177 lines
3.6 KiB
C
177 lines
3.6 KiB
C
/*
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* 类型
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*/
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typedef int i32;
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typedef unsigned int u32;
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typedef short i16;
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typedef unsigned short u16;
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typedef char i8;
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typedef unsigned char u8;
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// 通常描述一个对象的大小，会根据机器的型号变化类型
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typedef u32 size_t;
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// elf文件格式会用
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typedef u32 Elf32_Addr;
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typedef u16 Elf32_Half;
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typedef u32 Elf32_Off;
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typedef i32 Elf32_Sword;
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typedef u32 Elf32_Word;
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/*
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* elf相关
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*/
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#define KERNEL_ELF 0x80400
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#define EI_NIDENT 16
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typedef struct elf32_hdr {
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unsigned char e_ident[EI_NIDENT];
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Elf32_Half e_type;
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Elf32_Half e_machine;
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Elf32_Word e_version;
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Elf32_Addr e_entry; /* Entry point */
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Elf32_Off e_phoff;
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Elf32_Off e_shoff;
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Elf32_Word e_flags;
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Elf32_Half e_ehsize;
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Elf32_Half e_phentsize;
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Elf32_Half e_phnum;
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Elf32_Half e_shentsize;
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Elf32_Half e_shnum;
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Elf32_Half e_shstrndx;
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} Elf32_Ehdr;
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#define PT_NULL 0
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#define PT_LOAD 1
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#define PT_DYNAMIC 2
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#define PT_INTERP 3
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#define PT_NOTE 4
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#define PT_SHLIB 5
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#define PT_PHDR 6
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typedef struct elf32_phdr {
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Elf32_Word p_type;
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Elf32_Off p_offset;
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Elf32_Addr p_vaddr;
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Elf32_Addr p_paddr;
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Elf32_Word p_filesz;
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Elf32_Word p_memsz;
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Elf32_Word p_flags;
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Elf32_Word p_align;
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} Elf32_Phdr;
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/*
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* 显示相关
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*/
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#define TERMINAL_COLUMN 80
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#define TERMINAL_ROW 25
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#define TERMINAL_POS(row, column) ((u16)(row) * TERMINAL_COLUMN + (column))
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/*
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* 终端默认色，黑底白字
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*/
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#define DEFAULT_COLOR 0x0f00
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/*
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* 这个函数将content数据（2字节）写到终端第disp_pos个字符
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* 第0个字符在0行0列，第1个字符在0行1列，第80个字符在1行0列，以此类推
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* 用的是内联汇编，等价于mov word [gs:disp_pos * 2], content
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*/
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inline static void
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write_to_terminal(u16 disp_pos, u16 content)
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{
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asm(
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"mov %1, %%gs:(%0)" ::"r"(disp_pos * 2), "r"(content)
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: "memory");
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}
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/*
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* 清屏
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*/
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static void
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clear_screen()
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{
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for (int i = 0; i < TERMINAL_ROW; i++)
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for (int j = 0; j < TERMINAL_COLUMN; j++)
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write_to_terminal(TERMINAL_POS(i, j),
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DEFAULT_COLOR | ' ');
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}
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static void *
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memset(void *v, int c, size_t n)
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{
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char *p;
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int m;
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p = v;
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m = n;
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while (--m >= 0)
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*p++ = c;
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return v;
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}
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static void *
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memcpy(void *dst, const void *src, size_t n)
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{
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const char *s;
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char *d;
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s = src;
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d = dst;
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if (s < d && s + n > d) {
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s += n;
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d += n;
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while (n-- > 0)
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*--d = *--s;
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} else {
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while (n-- > 0)
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*d++ = *s++;
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}
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return dst;
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}
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/*
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* 初始化函数，加载kernel.bin的elf文件并跳过去。
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*/
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void
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load_kernel()
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{
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clear_screen();
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for (char *s = "----start loading kernel elf----", *st = s; *s; s++)
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write_to_terminal(s - st, DEFAULT_COLOR | *s);
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Elf32_Ehdr *kernel_ehdr = (Elf32_Ehdr *)KERNEL_ELF;
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u32* elf_magic = (u32*)KERNEL_ELF;
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if (*elf_magic != 0x464c457f) {
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// make sure it's a elf file
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for (char *s = "not a elf file", *st = s; *s; s++)
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write_to_terminal(80 + s - st, DEFAULT_COLOR | *s);
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while (1);
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}
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if (kernel_ehdr->e_machine != 0x03) {
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for (char *s = "not a x86 executable", *st = s; *s; s++)
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write_to_terminal(80 + s - st, DEFAULT_COLOR | *s);
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while (1);
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}
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Elf32_Phdr *kernel_phdr = (void *)kernel_ehdr + kernel_ehdr->e_phoff;
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for (u32 i = 0; i < kernel_ehdr->e_phnum; i++, kernel_phdr++)
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{
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if (kernel_phdr->p_type != PT_LOAD)
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continue;
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// 将elf的文件数据复制到指定位置
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memcpy(
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(void *)kernel_phdr->p_vaddr,
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(void *)kernel_ehdr + kernel_phdr->p_offset,
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kernel_phdr->p_filesz);
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// 将后面的字节清零(p_memsz >= p_filesz)
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memset(
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(void *)kernel_phdr->p_vaddr + kernel_phdr->p_filesz,
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0,
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kernel_phdr->p_memsz - kernel_phdr->p_filesz);
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}
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((void (*)(void))(kernel_ehdr->e_entry))();
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} |