I am paurea, but this is nemo's old patch to make the kernel serve its configuration
file so that it can be recreated after.

Reference: /n/sources/patch/applied/serveconf
Date: Mon Jan 17 16:03:31 CET 2011
Signed-off-by: nemo@lsub.org

--- /sys/src/9/port/portmkfile	Mon Jan 17 16:01:53 2011
+++ /sys/src/9/port/portmkfile	Mon Jan 17 16:01:50 2011
@@ -50,6 +50,11 @@
 
 $CONF.c:	../port/mkdevc $CONF
 	rc ../port/mkdevc $CONF > $CONF.c
+	{echo 'uchar configfile[]={'
+	 xd -1x $CONF |
+		sed -e 's/^[0-9a-f]+ //' -e 's/ ([0-9a-f][0-9a-f])/0x\1,/g'
+	 echo 0,
+	 echo '};'} >> $CONF.c
 
 errstr.h:	../port/mkerrstr ../port/error.h
 	rc ../port/mkerrstr > errstr.h
--- /sys/src/9/port/devcons.c	Mon Jan 17 16:02:00 2011
+++ /sys/src/9/port/devcons.c	Mon Jan 17 16:01:56 2011
@@ -594,6 +594,7 @@
 	Qtime,
 	Quser,
 	Qzero,
+	Qconfig,
 };
 
 enum
@@ -625,6 +626,7 @@
 	"time",		{Qtime},	NUMSIZE+3*VLNUMSIZE,	0664,
 	"user",		{Quser},	0,		0666,
 	"zero",		{Qzero},	0,		0444,
+	"config",	{Qconfig, 0, 0},	0,	0444,
 };
 
 int
@@ -747,6 +749,7 @@
 	char tmp[256];		/* must be >= 18*NUMSIZE (Qswap) */
 	int i, k, id, send;
 	vlong offset = off;
+	extern char configfile[];
 
 	if(n <= 0)
 		return n;
@@ -863,6 +866,10 @@
 	case Qnull:
 		return 0;
 
+	case Qconfig:
+		return readstr((ulong)offset, buf, n, configfile);
+
+
 	case Qsysstat:
 		b = smalloc(conf.nmach*(NUMSIZE*11+1) + 1);	/* +1 for NUL */
 		bp = b;
@@ -1041,6 +1048,10 @@
 		return userwrite(a, n);
 
 	case Qnull:
+		break;
+
+	case Qconfig:
+		error(Eperm);
 		break;
 
 	case Qreboot:
--- /sys/man/3/cons	Mon Jan 17 16:02:10 2011
+++ /sys/man/3/cons	Mon Jan 17 16:02:04 2011
@@ -6,6 +6,7 @@
 .B bind #c /dev
 
 .B /dev/bintime
+.B /dev/config
 .B /dev/cons
 .B /dev/consctl
 .B /dev/cputime
@@ -111,6 +112,10 @@
 file contains a textual representation of the operating system's version and parameters.
 At the moment, it contains one field: the 9P protocol version, currently
 .BR 2000 .
+.PP
+The
+.B config
+file contains a copy of the kernel configuration file used to build the kernel.
 .PP
 The
 .B kmesg