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linux/arch/x86_64/kernel/head.S
Andi Kleen 3829ee6b1b [PATCH] x86_64: Small assembly improvements 
Save a byte here and there.  Ultimatively useless, but these things always
catch my eyes when reading the code so just fix them for now.

Also I got at least one patch fixing of them already, which gives a good
excuse.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-28 21:46:02 -07:00

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9.9 KiB
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/*
* linux/arch/x86_64/kernel/head.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>
*
* $Id: head.S,v 1.49 2002/03/19 17:39:25 ak Exp $
*/
#include <linux/linkage.h>
#include <linux/threads.h>
#include <asm/desc.h>
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/cache.h>
/* we are not able to switch in one step to the final KERNEL ADRESS SPACE
* because we need identity-mapped pages on setup so define __START_KERNEL to
* 0x100000 for this stage
*
*/
.text
.code32
.globl startup_32
/* %bx: 1 if coming from smp trampoline on secondary cpu */
startup_32:
/*
* At this point the CPU runs in 32bit protected mode (CS.D = 1) with
* paging disabled and the point of this file is to switch to 64bit
* long mode with a kernel mapping for kerneland to jump into the
* kernel virtual addresses.
* There is no stack until we set one up.
*/
/* Initialize the %ds segment register */
movl $__KERNEL_DS,%eax
movl %eax,%ds
/* Load new GDT with the 64bit segments using 32bit descriptor */
lgdt pGDT32 - __START_KERNEL_map
/* If the CPU doesn't support CPUID this will double fault.
* Unfortunately it is hard to check for CPUID without a stack.
*/
/* Check if extended functions are implemented */
movl $0x80000000, %eax
cpuid
cmpl $0x80000000, %eax
jbe no_long_mode
/* Check if long mode is implemented */
mov $0x80000001, %eax
cpuid
btl $29, %edx
jnc no_long_mode
/*
* Prepare for entering 64bits mode
*/
/* Enable PAE mode */
xorl %eax, %eax
btsl $5, %eax
movl %eax, %cr4
/* Setup early boot stage 4 level pagetables */
movl $(init_level4_pgt - __START_KERNEL_map), %eax
movl %eax, %cr3
/* Setup EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
/* Enable Long Mode */
btsl $_EFER_LME, %eax
/* Make changes effective */
wrmsr
xorl %eax, %eax
btsl $31, %eax /* Enable paging and in turn activate Long Mode */
btsl $0, %eax /* Enable protected mode */
/* Make changes effective */
movl %eax, %cr0
/*
* At this point we're in long mode but in 32bit compatibility mode
* with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
* EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use
* the new gdt/idt that has __KERNEL_CS with CS.L = 1.
*/
ljmp $__KERNEL_CS, $(startup_64 - __START_KERNEL_map)
.code64
.org 0x100
.globl startup_64
startup_64:
/* We come here either from startup_32
* or directly from a 64bit bootloader.
* Since we may have come directly from a bootloader we
* reload the page tables here.
*/
/* Enable PAE mode and PGE */
xorq %rax, %rax
btsq $5, %rax
btsq $7, %rax
movq %rax, %cr4
/* Setup early boot stage 4 level pagetables. */
movq $(init_level4_pgt - __START_KERNEL_map), %rax
movq %rax, %cr3
/* Check if nx is implemented */
movl $0x80000001, %eax
cpuid
movl %edx,%edi
/* Setup EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
/* Enable System Call */
btsl $_EFER_SCE, %eax
/* No Execute supported? */
btl $20,%edi
jnc 1f
btsl $_EFER_NX, %eax
1:
/* Make changes effective */
wrmsr
/* Setup cr0 */
#define CR0_PM 1 /* protected mode */
#define CR0_MP (1<<1)
#define CR0_ET (1<<4)
#define CR0_NE (1<<5)
#define CR0_WP (1<<16)
#define CR0_AM (1<<18)
#define CR0_PAGING (1<<31)
movl $CR0_PM|CR0_MP|CR0_ET|CR0_NE|CR0_WP|CR0_AM|CR0_PAGING,%eax
/* Make changes effective */
movq %rax, %cr0
/* Setup a boot time stack */
movq init_rsp(%rip),%rsp
/* zero EFLAGS after setting rsp */
pushq $0
popfq
/*
* 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.
*/
lgdt cpu_gdt_descr
/*
* Setup up a dummy PDA. this is just for some early bootup code
* that does in_interrupt()
*/
movl $MSR_GS_BASE,%ecx
movq $empty_zero_page,%rax
movq %rax,%rdx
shrq $32,%rdx
wrmsr
/* set up data segments. actually 0 would do too */
movl $__KERNEL_DS,%eax
movl %eax,%ds
movl %eax,%ss
movl %eax,%es
/* esi is pointer to real mode structure with interesting info.
pass it to C */
movl %esi, %edi
/* Finally jump to run C code and to be on real kernel address
* Since we are running on identity-mapped space we have to jump
* to the full 64bit address , this is only possible as indirect
* jump
*/
movq initial_code(%rip),%rax
jmp *%rax
/* SMP bootup changes these two */
.globl initial_code
initial_code:
.quad x86_64_start_kernel
.globl init_rsp
init_rsp:
.quad init_thread_union+THREAD_SIZE-8
ENTRY(early_idt_handler)
cmpl $2,early_recursion_flag(%rip)
jz 1f
incl early_recursion_flag(%rip)
xorl %eax,%eax
movq 8(%rsp),%rsi # get rip
movq (%rsp),%rdx
movq %cr2,%rcx
leaq early_idt_msg(%rip),%rdi
call early_printk
cmpl $2,early_recursion_flag(%rip)
jz 1f
call dump_stack
1: hlt
jmp 1b
early_recursion_flag:
.long 0
early_idt_msg:
.asciz "PANIC: early exception rip %lx error %lx cr2 %lx\n"
.code32
ENTRY(no_long_mode)
/* This isn't an x86-64 CPU so hang */
1:
jmp 1b
.org 0xf00
.globl pGDT32
pGDT32:
.word gdt_end-cpu_gdt_table
.long cpu_gdt_table-__START_KERNEL_map
.org 0xf10
ljumpvector:
.long startup_64-__START_KERNEL_map
.word __KERNEL_CS
ENTRY(stext)
ENTRY(_stext)
/*
* This default setting generates an ident mapping at address 0x100000
* and a mapping for the kernel that precisely maps virtual address
* 0xffffffff80000000 to physical address 0x000000. (always using
* 2Mbyte large pages provided by PAE mode)
*/
.org 0x1000
ENTRY(init_level4_pgt)
.quad 0x0000000000002007 + __PHYSICAL_START /* -> level3_ident_pgt */
.fill 255,8,0
.quad 0x000000000000a007 + __PHYSICAL_START
.fill 254,8,0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad 0x0000000000003007 + __PHYSICAL_START /* -> level3_kernel_pgt */
.org 0x2000
ENTRY(level3_ident_pgt)
.quad 0x0000000000004007 + __PHYSICAL_START
.fill 511,8,0
.org 0x3000
ENTRY(level3_kernel_pgt)
.fill 510,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad 0x0000000000005007 + __PHYSICAL_START /* -> level2_kernel_pgt */
.fill 1,8,0
.org 0x4000
ENTRY(level2_ident_pgt)
/* 40MB for bootup. */
.quad 0x0000000000000283
.quad 0x0000000000200183
.quad 0x0000000000400183
.quad 0x0000000000600183
.quad 0x0000000000800183
.quad 0x0000000000A00183
.quad 0x0000000000C00183
.quad 0x0000000000E00183
.quad 0x0000000001000183
.quad 0x0000000001200183
.quad 0x0000000001400183
.quad 0x0000000001600183
.quad 0x0000000001800183
.quad 0x0000000001A00183
.quad 0x0000000001C00183
.quad 0x0000000001E00183
.quad 0x0000000002000183
.quad 0x0000000002200183
.quad 0x0000000002400183
.quad 0x0000000002600183
/* Temporary mappings for the super early allocator in arch/x86_64/mm/init.c */
.globl temp_boot_pmds
temp_boot_pmds:
.fill 492,8,0
.org 0x5000
ENTRY(level2_kernel_pgt)
/* 40MB kernel mapping. The kernel code cannot be bigger than that.
When you change this change KERNEL_TEXT_SIZE in page.h too. */
/* (2^48-(2*1024*1024*1024)-((2^39)*511)-((2^30)*510)) = 0 */
.quad 0x0000000000000183
.quad 0x0000000000200183
.quad 0x0000000000400183
.quad 0x0000000000600183
.quad 0x0000000000800183
.quad 0x0000000000A00183
.quad 0x0000000000C00183
.quad 0x0000000000E00183
.quad 0x0000000001000183
.quad 0x0000000001200183
.quad 0x0000000001400183
.quad 0x0000000001600183
.quad 0x0000000001800183
.quad 0x0000000001A00183
.quad 0x0000000001C00183
.quad 0x0000000001E00183
.quad 0x0000000002000183
.quad 0x0000000002200183
.quad 0x0000000002400183
.quad 0x0000000002600183
/* Module mapping starts here */
.fill 492,8,0
.org 0x6000
ENTRY(empty_zero_page)
.org 0x7000
ENTRY(empty_bad_page)
.org 0x8000
ENTRY(empty_bad_pte_table)
.org 0x9000
ENTRY(empty_bad_pmd_table)
.org 0xa000
ENTRY(level3_physmem_pgt)
.quad 0x0000000000005007 + __PHYSICAL_START /* -> level2_kernel_pgt (so that __va works even before pagetable_init) */
.org 0xb000
#ifdef CONFIG_ACPI_SLEEP
ENTRY(wakeup_level4_pgt)
.quad 0x0000000000002007 + __PHYSICAL_START /* -> level3_ident_pgt */
.fill 255,8,0
.quad 0x000000000000a007 + __PHYSICAL_START
.fill 254,8,0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad 0x0000000000003007 + __PHYSICAL_START /* -> level3_kernel_pgt */
#endif
.data
.align 16
.globl cpu_gdt_descr
cpu_gdt_descr:
.word gdt_end-cpu_gdt_table
gdt:
.quad cpu_gdt_table
#ifdef CONFIG_SMP
.rept NR_CPUS-1
.word 0
.quad 0
.endr
#endif
/* We need valid kernel segments for data and code in long mode too
* IRET will check the segment types kkeil 2000/10/28
* Also sysret mandates a special GDT layout
*/
.align L1_CACHE_BYTES
/* The TLS descriptors are currently at a different place compared to i386.
Hopefully nobody expects them at a fixed place (Wine?) */
ENTRY(cpu_gdt_table)
.quad 0x0000000000000000 /* NULL descriptor */
.quad 0x008f9a000000ffff /* __KERNEL_COMPAT32_CS */
.quad 0x00af9a000000ffff /* __KERNEL_CS */
.quad 0x00cf92000000ffff /* __KERNEL_DS */
.quad 0x00cffa000000ffff /* __USER32_CS */
.quad 0x00cff2000000ffff /* __USER_DS, __USER32_DS */
.quad 0x00affa000000ffff /* __USER_CS */
.quad 0x00cf9a000000ffff /* __KERNEL32_CS */
.quad 0,0 /* TSS */
.quad 0,0 /* LDT */
.quad 0,0,0 /* three TLS descriptors */
.quad 0x00009a000000ffff /* __KERNEL16_CS - 16bit PM for S3 wakeup. */
/* base must be patched for real base address. */
gdt_end:
/* asm/segment.h:GDT_ENTRIES must match this */
/* This should be a multiple of the cache line size */
/* GDTs of other CPUs: */
.fill (GDT_SIZE * NR_CPUS) - (gdt_end - cpu_gdt_table)
.align L1_CACHE_BYTES
ENTRY(idt_table)
.rept 256
.quad 0
.quad 0
.endr
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