Question

我正在尝试在Qemu上启用x86架构上的分页但是这段代码会导致三重错误。

此代码段以保护模式执行代码：https://github.com/mridulv/simpleOperatingSystem

这是内核条目文件

[bits 32]

[extern main]
[extern main2]
[extern page_table]

call main

lea ECX, [page_table - 0xC0000000]
mov CR3, ECX

mov ECX, CR0
or ECX, 0x80000000
mov CR0, ECX

;lea ECX, [StartInHigherHalf]
;jmp ECX

;StartInHigherHalf:
;   call main2

jmp $

这是创建页面目录的内核文件。

unsigned int page_table[1024] __attribute__((aligned(4096)));;

void set_page_tables() {
    unsigned int pages_entry[1024 * 1024] __attribute__((aligned(4096)));

    unsigned int KERNEL_VIRTUAL_OFFSET = 0xC0000000;
    unsigned int KERNEL_FIRST_VIRTUAL_ADDRESS = 0xC0000000 >> 12;

    int numPageTables = 4;
    int numPagesInPageTable = 1024;
    int numPageTableEntriesInPageDirectory = 1024;
    int totalPages = numPageTables * numPagesInPageTable;

    unsigned int index = 0;
    unsigned int *pages_ptr = (unsigned int *)(pages_entry - KERNEL_VIRTUAL_OFFSET);
    unsigned int *page_table_ptr = (unsigned int *)(pages_entry - KERNEL_VIRTUAL_OFFSET);

    unsigned int positionAndFlags = 7;

    while (index < totalPages) {
        pages_ptr[index] = positionAndFlags;
        index = index + 1;
        positionAndFlags += 4096;
    }

    positionAndFlags = 7;
    index = KERNEL_FIRST_VIRTUAL_ADDRESS;
    unsigned int totalPagesLeft = KERNEL_FIRST_VIRTUAL_ADDRESS + totalPages;
    while (index < totalPagesLeft) {
        pages_ptr[index] = positionAndFlags;
        index = index + 1;
        positionAndFlags += 4096;
    }

    positionAndFlags = (unsigned int)&pages_ptr[0];
    positionAndFlags = positionAndFlags | 7;
    index = 0;
    while (index < numPageTableEntriesInPageDirectory) {
        page_table_ptr[index] = positionAndFlags;
        index = index + 1;
        positionAndFlags += 4096;
    }
}

void main() {
    char* video_memory = (char*) 0xb8000;
    *video_memory = 'X';
    set_page_tables();
}

void main2() {
    char* video_memory = (char*) 0xb8004;
    *video_memory = 'Y';
    // __asm__ 
    // (
    //  "leal (page_table, ), %ecx\n\t" // 0xC0000000 = KERNEL_VIRTUAL_BASE
    //  "movl %cr3, %ecx"
    // );
}

Linker.ld

SECTIONS {
    . = 0xC0100000;

    .text : AT(ADDR(.text) - 0xC0000000) {
        *(.text);
    }

    . = ALIGN(0x1000);
    .bss : AT(ADDR(.bss) - 0xC0000000) {
        *(.text);
    }

    . = ALIGN(0x1000);
    .data : AT(ADDR(.data) - 0xC0000000) {
        *(.text);
    }
}

Answer 1

我建议你在代码顶部添加章节声明，以便明确 -

section .text

并且代码中的错误是在执行

之前的错误

call main

你的代码没有（根本没有）通过填写ESP寄存器来设置堆栈。

为此，您的代码应该像

像这样创建一个常量'STACK_SIZE' -
```
STACK_SIZE equ <valueOfSizeOfStack>
```

为堆栈创建空间

section .bss
kernelStack: RESB <valueOfSizeOfStack>

在“valueOfSizeOfStack”字段中，您可以为堆栈添加4096（4-KB）或其任意倍数（不是很大，它将以二进制大小计算）。

在x86 Qemu中启用分页

1 个答案: