vmd(8): zero consdev in bootargs to fix booting ramdisks

Mischa Peters reported that booting a bsd.rd from 7.2 or newer
stopped working with vmd(8) in 7.2.

Direct booting kernels requires vmd to build boot args in guest
memory. Recently, the bios_consdev_t struct changed in amd64
machdep.c, adding additional struct members. vmd wasn't zeroing out
the struct, causing the booted kernel to read garbage.

While here, cleanup some of push_bootargs to use descriptive names
for boot args and standardize on explicit usage of uint32_t.

ok claudio, mlarkin

1 files changed, 18 insertions, 16 deletions

diff --git a/usr.sbin/vmd/loadfile_elf.c b/usr.sbin/vmd/loadfile_elf.c
index b367721e32b..651719542d2 100644
--- a/usr.sbin/vmd/loadfile_elf.c
+++ b/usr.sbin/vmd/loadfile_elf.c
@@ -1,5 +1,5 @@
 /* $NetBSD: loadfile.c,v 1.10 2000/12/03 02:53:04 tsutsui Exp $ */
-/* $OpenBSD: loadfile_elf.c,v 1.42 2022/01/28 06:33:27 guenther Exp $ */
+/* $OpenBSD: loadfile_elf.c,v 1.43 2022/11/28 18:24:52 dv Exp $ */
 
 /*-
  * Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -382,9 +382,10 @@ create_bios_memmap(struct vm_create_params *vcp, bios_memmap_t *memmap)
  * Parameters:
  *  memmap: the BIOS memory map
  *  n: number of entries in memmap
+ *  bootmac: optional PXE boot MAC address
  *
  * Return values:
- *  The size of the bootargs
+ *  The size of the bootargs in bytes
  */
 static uint32_t
 push_bootargs(bios_memmap_t *memmap, size_t n, bios_bootmac_t *bootmac)
@@ -393,40 +394,41 @@ push_bootargs(bios_memmap_t *memmap, size_t n, bios_bootmac_t *bootmac)
 	bios_consdev_t consdev;
 	uint32_t ba[1024];
 
-	memmap_sz = 3 * sizeof(int) + n * sizeof(bios_memmap_t);
-	ba[0] = 0x0;    /* memory map */
+	memmap_sz = 3 * sizeof(uint32_t) + n * sizeof(bios_memmap_t);
+	ba[0] = BOOTARG_MEMMAP;
 	ba[1] = memmap_sz;
-	ba[2] = memmap_sz;	/* next */
+	ba[2] = memmap_sz;
 	memcpy(&ba[3], memmap, n * sizeof(bios_memmap_t));
-	i = memmap_sz / sizeof(int);
+	i = memmap_sz / sizeof(uint32_t);
 
 	/* Serial console device, COM1 @ 0x3f8 */
-	consdev.consdev = makedev(8, 0);	/* com1 @ 0x3f8 */
+	memset(&consdev, 0, sizeof(consdev));
+	consdev.consdev = makedev(8, 0);
 	consdev.conspeed = 115200;
 	consdev.consaddr = 0x3f8;
-	consdev.consfreq = 0;
 
-	consdev_sz = 3 * sizeof(int) + sizeof(bios_consdev_t);
-	ba[i] = 0x5;   /* consdev */
+	consdev_sz = 3 * sizeof(uint32_t) + sizeof(bios_consdev_t);
+	ba[i] = BOOTARG_CONSDEV;
 	ba[i + 1] = consdev_sz;
 	ba[i + 2] = consdev_sz;
 	memcpy(&ba[i + 3], &consdev, sizeof(bios_consdev_t));
-	i += consdev_sz / sizeof(int);
+	i += consdev_sz / sizeof(uint32_t);
 
 	if (bootmac) {
-		bootmac_sz = 3 * sizeof(int) + (sizeof(bios_bootmac_t) + 3) & ~3;
-		ba[i] = 0x7;   /* bootmac */
+		bootmac_sz = 3 * sizeof(uint32_t) +
+		    (sizeof(bios_bootmac_t) + 3) & ~3;
+		ba[i] = BOOTARG_BOOTMAC;
 		ba[i + 1] = bootmac_sz;
 		ba[i + 2] = bootmac_sz;
 		memcpy(&ba[i + 3], bootmac, sizeof(bios_bootmac_t));
-		i += bootmac_sz / sizeof(int);
-	} 
+		i += bootmac_sz / sizeof(uint32_t);
+	}
 
 	ba[i++] = 0xFFFFFFFF; /* BOOTARG_END */
 
 	write_mem(BOOTARGS_PAGE, ba, PAGE_SIZE);
 
-	return (i * sizeof(int));
+	return (i * sizeof(uint32_t));
 }
 
 /*