Pass boothowto from bootloader to kernel using .openbsd.bootdata. To make

sure that an old bootloader can boot a new kernel and a new bootloader
can still boot an old kernel some hackery is needed as old kernels check for
an exact size of the openbsd_bootdata struct.

tested (with softraid) by kn@
ok stsp@, deraadt@

4 files changed, 34 insertions, 8 deletions

diff --git a/sys/arch/sparc64/include/boot_flag.h b/sys/arch/sparc64/include/boot_flag.h
index 782e87748ec..e4c3fa4acd8 100644
--- a/sys/arch/sparc64/include/boot_flag.h
+++ b/sys/arch/sparc64/include/boot_flag.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: boot_flag.h,v 1.6 2020/01/04 18:32:15 kettenis Exp $	*/
+/*	$OpenBSD: boot_flag.h,v 1.7 2020/05/25 15:31:59 kettenis Exp $	*/
 /*	$NetBSD: boot_flag.h,v 1.3 2001/07/01 02:56:21 gmcgarry Exp $	*/
 
 /*-
@@ -41,8 +41,11 @@ struct openbsd_bootdata {
 
 	u_int8_t	sr_uuid[BOOTSR_UUID_MAX];
 	u_int8_t	sr_maskkey[BOOTSR_CRYPTO_MAXKEYBYTES];
+	u_int32_t	boothowto;
 } __packed;
 
 #define BOOTDATA_VERSION	1
+#define BOOTDATA_LEN_SOFTRAID	64
+#define BOOTDATA_LEN_BOOTHOWTO	68
 
 #endif /* _MACHINE_BOOT_FLAG_H_ */
diff --git a/sys/arch/sparc64/sparc64/autoconf.c b/sys/arch/sparc64/sparc64/autoconf.c
index c98aa201221..2ee25767870 100644
--- a/sys/arch/sparc64/sparc64/autoconf.c
+++ b/sys/arch/sparc64/sparc64/autoconf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: autoconf.c,v 1.134 2020/01/04 23:43:54 kn Exp $	*/
+/*	$OpenBSD: autoconf.c,v 1.135 2020/05/25 15:31:59 kettenis Exp $	*/
 /*	$NetBSD: autoconf.c,v 1.51 2001/07/24 19:32:11 eeh Exp $ */
 
 /*
@@ -435,6 +435,15 @@ bootstrap(int nctx)
 	ncpus = get_ncpus();
 	pmap_bootstrap(KERNBASE, (u_long)&end, nctx, ncpus);
 
+	/*
+	 * This length check deliberately checks BOOTDATA_LEN_SOFTRAID
+	 * instead of BOOTDATA_LEN_BOOTHOWTO.  See the ofwboot code
+	 * for an explanation.
+	 */
+	if (obd.version == BOOTDATA_VERSION &&
+	    obd.len >= BOOTDATA_LEN_SOFTRAID)
+		boothowto = obd.boothowto;
+
 #ifdef SUN4V
 	if (CPU_ISSUN4V) {
 		sun4v_soft_state_init();
@@ -539,7 +548,7 @@ bootpath_build(void)
 	bp->name[0] = 0;
 	
 	bootpath_nodes(bootpath, nbootpath);
-	
+
 	/* Setup pointer to boot flags */
 	OF_getprop(chosen, "bootargs", buf, sizeof(buf));
 	cp = buf;
@@ -691,7 +700,7 @@ cpu_configure(void)
 #endif
 
 	if (obd.version == BOOTDATA_VERSION &&
-	    obd.len == sizeof(struct openbsd_bootdata)) {
+	    obd.len >= BOOTDATA_LEN_SOFTRAID) {
 #if NSOFTRAID > 0
 		memcpy(sr_bootuuid.sui_id, obd.sr_uuid,
 		    sizeof(sr_bootuuid.sui_id));
diff --git a/sys/arch/sparc64/stand/ofwboot/elf64_exec.c b/sys/arch/sparc64/stand/ofwboot/elf64_exec.c
index f50d2d23d49..887aa57453d 100644
--- a/sys/arch/sparc64/stand/ofwboot/elf64_exec.c
+++ b/sys/arch/sparc64/stand/ofwboot/elf64_exec.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: elf64_exec.c,v 1.10 2019/10/29 02:55:52 deraadt Exp $	*/
+/*	$OpenBSD: elf64_exec.c,v 1.11 2020/05/25 15:31:59 kettenis Exp $	*/
 /*	$NetBSD: elfXX_exec.c,v 1.2 2001/08/15 20:08:15 eeh Exp $	*/
 
 /*
@@ -71,6 +71,8 @@
 
 #include "openfirm.h"
 
+extern int boothowto;
+
 void syncicache(void *, int);
 
 int
@@ -103,12 +105,19 @@ elf64_exec(int fd, Elf_Ehdr *elf, u_int64_t *entryp, void **ssymp, void **esymp)
 		if (phdr.p_type == PT_OPENBSD_BOOTDATA) {
 			memset((void *) (long)phdr.p_paddr, 0, phdr.p_filesz);
 
-			if (phdr.p_filesz < sizeof(struct openbsd_bootdata))
+			if (phdr.p_filesz < BOOTDATA_LEN_SOFTRAID)
 				continue;
 
+			/*
+			 * Kernels up to and including OpenBSD 6.7
+			 * check for an exact match if the length.
+			 * Lie here to make sure we can still boot
+			 * older kernels with softraid.
+			 */
 			obd = (struct openbsd_bootdata *)(long)phdr.p_paddr;
 			obd->version = BOOTDATA_VERSION;
-			obd->len = sizeof(struct openbsd_bootdata);
+			obd->len = BOOTDATA_LEN_SOFTRAID;
+
 #ifdef SOFTRAID
 			/* 
 			 * If booting from softraid we must pass additional
@@ -126,6 +135,11 @@ elf64_exec(int fd, Elf_Ehdr *elf, u_int64_t *entryp, void **ssymp, void **esymp)
 			}
 
 #endif
+
+			if (phdr.p_filesz < BOOTDATA_LEN_BOOTHOWTO)
+				continue;
+
+			obd->boothowto = boothowto;
 			continue;
 		}
 
diff --git a/sys/arch/sparc64/stand/ofwboot/vers.c b/sys/arch/sparc64/stand/ofwboot/vers.c
index 4193339e082..1809042a243 100644
--- a/sys/arch/sparc64/stand/ofwboot/vers.c
+++ b/sys/arch/sparc64/stand/ofwboot/vers.c
@@ -1 +1 @@
-const char version[] = "1.17";
+const char version[] = "1.18";