/*
   *  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/boot.h>
  #include <asm/msr.h>
  #include <asm/processor-flags.h>
  #include <asm/asm-offsets.h>
  #include <asm/bootparam.h>
  
  /*
   * Locally defined symbols should be marked hidden:
   */
  	.hidden _bss
  	.hidden _ebss
  	.hidden _got
  	.hidden _egot
  
  	__HEAD
  	.code32
  ENTRY(startup_32)
  	/*
  	 * 32bit entry is 0 and it is ABI so immutable!
  	 * If we come here directly from a bootloader,
  	 * kernel(text+data+bss+brk) ramdisk, zero_page, command line
  	 * all need to be under the 4G limit.
  	 */
  	cld
  	/*
  	 * Test KEEP_SEGMENTS flag to see if the bootloader is asking
  	 * us to not reload segments
  	 */
  	testb $KEEP_SEGMENTS, BP_loadflags(%esi)
  	jnz 1f
  
  	cli
  	movl	$(__BOOT_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
  	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
  	jge	1f
  #endif
  	movl	$LOAD_PHYSICAL_ADDR, %ebx
  1:
  
  	/* 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	%cr4, %eax
  	orl	$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
  
  	/* After gdt is loaded */
  	xorl	%eax, %eax
  	lldt	%ax
  	movl    $__BOOT_TSS, %eax
  	ltr	%ax
  
  	/*
  	 * 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
  #ifdef CONFIG_EFI_MIXED
  	movl	efi32_config(%ebp), %ebx
  	cmp	$0, %ebx
  	jz	1f
  	leal	handover_entry(%ebp), %eax
  1:
  #endif
  	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)
  
  #ifdef CONFIG_EFI_MIXED
  	.org 0x190
  ENTRY(efi32_stub_entry)
  	add	$0x4, %esp		/* Discard return address */
  	popl	%ecx
  	popl	%edx
  	popl	%esi
  
  	leal	(BP_scratch+4)(%esi), %esp
  	call	1f
  1:	pop	%ebp
  	subl	$1b, %ebp
  
  	movl	%ecx, efi32_config(%ebp)
  	movl	%edx, efi32_config+8(%ebp)
  	sgdtl	efi32_boot_gdt(%ebp)
  
  	leal	efi32_config(%ebp), %eax
  	movl	%eax, efi_config(%ebp)
  
  	jmp	startup_32
  ENDPROC(efi32_stub_entry)
  #endif
  
  	.code64
  	.org 0x200
  ENTRY(startup_64)
  	/*
  	 * 64bit entry is 0x200 and it is ABI so immutable!
  	 * We come here either from startup_32 or directly from a
  	 * 64bit bootloader.
  	 * If we come here from a bootloader, kernel(text+data+bss+brk),
  	 * ramdisk, zero_page, command line could be above 4G.
  	 * We depend on an identity mapped page table being provided
  	 * that maps our entire kernel(text+data+bss+brk), zero page
  	 * and command line.
  	 */
  #ifdef CONFIG_EFI_STUB
  	/*
  	 * The entry point for the PE/COFF executable is efi_pe_entry, so
  	 * only legacy boot loaders will execute this jmp.
  	 */
  	jmp	preferred_addr
  
  ENTRY(efi_pe_entry)
  	movq	%rcx, efi64_config(%rip)	/* Handle */
  	movq	%rdx, efi64_config+8(%rip) /* EFI System table pointer */
  
  	leaq	efi64_config(%rip), %rax
  	movq	%rax, efi_config(%rip)
  
  	call	1f
  1:	popq	%rbp
  	subq	$1b, %rbp
  
  	/*
  	 * Relocate efi_config->call().
  	 */
  	addq	%rbp, efi64_config+88(%rip)
  
  	movq	%rax, %rdi
  	call	make_boot_params
  	cmpq	$0,%rax
  	je	fail
  	mov	%rax, %rsi
  	leaq	startup_32(%rip), %rax
  	movl	%eax, BP_code32_start(%rsi)
  	jmp	2f		/* Skip the relocation */
  
  handover_entry:
  	call	1f
  1:	popq	%rbp
  	subq	$1b, %rbp
  
  	/*
  	 * Relocate efi_config->call().
  	 */
  	movq	efi_config(%rip), %rax
  	addq	%rbp, 88(%rax)
  2:
  	movq	efi_config(%rip), %rdi
  	call	efi_main
  	movq	%rax,%rsi
  	cmpq	$0,%rax
  	jne	2f
  fail:
  	/* EFI init failed, so hang. */
  	hlt
  	jmp	fail
  2:
  	movl	BP_code32_start(%esi), %eax
  	leaq	preferred_addr(%rax), %rax
  	jmp	*%rax
  
  preferred_addr:
  #endif
  
  	/* Setup data segments. */
  	xorl	%eax, %eax
  	movl	%eax, %ds
  	movl	%eax, %es
  	movl	%eax, %ss
  	movl	%eax, %fs
  	movl	%eax, %gs
  
  	/*
  	 * 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
  	cmpq	$LOAD_PHYSICAL_ADDR, %rbp
  	jge	1f
  #endif
  	movq	$LOAD_PHYSICAL_ADDR, %rbp
  1:
  
  	/* 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
  
  #ifdef CONFIG_EFI_STUB
  	.org 0x390
  ENTRY(efi64_stub_entry)
  	movq	%rdi, efi64_config(%rip)	/* Handle */
  	movq	%rsi, efi64_config+8(%rip) /* EFI System table pointer */
  
  	leaq	efi64_config(%rip), %rax
  	movq	%rax, efi_config(%rip)
  
  	movq	%rdx, %rsi
  	jmp	handover_entry
  ENDPROC(efi64_stub_entry)
  #endif
  
  	.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	$z_run_size, %r9	/* size of kernel with .bss and .brk */
  	pushq	%r9
  	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 */
  	movq	$z_output_len, %r9	/* decompressed length, end of relocs */
  	call	decompress_kernel	/* returns kernel location in %rax */
  	popq	%r9
  	popq	%rsi
  
  /*
   * Jump to the decompressed kernel.
   */
  	jmp	*%rax
  
  	.code32
  no_longmode:
  	/* This isn't an x86-64 CPU so hang */
  1:
  	hlt
  	jmp     1b
  
  #include "../../kernel/verify_cpu.S"
  
  	.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:
  
  #ifdef CONFIG_EFI_STUB
  efi_config:
  	.quad	0
  
  #ifdef CONFIG_EFI_MIXED
  	.global efi32_config
  efi32_config:
  	.fill	11,8,0
  	.quad	efi64_thunk
  	.byte	0
  #endif
  
  	.global efi64_config
  efi64_config:
  	.fill	11,8,0
  	.quad	efi_call
  	.byte	1
  #endif /* CONFIG_EFI_STUB */
  
  /*
   * 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