MIPS: ZBOOT: Support XZ compression scheme

Add support for the XZ compression scheme in the ZBOOT decompression
stub, in order to support it we need to:

- select the "xzkern" compression tool to compress the vmlinux.bin
  payload
- link with ashldi3.o for xz_dec_run() to work
- memcpy() is also required for decompress_unxz.c so we share the
  implementation between GZIP and XZ

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: blogic@openwrt.org
Cc: james.hogan@imgtec.com
Patchwork: https://patchwork.linux-mips.org/patch/5818/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -1491,6 +1491,7 @@ config SYS_SUPPORTS_ZBOOT
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
+	select HAVE_KERNEL_XZ
 
 config SYS_SUPPORTS_ZBOOT_UART16550
 	bool

arch/mips/boot/compressed/Makefile

@@ -37,6 +37,10 @@ vmlinuzobjs-$(CONFIG_SYS_SUPPORTS_ZBOOT_UART16550) += $(obj)/uart-16550.o
 vmlinuzobjs-$(CONFIG_MIPS_ALCHEMY)		   += $(obj)/uart-alchemy.o
 endif
 
+ifdef CONFIG_KERNEL_XZ
+vmlinuzobjs-y += $(obj)/../../lib/ashldi3.o
+endif
+
 targets += vmlinux.bin
 OBJCOPYFLAGS_vmlinux.bin := $(OBJCOPYFLAGS) -O binary -R .comment -S
 $(obj)/vmlinux.bin: $(KBUILD_IMAGE) FORCE
@@ -46,6 +50,7 @@ tool_$(CONFIG_KERNEL_GZIP)    = gzip
 tool_$(CONFIG_KERNEL_BZIP2)   = bzip2
 tool_$(CONFIG_KERNEL_LZMA)    = lzma
 tool_$(CONFIG_KERNEL_LZO)     = lzo
+tool_$(CONFIG_KERNEL_XZ)      = xzkern
 
 targets += vmlinux.bin.z
 $(obj)/vmlinux.bin.z: $(obj)/vmlinux.bin FORCE

arch/mips/boot/compressed/decompress.c

@@ -43,7 +43,7 @@ void error(char *x)
 /* activate the code for pre-boot environment */
 #define STATIC static
 
-#ifdef CONFIG_KERNEL_GZIP
+#if defined(CONFIG_KERNEL_GZIP) || defined(CONFIG_KERNEL_XZ)
 void *memcpy(void *dest, const void *src, size_t n)
 {
 	int i;
@@ -54,6 +54,8 @@ void *memcpy(void *dest, const void *src, size_t n)
 		d[i] = s[i];
 	return dest;
 }
+#endif
+#ifdef CONFIG_KERNEL_GZIP
 #include "../../../../lib/decompress_inflate.c"
 #endif
 
@@ -78,6 +80,10 @@ void *memset(void *s, int c, size_t n)
 #include "../../../../lib/decompress_unlzo.c"
 #endif
 
+#ifdef CONFIG_KERNEL_XZ
+#include "../../../../lib/decompress_unxz.c"
+#endif
+
 void decompress_kernel(unsigned long boot_heap_start)
 {
 	unsigned long zimage_start, zimage_size;