chain.c32: add option to set hidden sectors; load boot sector for NTLDR

Add an option to update the in-memory version of FAT/NTFS hidden
sectors (== partition offset); load the boot sector for NTLDR.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/com32/modules/chain.c b/com32/modules/chain.c
index 458ea89..a559792 100644 (file)
--- a/com32/modules/chain.c
+++ b/com32/modules/chain.c
@@ -46,18 +46,22 @@
  *     when you want more than one ISOLINUX per CD/DVD.
  *
  * ntldr=<loader>:
- *     equivalent to -seg 0x2000 -file <loader>, used with WinNT's loaders
+ *     equivalent to seg=0x2000 file=<loader> sethidden,
+ *      used with WinNT's loaders
  *
  * cmldr=<loader>:
  *      used with Recovery Console of Windows NT/2K/XP.
- *      same as ntldr=<loader> & "cmdcons\0" written to memory address 0000:7C03
+ *      same as ntldr=<loader> & "cmdcons\0" written to
+ *      the system name field in the bootsector
  *
  * freedos=<loader>:
- *     equivalent to -seg 0x60 -file <loader>, used with FreeDOS kernel.sys.
+ *     equivalent to seg=0x60 file=<loader> sethidden,
+ *      used with FreeDOS kernel.sys.
  *
  * msdos=<loader>
  * pcdos=<loader>
- *     equivalent to -seg 0x70 -file <loader>, used with DOS' io.sys.
+ *     equivalent to seg=0x70 file=<loader> sethidden,
+ *      used with DOS' io.sys.
  *
  * swap:
  *     if the disk is not fd0/hd0, install a BIOS stub which swaps
@@ -67,6 +71,10 @@
  *     change type of primary partitions with IDs 01, 04, 06, 07,
  *     0b, 0c, or 0e to 1x, except for the selected partition, which
  *     is converted the other way.
+ *
+ * sethidden:
+ *      update the "hidden sectors" (partition offset) field in a
+ *      FAT/NTFS boot sector.
  */
 
 #include <com32.h>
@@ -92,8 +100,15 @@ static struct options {
     bool cmldr;
     bool swap;
     bool hide;
+    bool sethidden;
 } opt;
 
+struct data_area {
+    void *data;
+    addr_t base;
+    addr_t size;
+};
+
 static inline void error(const char *msg)
 {
     fputs(msg, stderr);
@@ -446,7 +461,7 @@ static struct part_entry *find_logical_partition(int whichpart, char *table,
     return NULL;
 }
 
-static void do_boot(void *boot_sector, size_t boot_size,
+static void do_boot(struct data_area *data, int ndata,
                    struct syslinux_rm_regs *regs)
 {
     uint16_t *const bios_fbm = (uint16_t *) 0x413;
@@ -457,8 +472,6 @@ static void do_boot(void *boot_sector, size_t boot_size,
     uint8_t driveno = regs->edx.b[0];
     uint8_t swapdrive = driveno & 0x80;
     int i;
-    addr_t loadbase = opt.seg ? (opt.seg << 4) : 0x7c00;
-    static const char cmldr_signature[8] = "cmdcons";
 
     mmap = syslinux_memory_map();
 
@@ -467,25 +480,17 @@ static void do_boot(void *boot_sector, size_t boot_size,
        return;
     }
 
-    /* Nothing below 0x7c00, much simpler... */
-
-    if (boot_size >= dosmem - loadbase)
+    endimage = 0;
+    for (i = 0; i < ndata; i++) {
+       if (data[i].base + data[i].size > endimage)
+           endimage = data[i].base + data[i].size;
+    }
+    if (endimage > dosmem)
        goto too_big;
 
-    endimage = loadbase + boot_size;
-
-    if (syslinux_add_movelist(&mlist, loadbase,
-                             (addr_t) boot_sector, boot_size))
-       goto enomem;
-
-    /*
-     * To boot the Recovery Console of Windows NT/2K/XP we need to write
-     * the string "cmdcons\0" to memory location 0000:7C03.
-     * Memory location 0000:7C00 contains the bootsector of the partition.
-     */
-    if (opt.cmldr) {
-       if (syslinux_add_movelist(&mlist, 0x7c03, (addr_t)cmldr_signature,
-                                 sizeof cmldr_signature))
+    for (i = 0; i < ndata; i++) {
+       if (syslinux_add_movelist(&mlist, data[i].base,
+                                 (addr_t)data[i].data, data[i].size))
            goto enomem;
     }
 
@@ -661,6 +666,27 @@ static uint32_t get_file_lba(const char *filename)
     return lba;
 }
 
+static void usage(void)
+{
+    error("Usage:   chain.c32 hd<disk#> [<partition>] [options]\n"
+         "         chain.c32 fd<disk#> [options]\n"
+         "         chain.c32 mbr:<id> [<partition>] [options]\n"
+         "         chain.c32 boot [<partition>] [options]\n"
+         "Options: file=<loader>      load file, instead of boot sector\n"
+         "         isolinux=<loader>  load another version of ISOLINUX\n"
+         "         ntldr=<loader>     load Windows NTLDR, SETUPLDR.BIN or BOOTMGR\n"
+         "         cmldr=<loader>     load Recovery Console of Windows NT/2K/XP\n"
+         "         freedos=<loader>   load FreeDOS kernel.sys\n"
+         "         msdos=<loader>     load MS-DOS io.sys\n"
+         "         pcdos=<loader>     load PC-DOS ibmbio.com\n"
+         "         seg=<segment>      jump to <seg>:0000 instead of 0000:7C00\n"
+         "         swap               swap drive numbers, if bootdisk is not fd0/hd0\n"
+         "         hide               hide primary partitions, except selected partition\n"
+         "         sethidden          set the FAT/NTFS hidden sectors field\n"
+       );
+}
+
+
 int main(int argc, char *argv[])
 {
     char *mbr, *p;
@@ -673,7 +699,10 @@ int main(int argc, char *argv[])
     uint32_t file_lba = 0;
     unsigned char *isolinux_bin;
     uint32_t *checksum, *chkhead, *chktail;
-    size_t boot_size = SECTOR;
+    struct data_area data[3];
+    int ndata = 0;
+    addr_t load_base;
+    static const char cmldr_signature[8] = "cmdcons";
 
     openconsole(&dev_null_r, &dev_stdcon_w);
 
@@ -699,28 +728,41 @@ int main(int argc, char *argv[])
        } else if (!strncmp(argv[i], "ntldr=", 6)) {
            opt.seg = 0x2000;   /* NTLDR wants this address */
            opt.loadfile = argv[i] + 6;
+           opt.sethidden = true;
        } else if (!strncmp(argv[i], "cmldr=", 6)) {
            opt.seg = 0x2000;    /* CMLDR wants this address */
            opt.loadfile = argv[i] + 6;
            opt.cmldr = true;
+           opt.sethidden = true;
        } else if (!strncmp(argv[i], "freedos=", 8)) {
            opt.seg = 0x60;     /* FREEDOS wants this address */
            opt.loadfile = argv[i] + 8;
+           opt.sethidden = true;
        } else if (!strncmp(argv[i], "msdos=", 6) ||
                   !strncmp(argv[i], "pcdos=", 6)) {
            opt.seg = 0x70;     /* MS-DOS 2.0+ wants this address */
            opt.loadfile = argv[i] + 6;
+           opt.sethidden = true;
        } else if (!strcmp(argv[i], "swap")) {
            opt.swap = true;
+       } else if (!strcmp(argv[i], "noswap")) {
+           opt.swap = false;
        } else if (!strcmp(argv[i], "hide")) {
            opt.hide = true;
+       } else if (!strcmp(argv[i], "nohide")) {
+           opt.hide = false;
        } else if (!strcmp(argv[i], "keeppxe")) {
            opt.keeppxe = 3;
-       } else
-           if (((argv[i][0] == 'h' || argv[i][0] == 'f') && argv[i][1] == 'd')
-               || !strncmp(argv[i], "mbr:", 4)
-               || !strncmp(argv[i], "mbr=", 4)
-               || !strcmp(argv[i], "boot") || !strncmp(argv[i], "boot,", 5)) {
+       } else if (!strcmp(argv[i], "sethidden")) {
+           opt.sethidden = true;
+       } else if (!strcmp(argv[i], "nosethidden")) {
+           opt.sethidden = false;
+       } else if (((argv[i][0] == 'h' || argv[i][0] == 'f')
+                   && argv[i][1] == 'd')
+                  || !strncmp(argv[i], "mbr:", 4)
+                  || !strncmp(argv[i], "mbr=", 4)
+                  || !strcmp(argv[i], "boot")
+                  || !strncmp(argv[i], "boot,", 5)) {
            drivename = argv[i];
            p = strchr(drivename, ',');
            if (p) {
@@ -731,21 +773,7 @@ int main(int argc, char *argv[])
                partition = argv[++i];
            }
        } else {
-           error
-               ("Usage:   chain.c32 hd<disk#> [<partition>] [options]\n"
-                "         chain.c32 fd<disk#> [options]\n"
-                "         chain.c32 mbr:<id> [<partition>] [options]\n"
-                "         chain.c32 boot [<partition>] [options]\n"
-                "Options: file=<loader>      load file, instead of boot sector\n"
-                "         isolinux=<loader>  load another version of ISOLINUX\n"
-         "         ntldr=<loader>     load Windows NTLDR, SETUPLDR.BIN or BOOTMGR\n"
-                "         cmldr=<loader>     load Recovery Console of Windows NT/2K/XP\n"
-                "         freedos=<loader>   load FreeDOS kernel.sys\n"
-                "         msdos=<loader>     load MS-DOS io.sys\n"
-                "         pcdos=<loader>     load PC-DOS ibmbio.com\n"
-                "         seg=<segment>      jump to <seg>:0000 instead of 0000:7C00\n"
-                "         swap               swap drive numbers, if bootdisk is not fd0/hd0\n"
-                "         hide               hide primary partitions, except selected partition\n");
+           usage();
            goto bail;
        }
     }
@@ -844,12 +872,16 @@ int main(int argc, char *argv[])
     }
 
     /* Do the actual chainloading */
+    load_base = opt.seg ? (opt.seg << 4) : 0x7c00;
+
     if (opt.loadfile) {
        fputs("Loading the boot file...\n", stdout);
-       if (loadfile(opt.loadfile, &boot_sector, &boot_size)) {
+       if (loadfile(opt.loadfile, &data[ndata].data, &data[ndata].size)) {
            error("Failed to load the boot file\n");
            goto bail;
        }
+       data[ndata].base = load_base;
+       load_base = 0x7c00;     /* If we also load a boot sector */
 
        /* Create boot info table: needed when you want to chainload
           another version of ISOLINUX (or another bootlaoder that needs
@@ -876,7 +908,7 @@ int main(int argc, char *argv[])
                   LBA of primary volume descriptor should already be set to 16. 
                 */
 
-               isolinux_bin = (unsigned char *)boot_sector;
+               isolinux_bin = (unsigned char *)data[ndata].data;
 
                /* Get LBA address of bootfile */
                file_lba = get_file_lba(opt.loadfile);
@@ -886,20 +918,27 @@ int main(int argc, char *argv[])
                    goto bail;
                }
                /* Set it */
-               *((uint32_t *) & isolinux_bin[12]) = file_lba;
+               *((uint32_t *) &isolinux_bin[12]) = file_lba;
 
                /* Set boot file length */
-               *((uint32_t *) & isolinux_bin[16]) = boot_size;
+               *((uint32_t *) &isolinux_bin[16]) = data[ndata].size;
 
                /* Calculate checksum */
-               checksum = (uint32_t *) & isolinux_bin[20];
-               chkhead = (uint32_t *) & isolinux_bin[64];
-               chktail = (uint32_t *) & isolinux_bin[boot_size - 1];
-               /* Fresh checksum and clear possibly fractional uint32_t at the end */
-               *checksum = *((uint32_t *) & isolinux_bin[boot_size]) = 0;
-
-               while (chkhead <= chktail) {
+               checksum = (uint32_t *) &isolinux_bin[20];
+               chkhead = (uint32_t *) &isolinux_bin[64];
+               chktail = (uint32_t *) &isolinux_bin[data[ndata].size & ~3];
+               *checksum = 0;
+               while (chkhead < chktail)
                    *checksum += *chkhead++;
+
+               /*
+                * Deal with possible fractional dword at the end;
+                * this *should* never happen...
+                */
+               if (data[ndata].size & 3) {
+                   uint32_t xword = 0;
+                   memcpy(&xword, chkhead, data[ndata].size & 3);
+                   *checksum += xword;
                }
            } else {
                error
@@ -908,30 +947,59 @@ int main(int argc, char *argv[])
            }
        }
 
-    } else if (partinfo) {
+       ndata++;
+    }
+
+    if (partinfo && (!opt.loadfile || data[0].base >= 0x7c00 + SECTOR)) {
        /* Actually read the boot sector */
        /* Pick the first buffer that isn't already in use */
-       if (!(boot_sector = read_sector(partinfo->start_lba))) {
+       if (!(data[ndata].data = read_sector(partinfo->start_lba))) {
            error("Cannot read boot sector\n");
            goto bail;
        }
-    }
-
-    if (!opt.loadfile) {
-       if (*(uint16_t *) ((char *)boot_sector + boot_size - 2) != 0xaa55) {
-           error
-               ("Boot sector signature not found (unbootable disk/partition?)\n");
+       data[ndata].size = SECTOR;
+       data[ndata].base = load_base;
+       
+       if (!opt.loadfile &&
+           *(uint16_t *)((char *)data[ndata].data +
+                         data[ndata].size - 2) != 0xaa55) {
+           error("Boot sector signature not found (unbootable disk/partition?)\n");
            goto bail;
        }
+
+       /*
+        * To boot the Recovery Console of Windows NT/2K/XP we need to write
+        * the string "cmdcons\0" to memory location 0000:7C03.
+        * Memory location 0000:7C00 contains the bootsector of the partition.
+        */
+       if (opt.cmldr) {
+           memcpy((char *)data[ndata].data+3, cmldr_signature,
+                  sizeof cmldr_signature);
+       }
+
+       /*
+        * Modify the hidden sectors (partition offset) copy in memory;
+        * this modifies the field used by FAT and NTFS filesystems, and
+        * possibly other boot loaders which use the same format.
+        */
+       if (partinfo && opt.sethidden) {
+           *((uint32_t *)(char *)data[ndata].data + 28) =
+               part_info->start_lba;
+       }
+
+       ndata++;
     }
 
     if (partinfo) {
        /* 0x7BE is the canonical place for the first partition entry. */
+       data[ndata].data = partinfo;
+       data[ndata].base = 0x7be;
+       data[ndata].size = sizeof *partinfo;
+       ndata++;
        regs.esi.w[0] = 0x7be;
-       memcpy((char *)0x7be, partinfo, sizeof(*partinfo));
     }
 
-    do_boot(boot_sector, boot_size, &regs);
+    do_boot(data, ndata, &regs);
 
   bail:
     return 255;