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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-08-05 17:04:01 -0300
commit57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch)
tree5e910f0e82173f4ef4f51111366a3f1299037a7b /arch/x86/kernel/head_32.S
Initial import
Diffstat (limited to 'arch/x86/kernel/head_32.S')
-rw-r--r--arch/x86/kernel/head_32.S771
1 files changed, 771 insertions, 0 deletions
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
new file mode 100644
index 000000000..7e429c99c
--- /dev/null
+++ b/arch/x86/kernel/head_32.S
@@ -0,0 +1,771 @@
+/*
+ *
+ * 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>
+#include <asm/bootparam.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.
+ *
+ * We shift 2 by 31 instead of 1 by 32 to the left in order to avoid a
+ * gas warning about overflowing shift count when gas has been compiled
+ * with only a host target support using a 32-bit type for internal
+ * representation.
+ */
+LOWMEM_PAGES = (((2<<31) - __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 $KEEP_SEGMENTS, 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
+ */
+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
+ */
+ movb $4,X86 # at least 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:
+ 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
+
+ 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)
+
+#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 interrupt gates that push zero if there
+ * is no error code and then jump to early_idt_handler_common.
+ * It doesn't actually load the 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_handler_array,%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 $EARLY_IDT_HANDLER_SIZE,%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_handler_array)
+ # 36(%esp) %eflags
+ # 32(%esp) %cs
+ # 28(%esp) %eip
+ # 24(%rsp) error code
+ i = 0
+ .rept NUM_EXCEPTION_VECTORS
+ .ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
+ pushl $0 # Dummy error code, to make stack frame uniform
+ .endif
+ pushl $i # 20(%esp) Vector number
+ jmp early_idt_handler_common
+ i = i + 1
+ .fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
+ .endr
+ENDPROC(early_idt_handler_array)
+
+early_idt_handler_common:
+ /*
+ * The stack is the hardware frame, an error code or zero, and the
+ * vector number.
+ */
+ 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_common)
+
+/* 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 */