diff --git a/lib/bootargs/bootargs.c b/lib/bootargs/bootargs.c
index 91522626..ffffcad4 100644
--- a/lib/bootargs/bootargs.c
+++ b/lib/bootargs/bootargs.c
@@ -7,12 +7,13 @@
  */
 #include <lib/bootargs.h>
 
-#include <lk/trace.h>
-#include <stdlib.h>
-#include <stdio.h>
 #include <lk/err.h>
-#include <string.h>
 #include <lk/init.h>
+#include <lk/main.h>
+#include <lk/trace.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 
 #if WITH_KERNEL_VM
 #include <kernel/vm.h>
@@ -20,9 +21,6 @@
 
 #define LOCAL_TRACE 0
 
-/* saved by the main entry point in lk */
-extern ulong lk_boot_args[4];
-
 static bool boot_args_valid = false;
 static struct lk_boot_arg *boot_args;
 
diff --git a/platform/jh7110/platform.c b/platform/jh7110/platform.c
index db2d579b..77bfe2a4 100644
--- a/platform/jh7110/platform.c
+++ b/platform/jh7110/platform.c
@@ -7,6 +7,7 @@
  */
 #include <inttypes.h>
 #include <lk/err.h>
+#include <lk/main.h>
 #include <lk/reg.h>
 #include <lk/trace.h>
 #include <kernel/thread.h>
@@ -30,8 +31,6 @@
 
 #define LOCAL_TRACE 1
 
-extern ulong lk_boot_args[4];
-
 #if WITH_KERNEL_VM
 #define DEFAULT_MEMORY_SIZE (MEMSIZE) /* try to fetch from the emulator via the fdt */
 
diff --git a/platform/qemu-virt-riscv/platform.c b/platform/qemu-virt-riscv/platform.c
index 53255027..9fbfc371 100644
--- a/platform/qemu-virt-riscv/platform.c
+++ b/platform/qemu-virt-riscv/platform.c
@@ -7,6 +7,7 @@
  */
 #include <inttypes.h>
 #include <lk/err.h>
+#include <lk/main.h>
 #include <lk/reg.h>
 #include <lk/trace.h>
 #include <kernel/thread.h>
@@ -37,8 +38,6 @@
 
 #define LOCAL_TRACE 0
 
-extern ulong lk_boot_args[4];
-
 #if WITH_KERNEL_VM
 #define DEFAULT_MEMORY_SIZE (MEMSIZE) /* try to fetch from the emulator via the fdt */
 
diff --git a/platform/rosco-m68k/platform.c b/platform/rosco-m68k/platform.c
index c5e16fb2..c3f5d568 100644
--- a/platform/rosco-m68k/platform.c
+++ b/platform/rosco-m68k/platform.c
@@ -6,6 +6,7 @@
  * https://opensource.org/licenses/MIT
  */
 #include <lk/err.h>
+#include <lk/main.h>
 #include <lk/reg.h>
 #include <lk/trace.h>
 #include <kernel/thread.h>
@@ -44,19 +45,19 @@ struct rosco_system_data_block {
 };
 STATIC_ASSERT(sizeof(struct rosco_system_data_block) == 0x20);
 
-const volatile struct rosco_system_data_block *sdb = (void *)0x400;
-
 void platform_early_init(void) {
     duart_early_init();
 
+    volatile struct rosco_system_data_block *sdb = (void *)lk_boot_args[0];
+
     // default to 1MB memory at 0
     uint32_t membase = 0x0;
     uint32_t memsize = 0x100000; // 1MB
 
     if (sdb->magic != ROSCO_SDB_MAGIC) {
-        dprintf(INFO, "ROSCO-M68K: firmware failed magic check\n");
+        dprintf(INFO, "ROSCO-M68K: firmware failed magic check at %p\n", sdb);
     } else {
-        dprintf(INFO, "ROSCO-M68K: firmware structure at 0x400 - 0x41f:\n");
+        dprintf(INFO, "ROSCO-M68K: firmware structure at %p - %p:\n", sdb, sdb + 0x1f);
         hexdump((void *)sdb, sizeof(*sdb));
 
         printf("cpu family %u speed %u\n", sdb->cpu_info >> 29, sdb->cpu_info & 0x1fffffff);
diff --git a/top/include/lk/main.h b/top/include/lk/main.h
index d473f61f..6bfc230b 100644
--- a/top/include/lk/main.h
+++ b/top/include/lk/main.h
@@ -12,6 +12,9 @@
 
 __BEGIN_CDECLS
 
+// Possible boot args passed from various arch's start.S
+extern ulong lk_boot_args[4];
+
 void lk_main(ulong arg0, ulong arg1, ulong arg2, ulong arg3) __NO_RETURN __EXTERNALLY_VISIBLE;
 void lk_secondary_cpu_entry(void);
 void lk_init_secondary_cpus(uint secondary_cpu_count);