--- /dev/null
+/* drivemap.c - command to manage the BIOS drive mappings. */
+/*
+ * GRUB -- GRand Unified Bootloader
+ * Copyright (C) 2008, 2009 Free Software Foundation, Inc.
+ *
+ * GRUB 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, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GRUB is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GRUB. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/extcmd.h>
+#include <grub/dl.h>
+#include <grub/mm.h>
+#include <grub/misc.h>
+#include <grub/disk.h>
+#include <grub/loader.h>
+#include <grub/machine/memory.h>
+
+
+#define MODNAME "drivemap"
+
+/* Real mode IVT slot (seg:off far pointer) for interrupt 0x13. */
+static grub_uint32_t *const int13slot = UINT_TO_PTR (4 * 0x13);
+
+/* Remember to update enum opt_idxs accordingly. */
+static const struct grub_arg_option options[] = {
+ {"list", 'l', 0, "show the current mappings", 0, 0},
+ {"reset", 'r', 0, "reset all mappings to the default values", 0, 0},
+ {"swap", 's', 0, "perform both direct and reverse mappings", 0, 0},
+ {0, 0, 0, 0, 0, 0}
+};
+
+/* Remember to update options[] accordingly. */
+enum opt_idxs
+{
+ OPTIDX_LIST = 0,
+ OPTIDX_RESET,
+ OPTIDX_SWAP,
+};
+
+/* Realmode far ptr (2 * 16b) to the previous INT13h handler. */
+extern grub_uint32_t grub_drivemap_oldhandler;
+
+/* The type "void" is used for imported assembly labels, takes no storage and
+ serves just to take the address with &label. */
+
+/* The assembly function to replace the old INT13h handler. It does not follow
+ any C callspecs and returns with IRET. */
+extern const void grub_drivemap_handler;
+
+/* Start of the drive mappings area (space reserved at runtime). */
+extern const void grub_drivemap_mapstart;
+
+typedef struct drivemap_node
+{
+ struct drivemap_node *next;
+ grub_uint8_t newdrive;
+ grub_uint8_t redirto;
+} drivemap_node_t;
+
+typedef struct __attribute__ ((packed)) int13map_node
+{
+ grub_uint8_t disknum;
+ grub_uint8_t mapto;
+} int13map_node_t;
+
+#define INT13H_OFFSET(x) \
+ (((grub_uint8_t *)(x)) - ((grub_uint8_t *)&grub_drivemap_handler))
+
+static drivemap_node_t *map_head;
+static void *drivemap_hook;
+static int drivemap_mmap;
+
+/* Puts the specified mapping into the table, replacing an existing mapping
+ for newdrive or adding a new one if required. */
+static grub_err_t
+drivemap_set (grub_uint8_t newdrive, grub_uint8_t redirto)
+{
+ drivemap_node_t *mapping = 0;
+ drivemap_node_t *search = map_head;
+ while (search)
+ {
+ if (search->newdrive == newdrive)
+ {
+ mapping = search;
+ break;
+ }
+ search = search->next;
+ }
+
+ /* Check for pre-existing mappings to modify before creating a new one. */
+ if (mapping)
+ mapping->redirto = redirto;
+ else
+ {
+ mapping = grub_malloc (sizeof (drivemap_node_t));
+ if (! mapping)
+ return grub_error (GRUB_ERR_OUT_OF_MEMORY,
+ "cannot allocate map entry, not enough memory");
+ mapping->newdrive = newdrive;
+ mapping->redirto = redirto;
+ mapping->next = map_head;
+ map_head = mapping;
+ }
+ return GRUB_ERR_NONE;
+}
+
+/* Removes the mapping for newdrive from the table. If there is no mapping,
+ then this function behaves like a no-op on the map. */
+static void
+drivemap_remove (grub_uint8_t newdrive)
+{
+ drivemap_node_t *mapping = 0;
+ drivemap_node_t *search = map_head;
+ drivemap_node_t *previous = 0;
+
+ while (search)
+ {
+ if (search->newdrive == newdrive)
+ {
+ mapping = search;
+ break;
+ }
+ previous = search;
+ search = search->next;
+ }
+
+ if (mapping)
+ {
+ if (previous)
+ previous->next = mapping->next;
+ else
+ map_head = mapping->next;
+ grub_free (mapping);
+ }
+}
+
+/* Given a device name, resolves its BIOS disk number and stores it in the
+ passed location, which should only be trusted if ERR_NONE is returned. */
+static grub_err_t
+parse_biosdisk (const char *name, grub_uint8_t *disknum)
+{
+ grub_disk_t disk;
+ /* Skip the first ( in (hd0) - disk_open wants just the name. */
+ if (*name == '(')
+ name++;
+
+ disk = grub_disk_open (name);
+ if (! disk)
+ return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "unknown device \"%s\"",
+ name);
+ const enum grub_disk_dev_id id = disk->dev->id;
+ /* The following assignment is only sound if the device is indeed a
+ biosdisk. The caller must check the return value. */
+ if (disknum)
+ *disknum = disk->id;
+ grub_disk_close (disk);
+ if (id != GRUB_DISK_DEVICE_BIOSDISK_ID)
+ return grub_error (GRUB_ERR_BAD_DEVICE, "%s is not a BIOS disk", name);
+ return GRUB_ERR_NONE;
+}
+
+/* Given a BIOS disk number, returns its GRUB device name if it exists.
+ If the call succeeds, the resulting device string must be freed.
+ For nonexisting BIOS disk numbers, this function returns
+ GRUB_ERR_UNKNOWN_DEVICE. */
+static grub_err_t
+revparse_biosdisk (const grub_uint8_t dnum, const char **output)
+{
+ int found = 0;
+ auto int find (const char *name);
+ int find (const char *name)
+ {
+ const grub_disk_t disk = grub_disk_open (name);
+ if (! disk)
+ return 0;
+ if (disk->id == dnum && disk->dev->id == GRUB_DISK_DEVICE_BIOSDISK_ID)
+ {
+ found = 1;
+ if (output)
+ *output = grub_strdup (name);
+ }
+ grub_disk_close (disk);
+ return found;
+ }
+
+ grub_disk_dev_iterate (find);
+ if (found)
+ return GRUB_ERR_NONE;
+ return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "BIOS disk %02x not found",
+ dnum);
+}
+
+/* Given a GRUB-like device name and a convenient location, stores the
+ related BIOS disk number. Accepts devices like \((f|h)dN\), with
+ 0 <= N < 128. */
+static grub_err_t
+tryparse_diskstring (const char *str, grub_uint8_t *output)
+{
+ /* Skip opening paren in order to allow both (hd0) and hd0. */
+ if (*str == '(')
+ str++;
+ if ((str[0] == 'f' || str[0] == 'h') && str[1] == 'd')
+ {
+ grub_uint8_t bios_num = (str[0] == 'h') ? 0x80 : 0x00;
+ unsigned long drivenum = grub_strtoul (str + 2, 0, 0);
+ if (grub_errno == GRUB_ERR_NONE && drivenum < 128)
+ {
+ bios_num |= drivenum;
+ if (output)
+ *output = bios_num;
+ return GRUB_ERR_NONE;
+ }
+ }
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, "device format \"%s\" "
+ "invalid: must be (f|h)dN, with 0 <= N < 128", str);
+}
+
+static grub_err_t
+list_mappings (void)
+{
+ /* Show: list mappings. */
+ if (! map_head)
+ {
+ grub_printf ("No drives have been remapped\n");
+ return GRUB_ERR_NONE;
+ }
+
+ grub_printf ("OS disk #num ------> GRUB/BIOS device\n");
+ drivemap_node_t *curnode = map_head;
+ while (curnode)
+ {
+ const char *dname = 0;
+ grub_err_t err = revparse_biosdisk (curnode->redirto, &dname);
+ if (err != GRUB_ERR_NONE)
+ return err;
+ grub_printf ("%cD #%-3u (0x%02x) %s\n",
+ (curnode->newdrive & 0x80) ? 'H' : 'F',
+ curnode->newdrive & 0x7F, curnode->newdrive, dname);
+ curnode = curnode->next;
+ grub_free ((char *) dname);
+ }
+ return GRUB_ERR_NONE;
+}
+
+static grub_err_t
+grub_cmd_drivemap (struct grub_extcmd *cmd, int argc, char **args)
+{
+ if (cmd->state[OPTIDX_LIST].set)
+ {
+ return list_mappings ();
+ }
+ else if (cmd->state[OPTIDX_RESET].set)
+ {
+ /* Reset: just delete all mappings, freeing their memory. */
+ drivemap_node_t *curnode = map_head;
+ drivemap_node_t *prevnode = 0;
+ while (curnode)
+ {
+ prevnode = curnode;
+ curnode = curnode->next;
+ grub_free (prevnode);
+ }
+ map_head = 0;
+ return GRUB_ERR_NONE;
+ }
+ else if (!cmd->state[OPTIDX_SWAP].set && argc == 0)
+ {
+ /* No arguments */
+ return list_mappings ();
+ }
+
+ /* Neither flag: put mapping. */
+ grub_uint8_t mapfrom = 0;
+ grub_uint8_t mapto = 0xFF;
+ grub_err_t err;
+
+ if (argc != 2)
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, "two arguments required");
+
+ err = parse_biosdisk (args[0], &mapfrom);
+ if (err != GRUB_ERR_NONE)
+ return err;
+
+ /* When swapping we require both devices to be BIOS disks, but when
+ performing direct mappings we only require the 2nd argument to look
+ like a BIOS disk in order to resolve it into a BIOS disk number. */
+ if (cmd->state[OPTIDX_SWAP].set)
+ err = parse_biosdisk (args[1], &mapto);
+ else
+ err = tryparse_diskstring (args[1], &mapto);
+ if (err != GRUB_ERR_NONE)
+ return err;
+
+ if (mapto == mapfrom)
+ {
+ /* Reset to default. */
+ grub_dprintf (MODNAME, "Removing mapping for %s (%02x)\n",
+ args[0], mapfrom);
+ drivemap_remove (mapfrom);
+ return GRUB_ERR_NONE;
+ }
+ /* Set the mapping for the disk (overwrites any existing mapping). */
+ grub_dprintf (MODNAME, "%s %s (%02x) = %s (%02x)\n",
+ cmd->state[OPTIDX_SWAP].set ? "Swapping" : "Mapping",
+ args[1], mapto, args[0], mapfrom);
+ err = drivemap_set (mapto, mapfrom);
+ /* If -s, perform the reverse mapping too (only if the first was OK). */
+ if (cmd->state[OPTIDX_SWAP].set && err == GRUB_ERR_NONE)
+ err = drivemap_set (mapfrom, mapto);
+ return err;
+}
+
+/* Int13h handler installer - reserves conventional memory for the handler,
+ copies it over and sets the IVT entry for int13h.
+ This code rests on the assumption that GRUB does not activate any kind
+ of memory mapping apart from identity paging, since it accesses
+ realmode structures by their absolute addresses, like the IVT at 0;
+ and transforms a pmode pointer into a rmode seg:off far ptr. */
+static grub_err_t
+install_int13_handler (int noret __attribute__ ((unused)))
+{
+ /* Size of the full int13 handler "bundle", including code and map. */
+ grub_uint32_t total_size;
+ /* Base address of the space reserved for the handler bundle. */
+ grub_uint8_t *handler_base = 0;
+ /* Address of the map within the deployed bundle. */
+ int13map_node_t *handler_map;
+
+ int i;
+ int entries = 0;
+ drivemap_node_t *curentry = map_head;
+
+ /* Count entries to prepare a contiguous map block. */
+ while (curentry)
+ {
+ entries++;
+ curentry = curentry->next;
+ }
+ if (entries == 0)
+ {
+ /* No need to install the int13h handler. */
+ grub_dprintf (MODNAME, "No drives marked as remapped, not installing "
+ "our int13h handler.\n");
+ return GRUB_ERR_NONE;
+ }
+
+ grub_dprintf (MODNAME, "Installing our int13h handler\n");
+
+ /* Save the pointer to the old handler. */
+ grub_drivemap_oldhandler = *int13slot;
+ grub_dprintf (MODNAME, "Original int13 handler: %04x:%04x\n",
+ (grub_drivemap_oldhandler >> 16) & 0x0ffff,
+ grub_drivemap_oldhandler & 0x0ffff);
+
+ /* Find a rmode-segment-aligned zone in conventional memory big
+ enough to hold the handler and its data. */
+ total_size = INT13H_OFFSET (&grub_drivemap_mapstart)
+ + (entries + 1) * sizeof (int13map_node_t);
+ grub_dprintf (MODNAME, "Payload is %u bytes long\n", total_size);
+ handler_base = grub_mmap_malign_and_register (16, total_size,
+ &drivemap_mmap,
+ GRUB_MACHINE_MEMORY_RESERVED,
+ GRUB_MMAP_MALLOC_LOW);
+ if (! handler_base)
+ return grub_error (GRUB_ERR_OUT_OF_MEMORY, "Could not reserve "
+ "memory for the int13h handler");
+
+ /* Copy int13h handler bundle to reserved area. */
+ grub_dprintf (MODNAME, "Reserved memory at %p, copying handler\n",
+ handler_base);
+ grub_memcpy (handler_base, &grub_drivemap_handler,
+ INT13H_OFFSET (&grub_drivemap_mapstart));
+
+ /* Copy the mappings to the reserved area. */
+ curentry = map_head;
+ handler_map = (int13map_node_t *) (handler_base +
+ INT13H_OFFSET (&grub_drivemap_mapstart));
+ grub_dprintf (MODNAME, "Target map at %p, copying mappings\n", handler_map);
+ for (i = 0; i < entries; ++i, curentry = curentry->next)
+ {
+ handler_map[i].disknum = curentry->newdrive;
+ handler_map[i].mapto = curentry->redirto;
+ grub_dprintf (MODNAME, "\t#%d: 0x%02x <- 0x%02x\n", i,
+ handler_map[i].disknum, handler_map[i].mapto);
+ }
+ /* Signal end-of-map. */
+ handler_map[i].disknum = 0;
+ handler_map[i].mapto = 0;
+ grub_dprintf (MODNAME, "\t#%d: 0x00 <- 0x00 (end)\n", i);
+
+ /* Install our function as the int13h handler in the IVT. */
+ *int13slot = ((grub_uint32_t) handler_base) << 12; /* Segment address. */
+ grub_dprintf (MODNAME, "New int13 handler: %04x:%04x\n",
+ (*int13slot >> 16) & 0x0ffff, *int13slot & 0x0ffff);
+
+ return GRUB_ERR_NONE;
+}
+
+static grub_err_t
+uninstall_int13_handler (void)
+{
+ if (! grub_drivemap_oldhandler)
+ return GRUB_ERR_NONE;
+
+ *int13slot = grub_drivemap_oldhandler;
+ grub_mmap_free_and_unregister (drivemap_mmap);
+ grub_drivemap_oldhandler = 0;
+ grub_dprintf (MODNAME, "Restored int13 handler: %04x:%04x\n",
+ (*int13slot >> 16) & 0x0ffff, *int13slot & 0x0ffff);
+
+ return GRUB_ERR_NONE;
+}
+
+static grub_extcmd_t cmd;
+
+GRUB_MOD_INIT (drivemap)
+{
+ cmd = grub_register_extcmd (MODNAME, grub_cmd_drivemap,
+ GRUB_COMMAND_FLAG_BOTH,
+ MODNAME
+ " -l | -r | [-s] grubdev osdisk",
+ "Manage the BIOS drive mappings",
+ options);
+ drivemap_hook =
+ grub_loader_register_preboot_hook (&install_int13_handler,
+ &uninstall_int13_handler,
+ GRUB_LOADER_PREBOOT_HOOK_PRIO_NORMAL);
+}
+
+GRUB_MOD_FINI (drivemap)
+{
+ grub_loader_unregister_preboot_hook (drivemap_hook);
+ drivemap_hook = 0;
+ grub_unregister_extcmd (cmd);
+}
projects / thirdparty / grub.git / commitdiff
