Initial commit

arch/x86/kernel/head_32.S

@@ -0,0 +1,782 @@
+/*
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  Enhanced CPU detection and feature setting code by Mike Jagdis
+ *  and Martin Mares, November 1997.
+ */
+
+.text
+#include <linux/threads.h>
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page_types.h>
+#include <asm/pgtable_types.h>
+#include <asm/cache.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
+#include <asm/setup.h>
+#include <asm/processor-flags.h>
+#include <asm/msr-index.h>
+#include <asm/cpufeature.h>
+#include <asm/percpu.h>
+#include <asm/nops.h>
+
+/* Physical address */
+#define pa(X) ((X) - __PAGE_OFFSET)
+
+/*
+ * References to members of the new_cpu_data structure.
+ */
+
+#define X86		new_cpu_data+CPUINFO_x86
+#define X86_VENDOR	new_cpu_data+CPUINFO_x86_vendor
+#define X86_MODEL	new_cpu_data+CPUINFO_x86_model
+#define X86_MASK	new_cpu_data+CPUINFO_x86_mask
+#define X86_HARD_MATH	new_cpu_data+CPUINFO_hard_math
+#define X86_CPUID	new_cpu_data+CPUINFO_cpuid_level
+#define X86_CAPABILITY	new_cpu_data+CPUINFO_x86_capability
+#define X86_VENDOR_ID	new_cpu_data+CPUINFO_x86_vendor_id
+
+/*
+ * This is how much memory in addition to the memory covered up to
+ * and including _end we need mapped initially.
+ * We need:
+ *     (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
+ *     (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
+ *
+ * Modulo rounding, each megabyte assigned here requires a kilobyte of
+ * memory, which is currently unreclaimed.
+ *
+ * This should be a multiple of a page.
+ *
+ * KERNEL_IMAGE_SIZE should be greater than pa(_end)
+ * and small than max_low_pfn, otherwise will waste some page table entries
+ */
+
+#if PTRS_PER_PMD > 1
+#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
+#else
+#define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
+#endif
+
+/* Number of possible pages in the lowmem region */
+LOWMEM_PAGES = (((1<<32) - __PAGE_OFFSET) >> PAGE_SHIFT)
+	
+/* Enough space to fit pagetables for the low memory linear map */
+MAPPING_BEYOND_END = PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT
+
+/*
+ * Worst-case size of the kernel mapping we need to make:
+ * a relocatable kernel can live anywhere in lowmem, so we need to be able
+ * to map all of lowmem.
+ */
+KERNEL_PAGES = LOWMEM_PAGES
+
+INIT_MAP_SIZE = PAGE_TABLE_SIZE(KERNEL_PAGES) * PAGE_SIZE
+RESERVE_BRK(pagetables, INIT_MAP_SIZE)
+
+/*
+ * 32-bit kernel entrypoint; only used by the boot CPU.  On entry,
+ * %esi points to the real-mode code as a 32-bit pointer.
+ * CS and DS must be 4 GB flat segments, but we don't depend on
+ * any particular GDT layout, because we load our own as soon as we
+ * can.
+ */
+__HEAD
+ENTRY(startup_32)
+	movl pa(stack_start),%ecx
+	
+	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
+		us to not reload segments */
+	testb $(1<<6), BP_loadflags(%esi)
+	jnz 2f
+
+/*
+ * Set segments to known values.
+ */
+	lgdt pa(boot_gdt_descr)
+	movl $(__BOOT_DS),%eax
+	movl %eax,%ds
+	movl %eax,%es
+	movl %eax,%fs
+	movl %eax,%gs
+	movl %eax,%ss
+2:
+	leal -__PAGE_OFFSET(%ecx),%esp
+
+/*
+ * Clear BSS first so that there are no surprises...
+ */
+	cld
+	xorl %eax,%eax
+	movl $pa(__bss_start),%edi
+	movl $pa(__bss_stop),%ecx
+	subl %edi,%ecx
+	shrl $2,%ecx
+	rep ; stosl
+/*
+ * Copy bootup parameters out of the way.
+ * Note: %esi still has the pointer to the real-mode data.
+ * With the kexec as boot loader, parameter segment might be loaded beyond
+ * kernel image and might not even be addressable by early boot page tables.
+ * (kexec on panic case). Hence copy out the parameters before initializing
+ * page tables.
+ */
+	movl $pa(boot_params),%edi
+	movl $(PARAM_SIZE/4),%ecx
+	cld
+	rep
+	movsl
+	movl pa(boot_params) + NEW_CL_POINTER,%esi
+	andl %esi,%esi
+	jz 1f			# No command line
+	movl $pa(boot_command_line),%edi
+	movl $(COMMAND_LINE_SIZE/4),%ecx
+	rep
+	movsl
+1:
+
+#ifdef CONFIG_OLPC
+	/* save OFW's pgdir table for later use when calling into OFW */
+	movl %cr3, %eax
+	movl %eax, pa(olpc_ofw_pgd)
+#endif
+
+#ifdef CONFIG_MICROCODE_EARLY
+	/* Early load ucode on BSP. */
+	call load_ucode_bsp
+#endif
+
+/*
+ * Initialize page tables.  This creates a PDE and a set of page
+ * tables, which are located immediately beyond __brk_base.  The variable
+ * _brk_end is set up to point to the first "safe" location.
+ * Mappings are created both at virtual address 0 (identity mapping)
+ * and PAGE_OFFSET for up to _end.
+ */
+#ifdef CONFIG_X86_PAE
+
+	/*
+	 * In PAE mode initial_page_table is statically defined to contain
+	 * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
+	 * entries). The identity mapping is handled by pointing two PGD entries
+	 * to the first kernel PMD.
+	 *
+	 * Note the upper half of each PMD or PTE are always zero at this stage.
+	 */
+
+#define KPMDS (((-__PAGE_OFFSET) >> 30) & 3) /* Number of kernel PMDs */
+
+	xorl %ebx,%ebx				/* %ebx is kept at zero */
+
+	movl $pa(__brk_base), %edi
+	movl $pa(initial_pg_pmd), %edx
+	movl $PTE_IDENT_ATTR, %eax
+10:
+	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PMD entry */
+	movl %ecx,(%edx)			/* Store PMD entry */
+						/* Upper half already zero */
+	addl $8,%edx
+	movl $512,%ecx
+11:
+	stosl
+	xchgl %eax,%ebx
+	stosl
+	xchgl %eax,%ebx
+	addl $0x1000,%eax
+	loop 11b
+
+	/*
+	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
+	 */
+	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
+	cmpl %ebp,%eax
+	jb 10b
+1:
+	addl $__PAGE_OFFSET, %edi
+	movl %edi, pa(_brk_end)
+	shrl $12, %eax
+	movl %eax, pa(max_pfn_mapped)
+
+	/* Do early initialization of the fixmap area */
+	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
+	movl %eax,pa(initial_pg_pmd+0x1000*KPMDS-8)
+#else	/* Not PAE */
+
+page_pde_offset = (__PAGE_OFFSET >> 20);
+
+	movl $pa(__brk_base), %edi
+	movl $pa(initial_page_table), %edx
+	movl $PTE_IDENT_ATTR, %eax
+10:
+	leal PDE_IDENT_ATTR(%edi),%ecx		/* Create PDE entry */
+	movl %ecx,(%edx)			/* Store identity PDE entry */
+	movl %ecx,page_pde_offset(%edx)		/* Store kernel PDE entry */
+	addl $4,%edx
+	movl $1024, %ecx
+11:
+	stosl
+	addl $0x1000,%eax
+	loop 11b
+	/*
+	 * End condition: we must map up to the end + MAPPING_BEYOND_END.
+	 */
+	movl $pa(_end) + MAPPING_BEYOND_END + PTE_IDENT_ATTR, %ebp
+	cmpl %ebp,%eax
+	jb 10b
+	addl $__PAGE_OFFSET, %edi
+	movl %edi, pa(_brk_end)
+	shrl $12, %eax
+	movl %eax, pa(max_pfn_mapped)
+
+	/* Do early initialization of the fixmap area */
+	movl $pa(initial_pg_fixmap)+PDE_IDENT_ATTR,%eax
+	movl %eax,pa(initial_page_table+0xffc)
+#endif
+
+#ifdef CONFIG_PARAVIRT
+	/* This is can only trip for a broken bootloader... */
+	cmpw $0x207, pa(boot_params + BP_version)
+	jb default_entry
+
+	/* Paravirt-compatible boot parameters.  Look to see what architecture
+		we're booting under. */
+	movl pa(boot_params + BP_hardware_subarch), %eax
+	cmpl $num_subarch_entries, %eax
+	jae bad_subarch
+
+	movl pa(subarch_entries)(,%eax,4), %eax
+	subl $__PAGE_OFFSET, %eax
+	jmp *%eax
+
+bad_subarch:
+WEAK(lguest_entry)
+WEAK(xen_entry)
+	/* Unknown implementation; there's really
+	   nothing we can do at this point. */
+	ud2a
+
+	__INITDATA
+
+subarch_entries:
+	.long default_entry		/* normal x86/PC */
+	.long lguest_entry		/* lguest hypervisor */
+	.long xen_entry			/* Xen hypervisor */
+	.long default_entry		/* Moorestown MID */
+num_subarch_entries = (. - subarch_entries) / 4
+.previous
+#else
+	jmp default_entry
+#endif /* CONFIG_PARAVIRT */
+
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
+ * up already except stack. We just set up stack here. Then call
+ * start_secondary().
+ */
+ENTRY(start_cpu0)
+	movl stack_start, %ecx
+	movl %ecx, %esp
+	jmp  *(initial_code)
+ENDPROC(start_cpu0)
+#endif
+
+/*
+ * Non-boot CPU entry point; entered from trampoline.S
+ * We can't lgdt here, because lgdt itself uses a data segment, but
+ * we know the trampoline has already loaded the boot_gdt for us.
+ *
+ * If cpu hotplug is not supported then this code can go in init section
+ * which will be freed later
+ */
+__CPUINIT
+ENTRY(startup_32_smp)
+	cld
+	movl $(__BOOT_DS),%eax
+	movl %eax,%ds
+	movl %eax,%es
+	movl %eax,%fs
+	movl %eax,%gs
+	movl pa(stack_start),%ecx
+	movl %eax,%ss
+	leal -__PAGE_OFFSET(%ecx),%esp
+
+#ifdef CONFIG_MICROCODE_EARLY
+	/* Early load ucode on AP. */
+	call load_ucode_ap
+#endif
+
+
+default_entry:
+#define CR0_STATE	(X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
+			 X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
+			 X86_CR0_PG)
+	movl $(CR0_STATE & ~X86_CR0_PG),%eax
+	movl %eax,%cr0
+
+/*
+ * We want to start out with EFLAGS unambiguously cleared. Some BIOSes leave
+ * bits like NT set. This would confuse the debugger if this code is traced. So
+ * initialize them properly now before switching to protected mode. That means
+ * DF in particular (even though we have cleared it earlier after copying the
+ * command line) because GCC expects it.
+ */
+	pushl $0
+	popfl
+
+/*
+ * New page tables may be in 4Mbyte page mode and may be using the global pages.
+ *
+ * NOTE! If we are on a 486 we may have no cr4 at all! Specifically, cr4 exists
+ * if and only if CPUID exists and has flags other than the FPU flag set.
+ */
+	movl $-1,pa(X86_CPUID)		# preset CPUID level
+	movl $X86_EFLAGS_ID,%ecx
+	pushl %ecx
+	popfl				# set EFLAGS=ID
+	pushfl
+	popl %eax			# get EFLAGS
+	testl $X86_EFLAGS_ID,%eax	# did EFLAGS.ID remained set?
+	jz enable_paging		# hw disallowed setting of ID bit
+					# which means no CPUID and no CR4
+
+	xorl %eax,%eax
+	cpuid
+	movl %eax,pa(X86_CPUID)		# save largest std CPUID function
+
+	movl $1,%eax
+	cpuid
+	andl $~1,%edx			# Ignore CPUID.FPU
+	jz enable_paging		# No flags or only CPUID.FPU = no CR4
+
+	movl pa(mmu_cr4_features),%eax
+	movl %eax,%cr4
+
+	testb $X86_CR4_PAE, %al		# check if PAE is enabled
+	jz enable_paging
+
+	/* Check if extended functions are implemented */
+	movl $0x80000000, %eax
+	cpuid
+	/* Value must be in the range 0x80000001 to 0x8000ffff */
+	subl $0x80000001, %eax
+	cmpl $(0x8000ffff-0x80000001), %eax
+	ja enable_paging
+
+	/* Clear bogus XD_DISABLE bits */
+	call verify_cpu
+
+	mov $0x80000001, %eax
+	cpuid
+	/* Execute Disable bit supported? */
+	btl $(X86_FEATURE_NX & 31), %edx
+	jnc enable_paging
+
+	/* Setup EFER (Extended Feature Enable Register) */
+	movl $MSR_EFER, %ecx
+	rdmsr
+
+	btsl $_EFER_NX, %eax
+	/* Make changes effective */
+	wrmsr
+
+enable_paging:
+
+/*
+ * Enable paging
+ */
+	movl $pa(initial_page_table), %eax
+	movl %eax,%cr3		/* set the page table pointer.. */
+	movl $CR0_STATE,%eax
+	movl %eax,%cr0		/* ..and set paging (PG) bit */
+	ljmp $__BOOT_CS,$1f	/* Clear prefetch and normalize %eip */
+1:
+	/* Shift the stack pointer to a virtual address */
+	addl $__PAGE_OFFSET, %esp
+
+/*
+ * start system 32-bit setup. We need to re-do some of the things done
+ * in 16-bit mode for the "real" operations.
+ */
+	movl setup_once_ref,%eax
+	andl %eax,%eax
+	jz 1f				# Did we do this already?
+	call *%eax
+1:
+
+/*
+ * Check if it is 486
+ */
+	cmpl $-1,X86_CPUID
+	je is486
+
+	/* get vendor info */
+	xorl %eax,%eax			# call CPUID with 0 -> return vendor ID
+	cpuid
+	movl %eax,X86_CPUID		# save CPUID level
+	movl %ebx,X86_VENDOR_ID		# lo 4 chars
+	movl %edx,X86_VENDOR_ID+4	# next 4 chars
+	movl %ecx,X86_VENDOR_ID+8	# last 4 chars
+
+	orl %eax,%eax			# do we have processor info as well?
+	je is486
+
+	movl $1,%eax		# Use the CPUID instruction to get CPU type
+	cpuid
+	movb %al,%cl		# save reg for future use
+	andb $0x0f,%ah		# mask processor family
+	movb %ah,X86
+	andb $0xf0,%al		# mask model
+	shrb $4,%al
+	movb %al,X86_MODEL
+	andb $0x0f,%cl		# mask mask revision
+	movb %cl,X86_MASK
+	movl %edx,X86_CAPABILITY
+
+is486:
+	movb $4,X86
+	movl $0x50022,%ecx	# set AM, WP, NE and MP
+	movl %cr0,%eax
+	andl $0x80000011,%eax	# Save PG,PE,ET
+	orl %ecx,%eax
+	movl %eax,%cr0
+
+	call check_x87
+	lgdt early_gdt_descr
+	lidt idt_descr
+	ljmp $(__KERNEL_CS),$1f
+1:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
+	movl %eax,%ss			# after changing gdt.
+
+	movl $(__USER_DS),%eax		# DS/ES contains default USER segment
+	movl %eax,%ds
+	movl %eax,%es
+
+	movl $(__KERNEL_PERCPU), %eax
+	movl %eax,%fs			# set this cpu's percpu
+
+	movl $(__KERNEL_STACK_CANARY),%eax
+	movl %eax,%gs
+
+	xorl %eax,%eax			# Clear LDT
+	lldt %ax
+
+	pushl $0		# fake return address for unwinder
+	jmp *(initial_code)
+
+/*
+ * We depend on ET to be correct. This checks for 287/387.
+ */
+check_x87:
+	movb $0,X86_HARD_MATH
+	clts
+	fninit
+	fstsw %ax
+	cmpb $0,%al
+	je 1f
+	movl %cr0,%eax		/* no coprocessor: have to set bits */
+	xorl $4,%eax		/* set EM */
+	movl %eax,%cr0
+	ret
+	ALIGN
+1:	movb $1,X86_HARD_MATH
+	.byte 0xDB,0xE4		/* fsetpm for 287, ignored by 387 */
+	ret
+
+	
+#include "verify_cpu.S"
+
+/*
+ *  setup_once
+ *
+ *  The setup work we only want to run on the BSP.
+ *
+ *  Warning: %esi is live across this function.
+ */
+__INIT
+setup_once:
+	/*
+	 * Set up a idt with 256 entries pointing to ignore_int,
+	 * interrupt gates. It doesn't actually load idt - that needs
+	 * to be done on each CPU. Interrupts are enabled elsewhere,
+	 * when we can be relatively sure everything is ok.
+	 */
+
+	movl $idt_table,%edi
+	movl $early_idt_handlers,%eax
+	movl $NUM_EXCEPTION_VECTORS,%ecx
+1:
+	movl %eax,(%edi)
+	movl %eax,4(%edi)
+	/* interrupt gate, dpl=0, present */
+	movl $(0x8E000000 + __KERNEL_CS),2(%edi)
+	addl $9,%eax
+	addl $8,%edi
+	loop 1b
+
+	movl $256 - NUM_EXCEPTION_VECTORS,%ecx
+	movl $ignore_int,%edx
+	movl $(__KERNEL_CS << 16),%eax
+	movw %dx,%ax		/* selector = 0x0010 = cs */
+	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
+2:
+	movl %eax,(%edi)
+	movl %edx,4(%edi)
+	addl $8,%edi
+	loop 2b
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+	/*
+	 * Configure the stack canary. The linker can't handle this by
+	 * relocation.  Manually set base address in stack canary
+	 * segment descriptor.
+	 */
+	movl $gdt_page,%eax
+	movl $stack_canary,%ecx
+	movw %cx, 8 * GDT_ENTRY_STACK_CANARY + 2(%eax)
+	shrl $16, %ecx
+	movb %cl, 8 * GDT_ENTRY_STACK_CANARY + 4(%eax)
+	movb %ch, 8 * GDT_ENTRY_STACK_CANARY + 7(%eax)
+#endif
+
+	andl $0,setup_once_ref	/* Once is enough, thanks */
+	ret
+
+ENTRY(early_idt_handlers)
+	# 36(%esp) %eflags
+	# 32(%esp) %cs
+	# 28(%esp) %eip
+	# 24(%rsp) error code
+	i = 0
+	.rept NUM_EXCEPTION_VECTORS
+	.if (EXCEPTION_ERRCODE_MASK >> i) & 1
+	ASM_NOP2
+	.else
+	pushl $0		# Dummy error code, to make stack frame uniform
+	.endif
+	pushl $i		# 20(%esp) Vector number
+	jmp early_idt_handler
+	i = i + 1
+	.endr
+ENDPROC(early_idt_handlers)
+	
+	/* This is global to keep gas from relaxing the jumps */
+ENTRY(early_idt_handler)
+	cld
+
+	cmpl $2,(%esp)		# X86_TRAP_NMI
+	je is_nmi		# Ignore NMI
+
+	cmpl $2,%ss:early_recursion_flag
+	je hlt_loop
+	incl %ss:early_recursion_flag
+
+	push %eax		# 16(%esp)
+	push %ecx		# 12(%esp)
+	push %edx		#  8(%esp)
+	push %ds		#  4(%esp)
+	push %es		#  0(%esp)
+	movl $(__KERNEL_DS),%eax
+	movl %eax,%ds
+	movl %eax,%es
+
+	cmpl $(__KERNEL_CS),32(%esp)
+	jne 10f
+
+	leal 28(%esp),%eax	# Pointer to %eip
+	call early_fixup_exception
+	andl %eax,%eax
+	jnz ex_entry		/* found an exception entry */
+
+10:
+#ifdef CONFIG_PRINTK
+	xorl %eax,%eax
+	movw %ax,2(%esp)	/* clean up the segment values on some cpus */
+	movw %ax,6(%esp)
+	movw %ax,34(%esp)
+	leal  40(%esp),%eax
+	pushl %eax		/* %esp before the exception */
+	pushl %ebx
+	pushl %ebp
+	pushl %esi
+	pushl %edi
+	movl %cr2,%eax
+	pushl %eax
+	pushl (20+6*4)(%esp)	/* trapno */
+	pushl $fault_msg
+	call printk
+#endif
+	call dump_stack
+hlt_loop:
+	hlt
+	jmp hlt_loop
+
+ex_entry:
+	pop %es
+	pop %ds
+	pop %edx
+	pop %ecx
+	pop %eax
+	decl %ss:early_recursion_flag
+is_nmi:
+	addl $8,%esp		/* drop vector number and error code */
+	iret
+ENDPROC(early_idt_handler)
+
+/* This is the default interrupt "handler" :-) */
+	ALIGN
+ignore_int:
+	cld
+#ifdef CONFIG_PRINTK
+	pushl %eax
+	pushl %ecx
+	pushl %edx
+	pushl %es
+	pushl %ds
+	movl $(__KERNEL_DS),%eax
+	movl %eax,%ds
+	movl %eax,%es
+	cmpl $2,early_recursion_flag
+	je hlt_loop
+	incl early_recursion_flag
+	pushl 16(%esp)
+	pushl 24(%esp)
+	pushl 32(%esp)
+	pushl 40(%esp)
+	pushl $int_msg
+	call printk
+
+	call dump_stack
+
+	addl $(5*4),%esp
+	popl %ds
+	popl %es
+	popl %edx
+	popl %ecx
+	popl %eax
+#endif
+	iret
+ENDPROC(ignore_int)
+__INITDATA
+	.align 4
+early_recursion_flag:
+	.long 0
+
+__REFDATA
+	.align 4
+ENTRY(initial_code)
+	.long i386_start_kernel
+ENTRY(setup_once_ref)
+	.long setup_once
+
+/*
+ * BSS section
+ */
+__PAGE_ALIGNED_BSS
+	.align PAGE_SIZE
+#ifdef CONFIG_X86_PAE
+initial_pg_pmd:
+	.fill 1024*KPMDS,4,0
+#else
+ENTRY(initial_page_table)
+	.fill 1024,4,0
+#endif
+initial_pg_fixmap:
+	.fill 1024,4,0
+ENTRY(empty_zero_page)
+	.fill 4096,1,0
+ENTRY(swapper_pg_dir)
+	.fill 1024,4,0
+
+/*
+ * This starts the data section.
+ */
+#ifdef CONFIG_X86_PAE
+__PAGE_ALIGNED_DATA
+	/* Page-aligned for the benefit of paravirt? */
+	.align PAGE_SIZE
+ENTRY(initial_page_table)
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0	/* low identity map */
+# if KPMDS == 3
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x2000),0
+# elif KPMDS == 2
+	.long	0,0
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR+0x1000),0
+# elif KPMDS == 1
+	.long	0,0
+	.long	0,0
+	.long	pa(initial_pg_pmd+PGD_IDENT_ATTR),0
+# else
+#  error "Kernel PMDs should be 1, 2 or 3"
+# endif
+	.align PAGE_SIZE		/* needs to be page-sized too */
+#endif
+
+.data
+.balign 4
+ENTRY(stack_start)
+	.long init_thread_union+THREAD_SIZE
+
+__INITRODATA
+int_msg:
+	.asciz "Unknown interrupt or fault at: %p %p %p\n"
+
+fault_msg:
+/* fault info: */
+	.ascii "BUG: Int %d: CR2 %p\n"
+/* regs pushed in early_idt_handler: */
+	.ascii "     EDI %p  ESI %p  EBP %p  EBX %p\n"
+	.ascii "     ESP %p   ES %p   DS %p\n"
+	.ascii "     EDX %p  ECX %p  EAX %p\n"
+/* fault frame: */
+	.ascii "     vec %p  err %p  EIP %p   CS %p  flg %p\n"
+	.ascii "Stack: %p %p %p %p %p %p %p %p\n"
+	.ascii "       %p %p %p %p %p %p %p %p\n"
+	.asciz "       %p %p %p %p %p %p %p %p\n"
+
+#include "../../x86/xen/xen-head.S"
+
+/*
+ * The IDT and GDT 'descriptors' are a strange 48-bit object
+ * only used by the lidt and lgdt instructions. They are not
+ * like usual segment descriptors - they consist of a 16-bit
+ * segment size, and 32-bit linear address value:
+ */
+
+	.data
+.globl boot_gdt_descr
+.globl idt_descr
+
+	ALIGN
+# early boot GDT descriptor (must use 1:1 address mapping)
+	.word 0				# 32 bit align gdt_desc.address
+boot_gdt_descr:
+	.word __BOOT_DS+7
+	.long boot_gdt - __PAGE_OFFSET
+
+	.word 0				# 32-bit align idt_desc.address
+idt_descr:
+	.word IDT_ENTRIES*8-1		# idt contains 256 entries
+	.long idt_table
+
+# boot GDT descriptor (later on used by CPU#0):
+	.word 0				# 32 bit align gdt_desc.address
+ENTRY(early_gdt_descr)
+	.word GDT_ENTRIES*8-1
+	.long gdt_page			/* Overwritten for secondary CPUs */
+
+/*
+ * The boot_gdt must mirror the equivalent in setup.S and is
+ * used only for booting.
+ */
+	.align L1_CACHE_BYTES
+ENTRY(boot_gdt)
+	.fill GDT_ENTRY_BOOT_CS,8,0
+	.quad 0x00cf9a000000ffff	/* kernel 4GB code at 0x00000000 */
+	.quad 0x00cf92000000ffff	/* kernel 4GB data at 0x00000000 */