arch/x86/boot/compressed/head_64.S - kernel/bruno - 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/init.h>
 #include <linux/linkage.h>
 #include <asm/segment.h>
 #include <asm/pgtable_types.h>
 #include <asm/page_types.h>
 #include <asm/boot.h>
 #include <asm/msr.h>
 #include <asm/processor-flags.h>
 #include <asm/asm-offsets.h>

 	__HEAD
 	.code32
 ENTRY(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	(BP_scratch+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
 	movl	BP_kernel_alignment(%esi), %eax
 	decl	%eax
 	addl	%eax, %ebx
 	notl	%eax
 	andl	%eax, %ebx
 #else
 	movl	$LOAD_PHYSICAL_ADDR, %ebx
 #endif

 	/* Target address to relocate to for decompression */
 	addl	$z_extract_offset, %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 */
 	movl	$(X86_CR4_PAE), %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	$(X86_CR0_PG | X86_CR0_PE), %eax /* Enable Paging and Protected mode */
 	movl	%eax, %cr0

 	/* Jump from 32bit compatibility mode into 64bit mode. */
 	lret
 ENDPROC(startup_32)

 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 LOAD_PHYSICAL_ADDR
 	 *
 	 * We cannot rely on the calculation done in 32-bit mode, since we
 	 * may have been invoked via the 64-bit entry point.
 	 */

 	/* Start with the delta to where the kernel will run at. */
 #ifdef CONFIG_RELOCATABLE
 	leaq	startup_32(%rip) /* - $startup_32 */, %rbp
 	movl	BP_kernel_alignment(%rsi), %eax
 	decl	%eax
 	addq	%rax, %rbp
 	notq	%rax
 	andq	%rax, %rbp
 #else
 	movq	$LOAD_PHYSICAL_ADDR, %rbp
 #endif

 	/* Target address to relocate to for decompression */
 	leaq	z_extract_offset(%rbp), %rbx

 	/* Set up the stack */
 	leaq	boot_stack_end(%rbx), %rsp

 	/* Zero EFLAGS */
 	pushq	$0
 	popfq

 /*
  * Copy the compressed kernel to the end of our buffer
  * where decompression in place becomes safe.
  */
 	pushq	%rsi
 	leaq	(_bss-8)(%rip), %rsi
 	leaq	(_bss-8)(%rbx), %rdi
 	movq	$_bss /* - $startup_32 */, %rcx
 	shrq	$3, %rcx
 	std
 	rep	movsq
 	cld
 	popq	%rsi

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

 	.text
 relocated:

 /*
  * Clear BSS (stack is currently empty)
  */
 	xorl	%eax, %eax
 	leaq    _bss(%rip), %rdi
 	leaq    _ebss(%rip), %rcx
 	subq	%rdi, %rcx
 	shrq	$3, %rcx
 	rep	stosq

 /*
  * Adjust our own GOT
  */
 	leaq	_got(%rip), %rdx
 	leaq	_egot(%rip), %rcx
 1:
 	cmpq	%rcx, %rdx
 	jae	2f
 	addq	%rbx, (%rdx)
 	addq	$8, %rdx
 	jmp	1b
 2:

 /*
  * 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	$z_input_len, %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
 	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:

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

 /*
  * Space for page tables (not in .bss so not zeroed)
  */
 	.section ".pgtable","a",@nobits
 	.balign 4096
 pgtable:
 	.fill 6*4096, 1, 0
	/*
	* 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/init.h>
	#include <linux/linkage.h>
	#include <asm/segment.h>
	#include <asm/pgtable_types.h>
	#include <asm/page_types.h>
	#include <asm/boot.h>
	#include <asm/msr.h>
	#include <asm/processor-flags.h>
	#include <asm/asm-offsets.h>

	__HEAD
	.code32
	ENTRY(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 (BP_scratch+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
	movl BP_kernel_alignment(%esi), %eax
	decl %eax
	addl %eax, %ebx
	notl %eax
	andl %eax, %ebx
	#else
	movl $LOAD_PHYSICAL_ADDR, %ebx
	#endif

	/* Target address to relocate to for decompression */
	addl $z_extract_offset, %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 */
	movl $(X86_CR4_PAE), %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 $(X86_CR0_PG \| X86_CR0_PE), %eax /* Enable Paging and Protected mode */
	movl %eax, %cr0

	/* Jump from 32bit compatibility mode into 64bit mode. */
	lret
	ENDPROC(startup_32)

	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 LOAD_PHYSICAL_ADDR
	*
	* We cannot rely on the calculation done in 32-bit mode, since we
	* may have been invoked via the 64-bit entry point.
	*/

	/* Start with the delta to where the kernel will run at. */
	#ifdef CONFIG_RELOCATABLE
	leaq startup_32(%rip) /* - $startup_32 */, %rbp
	movl BP_kernel_alignment(%rsi), %eax
	decl %eax
	addq %rax, %rbp
	notq %rax
	andq %rax, %rbp
	#else
	movq $LOAD_PHYSICAL_ADDR, %rbp
	#endif

	/* Target address to relocate to for decompression */
	leaq z_extract_offset(%rbp), %rbx

	/* Set up the stack */
	leaq boot_stack_end(%rbx), %rsp

	/* Zero EFLAGS */
	pushq $0
	popfq

	/*
	* Copy the compressed kernel to the end of our buffer
	* where decompression in place becomes safe.
	*/
	pushq %rsi
	leaq (_bss-8)(%rip), %rsi
	leaq (_bss-8)(%rbx), %rdi
	movq $_bss /* - $startup_32 */, %rcx
	shrq $3, %rcx
	std
	rep movsq
	cld
	popq %rsi

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

	.text
	relocated:

	/*
	* Clear BSS (stack is currently empty)
	*/
	xorl %eax, %eax
	leaq _bss(%rip), %rdi
	leaq _ebss(%rip), %rcx
	subq %rdi, %rcx
	shrq $3, %rcx
	rep stosq

	/*
	* Adjust our own GOT
	*/
	leaq _got(%rip), %rdx
	leaq _egot(%rip), %rcx
	1:
	cmpq %rcx, %rdx
	jae 2f
	addq %rbx, (%rdx)
	addq $8, %rdx
	jmp 1b
	2:

	/*
	* 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 $z_input_len, %ecx /* input_len */
	movq %rbp, %r8 /* output target address */
	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:

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

	/*
	* Space for page tables (not in .bss so not zeroed)
	*/
	.section ".pgtable","a",@nobits
	.balign 4096
	pgtable:
	.fill 6*4096, 1, 0