Date: Fri, 8 Mar 2002 02:00:09 -0800 From: Luigi Rizzo <rizzo@icir.org> To: arch@FreeBSD.ORG Subject: Proposed patch: kern.bootdev* sysctl variables Message-ID: <20020308020009.A6535@iguana.icir.org>
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Any objection to the following patch to i386/i386/autoconf.c
to let userland apps know [an approximation of] the name
of the device the kernel was booted from ?
The main use would be for startup scripts, such as
/etc/rc, which could this way differentiate their
behaviour based on the returned result.
(I know it can be perfected by not assuming that
any hard disk is /dev/ad, but you get the idea...)
cheers
luigi
Index: autoconf.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/autoconf.c,v
retrieving revision 1.146.2.2
diff -u -r1.146.2.2 autoconf.c
--- autoconf.c 7 Jun 2001 06:05:58 -0000 1.146.2.2
+++ autoconf.c 8 Mar 2002 09:32:36 -0000
@@ -66,6 +66,7 @@
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/cons.h>
+#include <sys/sysctl.h>
#include <machine/bootinfo.h>
#include <machine/ipl.h>
@@ -105,6 +106,11 @@
device_t nexus_dev;
+SYSCTL_ULONG(_kern, OID_AUTO, bootdev, CTLFLAG_RD, &bootdev, 0, "");
+static char bootdevname[MAXPATHLEN];
+SYSCTL_STRING(_kern, OID_AUTO, bootdevname, CTLFLAG_RD,
+ bootdevname, 0, "Boot device name");
+
/*
* Determine i/o configuration for a machine.
*/
@@ -300,9 +306,13 @@
slice = COMPATIBILITY_SLICE;
part = RAW_PART;
mindev = unit << FDUNITSHIFT;
+ sprintf(bootdevname, "/dev/fd%d", unit);
} else {
part = B_PARTITION(bootdev);
mindev = dkmakeminor(unit, slice, part);
+ sprintf(bootdevname,
+ (slice < BASE_SLICE ? "/dev/ad%d" : "/dev/ad%ds%d"),
+ unit, slice - BASE_SLICE + 1);
}
newrootdev = makebdev(majdev, mindev);
On Mon, Feb 25, 2002 at 02:30:13PM -0800, Luigi Rizzo wrote:
> [bcc-ed to some recent committers to boot2.c]
> Hi,
> for some stuff I am doing with picobsd (and i think in general this
> is useful) it would be nice to know where the kernel was loaded
> from. In /sys/boot/i386/boot2/boot2.c this information is stored
> in three 8-bit variables:
>
> dsk.drive also goes into bootinfo.bi_bios_dev
> dsk.slice
> dsk.part
>
> Although the latter two are not made available to the kernel,
> there are two empty 8-bit fields in struct bootinfo
>
> u_int8_t bi_pad[2];
>
> which could do the job without breaking binary compatibility.
>
> Any objection on exporting dsk.slice and dsk.part into the bi_pad
> fields, possibly starting from 1 so the kernel can tell an uninitialized
> value from a good one ?
>
> (and together with this, perhaps a sysctl variable which builds a
> device name from these three values...)
>
> cheers
> luigi
> ----------------------------------+-----------------------------------------
> Luigi RIZZO, luigi@iet.unipi.it . ICSI (on leave from Univ. di Pisa)
> http://www.iet.unipi.it/~luigi/ . 1947 Center St, Berkeley CA 94704
> Phone: (510) 666 2927
> ----------------------------------+-----------------------------------------
>
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