Prevent fdt data loaded from a file from overwriting the kernel environment,

by having uboot_autoload() do the fdt setup (which may load a file) rather
than waiting until we're actually in the process of launching the kernel.

As part of making this happen...
 - Define LOADER_FDT_SUPPORT on the uboot/lib compile command line when
   MK_FDT is set.
 - Make fdt_setup_fdtb() public.
 - Declare public fdt_whatever() functions in a header instead of using
   scattered extern decls in .c files.

sys/boot/fdt/fdt_loader_cmd.c

@@ -279,7 +279,7 @@ fdt_load_dtb_file(const char * filename)
 	return (0);
 }
 
-static int
+int
 fdt_setup_fdtp()
 {
 	struct preloaded_file *bfp;

sys/boot/uboot/common/metadata.c

@@ -41,10 +41,6 @@ __FBSDID("$FreeBSD$");
 #include "bootstrap.h"
 #include "glue.h"
 
-#if defined(LOADER_FDT_SUPPORT)
-extern int fdt_copy(vm_offset_t);
-#endif
-
 /*
  * Return a 'boothowto' value corresponding to the kernel arguments in
  * (kargs) and any relevant environment variables.

sys/boot/uboot/lib/Makefile

@@ -1,5 +1,7 @@
 # $FreeBSD$
 
+.include <bsd.own.mk>
+
 .PATH: ${.CURDIR}/../../common
 
 LIB=		uboot
@@ -18,6 +20,16 @@ SRCS+=	disk.c
 CFLAGS+= -DLOADER_DISK_SUPPORT
 .endif
 
+.if ${MK_FDT} != "no"
+LOADER_FDT_SUPPORT=	yes
+.else
+LOADER_FDT_SUPPORT=	no
+.endif
+
+.if ${LOADER_FDT_SUPPORT} == "yes"
+CFLAGS+= -DLOADER_FDT_SUPPORT
+.endif
+
 # Pick up FDT includes
 CFLAGS+=	-I${.CURDIR}/../../../../sys/contrib/libfdt/
 

sys/boot/uboot/lib/libuboot.h

@@ -69,3 +69,9 @@ struct file_format;
 extern struct file_format uboot_elf;
 
 void reboot(void);
+
+#if defined(LOADER_FDT_SUPPORT)
+extern int fdt_setup_fdtp();
+extern int fdt_copy(vm_offset_t);
+#endif
+

sys/boot/uboot/lib/module.c

@@ -29,19 +29,23 @@ __FBSDID("$FreeBSD$");
 
 /*
  * U-Boot-specific module functionality.
- *
- * XXX not much for now...
- *
  */
 
 #include <stand.h>
 #include <string.h>
 
 #include "bootstrap.h"
+#include "libuboot.h"
 
 int
 uboot_autoload(void)
 {
+#if defined(LOADER_FDT_SUPPORT)
+	int err;
+
+	if ((err = fdt_setup_fdtp()) != 0)
+		return (err);
+#endif
 
 	return(0);
 }