Assemble via ELF, to enable future linking

Assemble all files to ELF instead of using the NASM built-in linker.
This can enable us to do actual linking in the future.

1 files changed, 1022 insertions, 0 deletions

diff --git a/extlinux/main.c b/extlinux/main.c
new file mode 100644
index 00000000..0edce5a5
--- /dev/null
+++ b/extlinux/main.c
@@ -0,0 +1,1022 @@
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 1998-2008 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Boston MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * extlinux.c
+ *
+ * Install the extlinux boot block on an ext2/3 filesystem
+ */
+
+#define  _GNU_SOURCE		/* Enable everything */
+#include <inttypes.h>
+/* This is needed to deal with the kernel headers imported into glibc 3.3.3. */
+typedef uint64_t u64;
+#include <alloca.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#ifndef __KLIBC__
+#include <mntent.h>
+#endif
+#include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include <sysexits.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/vfs.h>
+
+#include <linux/fd.h>		/* Floppy geometry */
+#include <linux/hdreg.h>	/* Hard disk geometry */
+#define statfs _kernel_statfs	/* HACK to deal with broken 2.4 distros */
+#include <linux/fs.h>		/* FIGETBSZ, FIBMAP */
+#undef statfs
+
+#include "ext2_fs.h"
+#include "../version.h"
+#include "syslxint.h"
+
+#ifdef DEBUG
+# define dprintf printf
+#else
+# define dprintf(...) ((void)0)
+#endif
+
+/* Global option handling */
+
+const char *program;
+
+/* These are the options we can set and their values */
+struct my_options {
+  unsigned int sectors;
+  unsigned int heads;
+  int raid_mode;
+  int reset_adv;
+  const char *set_once;
+} opt = {
+  .sectors = 0,
+  .heads = 0,
+  .raid_mode = 0,
+  .reset_adv = 0,
+  .set_once = NULL,
+};
+
+static void __attribute__((noreturn)) usage(int rv)
+{
+  fprintf(stderr,
+	  "Usage: %s [options] directory\n"
+	  "  --install    -i  Install over the current bootsector\n"
+	  "  --update     -U  Update a previous EXTLINUX installation\n"
+	  "  --zip        -z  Force zipdrive geometry (-H 64 -S 32)\n"
+	  "  --sectors=#  -S  Force the number of sectors per track\n"
+	  "  --heads=#    -H  Force number of heads\n"
+	  "  --raid       -r  Fall back to the next device on boot failure\n"
+	  "  --once=...   -o  Execute a command once upon boot\n"
+	  "  --clear-once -O  Clear the boot-once command\n"
+	  "  --reset-adv      Reset auxilliary data\n"
+	  "\n"
+	  "  Note: geometry is determined at boot time for devices which\n"
+	  "  are considered hard disks by the BIOS.  Unfortunately, this is\n"
+	  "  not possible for devices which are considered floppy disks,\n"
+	  "  which includes zipdisks and LS-120 superfloppies.\n"
+	  "\n"
+	  "  The -z option is useful for USB devices which are considered\n"
+	  "  hard disks by some BIOSes and zipdrives by other BIOSes.\n",
+	  program);
+
+  exit(rv);
+}
+
+enum long_only_opt {
+  OPT_NONE,
+  OPT_RESET_ADV,
+};
+
+static const struct option long_options[] = {
+  { "install",    0, NULL, 'i' },
+  { "update",     0, NULL, 'U' },
+  { "zipdrive",   0, NULL, 'z' },
+  { "sectors",    1, NULL, 'S' },
+  { "heads",      1, NULL, 'H' },
+  { "raid-mode",  0, NULL, 'r' },
+  { "version",    0, NULL, 'v' },
+  { "help",       0, NULL, 'h' },
+  { "once",       1, NULL, 'o' },
+  { "clear-once", 0, NULL, 'O' },
+  { "reset-adv",  0, NULL, OPT_RESET_ADV },
+  { 0, 0, 0, 0 }
+};
+
+static const char short_options[] = "iUuzS:H:rvho:O";
+
+#if defined(__linux__) && !defined(BLKGETSIZE64)
+/* This takes a u64, but the size field says size_t.  Someone screwed big. */
+# define BLKGETSIZE64 _IOR(0x12,114,size_t)
+#endif
+
+#define LDLINUX_MAGIC	0x3eb202fe
+
+enum bs_offsets {
+  bsJump            = 0x00,
+  bsOemName         = 0x03,
+  bsBytesPerSec     = 0x0b,
+  bsSecPerClust     = 0x0d,
+  bsResSectors      = 0x0e,
+  bsFATs            = 0x10,
+  bsRootDirEnts     = 0x11,
+  bsSectors         = 0x13,
+  bsMedia           = 0x15,
+  bsFATsecs         = 0x16,
+  bsSecPerTrack     = 0x18,
+  bsHeads           = 0x1a,
+  bsHiddenSecs      = 0x1c,
+  bsHugeSectors     = 0x20,
+
+  /* FAT12/16 only */
+  bs16DriveNumber   = 0x24,
+  bs16Reserved1     = 0x25,
+  bs16BootSignature = 0x26,
+  bs16VolumeID      = 0x27,
+  bs16VolumeLabel   = 0x2b,
+  bs16FileSysType   = 0x36,
+  bs16Code          = 0x3e,
+
+  /* FAT32 only */
+  bs32FATSz32       = 36,
+  bs32ExtFlags      = 40,
+  bs32FSVer         = 42,
+  bs32RootClus      = 44,
+  bs32FSInfo        = 48,
+  bs32BkBootSec     = 50,
+  bs32Reserved      = 52,
+  bs32DriveNumber   = 64,
+  bs32Reserved1     = 65,
+  bs32BootSignature = 66,
+  bs32VolumeID      = 67,
+  bs32VolumeLabel   = 71,
+  bs32FileSysType   = 82,
+  bs32Code          = 90,
+
+  bsSignature     = 0x1fe
+};
+
+#define bsHead      bsJump
+#define bsHeadLen   (bsOemName-bsHead)
+#define bsCode	    bs32Code	/* The common safe choice */
+#define bsCodeLen   (bsSignature-bs32Code)
+
+#ifndef EXT2_SUPER_OFFSET
+#define EXT2_SUPER_OFFSET 1024
+#endif
+
+const char *program;
+
+/*
+ * Boot block
+ */
+extern unsigned char extlinux_bootsect[];
+extern unsigned int  extlinux_bootsect_len;
+#define boot_block	extlinux_bootsect
+#define boot_block_len  extlinux_bootsect_len
+
+/*
+ * Image file
+ */
+extern unsigned char extlinux_image[];
+extern unsigned int  extlinux_image_len;
+#define boot_image	extlinux_image
+#define boot_image_len  extlinux_image_len
+
+/*
+ * Common abort function
+ */
+void __attribute__((noreturn)) die(const char *msg)
+{
+  fputs(msg, stderr);
+  exit(1);
+}
+
+/*
+ * read/write wrapper functions
+ */
+ssize_t xpread(int fd, void *buf, size_t count, off_t offset)
+{
+  char *bufp = (char *)buf;
+  ssize_t rv;
+  ssize_t done = 0;
+
+  while ( count ) {
+    rv = pread(fd, bufp, count, offset);
+    if ( rv == 0 ) {
+      die("short read");
+    } else if ( rv == -1 ) {
+      if ( errno == EINTR ) {
+	continue;
+      } else {
+	die(strerror(errno));
+      }
+    } else {
+      bufp += rv;
+      offset += rv;
+      done += rv;
+      count -= rv;
+    }
+  }
+
+  return done;
+}
+
+ssize_t xpwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+  const char *bufp = (const char *)buf;
+  ssize_t rv;
+  ssize_t done = 0;
+
+  while ( count ) {
+    rv = pwrite(fd, bufp, count, offset);
+    if ( rv == 0 ) {
+      die("short write");
+    } else if ( rv == -1 ) {
+      if ( errno == EINTR ) {
+	continue;
+      } else {
+	die(strerror(errno));
+      }
+    } else {
+      bufp += rv;
+      offset += rv;
+      done += rv;
+      count -= rv;
+    }
+  }
+
+  return done;
+}
+
+/*
+ * Produce file map
+ */
+int
+sectmap(int fd, uint32_t *sectors, int nsectors)
+{
+  unsigned int blksize, blk, nblk;
+  unsigned int i;
+
+  /* Get block size */
+  if ( ioctl(fd, FIGETBSZ, &blksize) )
+    return -1;
+
+  /* Number of sectors per block */
+  blksize >>= SECTOR_SHIFT;
+
+  nblk = 0;
+  while ( nsectors ) {
+
+    blk = nblk++;
+    dprintf("querying block %u\n", blk);
+    if ( ioctl(fd, FIBMAP, &blk) )
+      return -1;
+
+    blk *= blksize;
+    for ( i = 0 ; i < blksize ; i++ ) {
+      if ( !nsectors )
+	return 0;
+
+      dprintf("Sector: %10u\n", blk);
+      *sectors++ = blk++;
+      nsectors--;
+    }
+  }
+
+  return 0;
+}
+
+/*
+ * Get the size of a block device
+ */
+uint64_t get_size(int devfd)
+{
+  uint64_t bytes;
+  uint32_t sects;
+  struct stat st;
+
+#ifdef BLKGETSIZE64
+  if ( !ioctl(devfd, BLKGETSIZE64, &bytes) )
+    return bytes;
+#endif
+  if ( !ioctl(devfd, BLKGETSIZE, &sects) )
+    return (uint64_t)sects << 9;
+  else if ( !fstat(devfd, &st) && st.st_size )
+    return st.st_size;
+  else
+    return 0;
+}
+
+
+/*
+ * Get device geometry and partition offset
+ */
+struct geometry_table {
+  uint64_t bytes;
+  struct hd_geometry g;
+};
+
+/* Standard floppy disk geometries, plus LS-120.  Zipdisk geometry
+   (x/64/32) is the final fallback.  I don't know what LS-240 has
+   as its geometry, since I don't have one and don't know anyone that does,
+   and Google wasn't helpful... */
+static const struct geometry_table standard_geometries[] = {
+  {    360*1024, {  2,  9,  40, 0 } },
+  {    720*1024, {  2,  9,  80, 0 } },
+  {   1200*1024, {  2, 15,  80, 0 } },
+  {   1440*1024, {  2, 18,  80, 0 } },
+  {   1680*1024, {  2, 21,  80, 0 } },
+  {   1722*1024, {  2, 21,  80, 0 } },
+  {   2880*1024, {  2, 36,  80, 0 } },
+  {   3840*1024, {  2, 48,  80, 0 } },
+  { 123264*1024, {  8, 32, 963, 0 } }, /* LS120 */
+  { 0, {0,0,0,0} }
+};
+
+int
+get_geometry(int devfd, uint64_t totalbytes, struct hd_geometry *geo)
+{
+  struct floppy_struct fd_str;
+  const struct geometry_table *gp;
+
+  memset(geo, 0, sizeof *geo);
+
+  if ( !ioctl(devfd, HDIO_GETGEO, &geo) ) {
+    return 0;
+  } else if ( !ioctl(devfd, FDGETPRM, &fd_str) ) {
+    geo->heads     = fd_str.head;
+    geo->sectors   = fd_str.sect;
+    geo->cylinders = fd_str.track;
+    geo->start     = 0;
+    return 0;
+  }
+
+  /* Didn't work.  Let's see if this is one of the standard geometries */
+  for ( gp = standard_geometries ; gp->bytes ; gp++ ) {
+    if ( gp->bytes == totalbytes ) {
+      memcpy(geo, &gp->g, sizeof *geo);
+      return 0;
+    }
+  }
+
+  /* Didn't work either... assign a geometry of 64 heads, 32 sectors; this is
+     what zipdisks use, so this would help if someone has a USB key that
+     they're booting in USB-ZIP mode. */
+
+  geo->heads     = opt.heads ?: 64;
+  geo->sectors   = opt.sectors ?: 32;
+  geo->cylinders = totalbytes/(geo->heads*geo->sectors << SECTOR_SHIFT);
+  geo->start     = 0;
+
+  if ( !opt.sectors && !opt.heads )
+    fprintf(stderr, "Warning: unable to obtain device geometry (defaulting to %d heads, %d sectors)\n"
+	    "         (on hard disks, this is usually harmless.)\n",
+	    geo->heads, geo->sectors);
+
+  return 1;
+}
+
+/*
+ * Query the device geometry and put it into the boot sector.
+ * Map the file and put the map in the boot sector and file.
+ * Stick the "current directory" inode number into the file.
+ */
+void
+patch_file_and_bootblock(int fd, int dirfd, int devfd)
+{
+  struct stat dirst;
+  struct hd_geometry geo;
+  uint32_t *sectp;
+  uint64_t totalbytes, totalsectors;
+  int nsect;
+  unsigned char *p, *patcharea;
+  int i, dw;
+  uint32_t csum;
+
+  if ( fstat(dirfd, &dirst) ) {
+    perror("fstat dirfd");
+    exit(255);			/* This should never happen */
+  }
+
+  totalbytes = get_size(devfd);
+  get_geometry(devfd, totalbytes, &geo);
+
+  if ( opt.heads )
+    geo.heads = opt.heads;
+  if ( opt.sectors )
+    geo.sectors = opt.sectors;
+
+  /* Patch this into a fake FAT superblock.  This isn't because
+     FAT is a good format in any way, it's because it lets the
+     early bootstrap share code with the FAT version. */
+  dprintf("heads = %u, sect = %u\n", geo.heads, geo.sectors);
+
+  totalsectors = totalbytes >> SECTOR_SHIFT;
+  if ( totalsectors >= 65536 ) {
+    set_16(boot_block+bsSectors, 0);
+  } else {
+    set_16(boot_block+bsSectors, totalsectors);
+  }
+  set_32(boot_block+bsHugeSectors, totalsectors);
+
+  set_16(boot_block+bsBytesPerSec, SECTOR_SIZE);
+  set_16(boot_block+bsSecPerTrack, geo.sectors);
+  set_16(boot_block+bsHeads, geo.heads);
+  set_32(boot_block+bsHiddenSecs, geo.start);
+
+  /* If we're in RAID mode then patch the appropriate instruction;
+     either way write the proper boot signature */
+  i = get_16(boot_block+0x1FE);
+  if (opt.raid_mode)
+    set_16(boot_block+i, 0x18CD);	/* INT 18h */
+
+  set_16(boot_block+0x1FE, 0xAA55);
+
+  /* Construct the boot file */
+
+  dprintf("directory inode = %lu\n", (unsigned long) dirst.st_ino);
+  nsect = (boot_image_len+SECTOR_SIZE-1) >> SECTOR_SHIFT;
+  nsect += 2;			/* Two sectors for the ADV */
+  sectp = alloca(sizeof(uint32_t)*nsect);
+  if ( sectmap(fd, sectp, nsect) ) {
+    perror("bmap");
+    exit(1);
+  }
+
+  /* First sector need pointer in boot sector */
+  set_32(boot_block+0x1F8, *sectp++);
+  nsect--;
+
+  /* Search for LDLINUX_MAGIC to find the patch area */
+  for ( p = boot_image ; get_32(p) != LDLINUX_MAGIC ; p += 4 );
+  patcharea = p+8;
+
+  /* Set up the totals */
+  dw = boot_image_len >> 2;	/* COMPLETE dwords, excluding ADV */
+  set_16(patcharea, dw);
+  set_16(patcharea+2, nsect);	/* Not including the first sector, but
+				   including the ADV */
+  set_32(patcharea+8, dirst.st_ino); /* "Current" directory */
+
+  /* Set the sector pointers */
+  p = patcharea+12;
+
+  memset(p, 0, 64*4);
+  while ( nsect-- ) {
+    set_32(p, *sectp++);
+    p += 4;
+  }
+
+  /* Now produce a checksum */
+  set_32(patcharea+4, 0);
+
+  csum = LDLINUX_MAGIC;
+  for ( i = 0, p = boot_image ; i < dw ; i++, p += 4 )
+    csum -= get_32(p);		/* Negative checksum */
+
+  set_32(patcharea+4, csum);
+}
+
+/*
+ * Read the ADV from an existing instance, or initialize if invalid.
+ * Returns -1 on fatal errors, 0 if ADV is okay, and 1 if no valid
+ * ADV was found.
+ */
+int
+read_adv(const char *path)
+{
+  char *file;
+  int fd = -1;
+  struct stat st;
+  int err = 0;
+
+  asprintf(&file, "%s%sextlinux.sys",
+	   path,
+	   path[0] && path[strlen(path)-1] == '/' ? "" : "/");
+
+  if ( !file ) {
+    perror(program);
+    return -1;
+  }
+
+  fd = open(file, O_RDONLY);
+  if ( fd < 0 ) {
+    if ( errno != ENOENT ) {
+      err = -1;
+    } else {
+      syslinux_reset_adv(syslinux_adv);
+    }
+  } else if (fstat(fd, &st)) {
+    err = -1;
+  } else if (st.st_size < 2*ADV_SIZE) {
+    /* Too small to be useful */
+    syslinux_reset_adv(syslinux_adv);
+    err = 0;			/* Nothing to read... */
+  } else if (xpread(fd, syslinux_adv, 2*ADV_SIZE,
+		    st.st_size-2*ADV_SIZE) != 2*ADV_SIZE) {
+    err = -1;
+  } else {
+    /* We got it... maybe? */
+    err = syslinux_validate_adv(syslinux_adv) ? 1 : 0;
+  }
+
+  if (err < 0)
+    perror(file);
+
+  if (fd >= 0)
+    close(fd);
+  if (file)
+    free(file);
+
+  return err;
+}
+
+/*
+ * Update the ADV in an existing installation.
+ */
+int
+write_adv(const char *path)
+{
+  unsigned char advtmp[2*ADV_SIZE];
+  char *file;
+  int fd = -1;
+  struct stat st, xst;
+  int err = 0;
+  int flags, nflags;
+
+  asprintf(&file, "%s%sextlinux.sys",
+	   path,
+	   path[0] && path[strlen(path)-1] == '/' ? "" : "/");
+
+  if ( !file ) {
+    perror(program);
+    return -1;
+  }
+
+  fd = open(file, O_RDONLY);
+  if ( fd < 0 ) {
+    err = -1;
+  } else if (fstat(fd, &st)) {
+    err = -1;
+  } else if (st.st_size < 2*ADV_SIZE) {
+    /* Too small to be useful */
+    err = -2;
+  } else if (xpread(fd, advtmp, 2*ADV_SIZE,
+		    st.st_size-2*ADV_SIZE) != 2*ADV_SIZE) {
+    err = -1;
+  } else {
+    /* We got it... maybe? */
+    err = syslinux_validate_adv(advtmp) ? -2 : 0;
+    if (!err) {
+      /* Got a good one, write our own ADV here */
+      if (!ioctl(fd, EXT2_IOC_GETFLAGS, &flags)) {
+	nflags = flags & ~EXT2_IMMUTABLE_FL;
+	if (nflags != flags)
+	  ioctl(fd, EXT2_IOC_SETFLAGS, &nflags);
+      }
+      if (!(st.st_mode & S_IWUSR))
+	fchmod(fd, st.st_mode | S_IWUSR);
+
+      /* Need to re-open read-write */
+      close(fd);
+      fd = open(file, O_RDWR|O_SYNC);
+      if (fd < 0) {
+	err = -1;
+      } else if (fstat(fd, &xst) || xst.st_ino != st.st_ino ||
+		 xst.st_dev != st.st_dev || xst.st_size != st.st_size) {
+	fprintf(stderr, "%s: race condition on write\n", file);
+	err = -2;
+      }
+      /* Write our own version ... */
+      if (xpwrite(fd, syslinux_adv, 2*ADV_SIZE,
+		  st.st_size-2*ADV_SIZE) != 2*ADV_SIZE) {
+	err = -1;
+      }
+
+      sync();
+
+      if (!(st.st_mode & S_IWUSR))
+	fchmod(fd, st.st_mode);
+
+      if (nflags != flags)
+	ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
+    }
+  }
+
+  if (err == -2)
+    fprintf(stderr, "%s: cannot write auxilliary data (need --update)?\n",
+	    file);
+  else if (err == -1)
+    perror(file);
+
+  if (fd >= 0)
+    close(fd);
+  if (file)
+    free(file);
+
+  return err;
+}
+
+/*
+ * Make any user-specified ADV modifications
+ */
+int modify_adv(void)
+{
+  int rv = 0;
+
+  if (opt.set_once) {
+    if (syslinux_setadv(ADV_BOOTONCE, strlen(opt.set_once), opt.set_once)) {
+      fprintf(stderr, "%s: not enough space for boot-once command\n", program);
+      rv = -1;
+    }
+  }
+
+  return rv;
+}
+
+/*
+ * Install the boot block on the specified device.
+ * Must be run AFTER install_file()!
+ */
+int
+install_bootblock(int fd, const char *device)
+{
+  struct ext2_super_block sb;
+
+  if ( xpread(fd, &sb, sizeof sb, EXT2_SUPER_OFFSET) != sizeof sb ) {
+    perror("reading superblock");
+    return 1;
+  }
+
+  if ( sb.s_magic != EXT2_SUPER_MAGIC ) {
+    fprintf(stderr, "no ext2/ext3 superblock found on %s\n", device);
+    return 1;
+  }
+
+  if ( xpwrite(fd, boot_block, boot_block_len, 0) != boot_block_len ) {
+    perror("writing bootblock");
+    return 1;
+  }
+
+  return 0;
+}
+
+int
+install_file(const char *path, int devfd, struct stat *rst)
+{
+  char *file;
+  int fd = -1, dirfd = -1, flags;
+  struct stat st;
+
+  asprintf(&file, "%s%sextlinux.sys",
+	   path,
+	   path[0] && path[strlen(path)-1] == '/' ? "" : "/");
+  if ( !file ) {
+    perror(program);
+    return 1;
+  }
+
+  dirfd = open(path, O_RDONLY|O_DIRECTORY);
+  if ( dirfd < 0 ) {
+    perror(path);
+    goto bail;
+  }
+
+  fd = open(file, O_RDONLY);
+  if ( fd < 0 ) {
+    if ( errno != ENOENT ) {
+      perror(file);
+      goto bail;
+    }
+  } else {
+    /* If file exist, remove the immutable flag and set u+w mode */
+    if ( !ioctl(fd, EXT2_IOC_GETFLAGS, &flags) ) {
+      flags &= ~EXT2_IMMUTABLE_FL;
+      ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
+    }
+    if ( !fstat(fd, &st) ) {
+      fchmod(fd, st.st_mode | S_IWUSR);
+    }
+  }
+  close(fd);
+
+  fd = open(file, O_WRONLY|O_TRUNC|O_CREAT|O_SYNC, S_IRUSR|S_IRGRP|S_IROTH);
+  if ( fd < 0 ) {
+    perror(file);
+    goto bail;
+  }
+
+  /* Write it the first time */
+  if ( xpwrite(fd, boot_image, boot_image_len, 0) != boot_image_len ||
+       xpwrite(fd, syslinux_adv, 2*ADV_SIZE, boot_image_len) != 2*ADV_SIZE ) {
+    fprintf(stderr, "%s: write failure on %s\n", program, file);
+    goto bail;
+  }
+
+  /* Map the file, and patch the initial sector accordingly */
+  patch_file_and_bootblock(fd, dirfd, devfd);
+
+  /* Write the first sector again - this relies on the file being
+     overwritten in place! */
+  if ( xpwrite(fd, boot_image, SECTOR_SIZE, 0) != SECTOR_SIZE ) {
+    fprintf(stderr, "%s: write failure on %s\n", program, file);
+    goto bail;
+  }
+
+  /* Attempt to set immutable flag and remove all write access */
+  /* Only set immutable flag if file is owned by root */
+  if ( !fstat(fd, &st) ) {
+    fchmod(fd, st.st_mode & (S_IRUSR|S_IRGRP|S_IROTH));
+    if ( st.st_uid == 0 && !ioctl(fd, EXT2_IOC_GETFLAGS, &flags) ) {
+      flags |= EXT2_IMMUTABLE_FL;
+      ioctl(fd, EXT2_IOC_SETFLAGS, &flags);
+    }
+  }
+
+  if ( fstat(fd, rst) ) {
+    perror(file);
+    goto bail;
+  }
+
+  close(dirfd);
+  close(fd);
+  return 0;
+
+ bail:
+  if ( dirfd >= 0 )
+    close(dirfd);
+  if ( fd >= 0 )
+    close(fd);
+
+  return 1;
+}
+
+/* EXTLINUX installs the string 'EXTLINUX' at offset 3 in the boot
+   sector; this is consistent with FAT filesystems. */
+int
+already_installed(int devfd)
+{
+  char buffer[8];
+
+  xpread(devfd, buffer, 8, 3);
+  return !memcmp(buffer, "EXTLINUX", 8);
+}
+
+
+#ifdef __KLIBC__
+static char devname_buf[64];
+
+static void device_cleanup(void)
+{
+  unlink(devname_buf);
+}
+#endif
+
+/* Verify that a device fd and a pathname agree.
+   Return 0 on valid, -1 on error. */
+static int validate_device(const char *path, int devfd)
+{
+  struct stat pst, dst;
+
+  if (stat(path, &pst) || fstat(devfd, &dst))
+    return -1;
+
+  return (pst.st_dev == dst.st_rdev) ? 0 : -1;
+}
+
+int
+install_loader(const char *path, int update_only)
+{
+  struct stat st, fst;
+  int devfd, rv;
+  const char *devname = NULL;
+  struct statfs sfs;
+#ifndef __KLIBC__
+  struct mntent *mnt = NULL;
+  struct stat dst;
+  FILE *mtab;
+#endif
+
+  if ( stat(path, &st) || !S_ISDIR(st.st_mode) ) {
+    fprintf(stderr, "%s: Not a directory: %s\n", program, path);
+    return 1;
+  }
+
+  if ( statfs(path, &sfs) ) {
+    fprintf(stderr, "%s: statfs %s: %s\n", program, path, strerror(errno));
+    return 1;
+  }
+
+  if ( sfs.f_type != EXT2_SUPER_MAGIC ) {
+    fprintf(stderr, "%s: not an ext2/ext3 filesystem: %s\n", program, path);
+    return 1;
+  }
+
+  devfd = -1;
+
+#ifdef __KLIBC__
+
+  /* klibc doesn't have getmntent and friends; instead, just create
+     a new device with the appropriate device type */
+  snprintf(devname_buf, sizeof devname_buf, "/tmp/dev-%u:%u",
+	   major(st.st_dev), minor(st.st_dev));
+
+  if (mknod(devname_buf, S_IFBLK|0600, st.st_dev)) {
+    fprintf(stderr, "%s: cannot create device %s\n", program, devname);
+    return 1;
+  }
+
+  atexit(device_cleanup);	/* unlink the device node on exit */
+  devname = devname_buf;
+
+#else
+
+  if ( (mtab = setmntent("/proc/mounts", "r")) ) {
+    while ( (mnt = getmntent(mtab)) ) {
+      if ( (!strcmp(mnt->mnt_type, "ext2") ||
+	    !strcmp(mnt->mnt_type, "ext3")) &&
+	   !stat(mnt->mnt_fsname, &dst) &&
+	   dst.st_rdev == st.st_dev ) {
+	devname = mnt->mnt_fsname;
+	break;
+      }
+    }
+  }
+
+  if ( !devname ) {
+    /* Didn't find it in /proc/mounts, try /etc/mtab */
+    if ( (mtab = setmntent("/etc/mtab", "r")) ) {
+      while ( (mnt = getmntent(mtab)) ) {
+	devname = mnt->mnt_fsname;
+	break;
+      }
+    }
+  }
+
+  if ( !devname ) {
+    fprintf(stderr, "%s: cannot find device for path %s\n", program, path);
+    return 1;
+  }
+
+  fprintf(stderr, "%s is device %s\n", path, devname);
+
+#endif
+
+  if ( (devfd = open(devname, O_RDWR|O_SYNC)) < 0 ) {
+    fprintf(stderr, "%s: cannot open device %s\n", program, devname);
+    return 1;
+  }
+
+  /* Verify that the device we opened is the device intended */
+  if (validate_device(path, devfd)) {
+    fprintf(stderr, "%s: path %s doesn't match device %s\n",
+	    program, path, devname);
+    return 1;
+  }
+
+  if ( update_only && !already_installed(devfd) ) {
+    fprintf(stderr, "%s: no previous extlinux boot sector found\n", program);
+    return 1;
+  }
+
+  /* Read a pre-existing ADV, if already installed */
+  if (opt.reset_adv)
+    syslinux_reset_adv(syslinux_adv);
+  else if (read_adv(path) < 0)
+    return 1;
+
+  if (modify_adv() < 0)
+    return 1;
+
+  /* Install extlinux.sys */
+  if (install_file(path, devfd, &fst))
+    return 1;
+
+  if ( fst.st_dev != st.st_dev ) {
+    fprintf(stderr, "%s: file system changed under us - aborting!\n",
+	    program);
+    return 1;
+  }
+
+  sync();
+  rv = install_bootblock(devfd, devname);
+  close(devfd);
+  sync();
+
+  return rv;
+}
+
+/*
+ * Modify the ADV of an existing installation
+ */
+int
+modify_existing_adv(const char *path)
+{
+  if (opt.reset_adv)
+    syslinux_reset_adv(syslinux_adv);
+  else if (read_adv(path) < 0)
+    return 1;
+
+  if (modify_adv() < 0)
+    return 1;
+
+  if (write_adv(path) < 0)
+    return 1;
+
+  return 0;
+}
+
+int
+main(int argc, char *argv[])
+{
+  int o;
+  const char *directory;
+  int update_only = -1;
+
+  program = argv[0];
+
+  while ( (o = getopt_long(argc, argv, short_options,
+			     long_options, NULL)) != EOF ) {
+    switch ( o ) {
+    case 'z':
+      opt.heads = 64;
+      opt.sectors = 32;
+      break;
+    case 'S':
+      opt.sectors = strtoul(optarg, NULL, 0);
+      if ( opt.sectors < 1 || opt.sectors > 63 ) {
+	fprintf(stderr, "%s: invalid number of sectors: %u (must be 1-63)\n",
+		program, opt.sectors);
+	exit(EX_USAGE);
+      }
+      break;
+    case 'H':
+      opt.heads = strtoul(optarg, NULL, 0);
+      if ( opt.heads < 1 || opt.heads > 256 ) {
+	fprintf(stderr, "%s: invalid number of heads: %u (must be 1-256)\n",
+		program, opt.heads);
+	exit(EX_USAGE);
+      }
+      break;
+    case 'r':
+      opt.raid_mode = 1;
+      break;
+    case 'i':
+      update_only = 0;
+      break;
+    case 'u':
+    case 'U':
+      update_only = 1;
+      break;
+    case 'h':
+      usage(0);
+      break;
+    case 'o':
+      opt.set_once = optarg;
+      break;
+    case 'O':
+      opt.set_once = "";
+      break;
+    case OPT_RESET_ADV:
+      opt.reset_adv = 1;
+      break;
+    case 'v':
+      fputs("extlinux " VERSION "\n", stderr);
+      exit(0);
+    default:
+      usage(EX_USAGE);
+    }
+  }
+
+  directory = argv[optind];
+
+  if ( !directory )
+    usage(EX_USAGE);
+
+  if ( update_only == -1 ) {
+    if (opt.reset_adv || opt.set_once) {
+      return modify_existing_adv(directory);
+    } else {
+      usage(EX_USAGE);
+    }
+  }
+
+  return install_loader(directory, update_only);
+}