MIPS: ZBOOT: copy appended dtb to the end of the kernel

Instead of rewriting the arguments, just move the appended dtb to where
the decompressed kernel expects it. This eliminates the need for special
casing vmlinuz.bin appended dtb files.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: John Crispin <john@phrozen.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Alban Bedel <albeu@free.fr>
Cc: Daniel Gimpelevich <daniel@gimpelevich.san-francisco.ca.us>
Cc: Antony Pavlov <antonynpavlov@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/13698/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -2884,10 +2884,10 @@ choice
 		  the documented boot protocol using a device tree.
 
 	config MIPS_RAW_APPENDED_DTB
-		bool "vmlinux.bin"
+		bool "vmlinux.bin or vmlinuz.bin"
 		help
 		  With this option, the boot code will look for a device tree binary
-		  DTB) appended to raw vmlinux.bin (without decompressor).
+		  DTB) appended to raw vmlinux.bin or vmlinuz.bin.
 		  (e.g. cat vmlinux.bin <filename>.dtb > vmlinux_w_dtb).
 
 		  This is meant as a backward compatibility convenience for those
@@ -2899,24 +2899,6 @@ choice
 		  look like a DTB header after a reboot if no actual DTB is appended
 		  to vmlinux.bin.  Do not leave this option active in a production kernel
 		  if you don't intend to always append a DTB.
-
-	config MIPS_ZBOOT_APPENDED_DTB
-		bool "vmlinuz.bin"
-		depends on SYS_SUPPORTS_ZBOOT
-		help
-		  With this option, the boot code will look for a device tree binary
-		  DTB) appended to raw vmlinuz.bin (with decompressor).
-		  (e.g. cat vmlinuz.bin <filename>.dtb > vmlinuz_w_dtb).
-
-		  This is meant as a backward compatibility convenience for those
-		  systems with a bootloader that can't be upgraded to accommodate
-		  the documented boot protocol using a device tree.
-
-		  Beware that there is very little in terms of protection against
-		  this option being confused by leftover garbage in memory that might
-		  look like a DTB header after a reboot if no actual DTB is appended
-		  to vmlinuz.bin.  Do not leave this option active in a production kernel
-		  if you don't intend to always append a DTB.
 endchoice
 
 choice

arch/mips/boot/compressed/decompress.c

@@ -14,6 +14,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
+#include <linux/libfdt.h>
 
 #include <asm/addrspace.h>
 
@@ -36,6 +37,8 @@ extern void puthex(unsigned long long val);
 #define puthex(val) do {} while (0)
 #endif
 
+extern char __appended_dtb[];
+
 void error(char *x)
 {
 	puts("\n\n");
@@ -114,6 +117,20 @@ void decompress_kernel(unsigned long boot_heap_start)
 	__decompress((char *)zimage_start, zimage_size, 0, 0,
 		   (void *)VMLINUX_LOAD_ADDRESS_ULL, 0, 0, error);
 
+	if (IS_ENABLED(CONFIG_MIPS_RAW_APPENDED_DTB) &&
+	    fdt_magic((void *)&__appended_dtb) == FDT_MAGIC) {
+		unsigned int image_size, dtb_size;
+
+		dtb_size = fdt_totalsize((void *)&__appended_dtb);
+
+		/* last four bytes is always image size in little endian */
+		image_size = le32_to_cpup((void *)&__image_end - 4);
+
+		/* copy dtb to where the booted kernel will expect it */
+		memcpy((void *)VMLINUX_LOAD_ADDRESS_ULL + image_size,
+		       __appended_dtb, dtb_size);
+	}
+
 	/* FIXME: should we flush cache here? */
 	puts("Now, booting the kernel...\n");
 }

arch/mips/boot/compressed/head.S

@@ -25,22 +25,6 @@ start:
 	move	s2, a2
 	move	s3, a3
 
-#ifdef CONFIG_MIPS_ZBOOT_APPENDED_DTB
-	PTR_LA	t0, __appended_dtb
-#ifdef CONFIG_CPU_BIG_ENDIAN
-	li	t1, 0xd00dfeed
-#else
-	li	t1, 0xedfe0dd0
-#endif
-	lw	t2, (t0)
-	bne	t1, t2, not_found
-	 nop
-
-	move	s1, t0
-	PTR_LI	s0, -2
-not_found:
-#endif
-
 	/* Clear BSS */
 	PTR_LA	a0, _edata
 	PTR_LA	a2, _end