com32/lib/syslinux/load_linux.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * load_linux.c
 *
 * Load a Linux kernel (Image/zImage/bzImage).
 */

#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <syslinux/align.h>
#include <syslinux/linux.h>
#include <syslinux/bootrm.h>
#include <syslinux/movebits.h>

#ifndef DEBUG
# define DEBUG 0
#endif
#if DEBUG
# include <stdio.h>
# define dprintf printf
#else
# define dprintf(f, ...) ((void)0)
#endif

struct linux_header {
  uint8_t  boot_sector_1[0x0020];
  uint16_t old_cmd_line_magic;
  uint16_t old_cmd_line_offset;
  uint8_t  boot_sector_2[0x01f1-0x0024];
  uint8_t  setup_sects;
  uint16_t root_flags;
  uint32_t syssize;
  uint16_t ram_size;
  uint16_t vid_mode;
  uint16_t root_dev;
  uint16_t boot_flag;
  uint16_t jump;
  uint32_t header;
  uint16_t version;
  uint32_t realmode_swtch;
  uint16_t start_sys;
  uint16_t kernel_version;
  uint8_t  type_of_loader;
  uint8_t  loadflags;
  uint16_t setup_move_size;
  uint32_t code32_start;
  uint32_t ramdisk_image;
  uint32_t ramdisk_size;
  uint32_t bootsect_kludge;
  uint16_t heap_end_ptr;
  uint16_t pad1;
  uint32_t cmd_line_ptr;
  uint32_t initrd_addr_max;
  uint32_t kernel_alignment;
  uint8_t  relocatable_kernel;
  uint8_t  pad2[3];
  uint32_t cmdline_max_len;
} __packed;

#define BOOT_MAGIC 0xAA55
#define LINUX_MAGIC ('H' + ('d' << 8) + ('r' << 16) + ('S' << 24))
#define OLD_CMDLINE_MAGIC 0xA33F

/* loadflags */
#define LOAD_HIGH	0x01
#define CAN_USE_HEAP	0x80

/* Get a value with a potential suffix (k/m/g/t/p/e) */
static unsigned long long suffix_number(const char *str)
{
  char *ep;
  unsigned long long v;
  int shift;

  v = strtoull(str, &ep, 0);
  switch (*ep|0x20) {
  case 'k':
    shift = 10;
    break;
  case 'm':
    shift = 20;
    break;
  case 'g':
    shift = 30;
    break;
  case 't':
    shift = 40;
    break;
  case 'p':
    shift = 50;
    break;
  case 'e':
    shift = 60;
    break;
  default:
    shift = 0;
    break;
  }
  v <<= shift;

  return v;
}

/* 
 * Find the last instance of a particular command line argument
 * (which should include the final =; do not use for boolean arguments)
 * Note: the resulting string is typically not null-terminated.
 */
static const char *find_argument(const char *cmdline, const char *argument)
{
  const char *found = NULL;
  const char *p = cmdline;
  bool was_space = true;
  size_t la = strlen(argument);

  while (*p) {
    if (isspace(*p)) {
      was_space = true;
    } else if (was_space) {
      if (!memcmp(p, argument, la))
	found = p+la;
      was_space = false;
    }
    p++;
  }

  return found;
}

/* Truncate to 32 bits, with saturate */
static inline uint32_t saturate32(unsigned long long v)
{
  return (v > 0xffffffff) ? 0xffffffff : (uint32_t)v;
}

/* Get the combined size of the initramfs */
static addr_t initramfs_size(struct initramfs *initramfs)
{
  struct initramfs *ip;
  addr_t size = 0;

  if (!initramfs)
    return 0;

  for (ip = initramfs->next; ip->len; ip = ip->next) {
    size = (size+ip->align-1) & ~(ip->align-1);	/* Alignment */
    size += ip->len;
  }

  return size;
}

/* Create the appropriate mappings for the initramfs */
static int map_initramfs(struct syslinux_movelist **fraglist,
			 struct syslinux_memmap **mmap,
			 struct initramfs *initramfs,
			 addr_t addr)
{
  struct initramfs *ip;
  addr_t next_addr, len, pad;

  for (ip = initramfs->next; ip->len; ip = ip->next) {
    len = ip->len;
    next_addr = addr+len;

    /* If this isn't the last entry, extend the zero-pad region
       to enforce the alignment of the next chunk. */
    if (ip->next->len) {
      pad = -next_addr & (ip->next->align-1);
      len += pad;
      next_addr += pad;
    }

    if (ip->data_len) {
      if (syslinux_add_movelist(fraglist, addr, (addr_t)ip->data, len))
	return -1;
    }
    if (len > ip->data_len) {
      if (syslinux_add_memmap(mmap, addr+ip->data_len,
			      len-ip->data_len, SMT_ZERO))
	return -1;
    }
    addr = next_addr;
  }

  return 0;
}

int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
			struct initramfs *initramfs, char *cmdline)
{
  struct linux_header hdr, *whdr;
  size_t real_mode_size, prot_mode_size;
  addr_t real_mode_base, prot_mode_base;
  addr_t irf_size;
  size_t cmdline_size, cmdline_offset;
  struct syslinux_rm_regs regs;
  struct syslinux_movelist *fraglist = NULL;
  struct syslinux_memmap *mmap = NULL;
  struct syslinux_memmap *amap = NULL;
  bool ok;
  uint32_t memlimit = 0;
  uint16_t video_mode = 0;
  const char *arg;

  cmdline_size = strlen(cmdline)+1;

  if (kernel_size < 2*512)
    goto bail;

  /* Look for specific command-line arguments we care about */
  if ((arg = find_argument(cmdline, "mem=")))
    memlimit = saturate32(suffix_number(arg));

  if ((arg = find_argument(cmdline, "vga="))) {
    switch (arg[0] | 0x20) {
    case 'a':			/* "ask" */
      video_mode = 0xfffd;
      break;
    case 'e':			/* "ext" */
      video_mode = 0xfffe;
      break;
    case 'n':			/* "normal" */
      video_mode = 0xffff;
      break;
    default:
      video_mode = strtoul(arg, NULL, 0);
      break;
    }
  }

  /* Copy the header into private storage */
  /* Use whdr to modify the actual kernel header */
  memcpy(&hdr, kernel_buf, sizeof hdr);
  whdr = (struct linux_header *)kernel_buf;

  if (hdr.boot_flag != BOOT_MAGIC)
    goto bail;

  if (hdr.header != LINUX_MAGIC) {
    hdr.version = 0x0100;	/* Very old kernel */
    hdr.loadflags = 0;
  }

  whdr->vid_mode = video_mode;

  if (!hdr.setup_sects)
    hdr.setup_sects = 4;

  if (hdr.version < 0x0203)
    hdr.initrd_addr_max = 0x37ffffff;

  if (!memlimit && memlimit-1 > hdr.initrd_addr_max)
    memlimit = hdr.initrd_addr_max+1; /* Zero for no limit */

  if (hdr.version < 0x0205)
    hdr.relocatable_kernel = 0;

  if (hdr.version < 0x0206)
    hdr.cmdline_max_len = 256;

  if (cmdline_size > hdr.cmdline_max_len) {
    cmdline_size = hdr.cmdline_max_len;
    cmdline[cmdline_size-1] = '\0';
  }

  if (hdr.version < 0x0202 || !(hdr.loadflags & 0x01))
    cmdline_offset = (0x9ff0 - cmdline_size) & ~15;
  else
    cmdline_offset = 0x10000;

  real_mode_size = (hdr.setup_sects+1) << 9;
  real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
  prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
  prot_mode_size = kernel_size - real_mode_size;

  if (!(hdr.loadflags & LOAD_HIGH) && prot_mode_size > 512*1024)
    goto bail;			/* Kernel cannot be loaded low */

  if (initramfs && hdr.version < 0x0200)
    goto bail;			/* initrd/initramfs not supported */

  if (hdr.version >= 0x0200) {
    whdr->type_of_loader = 0x30; /* SYSLINUX unknown module */
    if (hdr.version >= 0x0201) {
      whdr->heap_end_ptr = cmdline_offset - 0x0200;
      whdr->loadflags |= CAN_USE_HEAP;
    }
    if (hdr.version >= 0x0202) {
      whdr->cmd_line_ptr = real_mode_base+cmdline_offset;
    } else {
      whdr->old_cmd_line_magic  = OLD_CMDLINE_MAGIC;
      whdr->old_cmd_line_offset = cmdline_offset;
      /* Be paranoid and round up to a multiple of 16 */
      whdr->setup_move_size = (cmdline_offset+cmdline_size+15) & ~15;
    }
  }

  /* Get the memory map */
  mmap = syslinux_memory_map();		/* Memory map for shuffle_boot */
  amap = syslinux_dup_memmap(mmap);	/* Keep track of available memory */
  if (!mmap || !amap)
    goto bail;

#if DEBUG
  dprintf("Initial memory map:\n");
  syslinux_dump_memmap(stdout, mmap);
#endif

  /* If the user has specified a memory limit, mark that as unavailable.
     Question: should we mark this off-limit in the mmap as well (meaning
     it's unavailable to the boot loader, which probably has already touched
     some of it), or just in the amap? */
  if (memlimit)
    if (syslinux_add_memmap(&amap, memlimit, -memlimit, SMT_RESERVED))
      goto bail;

  /* Place the kernel in memory */

  /* First, find a suitable place for the protected-mode code */
  if (syslinux_memmap_type(amap, prot_mode_base, prot_mode_size)
      != SMT_FREE) {
    const struct syslinux_memmap *mp;
    if (!hdr.relocatable_kernel)
      goto bail;		/* Can't relocate - no hope */

    ok = false;
    for (mp = amap; mp; mp = mp->next) {
      addr_t start, end;
      start = mp->start;
      end = mp->next->start;

      if (mp->type != SMT_FREE)
	continue;

      if (end <= prot_mode_base)
	continue;		/* Only relocate upwards */

      if (start <= prot_mode_base)
	start = prot_mode_base;

      start = ALIGN_UP(start, hdr.kernel_alignment);
      if (start >= end)
	continue;

      /* The 3* here is a total fudge factor... it's supposed to
	 account for the fact that the kernel needs to be decompressed,
	 and then followed by the BSS and BRK regions.  This doesn't,
	 however, account for the fact that the kernel is decompressed
	 into a whole other place, either. */
      if (end - start >= 3*prot_mode_size) {
	prot_mode_base = start;
	ok = true;
	break;
      }
    }

    if (!ok)
      goto bail;
  }

  /* Real mode code */
  if (syslinux_memmap_type(amap, real_mode_base,
			   cmdline_offset+cmdline_size) != SMT_FREE) {
    const struct syslinux_memmap *mp;

    ok = false;
    for (mp = amap; mp; mp = mp->next) {
      addr_t start, end;
      start = mp->start;
      end = mp->next->start;

      if (mp->type != SMT_FREE)
	continue;

      if (start < real_mode_base)
	start = real_mode_base;	/* Lowest address we'll use */
      if (end > 640*1024)
	end = 640*1024;

      start = ALIGN_UP(start, 16);
      if (start > 0x90000 || start >= end)
	continue;

      if (end - start >= cmdline_offset+cmdline_size) {
	real_mode_base = start;
	ok = true;
	break;
      }
    }
  }

  if (syslinux_add_movelist(&fraglist, real_mode_base, (addr_t)kernel_buf,
			    real_mode_size))
    goto bail;
  if (syslinux_add_memmap(&amap, real_mode_base, cmdline_offset+cmdline_size,
			  SMT_ALLOC))
    goto bail;

  /* Zero region between real mode code and cmdline */
  if (syslinux_add_memmap(&mmap, real_mode_base+real_mode_size,
			  cmdline_offset-real_mode_size, SMT_ZERO))
    goto bail;

  /* Command line */
  if (syslinux_add_movelist(&fraglist, real_mode_base+cmdline_offset,
			    (addr_t)cmdline, cmdline_size))
    goto bail;

  /* Protected-mode code */
  if (syslinux_add_movelist(&fraglist, prot_mode_base,
			    (addr_t)kernel_buf + real_mode_size,
			    prot_mode_size))
    goto bail;
  if (syslinux_add_memmap(&amap, prot_mode_base, prot_mode_size, SMT_ALLOC))
    goto bail;

  /* Figure out the size of the initramfs, and where to put it.
     We should put it at the highest possible address which is
     <= hdr.initrd_addr_max, which fits the entire initramfs. */

  irf_size = initramfs_size(initramfs);	/* Handles initramfs == NULL */

  if (irf_size) {
    addr_t best_addr = 0;
    struct syslinux_memmap *ml;
    const addr_t align_mask = INITRAMFS_MAX_ALIGN-1;

    if (irf_size) {
      for (ml = amap; ml->type != SMT_END; ml = ml->next) {
	addr_t adj_start = (ml->start+align_mask) & ~align_mask;
	addr_t adj_end   = ml->next->start & ~align_mask;
	if (ml->type == SMT_FREE && adj_end-adj_start >= irf_size)
	  best_addr = (adj_end - irf_size) & ~align_mask;
      }

      if (!best_addr)
	goto bail;		/* Insufficient memory for initramfs */

      whdr->ramdisk_image = best_addr;
      whdr->ramdisk_size = irf_size;

      if (syslinux_add_memmap(&amap, best_addr, irf_size, SMT_ALLOC))
	goto bail;

      if (map_initramfs(&fraglist, &mmap, initramfs, best_addr))
	goto bail;
    }
  }

  /* Set up the registers on entry */
  memset(&regs, 0, sizeof regs);
  regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
  regs.cs = (real_mode_base >> 4)+0x20;
  /* regs.ip = 0; */
  regs.esp.w[0] = cmdline_offset;

#if DEBUG
  dprintf("Final memory map:\n");
  syslinux_dump_memmap(stdout, mmap);

  dprintf("Final available map:\n");
  syslinux_dump_memmap(stdout, amap);

  dprintf("Initial movelist:\n");
  syslinux_dump_movelist(stdout, fraglist);
#endif

  syslinux_shuffle_boot_rm(fraglist, mmap, 0, &regs);

 bail:
  syslinux_free_movelist(fraglist);
  syslinux_free_memmap(mmap);
  syslinux_free_memmap(amap);
  return -1;
}