linux_load.c

open source bios with linux platform, very good and can be reused.

/*
 * Linux/i386 loader
 * Supports bzImage, zImage and Image format.
 *
 * Based on work by Steve Gehlbach.
 * Portions are taken from mkelfImage.
 *
 * 2003-09 by SONE Takeshi
 */

#include "openbios/config.h"
#include "openbios/kernel.h"
#include "openbios/bindings.h"
#include "sys_info.h"
#include "context.h"
#include "segment.h"
#include "loadfs.h"
#include "boot.h"

#define printf printk
#define debug printk
#define strtoull_with_suffix strtol

#define LINUX_PARAM_LOC 0x90000
#define COMMAND_LINE_LOC 0x91000
#define GDT_LOC 0x92000
#define STACK_LOC 0x93000

#define E820MAX	32		/* number of entries in E820MAP */
struct e820entry {
	unsigned long long addr;	/* start of memory segment */
	unsigned long long size;	/* size of memory segment */
	unsigned long type;		/* type of memory segment */
#define E820_RAM	1
#define E820_RESERVED	2
#define E820_ACPI	3 /* usable as RAM once ACPI tables have been read */
#define E820_NVS	4
};

/* The header of Linux/i386 kernel */
struct linux_header {
    uint8_t  reserved1[0x1f1];		/* 0x000 */
    uint8_t  setup_sects;		/* 0x1f1 */
    uint16_t root_flags;		/* 0x1f2 */
    uint8_t  reserved2[6];		/* 0x1f4 */
    uint16_t vid_mode;			/* 0x1fa */
    uint16_t root_dev;			/* 0x1fc */
    uint16_t boot_sector_magic;		/* 0x1fe */
    /* 2.00+ */
    uint8_t  reserved3[2];		/* 0x200 */
    uint8_t  header_magic[4];		/* 0x202 */
    uint16_t protocol_version;		/* 0x206 */
    uint32_t realmode_swtch;		/* 0x208 */
    uint16_t start_sys;			/* 0x20c */
    uint16_t kver_addr;			/* 0x20e */
    uint8_t  type_of_loader;		/* 0x210 */
    uint8_t  loadflags;			/* 0x211 */
    uint16_t setup_move_size;		/* 0x212 */
    uint32_t code32_start;		/* 0x214 */
    uint32_t ramdisk_image;		/* 0x218 */
    uint32_t ramdisk_size;		/* 0x21c */
    uint8_t  reserved4[4];		/* 0x220 */
    /* 2.01+ */
    uint16_t heap_end_ptr;		/* 0x224 */
    uint8_t  reserved5[2];		/* 0x226 */
    /* 2.02+ */
    uint32_t cmd_line_ptr;		/* 0x228 */
    /* 2.03+ */
    uint32_t initrd_addr_max;		/* 0x22c */
} __attribute__ ((packed));


/* Paramters passed to 32-bit part of Linux
 * This is another view of the structure above.. */
struct linux_params {
    uint8_t  orig_x;			/* 0x00 */
    uint8_t  orig_y;			/* 0x01 */
    uint16_t ext_mem_k;			/* 0x02 -- EXT_MEM_K sits here */
    uint16_t orig_video_page;		/* 0x04 */
    uint8_t  orig_video_mode;		/* 0x06 */
    uint8_t  orig_video_cols;		/* 0x07 */
    uint16_t unused2;			/* 0x08 */
    uint16_t orig_video_ega_bx;		/* 0x0a */
    uint16_t unused3;			/* 0x0c */
    uint8_t  orig_video_lines;		/* 0x0e */
    uint8_t  orig_video_isVGA;		/* 0x0f */
    uint16_t orig_video_points;		/* 0x10 */

    /* VESA graphic mode -- linear frame buffer */
    uint16_t lfb_width;			/* 0x12 */
    uint16_t lfb_height;		/* 0x14 */
    uint16_t lfb_depth;			/* 0x16 */
    uint32_t lfb_base;			/* 0x18 */
    uint32_t lfb_size;			/* 0x1c */
    uint16_t cl_magic;			/* 0x20 */
#define CL_MAGIC_VALUE 0xA33F
    uint16_t cl_offset;			/* 0x22 */
    uint16_t lfb_linelength;		/* 0x24 */
    uint8_t  red_size;			/* 0x26 */
    uint8_t  red_pos;			/* 0x27 */
    uint8_t  green_size;		/* 0x28 */
    uint8_t  green_pos;			/* 0x29 */
    uint8_t  blue_size;			/* 0x2a */
    uint8_t  blue_pos;			/* 0x2b */
    uint8_t  rsvd_size;			/* 0x2c */
    uint8_t  rsvd_pos;			/* 0x2d */
    uint16_t vesapm_seg;		/* 0x2e */
    uint16_t vesapm_off;		/* 0x30 */
    uint16_t pages;			/* 0x32 */
    uint8_t  reserved4[12];		/* 0x34 -- 0x3f reserved for future expansion */

    //struct apm_bios_info apm_bios_info;	/* 0x40 */
    uint8_t  apm_bios_info[0x40];
    //struct drive_info_struct drive_info;	/* 0x80 */
    uint8_t  drive_info[0x20];
    //struct sys_desc_table sys_desc_table;	/* 0xa0 */
    uint8_t  sys_desc_table[0x140];
    uint32_t alt_mem_k;			/* 0x1e0 */
    uint8_t  reserved5[4];		/* 0x1e4 */
    uint8_t  e820_map_nr;		/* 0x1e8 */
    uint8_t  reserved6[9];		/* 0x1e9 */
    uint16_t mount_root_rdonly;		/* 0x1f2 */
    uint8_t  reserved7[4];		/* 0x1f4 */
    uint16_t ramdisk_flags;		/* 0x1f8 */
#define RAMDISK_IMAGE_START_MASK  	0x07FF
#define RAMDISK_PROMPT_FLAG		0x8000
#define RAMDISK_LOAD_FLAG		0x4000	
    uint8_t  reserved8[2];		/* 0x1fa */
    uint16_t orig_root_dev;		/* 0x1fc */
    uint8_t  reserved9[1];		/* 0x1fe */
    uint8_t  aux_device_info;		/* 0x1ff */
    uint8_t  reserved10[2];		/* 0x200 */
    uint8_t  param_block_signature[4];	/* 0x202 */
    uint16_t param_block_version;	/* 0x206 */
    uint8_t  reserved11[8];		/* 0x208 */
    uint8_t  loader_type;		/* 0x210 */
#define LOADER_TYPE_LOADLIN         1
#define LOADER_TYPE_BOOTSECT_LOADER 2
#define LOADER_TYPE_SYSLINUX        3
#define LOADER_TYPE_ETHERBOOT       4
#define LOADER_TYPE_KERNEL          5
    uint8_t  loader_flags;		/* 0x211 */
    uint8_t  reserved12[2];		/* 0x212 */
    uint32_t kernel_start;		/* 0x214 */
    uint32_t initrd_start;		/* 0x218 */
    uint32_t initrd_size;		/* 0x21c */
    uint8_t  reserved12_5[8];		/* 0x220 */
    uint32_t cmd_line_ptr;		/* 0x228 */
    uint8_t  reserved13[164];		/* 0x22c */
    struct e820entry e820_map[E820MAX];	/* 0x2d0 */
    uint8_t  reserved16[688];		/* 0x550 */
#define COMMAND_LINE_SIZE 256
    /* Command line is copied here by 32-bit i386/kernel/head.S.
     * So I will follow the boot protocol, rather than putting it
     * directly here. --ts1 */
    uint8_t  command_line[COMMAND_LINE_SIZE]; /* 0x800 */
    uint8_t  reserved17[1792];		/* 0x900 - 0x1000 */
};

uint64_t forced_memsize;

/* Load the first part the file and check if it's Linux */
static uint32_t load_linux_header(struct linux_header *hdr)
{
    int load_high;
    uint32_t kern_addr;

    if (lfile_read(hdr, sizeof *hdr) != sizeof *hdr) {
	debug("Can't read Linux header\n");
	return 0;
    }
    if (hdr->boot_sector_magic != 0xaa55) {
	debug("Not a Linux kernel image\n");
	return 0;
    }

    /* Linux is found. Print some information */
    if (memcmp(hdr->header_magic, "HdrS", 4) != 0) {
	/* This may be floppy disk image or something.
	 * Perform a simple (incomplete) sanity check. */
	if (hdr->setup_sects >= 16
		|| file_size() - (hdr->setup_sects<<9) >= 512<<10) {
	    debug("This looks like a bootdisk image but not like Linux...\n");
	    return 0;
	}

	printf("Possible very old Linux");
	/* This kernel does not even have a protocol version.
	 * Force the value. */
	hdr->protocol_version = 0; /* pre-2.00 */
    } else
	printf("Found Linux");
    if (hdr->protocol_version >= 0x200 && hdr->kver_addr) {
	char kver[256];
	file_seek(hdr->kver_addr + 0x200);
	if (lfile_read(kver, sizeof kver) != 0) {
	    kver[255] = 0;
	    printf(" version %s", kver);
	}
    }
    debug(" (protocol %#x)", hdr->protocol_version);
    load_high = 0;
    if (hdr->protocol_version >= 0x200) {
	debug(" (loadflags %#x)", hdr->loadflags);
	load_high = hdr->loadflags & 1;
    }
    if (load_high) {
	printf(" bzImage");
	kern_addr = 0x100000;
    } else {
	printf(" zImage or Image");
	kern_addr = 0x1000;
    }
    printf(".\n");

    return kern_addr;
}

/* Set up parameters for 32-bit kernel */
static void
init_linux_params(struct linux_params *params, struct linux_header *hdr)
{
    debug("Setting up paramters at %#lx\n", virt_to_phys(params));
    memset(params, 0, sizeof *params);

    /* Copy some useful values from header */
    params->mount_root_rdonly = hdr->root_flags;
    params->orig_root_dev = hdr->root_dev;

    /* Video parameters.
     * This assumes we have VGA in standard 80x25 text mode,
     * just like our vga.c does.
     * Cursor position is filled later to allow some more printf's. */
    params->orig_video_mode = 3;
    params->orig_video_cols = 80;
    params->orig_video_lines = 25;
    params->orig_video_isVGA = 1;
    params->orig_video_points = 16;

    params->loader_type = 0xff; /* Unregistered Linux loader */
}

/* Memory map */
static void
set_memory_size(struct linux_params *params, struct sys_info *info)
{
    int i;
    uint64_t end;
    uint32_t ramtop = 0;
    struct e820entry *linux_map;
    struct memrange *filo_map;

    linux_map = params->e820_map;
    filo_map = info->memrange;
    for (i = 0; i < info->n_memranges; i++, linux_map++, filo_map++) {
	if (i < E820MAX) {
	    /* Convert to BIOS e820 style */
	    linux_map->addr = filo_map->base;
	    linux_map->size = filo_map->size;
	    linux_map->type = E820_RAM;
	    debug("%016Lx - %016Lx\n", linux_map->addr,
		    linux_map->addr + linux_map->size);
	    params->e820_map_nr = i+1;
	}

	/* Find out top of RAM. XXX This ignores hole above 1MB */
	end = filo_map->base + filo_map->size;
	if (end < (1ULL << 32)) { /* don't count memory above 4GB */
	    if (end > ramtop)
		ramtop = (uint32_t) end;
	}
    }
    debug("ramtop=%#x\n", ramtop);
    /* Size of memory above 1MB in KB */
    params->alt_mem_k = (ramtop - (1<<20)) >> 10;
    /* old style, 64MB max */
    if (ramtop >= (64<<20))
	params->ext_mem_k = (63<<10);
    else
	params->ext_mem_k = params->alt_mem_k;
    debug("ext_mem_k=%d, alt_mem_k=%d\n", params->ext_mem_k, params->alt_mem_k);
}

/*
 * Parse command line
 * Some parameters, like initrd=<file>, are not passed to kernel,
 * we are responsible to process them.
 * Parameters for kernel are copied to kern_cmdline. Returns name of initrd.
 */
static char *parse_command_line(const char *orig_cmdline, char *kern_cmdline)
{
    const char *start, *sep, *end, *val;
    char name[64];
    int len;
    int k_len;
    int to_kern;
    char *initrd = 0;
    int toolong = 0;

    forced_memsize = 0;

    if (!orig_cmdline) {
	*kern_cmdline = 0;
	return 0;
    }

    k_len = 0;
    debug("original command line: \"%s\"\n", orig_cmdline);
    debug("kernel command line at %#lx\n", virt_to_phys(kern_cmdline));

    start = orig_cmdline;
    while (*start == ' ')
	start++;
    while (*start) {
	end = strchr(start, ' ');
	if (!end)
	    end = start + strlen(start);
	sep = strchr(start, '=');
	if (!sep || sep > end)
	    sep = end;
	len = sep - start;
	if (len >= sizeof(name))
	    len = sizeof(name) - 1;
	memcpy(name, start, len);
	name[len] = 0;