| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * 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/boot.h> |
| #include <asm/msr.h> |
| #include <asm/processor-flags.h> |
| #include <asm/asm-offsets.h> |
| #include <asm/bootparam.h> |
| #include "pgtable.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 */ |
| movl BP_init_size(%esi), %eax |
| subl $_end, %eax |
| addl %eax, %ebx |
| |
| /* |
| * Prepare for entering 64 bit mode |
| */ |
| |
| /* Load new GDT with the 64bit segments using 32bit descriptor */ |
| addl %ebp, 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 |
| */ |
| /* |
| * If SEV is active then set the encryption mask in the page tables. |
| * This will insure that when the kernel is copied and decompressed |
| * it will be done so encrypted. |
| */ |
| call get_sev_encryption_bit |
| xorl %edx, %edx |
| testl %eax, %eax |
| jz 1f |
| subl $32, %eax /* Encryption bit is always above bit 31 */ |
| bts %eax, %edx /* Set encryption mask for page tables */ |
| 1: |
| |
| /* Initialize Page tables to 0 */ |
| leal pgtable(%ebx), %edi |
| xorl %eax, %eax |
| movl $(BOOT_INIT_PGT_SIZE/4), %ecx |
| rep stosl |
| |
| /* Build Level 4 */ |
| leal pgtable + 0(%ebx), %edi |
| leal 0x1007 (%edi), %eax |
| movl %eax, 0(%edi) |
| addl %edx, 4(%edi) |
| |
| /* Build Level 3 */ |
| leal pgtable + 0x1000(%ebx), %edi |
| leal 0x1007(%edi), %eax |
| movl $4, %ecx |
| 1: movl %eax, 0x00(%edi) |
| addl %edx, 0x04(%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 %edx, 4(%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. |
| */ |
| |
| /* 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 */ |
| movl BP_init_size(%rsi), %ebx |
| subl $_end, %ebx |
| addq %rbp, %rbx |
| |
| /* Set up the stack */ |
| leaq boot_stack_end(%rbx), %rsp |
| |
| /* |
| * At this point we are in long mode with 4-level paging enabled, |
| * but we might want to enable 5-level paging or vice versa. |
| * |
| * The problem is that we cannot do it directly. Setting or clearing |
| * CR4.LA57 in long mode would trigger #GP. So we need to switch off |
| * long mode and paging first. |
| * |
| * We also need a trampoline in lower memory to switch over from |
| * 4- to 5-level paging for cases when the bootloader puts the kernel |
| * above 4G, but didn't enable 5-level paging for us. |
| * |
| * The same trampoline can be used to switch from 5- to 4-level paging |
| * mode, like when starting 4-level paging kernel via kexec() when |
| * original kernel worked in 5-level paging mode. |
| * |
| * For the trampoline, we need the top page table to reside in lower |
| * memory as we don't have a way to load 64-bit values into CR3 in |
| * 32-bit mode. |
| * |
| * We go though the trampoline even if we don't have to: if we're |
| * already in a desired paging mode. This way the trampoline code gets |
| * tested on every boot. |
| */ |
| |
| /* Make sure we have GDT with 32-bit code segment */ |
| leaq gdt(%rip), %rax |
| movq %rax, gdt64+2(%rip) |
| lgdt gdt64(%rip) |
| |
| /* |
| * paging_prepare() sets up the trampoline and checks if we need to |
| * enable 5-level paging. |
| * |
| * Address of the trampoline is returned in RAX. |
| * Non zero RDX on return means we need to enable 5-level paging. |
| * |
| * RSI holds real mode data and needs to be preserved across |
| * this function call. |
| */ |
| pushq %rsi |
| call paging_prepare |
| popq %rsi |
| |
| /* Save the trampoline address in RCX */ |
| movq %rax, %rcx |
| |
| /* |
| * Load the address of trampoline_return() into RDI. |
| * It will be used by the trampoline to return to the main code. |
| */ |
| leaq trampoline_return(%rip), %rdi |
| |
| /* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */ |
| pushq $__KERNEL32_CS |
| leaq TRAMPOLINE_32BIT_CODE_OFFSET(%rax), %rax |
| pushq %rax |
| lretq |
| trampoline_return: |
| /* Restore the stack, the 32-bit trampoline uses its own stack */ |
| leaq boot_stack_end(%rbx), %rsp |
| |
| /* |
| * cleanup_trampoline() would restore trampoline memory. |
| * |
| * RSI holds real mode data and needs to be preserved across |
| * this function call. |
| */ |
| pushq %rsi |
| call cleanup_trampoline |
| popq %rsi |
| |
| /* 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 |
| |
| /* The entry point for the PE/COFF executable is efi_pe_entry. */ |
| 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+40(%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, 40(%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 startup_64(%rax), %rax |
| jmp *%rax |
| ENDPROC(efi_pe_entry) |
| |
| .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 extraction, 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 */ |
| movq $z_output_len, %r9 /* decompressed length, end of relocs */ |
| call extract_kernel /* returns kernel location in %rax */ |
| popq %rsi |
| |
| /* |
| * Jump to the decompressed kernel. |
| */ |
| jmp *%rax |
| |
| .code32 |
| /* |
| * This is the 32-bit trampoline that will be copied over to low memory. |
| * |
| * RDI contains the return address (might be above 4G). |
| * ECX contains the base address of the trampoline memory. |
| * Non zero RDX on return means we need to enable 5-level paging. |
| */ |
| ENTRY(trampoline_32bit_src) |
| /* Set up data and stack segments */ |
| movl $__KERNEL_DS, %eax |
| movl %eax, %ds |
| movl %eax, %ss |
| |
| /* Set up new stack */ |
| leal TRAMPOLINE_32BIT_STACK_END(%ecx), %esp |
| |
| /* Disable paging */ |
| movl %cr0, %eax |
| btrl $X86_CR0_PG_BIT, %eax |
| movl %eax, %cr0 |
| |
| /* Check what paging mode we want to be in after the trampoline */ |
| cmpl $0, %edx |
| jz 1f |
| |
| /* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */ |
| movl %cr4, %eax |
| testl $X86_CR4_LA57, %eax |
| jnz 3f |
| jmp 2f |
| 1: |
| /* We want 4-level paging: don't touch CR3 if it already points to 4-level page tables */ |
| movl %cr4, %eax |
| testl $X86_CR4_LA57, %eax |
| jz 3f |
| 2: |
| /* Point CR3 to the trampoline's new top level page table */ |
| leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%ecx), %eax |
| movl %eax, %cr3 |
| 3: |
| /* Enable PAE and LA57 (if required) paging modes */ |
| movl $X86_CR4_PAE, %eax |
| cmpl $0, %edx |
| jz 1f |
| orl $X86_CR4_LA57, %eax |
| 1: |
| movl %eax, %cr4 |
| |
| /* Calculate address of paging_enabled() once we are executing in the trampoline */ |
| leal paging_enabled - trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_OFFSET(%ecx), %eax |
| |
| /* Prepare the stack for far return to Long Mode */ |
| pushl $__KERNEL_CS |
| pushl %eax |
| |
| /* Enable paging again */ |
| movl $(X86_CR0_PG | X86_CR0_PE), %eax |
| movl %eax, %cr0 |
| |
| lret |
| |
| .code64 |
| paging_enabled: |
| /* Return from the trampoline */ |
| jmp *%rdi |
| |
| /* |
| * The trampoline code has a size limit. |
| * Make sure we fail to compile if the trampoline code grows |
| * beyond TRAMPOLINE_32BIT_CODE_SIZE bytes. |
| */ |
| .org trampoline_32bit_src + TRAMPOLINE_32BIT_CODE_SIZE |
| |
| .code32 |
| no_longmode: |
| /* This isn't an x86-64 CPU, so hang intentionally, we cannot continue */ |
| 1: |
| hlt |
| jmp 1b |
| |
| #include "../../kernel/verify_cpu.S" |
| |
| .data |
| gdt64: |
| .word gdt_end - gdt |
| .long 0 |
| .word 0 |
| .quad 0 |
| gdt: |
| .word gdt_end - gdt |
| .long gdt |
| .word 0 |
| .quad 0x00cf9a000000ffff /* __KERNEL32_CS */ |
| .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 5,8,0 |
| .quad efi64_thunk |
| .byte 0 |
| #endif |
| |
| .global efi64_config |
| efi64_config: |
| .fill 5,8,0 |
| .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 BOOT_PGT_SIZE, 1, 0 |
