ELF格式说明

ELF file header (ELF文件头)

/* The ELF file header.  This appears at the start of every ELF file.  */

#define EI_NIDENT (16)

typedef struct
{
  unsigned char	e_ident[EI_NIDENT];	/* Magic number and other info */
  Elf32_Half	e_type;			/* Object file type */
  Elf32_Half	e_machine;		/* Architecture */
  Elf32_Word	e_version;		/* Object file version */
  Elf32_Addr	e_entry;		/* Entry point virtual address */
  Elf32_Off	e_phoff;		/* Program header table file offset */
  Elf32_Off	e_shoff;		/* Section header table file offset */
  Elf32_Word	e_flags;		/* Processor-specific flags */
  Elf32_Half	e_ehsize;		/* ELF header size in bytes */
  Elf32_Half	e_phentsize;		/* Program header table entry size */
  Elf32_Half	e_phnum;		/* Program header table entry count */
  Elf32_Half	e_shentsize;		/* Section header table entry size */
  Elf32_Half	e_shnum;		/* Section header table entry count */
  Elf32_Half	e_shstrndx;		/* Section header string table index */
} Elf32_Ehdr;

typedef struct
{
  unsigned char	e_ident[EI_NIDENT];	/* Magic number and other info */
  Elf64_Half	e_type;			/* Object file type */
  Elf64_Half	e_machine;		/* Architecture */
  Elf64_Word	e_version;		/* Object file version */
  Elf64_Addr	e_entry;		/* Entry point virtual address */
  Elf64_Off	e_phoff;		/* Program header table file offset */
  Elf64_Off	e_shoff;		/* Section header table file offset */
  Elf64_Word	e_flags;		/* Processor-specific flags */
  Elf64_Half	e_ehsize;		/* ELF header size in bytes */
  Elf64_Half	e_phentsize;		/* Program header table entry size */
  Elf64_Half	e_phnum;		/* Program header table entry count */
  Elf64_Half	e_shentsize;		/* Section header table entry size */
  Elf64_Half	e_shnum;		/* Section header table entry count */
  Elf64_Half	e_shstrndx;		/* Section header string table index */
} Elf64_Ehdr;

程序头结构

/* Program segment header.  */

typedef struct
{
  Elf32_Word	p_type;			/* Segment type */
  Elf32_Off	p_offset;		/* Segment file offset */
  Elf32_Addr	p_vaddr;		/* Segment virtual address */
  Elf32_Addr	p_paddr;		/* Segment physical address */
  Elf32_Word	p_filesz;		/* Segment size in file */
  Elf32_Word	p_memsz;		/* Segment size in memory */
  Elf32_Word	p_flags;		/* Segment flags */
  Elf32_Word	p_align;		/* Segment alignment */
} Elf32_Phdr;

typedef struct
{
  Elf64_Word	p_type;			/* Segment type */
  Elf64_Word	p_flags;		/* Segment flags */
  Elf64_Off	p_offset;		/* Segment file offset */
  Elf64_Addr	p_vaddr;		/* Segment virtual address */
  Elf64_Addr	p_paddr;		/* Segment physical address */
  Elf64_Xword	p_filesz;		/* Segment size in file */
  Elf64_Xword	p_memsz;		/* Segment size in memory */
  Elf64_Xword	p_align;		/* Segment alignment */
} Elf64_Phdr;

ELF Section Header的结构

/* Section header.  */

typedef struct
{
  Elf32_Word	sh_name;		/* Section name (string tbl index) */
  Elf32_Word	sh_type;		/* Section type */
  Elf32_Word	sh_flags;		/* Section flags */
  Elf32_Addr	sh_addr;		/* Section virtual addr at execution */
  Elf32_Off	sh_offset;		/* Section file offset */
  Elf32_Word	sh_size;		/* Section size in bytes */
  Elf32_Word	sh_link;		/* Link to another section */
  Elf32_Word	sh_info;		/* Additional section information */
  Elf32_Word	sh_addralign;		/* Section alignment */
  Elf32_Word	sh_entsize;		/* Entry size if section holds table */
} Elf32_Shdr;

typedef struct
{
  Elf64_Word	sh_name;		/* Section name (string tbl index) */
  Elf64_Word	sh_type;		/* Section type */
  Elf64_Xword	sh_flags;		/* Section flags */
  Elf64_Addr	sh_addr;		/* Section virtual addr at execution */
  Elf64_Off	sh_offset;		/* Section file offset */
  Elf64_Xword	sh_size;		/* Section size in bytes */
  Elf64_Word	sh_link;		/* Link to another section */
  Elf64_Word	sh_info;		/* Additional section information */
  Elf64_Xword	sh_addralign;		/* Section alignment */
  Elf64_Xword	sh_entsize;		/* Entry size if section holds table */
} Elf64_Shdr;

int main()
{
	int i; 
	char *p;
	p = (char *) 0xa0000; /* 视频模式地址 */

	for (i = 0; i <= 0xffff; i++) {
		*(p + i) = i & 0x0f;
	}
	while(1)
	return 0;
}

将此main.c文件编译gcc -o main.o main.c 生成main.o文件

再进行链接ld -Ttext 0xc0001500 -e main -o kernel.bin main.o 生成kernel.bin文件，下面我们就来看一下kernel.bin具体文件