El sáb, 09-05-2009 a las 11:17 +0200, Vladimir 'phcoder' Serbinenko escribió: > +/* Realmode far ptr (2 * 16b) to the previous INT13h handler. */ > +extern grub_uint32_t grub_drivemap_int13_oldhandler; > I prefer it to be 2 variables because of the way they interract so > nobody would do something like (char *) > grub_drivemap_int13_oldhandler; Two variables? I don't understand. You want the CS and IP parts of the far pointer separated? Why would anyone try to use it like you said? The comment explicits that it is a realmode pointer, and as such it is not usable as a linear pmode pointer.
> +/* The type "void" is used for imported assembly labels, takes no
> storage and
> + serves just to take the address with &label. Do NOT put void*
> here. */
> +/* Start of the handler bundle. */
> +extern void grub_drivemap_int13_handler_base;
> The common practice is to use declarations like
> extern char grub_drivemap_int13_handler_base[];
> it makes pointer arithmetics easy
That variable is used only twice in the code: one in a call to memcpy
and another one inside the macro INT13_OFFSET. It would still be so even
if it were changed to a char array, with the added risk that a char
array can be modified with almost nothing to gain (as casts would still
be needed). In fact, I'm declaring all the labels as "const void" so
no-one tries to overwrite the "master" data instead of the deployed
data.
> +typedef struct drivemap_node
> +{
> + grub_uint8_t newdrive;
> + grub_uint8_t redirto;
> + struct drivemap_node *next;
> +} drivemap_node_t;
> Here you could reuse Bean's list functions
After examining the API, I think such a change would be too invasive for
a "mature" patch right now. However, once the patch is in and drivemap
is working for everyone, I can work on modifying it to use
<grub/list.h>. The biggest hurdle I see is that there is no way to
automatically maintain "key" uniqueness like the current methods do, so
an iteration over the list would be required.
As a side note/rant, <grub/list.h> desperately needs documentation
comments for other developers to be able to actually use it without
wondering if they're going into the darkness. In particular I need to
know what grub_list_insert does without delving into "list.c" (for
example: "if all tests fail, will the item be inserted last or not at
all?"). This rant also applies to other grub include files.
> + if (!mapping)
> Put a space after !. I know GCS can be PITA but grub has chosen to
> follow it. Not my decision
Oops... I see it has happened in every (! something) test in the file.
I've checked and definitely `indent' did it... I thought that its
default invocation was supposed to adhere to the GCS by default (I'm
using GNU indent 2.2.10).
> + else /* Entry was head of list. */
> + map_head = mapping->next;
> put the comment on a separate line
I removed the comment.
> + if (!name || *name == 0)
> + return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name empty");
> This check is unnecessary since your function is static and calling
> function already ensured that name isn't empty
I've checked, and actually the main function only ensures that the
pointer is valid, not that it is nonempty (try for example `drivemap
"" (hd1)'). However, trying to grub_disk_open the empty string will fail
and the error will be caught anyway, so the check has been removed.
> + /* Skip the first ( in (hd0) - disk_open wants just the name. */
> + if (*name == '(')
> + name++;
> AFAIK you need to remove ')' as well
No you don't, it seems that grub_disk_open chokes on the GRUB device
name opening paren but ignores the closing paren kinda like strtoul
stops parsing on the first non-digit. As there is no API documentation I
can't tell whether this is a precondition checking glitch or an intended
effect, but it sure makes the caller logic way simpler.
> It's not necessary to try to open the disk actually because for some
> reason biosdisk module may be not loaded (e.g. grub may use ata) and
> loading it may cause nasty effects (e.g. conflict between ata and
> biosdisk)
> Same applies for revparse_biosdisk. And if user wants to map to
> unexistant disk it's ok. So just use tryparse_diskstring
Hmm... this is a profound design issue: you are arguing that drivemap
should not care about actual BIOS disks, but just their drive numbers,
and let you map 0x86 to 0x80 even if you have no (hd6). I do not agree,
since the main use for GRUB is a bootloader, not a test platform (which
would be the only reason to perform that kind of mappings which are sure
to cause havoc). Thus, by default drivemap only lets you perform
mappings that will work - any stress tester is free to modify the code.
Regarding opening the disk, the biosdisk interface does not assure in
any way (and again there is almost no API documentation) that hd0 will
be 0x80, though it's the sensible thing to expect. However, expecting
sensible things from an unstable API prone to redesigns (like the
command API, for example) usually leads to nasty surprises later on, so
unless 1) the biosdisk interface so specifies and 2) hdN will _always_
refer to biosdisk and not another possible handler, I think the check is
a Good Thing (tm).
> + if ((str[0] == 'f' || str[0] == 'h') && str[1] == 'd')
> change this to something like
> if (! ((str[0] == 'f' || str[0] == 'h') && str[1] == 'd'))
> return ...
> It makes code nicer by avoiding unnecessary long else
I think the "else" you were talking about was one line long, but it was
not needed anyways and so I've removed it.
> + grub_errno = GRUB_ERR_NONE;
> No need to set grub_errno explicitely unless you want to ignore an
> error
I may have got it wrong, but I think that functions like strtoul only
_set_ errno if there _has_ been an error, but leave it unchanged if
there hasn't. As I want to check if the conversion failed, I need to
have the variable to check in a known pre-state.
> + unsigned long drivenum = grub_strtoul (str + 2, 0, 0);
> + if (grub_errno != GRUB_ERR_NONE || drivenum > 127)
> I think it's enough to just check the range
See above.
> + {
> + /* N not a number or out of range. */
> + goto fail;
> Since at fail you have just a return, just put a return here with
> informative error message
The function was rearranged so only the first goto is required now.
> + }
> + else
> else is unnecessary, just continue with the code
I fear you don't give me enough context to find this one. If it was
inside tryparse_diskstring, it has been removed.
> + if (cmd->state[OPTIDX_LIST].set || 0 == argc)
> argc == 0 sounds better. Also moving list function to a separate
> function is a good idea
Ok, changed. I'd just like to remark that if someone slipped and changed
the line to "argc = 0" it would pass unnoticed by the compiler, while "0
= argc" would create a compile-time error. Regarding slicing the listing
functionality, I don't see the advantages.
> + return grub_error (err, "invalid mapping: non-existent disk"
> + "or not managed by the BIOS");
> If you change error message change error number too. Use either
> return err;
> or
> return grub_error (GRUB_ERR_..., message);
Changed to "return err;"
> + map_head = 0;
> + }
> + else
> Use return rather then else
> + return GRUB_ERR_NONE;
> + }
> + else
> no need for "else"
Function reworked so as to add "return"s and remove "else"s.
> + for (i = 0; i < entries && curentry; ++i, curentry =
> curentry->next)
> You don't need to test for both conditions since theirequivalencyis
> ensured by preceding code
True. Changed.
> + if (0 != grub_drivemap_int13_oldhandler)
> Better swap the parts
Changed. See my reasoning above, though.
> + MODNAME
> + " -l | -r | [-s] grubdev biosdisk",
> Here MODNAME doesn't save any space and makes code less readable. Just
> write the command name explicitely
> + push %bp
> + mov %sp, %bp
> You don't need to change bp. Just use sp. In this case it makes code
> easier
That would make it more difficult to address passed parameters like the
flags at [BP+6] because their location would depend on the current
status of SP (which might change depending on code above the relevant
lines). I think that trying to shave off those 4 or so bytes would make
the code unnecessarily more complicated, which is usually a no-no when
assembly is involved. Besides, this prolog sequence and the
corresponding epilog before returning is practically a standard in x86.
> + lcall *%
> cs:GRUB_DRIVEMAP_INT13H_OFFSET(grub_drivemap_int13_oldhandler)
> + pop %bp /* The pushed flags were removed by iret. */
> Use rather:
> pushf
> lcall *%
> cs:GRUB_DRIVEMAP_INT13H_OFFSET(grub_drivemap_int13_oldhandler)
Why would we want to save our current flags? We want the old int13
handler to receive the flags it would have received if the drivemap
int13 handler were not present, that is, the original caller flags which
were stored above CS:IP in the stack when the "int $0x13" call was
issued. The comment means that "iret" pops not just CS:IP but also the
flags, so we can proceed directly to popping %bp.
> Also remember to restore original %dl after the call
I think there is no need to do so, because BIOS calls modify %dl anyway.
> I'm looking forward for your improved patch
Here it goes.
> Thank you for your effort
Thank _you_ for reviewing it, so many things slip past me (including the
convoluted GCS ._.)
> Could you also prepare a changelog entry for it?
Hmm... I don't really know how to write it, given that both files are
new and the patch does not modify any other GRUB function. Am I supposed
to also declare the modifications in the rmk files?
--
-- Lazy, Oblivious, Recurrent Disaster -- Habbit
Index: conf/i386-pc.rmk =================================================================== --- conf/i386-pc.rmk (revision 2201) +++ conf/i386-pc.rmk (working copy) @@ -185,8 +185,15 @@ aout.mod bsd.mod pxe.mod pxecmd.mod datetime.mod date.mod \ datehook.mod lsmmap.mod ata_pthru.mod hdparm.mod \ usb.mod uhci.mod ohci.mod usbtest.mod usbms.mod usb_keyboard.mod \ - efiemu.mod mmap.mod acpi.mod + efiemu.mod mmap.mod acpi.mod drivemap.mod +# For drivemap.mod. +drivemap_mod_SOURCES = commands/i386/pc/drivemap.c \ + commands/i386/pc/drivemap_int13h.S +drivemap_mod_ASFLAGS = $(COMMON_ASFLAGS) +drivemap_mod_CFLAGS = $(COMMON_CFLAGS) +drivemap_mod_LDFLAGS = $(COMMON_LDFLAGS) + # For efiemu.mod. efiemu_mod_SOURCES = efiemu/main.c efiemu/i386/loadcore32.c \ efiemu/i386/loadcore64.c efiemu/i386/pc/cfgtables.c \ Index: commands/i386/pc/drivemap.c =================================================================== --- commands/i386/pc/drivemap.c (revision 0) +++ commands/i386/pc/drivemap.c (revision 0) @@ -0,0 +1,447 @@ +/* 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/machine/biosdisk.h> +#include <grub/loader.h> +#include <grub/machine/memory.h> + + +#define MODNAME "drivemap" + +static grub_extcmd_t cmd_reghandle; + +/* 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_int13_oldhandler; + +/* The type "void" is used for imported assembly labels, takes no storage and + serves just to take the address with &label. Do NOT put void* here. */ +/* Start of the handler bundle. */ +extern const void grub_drivemap_int13_handler_base; +/* Start of the drive mappings area (space reserved at runtime). */ +extern const void grub_drivemap_int13_mapstart; +/* The assembly function to replace the old INT13h handler. It should not be + called because it does not follow any C callspecs and returns with IRET. */ +extern const void grub_drivemap_int13_handler; + +typedef struct drivemap_node +{ + struct drivemap_node *next; + grub_uint8_t newdrive; + grub_uint8_t redirto; +} drivemap_node_t; + +static drivemap_node_t *map_head; +static void *insthandler_hook; +static int handlermem_hnd; +static grub_err_t install_int13_handler (int noret __attribute__ ((unused))); +static grub_err_t uninstall_int13_handler (void); + +/* 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) +{ + if (! str || *str == 0) + goto fail; + /* 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; + grub_errno = GRUB_ERR_NONE; + 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; + } + } +fail: + 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 +grub_cmd_drivemap (struct grub_extcmd *cmd, int argc, char **args) +{ + if (cmd->state[OPTIDX_LIST].set || argc == 0) + { + /* Show: list mappings. */ + if (! map_head) + { + grub_printf ("No drives have been remapped"); + return GRUB_ERR_NONE; + } + grub_printf ("Showing only remapped drives.\n"); + grub_printf ("BIOS disk #num ----> GRUB 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; + } + 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; + } + + /* 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 the mapping for %s (%02x)", + 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; +} + +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_int13_handler_base) ) +#define INT13H_REBASE(x) ( (void*) (handler_base + (x)) ) +#define INT13H_TONEWADDR(x) INT13H_REBASE( INT13H_OFFSET( x ) ) + +/* 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))) +{ + grub_size_t 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, installation " + "of an int13h handler is not required."); + return GRUB_ERR_NONE; + } + else + { + /* Real mode IVT slot (seg:off far pointer) for interrupt 0x13. */ + grub_uint32_t *ivtslot = UINT_TO_PTR (0x0000004c); + /* Size of the full int13 handler "bundle", including code and map. */ + grub_uint64_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; + /* Real mode IVT entry (seg:off far pointer) for the new handler. */ + grub_uint32_t ivtentry; + + grub_dprintf (MODNAME, "Installing int13h handler...\n"); + + /* Save the pointer to the old handler. */ + grub_drivemap_int13_oldhandler = *ivtslot; + grub_dprintf (MODNAME, "Old int13 handler at %04x:%04x\n", + (grub_drivemap_int13_oldhandler >> 16) & 0x0ffff, + grub_drivemap_int13_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_int13_mapstart) + + (entries + 1) * sizeof (int13map_node_t); + grub_dprintf (MODNAME, "Payload is %llu bytes long\n", total_size); + handler_base = grub_mmap_malign_and_register (16, total_size, + &handlermem_hnd, + 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_int13_handler_base, + INT13H_OFFSET (&grub_drivemap_int13_mapstart)); + + /* Copy the mappings to the reserved area. */ + curentry = map_head; + grub_size_t i; + handler_map = INT13H_TONEWADDR (&grub_drivemap_int13_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. */ + ivtentry = ((grub_uint32_t) handler_base) << 12; /* Segment address. */ + ivtentry |= + (grub_uint16_t) INT13H_OFFSET (&grub_drivemap_int13_handler); + grub_dprintf (MODNAME, "New int13 handler IVT pointer: %04x:%04x\n", + (ivtentry >> 16) & 0x0ffff, ivtentry & 0x0ffff); + *ivtslot = ivtentry; + + return GRUB_ERR_NONE; + } +} + +static grub_err_t +uninstall_int13_handler (void) +{ + grub_uint32_t *ivtslot = UINT_TO_PTR (0x0000004c); + + if (grub_drivemap_int13_oldhandler != 0) + return GRUB_ERR_NONE; + + *ivtslot = grub_drivemap_int13_oldhandler; + grub_mmap_free_and_unregister (handlermem_hnd); + grub_drivemap_int13_oldhandler = 0; + + return GRUB_ERR_NONE; +} + +GRUB_MOD_INIT (drivemap) +{ + cmd_reghandle = grub_register_extcmd (MODNAME, grub_cmd_drivemap, + GRUB_COMMAND_FLAG_BOTH, + MODNAME + " -l | -r | [-s] grubdev biosdisk", + "Manage the BIOS drive mappings", + options); + insthandler_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 (insthandler_hook); + insthandler_hook = 0; + grub_unregister_extcmd (cmd_reghandle); +} Index: commands/i386/pc/drivemap_int13h.S =================================================================== --- commands/i386/pc/drivemap_int13h.S (revision 0) +++ commands/i386/pc/drivemap_int13h.S (revision 0) @@ -0,0 +1,85 @@ +/* drivemap_int13h.S - interrupt handler for the BIOS drive remapper */ +/* + * 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/symbol.h> + +#define GRUB_DRIVEMAP_INT13H_OFFSET(x) ((x) - grub_drivemap_int13_handler_base) + +.code16 + +/* Copy starts here. When deployed, this label must be segment-aligned. */ +VARIABLE(grub_drivemap_int13_handler_base) + +/* Far pointer to the old handler. Stored as a CS:IP in the style of real-mode + IVT entries (thus PI:SC in mem). */ +VARIABLE(grub_drivemap_int13_oldhandler) + .word 0x0, 0x0 + +/* Actual int13 handler. We use relative addressing with CS in order to be as + unintrusive as possible with registers and the stack. */ +FUNCTION(grub_drivemap_int13_handler) + push %bp + mov %sp, %bp + + /* Map the drive number (always in DL?). */ + push %ax + push %bx + push %si + mov $GRUB_DRIVEMAP_INT13H_OFFSET(grub_drivemap_int13_mapstart), %bx + xor %si, %si + +more_remaining: + movw %cs:(%bx,%si), %ax + cmp %ah, %al + jz not_found /* DRV=DST => map end - drive not remapped, keep DL. */ + cmp %dl, %al + jz found /* Found - drive remapped, modify DL. */ + add $2, %si + jmp more_remaining /* Not found, but more remaining, loop. */ + +found: + mov %ah, %dl + +not_found: + pop %si + pop %bx + pop %ax + + push %bp + /* Simulate interrupt call: push flags and do a far call in order to set + the stack the way the old handler expects it so that its iret works. */ + push 6(%bp) + movw (%bp), %bp /* Restore the caller BP (is this needed and/or sensible?). */ + lcall *%cs:GRUB_DRIVEMAP_INT13H_OFFSET(grub_drivemap_int13_oldhandler) + pop %bp /* The pushed flags were removed by iret. */ + /* Set the saved flags to what the int13h handler returned. */ + push %ax + pushf + pop %ax + movw %ax, 6(%bp) + pop %ax + + mov %bp, %sp + pop %bp + iret + +/* This label MUST be at the end of the copied block, since the installer code + reserves additional space for mappings at runtime and copies them over it. */ +.align 2 +VARIABLE(grub_drivemap_int13_mapstart)
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