Booting from gpt on i386/amd64? [PATCH]

Alexey Shuvaev shuvaev at physik.uni-wuerzburg.de
Sat Sep 20 02:21:53 UTC 2008


On Sun, Aug 31, 2008 at 12:35:55PM +0200, Alexey Shuvaev wrote:
> On Fri, Aug 29, 2008 at 11:16:07PM +0200, Paul B. Mahol wrote:
> > On 8/29/08, Alexey Shuvaev <shuvaev at physik.uni-wuerzburg.de> wrote:
> > > Hello list!
> > >
> > > I have tried to install a system with pure gpt partitioning,
> > > but haven't managed to boot from it.
> > >
> > > Partition table:
> > >
> > > =>       34  976773101  ad6  GPT  (500.1GB)
> > >          34    1571840    1  freebsd-ufs  (804.8MB)
> > >     1571874    8388608    2  freebsd-swap  (4.3GB)
> > >     9960482       1024    3  freebsd-boot  (524.3KB)
> > >     9961506    8388608    4  freebsd-ufs  (4.3GB)
> > >    18350114     524288    5  freebsd-ufs  (268.4MB)
> > >    18874402  134217728    6  freebsd-ufs  (68.7GB)
> > >   153092130  823681005       - free -  (421.7GB)
> > >
> > > All necessary files are already installed (ad6p1 = /, ad6p4 = /var, and
> > > so on). The system is 8.0-CURRENT from 8 August (bootable usb flash).
> > > Computer is Core2Duo E8400 3.0 GHz, 4 Gb RAM, ICH9, 500 GB SATA.
> > > What have been done:
> > >
> > > gpart bootcode -b /path/to/pmbr ad6
> > > [Successful]
> > >
> > > gpart bootcode -p /path/to/gptboot -i 3 ad6
> > > gpart: /dev/ad6p3: Invalid argument
> > >
> > > I have tried to 'newfs /dev/ad6p3' and then mounting it and copying
> > > gptboot into 'boot' directory on ad6p3, but looking at the sources it
> > > seems to be wrong.
> > >
> > > Then I tried to 'dd if=gptboot of=/dev/ad6p3 bs=512',
>                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This command writes gptboot only partially!!!
> I have padded gptboot to nearest sector boundary and dd-ed it to ad6p3.
> After that the system booted successfully.
> As I have expected GENERIC kernel is enough.
> 
> > > but in all cases during the boot the blinking cursor moves 1 line down
> > > and computer freezes here.
> > >
> The remaining question is what is the correct way to put gptboot to
> 'freebsd-boot' partition?
> It seems that this functionality was in gpt(8) but is missing in
> gpart(8). Any work in progress? While I am here should I look at it?
> 
Ok, I have digged the sources a little bit and ended with this simple
patch. Actually, the code is taken from gpt(8) utility.
It adds automatic padding of gptboot bootcode to the nearest sector boundary.

Alexey.
-------------- next part --------------
--- sbin/geom/class/part/geom_part.c.orig	2008-08-08 18:14:25.000000000 +0200
+++ sbin/geom/class/part/geom_part.c	2008-09-20 04:13:15.000000000 +0200
@@ -386,6 +386,8 @@
 	struct ggeom *gp;
 	struct gprovider *pp;
 	const char *s;
+	char *buf;
+	off_t bsize;
 	int error, fd;
 
 	s = gctl_get_ascii(req, "class");
@@ -421,7 +423,17 @@
 			errx(EXIT_FAILURE, "%s: not enough space", dsf);
 		if (lseek(fd, 0, SEEK_SET) != 0)
 			err(EXIT_FAILURE, "%s", dsf);
-		if (write(fd, code, size) != size)
+
+		/*
+		 * When writing to a disk device, the write must be
+		 * sector aligned and not write to any partial sectors,
+		 * so round up the buffer size to the next sector and zero it.
+		 */
+		bsize = (size + pp->lg_sectorsize - 1) /
+		    pp->lg_sectorsize * pp->lg_sectorsize;
+		buf = calloc(1, bsize);
+		bcopy(code, buf, size);
+		if (write(fd, buf, bsize) != bsize)
 			err(EXIT_FAILURE, "%s", dsf);
 		close(fd);
 	} else


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