2009/5/31 Javier Martín <[email protected]>:
> El sáb, 30-05-2009 a las 17:28 +0200, Vladimir 'phcoder' Serbinenko
> escribió:
>> >> > I'm fine with the change from "const void" to "const char", but we need
>> >> > to remove a preceding comment about void labels.
>> >> It's not that I'm opposed to void in principle. Just using the same
>> >> constructions to do the same things in different files makes code
>> >> easier to learn and port
>> >
>> > I wonder if we can go the other way and use void for all labels without
>> > storage. Indeed, it's too easy to misuse a char variable by forgetting
>> > the ampersand before it.
>> Not char []
> What if someone sees the code and thinks it's truly a char array? I
> insist: you are stirring a tempest in a teapot.
You're right. It turns into discussion about apple and oranges. Let's
forget this part
> Put it that way, I agree with your change. To the scrapper with
> parse_biosdisk then!
Sorry, I didn't mean to upset you. Here is a patch to do it
> I think the new behaviour
It's not a new behaviour on valid inputs since biosdisk does exactly
the same transformation.
> should be mentioned in
> the drivemap --help command, though I'm too tangled up with finals to be
> of any utility right now.
Good luck with your exams
Doing some tests I discovered that freedos MBR (but not the
bootsector) relies on %dl being preserved across int 0x13. In the
patch you can see additional hassle to preserve %dx.
Another problem I discovered is that %dl (chainloader) and bootdrive
(multiboot) passed to payload is out of sync.
Does anyone has a suggestion how to do it cleanly. The problems are:
-chainloader/multiboot shouldn't depend on biosdisk if possible
-%dl should be set accordingly to mapping
-%dl should be correct even if grub2 uses its own drivers (now it's
set to nonsense)
I have some ideas on this subject but would like to hear what others think.
--
Regards
Vladimir 'phcoder' Serbinenko
diff --git a/commands/i386/pc/drivemap.c b/commands/i386/pc/drivemap.c
index 98f4378..898fb51 100644
--- a/commands/i386/pc/drivemap.c
+++ b/commands/i386/pc/drivemap.c
@@ -143,62 +143,6 @@ drivemap_remove (grub_uint8_t newdrive)
}
}
-/* 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. */
@@ -238,15 +182,13 @@ list_mappings (void)
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",
+ grub_printf ("%cD #%-3u (0x%02x) %cd%d\n",
(curnode->newdrive & 0x80) ? 'H' : 'F',
- curnode->newdrive & 0x7F, curnode->newdrive, dname);
+ curnode->newdrive & 0x7F, curnode->newdrive,
+ (curnode->redirto & 0x80) ? 'h' : 'f',
+ curnode->redirto & 0x7F
+ );
curnode = curnode->next;
- grub_free ((char *) dname);
}
return GRUB_ERR_NONE;
}
@@ -286,17 +228,11 @@ grub_cmd_drivemap (struct grub_extcmd *cmd, int argc, char **args)
if (argc != 2)
return grub_error (GRUB_ERR_BAD_ARGUMENT, "two arguments required");
- err = parse_biosdisk (args[0], &mapfrom);
+ err = tryparse_diskstring (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);
+ err = tryparse_diskstring (args[1], &mapto);
if (err != GRUB_ERR_NONE)
return err;
diff --git a/commands/i386/pc/drivemap_int13h.S b/commands/i386/pc/drivemap_int13h.S
index 23b7302..328459a 100644
--- a/commands/i386/pc/drivemap_int13h.S
+++ b/commands/i386/pc/drivemap_int13h.S
@@ -27,6 +27,11 @@
/* The replacement int13 handler. Preserve all registers. */
FUNCTION(grub_drivemap_handler)
+ /* Save %dx for future restore. */
+ push %dx
+ /* Push flags. Used to simulate interrupt with original flags. */
+ pushf
+
/* Map the drive number (always in DL). */
push %ax
push %bx
@@ -46,16 +51,19 @@ not_found:
pop %bx
pop %ax
- /* Upon arrival to this point the stack must be exactly like at entry.
- This long jump will transfer the caller's stack to the old INT13
- handler, thus making it return directly to the original caller. */
- .byte 0xea
+ /* lcall */
+ .byte 0x9a
/* 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_oldhandler)
.word 0x0, 0x0
+ /* Restore %dx. */
+ pop %dx
+ 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
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