Split early startup code out of locore.S into locore0.S. Adjust link

run so that this locore0.o is always at the start of the executable.
But randomize the link order of all other .o files in the kernel, so
that their exec/rodata/data/bss segments land all over the place.

Late during kernel boot, smash the startup code with traps so that
it does not point to the other randomly placed code.  It has be smashed,
because loongson runs in the kseg0 space.

As a result, the internal layout of every newly build bsd kernel is
different from past kernels.  Internal relative offsets are not known
to an outside attacker.

Ramdisk kernels cannot be compiled like this, because they are gzip'd.
When the internal pointer references change, the compression dictionary
bloats and results in poorer compression.

5 files changed, 83 insertions, 14 deletions

diff --git a/sys/arch/loongson/conf/Makefile.loongson b/sys/arch/loongson/conf/Makefile.loongson
index 450c2060347..306d4e2b430 100644
--- a/sys/arch/loongson/conf/Makefile.loongson
+++ b/sys/arch/loongson/conf/Makefile.loongson
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile.loongson,v 1.56 2017/06/05 12:43:59 deraadt Exp $
+#	$OpenBSD: Makefile.loongson,v 1.57 2017/06/08 11:44:00 visa Exp $
 
 # For instructions on building kernels consult the config(8) and options(4)
 # manual pages.
@@ -36,9 +36,13 @@ CWARNFLAGS=	-Werror -Wall -Wimplicit-function-declaration \
 
 CMACHFLAGS=	-mno-abicalls ${ABI} -msoft-float -Wa,-mfix-loongson2f-btb -G 0
 CMACHFLAGS+=	-ffreestanding ${NOPIE_FLAGS}
+SORTR=		sort -R
 .if ${IDENT:M-DNO_PROPOLICE}
 CMACHFLAGS+=	-fno-stack-protector
 .endif
+.if ${IDENT:M-DSMALL_KERNEL}
+SORTR=		cat
+.endif
 
 DEBUG?=		-g
 COPTS?=		-O2
@@ -72,13 +76,14 @@ NORMAL_S=	${CC} ${AFLAGS} ${CPPFLAGS} -c $<
 #	${SYSTEM_LD_HEAD}
 #	${SYSTEM_LD} swapxxx.o
 #	${SYSTEM_LD_TAIL}
-SYSTEM_HEAD=	locore.o param.o ioconf.o
-SYSTEM_OBJ=	${SYSTEM_HEAD} ${OBJS}
+SYSTEM_HEAD=	locore0.o gap.o
+SYSTEM_OBJ=	${SYSTEM_HEAD} ${OBJS} param.o ioconf.o
 SYSTEM_DEP=	Makefile ${SYSTEM_OBJ} ld.script
 SYSTEM_LD_HEAD=	@rm -f $@
 SYSTEM_LD=	@echo ${LD} ${LINKFLAGS} -o $@ '$${SYSTEM_HEAD} vers.o $${OBJS}'; \
 		umask 007; \
-		${LD} ${LINKFLAGS} -o $@ ${SYSTEM_HEAD} vers.o ${OBJS}
+		echo ${OBJS} param.o ioconf.o vers.o | tr " " "\n" | ${SORTR} > lorder; \
+		${LD} ${LINKFLAGS} -o $@ ${SYSTEM_HEAD} `cat lorder`
 SYSTEM_LD_TAIL=	@${SIZE} $@
 
 .if ${DEBUG} == "-g"
@@ -125,8 +130,15 @@ vers.o: ${SYSTEM_DEP} ${SYSTEM_SWAP_DEP}
 	sh $S/conf/newvers.sh
 	${CC} ${CFLAGS} ${CPPFLAGS} ${PROF} -c vers.c
 
+gap.S:	${SYSTEM_SWAP_DEP} Makefile $S/conf/makegap.sh
+	umask 007; sh $S/conf/makegap.sh 0xef > gap.S
+
+gap.o:	gap.S
+	umask 007; ${CC} ${AFLAGS} ${CPPFLAGS} ${PROF} -c gap.S
+
 clean:
-	rm -f *bsd *bsd.gdb *.[dio] [a-z]*.s assym.* ${DB_STRUCTINFO} param.c
+	rm -f *bsd *bsd.gdb *.[dio] [a-z]*.s assym.* ${DB_STRUCTINFO} \
+	    gap.S lorder param.c
 
 cleandir: clean
 	rm -f Makefile *.h ioconf.c options machine ${_mach} vers.c
@@ -142,8 +154,8 @@ db_structinfo.h: $S/ddb/db_structinfo.c $S/ddb/parse_structinfo.pl
 	objdump -g db_structinfo.o | perl $S/ddb/parse_structinfo.pl > $@
 	rm -f db_structinfo.o
 
-locore.o: ${_machdir}/${_mach}/locore.S assym.h
-context.o cp0access.o exception.o: assym.h
+locore0.o: ${_machdir}/${_mach}/locore0.S assym.h
+context.o cp0access.o exception.o locore.o: assym.h
 lcore_access.o lcore_ddb.o lcore_float.o tlbhandler.o: assym.h
 pmon32.o: assym.h
 
diff --git a/sys/arch/loongson/conf/files.loongson b/sys/arch/loongson/conf/files.loongson
index f647efbd38c..c28f4b5b5c3 100644
--- a/sys/arch/loongson/conf/files.loongson
+++ b/sys/arch/loongson/conf/files.loongson
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.loongson,v 1.24 2016/11/17 14:41:21 visa Exp $
+#	$OpenBSD: files.loongson,v 1.25 2017/06/08 11:44:00 visa Exp $
 
 # Standard stanzas config(8) can't run without
 maxpartitions 16
@@ -21,6 +21,7 @@ file	arch/loongson/loongson/gdium_machdep.c		cpu_loongson2
 file	arch/loongson/loongson/generic2e_machdep.c	cpu_loongson2
 file	arch/loongson/loongson/generic3a_machdep.c	cpu_loongson3
 file	arch/loongson/loongson/isa_machdep.c		isa
+file	arch/loongson/loongson/locore.S
 file	arch/loongson/loongson/loongson2_machdep.c
 file	arch/loongson/loongson/loongson3_intr.c		cpu_loongson3
 file	arch/loongson/loongson/loongson3_machdep.c	cpu_loongson3
diff --git a/sys/arch/loongson/loongson/autoconf.c b/sys/arch/loongson/loongson/autoconf.c
index 40ea638e53c..00755ee5f1d 100644
--- a/sys/arch/loongson/loongson/autoconf.c
+++ b/sys/arch/loongson/loongson/autoconf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: autoconf.c,v 1.6 2013/06/02 21:46:04 pirofti Exp $	*/
+/*	$OpenBSD: autoconf.c,v 1.7 2017/06/08 11:44:00 visa Exp $	*/
 /*
  * Copyright (c) 2009 Miodrag Vallat.
  *
@@ -35,6 +35,17 @@ enum devclass bootdev_class = DV_DULL;
 extern char pmon_bootp[];
 
 void
+unmap_startup(void)
+{
+	extern uint32_t kernel_text[], endboot[];
+	uint32_t *word = kernel_text;
+
+	/* Cannot unmap kseg0; smash with trap. */
+	while (word < endboot)
+		*word++ = 0x00000034u;	/* TEQ zero, zero */
+}
+
+void
 cpu_configure(void)
 {
 	(void)splhigh();
@@ -42,6 +53,8 @@ cpu_configure(void)
 	softintr_init();
 	(void)config_rootfound("mainbus", NULL);
 
+	unmap_startup();
+
 	splinit();
 	cold = 0;
 }
diff --git a/sys/arch/loongson/loongson/locore.S b/sys/arch/loongson/loongson/locore.S
index 8fde8bf9ae0..481235ec782 100644
--- a/sys/arch/loongson/loongson/locore.S
+++ b/sys/arch/loongson/loongson/locore.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.S,v 1.7 2017/01/19 15:09:04 visa Exp $ */
+/*	$OpenBSD: locore.S,v 1.8 2017/06/08 11:44:00 visa Exp $ */
 
 /*
  * Copyright (c) 2001-2004 Opsycon AB  (www.opsycon.se / www.opsycon.com)
@@ -39,10 +39,9 @@
 
 	.set	noreorder		# Noreorder is default style!
 
-	.globl	start
-	.globl	kernel_text
-kernel_text = start
-start:
+	.globl	locore_start
+	.ent	locore_start, 0
+locore_start:
 	mfc0    v0, COP_0_STATUS_REG
 	li	v1, ~SR_INT_ENAB
 	and	v0, v1
@@ -74,6 +73,7 @@ start:
 	PTR_L	sp, 0(sp)
 	jr	ra
 	nop
+	.end	locore_start
 
 #ifdef HIBERNATE
 
diff --git a/sys/arch/loongson/loongson/locore0.S b/sys/arch/loongson/loongson/locore0.S
new file mode 100644
index 00000000000..7f2f381718d
--- /dev/null
+++ b/sys/arch/loongson/loongson/locore0.S
@@ -0,0 +1,43 @@
+/*	$OpenBSD: locore0.S,v 1.1 2017/06/08 11:44:00 visa Exp $	*/
+
+/*
+ * Copyright (c) 2001-2004 Opsycon AB  (www.opsycon.se / www.opsycon.com)
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
+ * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <machine/param.h>
+#include <machine/asm.h>
+
+#include "assym.h"
+
+	.set	noreorder		# Noreorder is default style!
+
+	.globl	kernel_text
+	.globl	start
+	.ent	start, 0
+kernel_text = start
+start:
+	j	locore_start
+	nop
+	.end	start