/* * 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> __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