arch/x86/boot/compressed/head_64.S - maze/linux - Git at Google

 /*
  *  linux/boot/head.S
  *
  *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
  */

 /*
  *  head.S contains the 32-bit startup code.
  *
  * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
  * the page directory will exist. The startup code will be overwritten by
  * the page directory. [According to comments etc elsewhere on a compressed
  * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
  *
  * Page 0 is deliberately kept safe, since System Management Mode code in
  * laptops may need to access the BIOS data stored there.  This is also
  * useful for future device drivers that either access the BIOS via VM86
  * mode.
  */

 /*
  * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
  */
 .code32
 .text

 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/pgtable.h>
 #include <asm/page.h>
 #include <asm/boot.h>
 #include <asm/msr.h>
 #include <asm/asm-offsets.h>

 .section ".text.head"
 	.code32
 	.globl startup_32

 startup_32:
 	cld
 	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
 	 * us to not reload segments */
 	testb $(1<<6), BP_loadflags(%esi)
 	jnz 1f

 	cli
 	movl	$(__KERNEL_DS), %eax
 	movl	%eax, %ds
 	movl	%eax, %es
 	movl	%eax, %ss
 1:

 /* Calculate the delta between where we were compiled to run
  * at and where we were actually loaded at.  This can only be done
  * with a short local call on x86.  Nothing  else will tell us what
  * address we are running at.  The reserved chunk of the real-mode
  * data at 0x1e4 (defined as a scratch field) are used as the stack
  * for this calculation. Only 4 bytes are needed.
  */
 	leal	(0x1e4+4)(%esi), %esp
 	call	1f
 1:	popl	%ebp
 	subl	$1b, %ebp

 /* setup a stack and make sure cpu supports long mode. */
 	movl	$boot_stack_end, %eax
 	addl	%ebp, %eax
 	movl	%eax, %esp

 	call	verify_cpu
 	testl	%eax, %eax
 	jnz	no_longmode

 /* Compute the delta between where we were compiled to run at
  * and where the code will actually run at.
  */
 /* %ebp contains the address we are loaded at by the boot loader and %ebx
  * contains the address where we should move the kernel image temporarily
  * for safe in-place decompression.
  */

 #ifdef CONFIG_RELOCATABLE
 	movl	%ebp, %ebx
 	addl	$(PMD_PAGE_SIZE -1), %ebx
 	andl	$PMD_PAGE_MASK, %ebx
 #else
 	movl	$CONFIG_PHYSICAL_START, %ebx
 #endif

 	/* Replace the compressed data size with the uncompressed size */
 	subl	input_len(%ebp), %ebx
 	movl	output_len(%ebp), %eax
 	addl	%eax, %ebx
 	/* Add 8 bytes for every 32K input block */
 	shrl	$12, %eax
 	addl	%eax, %ebx
 	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
 	addl	$(32768 + 18 + 4095), %ebx
 	andl	$~4095, %ebx

 /*
  * Prepare for entering 64 bit mode
  */

 	/* Load new GDT with the 64bit segments using 32bit descriptor */
 	leal	gdt(%ebp), %eax
 	movl	%eax, gdt+2(%ebp)
 	lgdt	gdt(%ebp)

 	/* Enable PAE mode */
 	xorl	%eax, %eax
 	orl	$(1 << 5), %eax
 	movl	%eax, %cr4

  /*
   * Build early 4G boot pagetable
   */
 	/* Initialize Page tables to 0*/
 	leal	pgtable(%ebx), %edi
 	xorl	%eax, %eax
 	movl	$((4096*6)/4), %ecx
 	rep	stosl

 	/* Build Level 4 */
 	leal	pgtable + 0(%ebx), %edi
 	leal	0x1007 (%edi), %eax
 	movl	%eax, 0(%edi)

 	/* Build Level 3 */
 	leal	pgtable + 0x1000(%ebx), %edi
 	leal	0x1007(%edi), %eax
 	movl	$4, %ecx
 1:	movl	%eax, 0x00(%edi)
 	addl	$0x00001000, %eax
 	addl	$8, %edi
 	decl	%ecx
 	jnz	1b

 	/* Build Level 2 */
 	leal	pgtable + 0x2000(%ebx), %edi
 	movl	$0x00000183, %eax
 	movl	$2048, %ecx
 1:	movl	%eax, 0(%edi)
 	addl	$0x00200000, %eax
 	addl	$8, %edi
 	decl	%ecx
 	jnz	1b

 	/* Enable the boot page tables */
 	leal	pgtable(%ebx), %eax
 	movl	%eax, %cr3

 	/* Enable Long mode in EFER (Extended Feature Enable Register) */
 	movl	$MSR_EFER, %ecx
 	rdmsr
 	btsl	$_EFER_LME, %eax
 	wrmsr

 	/* Setup for the jump to 64bit mode
 	 *
 	 * When the jump is performend we will be in long mode but
 	 * in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
 	 * (and in turn EFER.LMA = 1).	To jump into 64bit mode we use
 	 * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
 	 * We place all of the values on our mini stack so lret can
 	 * used to perform that far jump.
 	 */
 	pushl	$__KERNEL_CS
 	leal	startup_64(%ebp), %eax
 	pushl	%eax

 	/* Enter paged protected Mode, activating Long Mode */
 	movl	$0x80000001, %eax /* Enable Paging and Protected mode */
 	movl	%eax, %cr0

 	/* Jump from 32bit compatibility mode into 64bit mode. */
 	lret

 no_longmode:
 	/* This isn't an x86-64 CPU so hang */
 1:
 	hlt
 	jmp     1b

 #include "../../kernel/verify_cpu_64.S"

 	/* Be careful here startup_64 needs to be at a predictable
 	 * address so I can export it in an ELF header.  Bootloaders
 	 * should look at the ELF header to find this address, as
 	 * it may change in the future.
 	 */
 	.code64
 	.org 0x200
 ENTRY(startup_64)
 	/* We come here either from startup_32 or directly from a
 	 * 64bit bootloader.  If we come here from a bootloader we depend on
 	 * an identity mapped page table being provied that maps our
 	 * entire text+data+bss and hopefully all of memory.
 	 */

 	/* Setup data segments. */
 	xorl	%eax, %eax
 	movl	%eax, %ds
 	movl	%eax, %es
 	movl	%eax, %ss
 	movl	%eax, %fs
 	movl	%eax, %gs
 	lldt	%ax
 	movl    $0x20, %eax
 	ltr	%ax

 	/* Compute the decompressed kernel start address.  It is where
 	 * we were loaded at aligned to a 2M boundary. %rbp contains the
 	 * decompressed kernel start address.
 	 *
 	 * If it is a relocatable kernel then decompress and run the kernel
 	 * from load address aligned to 2MB addr, otherwise decompress and
 	 * run the kernel from CONFIG_PHYSICAL_START
 	 */

 	/* Start with the delta to where the kernel will run at. */
 #ifdef CONFIG_RELOCATABLE
 	leaq	startup_32(%rip) /* - $startup_32 */, %rbp
 	addq	$(PMD_PAGE_SIZE - 1), %rbp
 	andq	$PMD_PAGE_MASK, %rbp
 	movq	%rbp, %rbx
 #else
 	movq	$CONFIG_PHYSICAL_START, %rbp
 	movq	%rbp, %rbx
 #endif

 	/* Replace the compressed data size with the uncompressed size */
 	movl	input_len(%rip), %eax
 	subq	%rax, %rbx
 	movl	output_len(%rip), %eax
 	addq	%rax, %rbx
 	/* Add 8 bytes for every 32K input block */
 	shrq	$12, %rax
 	addq	%rax, %rbx
 	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
 	addq	$(32768 + 18 + 4095), %rbx
 	andq	$~4095, %rbx

 /* Copy the compressed kernel to the end of our buffer
  * where decompression in place becomes safe.
  */
 	leaq	_end(%rip), %r8
 	leaq	_end(%rbx), %r9
 	movq	$_end /* - $startup_32 */, %rcx
 1:	subq	$8, %r8
 	subq	$8, %r9
 	movq	0(%r8), %rax
 	movq	%rax, 0(%r9)
 	subq	$8, %rcx
 	jnz	1b

 /*
  * Jump to the relocated address.
  */
 	leaq	relocated(%rbx), %rax
 	jmp	*%rax

 .section ".text"
 relocated:

 /*
  * Clear BSS
  */
 	xorq	%rax, %rax
 	leaq    _edata(%rbx), %rdi
 	leaq    _end(%rbx), %rcx
 	subq	%rdi, %rcx
 	cld
 	rep
 	stosb

 	/* Setup the stack */
 	leaq	boot_stack_end(%rip), %rsp

 	/* zero EFLAGS after setting rsp */
 	pushq	$0
 	popfq

 /*
  * Do the decompression, and jump to the new kernel..
  */
 	pushq	%rsi			# Save the real mode argument
 	movq	%rsi, %rdi		# real mode address
 	leaq	boot_heap(%rip), %rsi	# malloc area for uncompression
 	leaq	input_data(%rip), %rdx  # input_data
 	movl	input_len(%rip), %eax
 	movq	%rax, %rcx		# input_len
 	movq	%rbp, %r8		# output
 	call	decompress_kernel
 	popq	%rsi


 /*
  * Jump to the decompressed kernel.
  */
 	jmp	*%rbp

 	.data
 gdt:
 	.word	gdt_end - gdt
 	.long	gdt
 	.word	0
 	.quad	0x0000000000000000	/* NULL descriptor */
 	.quad	0x00af9a000000ffff	/* __KERNEL_CS */
 	.quad	0x00cf92000000ffff	/* __KERNEL_DS */
 	.quad	0x0080890000000000	/* TS descriptor */
 	.quad   0x0000000000000000	/* TS continued */
 gdt_end:

 .bss
 /* Stack and heap for uncompression */
 .balign 4
 boot_heap:
 	.fill BOOT_HEAP_SIZE, 1, 0
 boot_stack:
 	.fill BOOT_STACK_SIZE, 1, 0
 boot_stack_end:
	/*
	* linux/boot/head.S
	*
	* Copyright (C) 1991, 1992, 1993 Linus Torvalds
	*/

	/*
	* head.S contains the 32-bit startup code.
	*
	* NOTE!!! Startup happens at absolute address 0x00001000, which is also where
	* the page directory will exist. The startup code will be overwritten by
	* the page directory. [According to comments etc elsewhere on a compressed
	* kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
	*
	* Page 0 is deliberately kept safe, since System Management Mode code in
	* laptops may need to access the BIOS data stored there. This is also
	* useful for future device drivers that either access the BIOS via VM86
	* mode.
	*/

	/*
	* High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
	*/
	.code32
	.text

	#include <linux/linkage.h>
	#include <asm/segment.h>
	#include <asm/pgtable.h>
	#include <asm/page.h>
	#include <asm/boot.h>
	#include <asm/msr.h>
	#include <asm/asm-offsets.h>

	.section ".text.head"
	.code32
	.globl startup_32

	startup_32:
	cld
	/* test KEEP_SEGMENTS flag to see if the bootloader is asking
	* us to not reload segments */
	testb $(1<<6), BP_loadflags(%esi)
	jnz 1f

	cli
	movl $(__KERNEL_DS), %eax
	movl %eax, %ds
	movl %eax, %es
	movl %eax, %ss
	1:

	/* Calculate the delta between where we were compiled to run
	* at and where we were actually loaded at. This can only be done
	* with a short local call on x86. Nothing else will tell us what
	* address we are running at. The reserved chunk of the real-mode
	* data at 0x1e4 (defined as a scratch field) are used as the stack
	* for this calculation. Only 4 bytes are needed.
	*/
	leal (0x1e4+4)(%esi), %esp
	call 1f
	1: popl %ebp
	subl $1b, %ebp

	/* setup a stack and make sure cpu supports long mode. */
	movl $boot_stack_end, %eax
	addl %ebp, %eax
	movl %eax, %esp

	call verify_cpu
	testl %eax, %eax
	jnz no_longmode

	/* Compute the delta between where we were compiled to run at
	* and where the code will actually run at.
	*/
	/* %ebp contains the address we are loaded at by the boot loader and %ebx
	* contains the address where we should move the kernel image temporarily
	* for safe in-place decompression.
	*/

	#ifdef CONFIG_RELOCATABLE
	movl %ebp, %ebx
	addl $(PMD_PAGE_SIZE -1), %ebx
	andl $PMD_PAGE_MASK, %ebx
	#else
	movl $CONFIG_PHYSICAL_START, %ebx
	#endif

	/* Replace the compressed data size with the uncompressed size */
	subl input_len(%ebp), %ebx
	movl output_len(%ebp), %eax
	addl %eax, %ebx
	/* Add 8 bytes for every 32K input block */
	shrl $12, %eax
	addl %eax, %ebx
	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
	addl $(32768 + 18 + 4095), %ebx
	andl $~4095, %ebx

	/*
	* Prepare for entering 64 bit mode
	*/

	/* Load new GDT with the 64bit segments using 32bit descriptor */
	leal gdt(%ebp), %eax
	movl %eax, gdt+2(%ebp)
	lgdt gdt(%ebp)

	/* Enable PAE mode */
	xorl %eax, %eax
	orl $(1 << 5), %eax
	movl %eax, %cr4

	/*
	* Build early 4G boot pagetable
	*/
	/* Initialize Page tables to 0*/
	leal pgtable(%ebx), %edi
	xorl %eax, %eax
	movl $((4096*6)/4), %ecx
	rep stosl

	/* Build Level 4 */
	leal pgtable + 0(%ebx), %edi
	leal 0x1007 (%edi), %eax
	movl %eax, 0(%edi)

	/* Build Level 3 */
	leal pgtable + 0x1000(%ebx), %edi
	leal 0x1007(%edi), %eax
	movl $4, %ecx
	1: movl %eax, 0x00(%edi)
	addl $0x00001000, %eax
	addl $8, %edi
	decl %ecx
	jnz 1b

	/* Build Level 2 */
	leal pgtable + 0x2000(%ebx), %edi
	movl $0x00000183, %eax
	movl $2048, %ecx
	1: movl %eax, 0(%edi)
	addl $0x00200000, %eax
	addl $8, %edi
	decl %ecx
	jnz 1b

	/* Enable the boot page tables */
	leal pgtable(%ebx), %eax
	movl %eax, %cr3

	/* Enable Long mode in EFER (Extended Feature Enable Register) */
	movl $MSR_EFER, %ecx
	rdmsr
	btsl $_EFER_LME, %eax
	wrmsr

	/* Setup for the jump to 64bit mode
	*
	* When the jump is performend we will be in long mode but
	* in 32bit compatibility mode with EFER.LME = 1, CS.L = 0, CS.D = 1
	* (and in turn EFER.LMA = 1). To jump into 64bit mode we use
	* the new gdt/idt that has __KERNEL_CS with CS.L = 1.
	* We place all of the values on our mini stack so lret can
	* used to perform that far jump.
	*/
	pushl $__KERNEL_CS
	leal startup_64(%ebp), %eax
	pushl %eax

	/* Enter paged protected Mode, activating Long Mode */
	movl $0x80000001, %eax /* Enable Paging and Protected mode */
	movl %eax, %cr0

	/* Jump from 32bit compatibility mode into 64bit mode. */
	lret

	no_longmode:
	/* This isn't an x86-64 CPU so hang */
	1:
	hlt
	jmp 1b

	#include "../../kernel/verify_cpu_64.S"

	/* Be careful here startup_64 needs to be at a predictable
	* address so I can export it in an ELF header. Bootloaders
	* should look at the ELF header to find this address, as
	* it may change in the future.
	*/
	.code64
	.org 0x200
	ENTRY(startup_64)
	/* We come here either from startup_32 or directly from a
	* 64bit bootloader. If we come here from a bootloader we depend on
	* an identity mapped page table being provied that maps our
	* entire text+data+bss and hopefully all of memory.
	*/

	/* Setup data segments. */
	xorl %eax, %eax
	movl %eax, %ds
	movl %eax, %es
	movl %eax, %ss
	movl %eax, %fs
	movl %eax, %gs
	lldt %ax
	movl $0x20, %eax
	ltr %ax

	/* Compute the decompressed kernel start address. It is where
	* we were loaded at aligned to a 2M boundary. %rbp contains the
	* decompressed kernel start address.
	*
	* If it is a relocatable kernel then decompress and run the kernel
	* from load address aligned to 2MB addr, otherwise decompress and
	* run the kernel from CONFIG_PHYSICAL_START
	*/

	/* Start with the delta to where the kernel will run at. */
	#ifdef CONFIG_RELOCATABLE
	leaq startup_32(%rip) /* - $startup_32 */, %rbp
	addq $(PMD_PAGE_SIZE - 1), %rbp
	andq $PMD_PAGE_MASK, %rbp
	movq %rbp, %rbx
	#else
	movq $CONFIG_PHYSICAL_START, %rbp
	movq %rbp, %rbx
	#endif

	/* Replace the compressed data size with the uncompressed size */
	movl input_len(%rip), %eax
	subq %rax, %rbx
	movl output_len(%rip), %eax
	addq %rax, %rbx
	/* Add 8 bytes for every 32K input block */
	shrq $12, %rax
	addq %rax, %rbx
	/* Add 32K + 18 bytes of extra slack and align on a 4K boundary */
	addq $(32768 + 18 + 4095), %rbx
	andq $~4095, %rbx

	/* Copy the compressed kernel to the end of our buffer
	* where decompression in place becomes safe.
	*/
	leaq _end(%rip), %r8
	leaq _end(%rbx), %r9
	movq $_end /* - $startup_32 */, %rcx
	1: subq $8, %r8
	subq $8, %r9
	movq 0(%r8), %rax
	movq %rax, 0(%r9)
	subq $8, %rcx
	jnz 1b

	/*
	* Jump to the relocated address.
	*/
	leaq relocated(%rbx), %rax
	jmp *%rax

	.section ".text"
	relocated:

	/*
	* Clear BSS
	*/
	xorq %rax, %rax
	leaq _edata(%rbx), %rdi
	leaq _end(%rbx), %rcx
	subq %rdi, %rcx
	cld
	rep
	stosb

	/* Setup the stack */
	leaq boot_stack_end(%rip), %rsp

	/* zero EFLAGS after setting rsp */
	pushq $0
	popfq

	/*
	* Do the decompression, and jump to the new kernel..
	*/
	pushq %rsi # Save the real mode argument
	movq %rsi, %rdi # real mode address
	leaq boot_heap(%rip), %rsi # malloc area for uncompression
	leaq input_data(%rip), %rdx # input_data
	movl input_len(%rip), %eax
	movq %rax, %rcx # input_len
	movq %rbp, %r8 # output
	call decompress_kernel
	popq %rsi


	/*
	* Jump to the decompressed kernel.
	*/
	jmp *%rbp

	.data
	gdt:
	.word gdt_end - gdt
	.long gdt
	.word 0
	.quad 0x0000000000000000 /* NULL descriptor */
	.quad 0x00af9a000000ffff /* __KERNEL_CS */
	.quad 0x00cf92000000ffff /* __KERNEL_DS */
	.quad 0x0080890000000000 /* TS descriptor */
	.quad 0x0000000000000000 /* TS continued */
	gdt_end:

	.bss
	/* Stack and heap for uncompression */
	.balign 4
	boot_heap:
	.fill BOOT_HEAP_SIZE, 1, 0
	boot_stack:
	.fill BOOT_STACK_SIZE, 1, 0
	boot_stack_end: