first entry in level2_kernel_pgt */
SYM_DATA(phys_base, .quad 0x0)
EXPORT_SYMBOL(phys_base)
#include "../xen/xen-head.S"
__PAGE_ALIGNED_BSS
SYM_DATA_START_PAGE_ALIGNED(empty_zero_page)
.skip PAGE_SIZE
SYM_DATA_END(empty_zero_page)
EXPORT_SYMBOL(empty_zero_page)
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