x86: support XZ-compressed kernel

This integrates the XZ decompression code to the x86 pre-boot code.

mkpiggy.c is updated to reserve about 32 KiB more buffer safety margin for
kernel decompression.  It is done unconditionally for all decompressors to
keep the code simpler.

The XZ decompressor needs around 30 KiB of heap, so the heap size is
increased to 32 KiB on both x86-32 and x86-64.

Documentation/x86/boot.txt is updated to list the XZ magic number.

With the x86 BCJ filter in XZ, XZ-compressed x86 kernel tends to be a few
percent smaller than the equivalent LZMA-compressed kernel.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alain Knaff <alain@knaff.lu>
Cc: Albin Tonnerre <albin.tonnerre@free-electrons.com>
Cc: Phillip Lougher <phillip@lougher.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 14 insertions, 10 deletions

diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index bdeb81ccb5f6..9b7221a86df2 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -622,9 +622,9 @@ Protocol:	2.08+
   The payload may be compressed. The format of both the compressed and
   uncompressed data should be determined using the standard magic
   numbers.  The currently supported compression formats are gzip
-  (magic numbers 1F 8B or 1F 9E), bzip2 (magic number 42 5A) and LZMA
-  (magic number 5D 00).  The uncompressed payload is currently always ELF
-  (magic number 7F 45 4C 46).
+  (magic numbers 1F 8B or 1F 9E), bzip2 (magic number 42 5A), LZMA
+  (magic number 5D 00), and XZ (magic number FD 37).  The uncompressed
+  payload is currently always ELF (magic number 7F 45 4C 46).
   
 Field name:     payload_length
 Type:           read
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8734db3c5830..6e15fa9455e0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -51,6 +51,7 @@ config X86
         select HAVE_KERNEL_GZIP
         select HAVE_KERNEL_BZIP2
         select HAVE_KERNEL_LZMA
+        select HAVE_KERNEL_XZ
         select HAVE_KERNEL_LZO
         select HAVE_HW_BREAKPOINT
         select HAVE_MIXED_BREAKPOINTS_REGS
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 0c229551eead..09664efb9cee 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -4,7 +4,7 @@
 # create a compressed vmlinux image from the original vmlinux
 #
 
-targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma vmlinux.bin.lzo head_$(BITS).o misc.o string.o cmdline.o early_serial_console.o piggy.o
+targets := vmlinux.lds vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma vmlinux.bin.xz vmlinux.bin.lzo head_$(BITS).o misc.o string.o cmdline.o early_serial_console.o piggy.o
 
 KBUILD_CFLAGS := -m$(BITS) -D__KERNEL__ $(LINUX_INCLUDE) -O2
 KBUILD_CFLAGS += -fno-strict-aliasing -fPIC
@@ -49,12 +49,15 @@ $(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
         $(call if_changed,bzip2)
 $(obj)/vmlinux.bin.lzma: $(vmlinux.bin.all-y) FORCE
         $(call if_changed,lzma)
+$(obj)/vmlinux.bin.xz: $(vmlinux.bin.all-y) FORCE
+        $(call if_changed,xzkern)
 $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
         $(call if_changed,lzo)
 
 suffix-$(CONFIG_KERNEL_GZIP)    := gz
 suffix-$(CONFIG_KERNEL_BZIP2)   := bz2
 suffix-$(CONFIG_KERNEL_LZMA)    := lzma
+suffix-$(CONFIG_KERNEL_XZ)      := xz
 suffix-$(CONFIG_KERNEL_LZO)     := lzo
 
 quiet_cmd_mkpiggy = MKPIGGY $@
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 325c05294fc4..3a19d04cebeb 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -139,6 +139,10 @@ static int lines, cols;
 #include "../../../../lib/decompress_unlzma.c"
 #endif
 
+#ifdef CONFIG_KERNEL_XZ
+#include "../../../../lib/decompress_unxz.c"
+#endif
+
 #ifdef CONFIG_KERNEL_LZO
 #include "../../../../lib/decompress_unlzo.c"
 #endif
diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
index 5c228129d175..646aa78ba5fd 100644
--- a/arch/x86/boot/compressed/mkpiggy.c
+++ b/arch/x86/boot/compressed/mkpiggy.c
@@ -74,7 +74,7 @@ int main(int argc, char *argv[])
 
         offs = (olen > ilen) ? olen - ilen : 0;
         offs += olen >> 12;     /* Add 8 bytes for each 32K block */
-        offs += 32*1024 + 18;   /* Add 32K + 18 bytes slack */
+        offs += 64*1024 + 128;  /* Add 64K + 128 bytes slack */
         offs = (offs+4095) & ~4095; /* Round to a 4K boundary */
 
         printf(".section \".rodata..compressed\",\"a\",@progbits\n");
diff --git a/arch/x86/include/asm/boot.h b/arch/x86/include/asm/boot.h
index 3b62ab56c7a0..5e1a2eef3e7c 100644
--- a/arch/x86/include/asm/boot.h
+++ b/arch/x86/include/asm/boot.h
@@ -32,11 +32,7 @@
 #define BOOT_HEAP_SIZE             0x400000
 #else /* !CONFIG_KERNEL_BZIP2 */
 
-#ifdef CONFIG_X86_64
-#define BOOT_HEAP_SIZE  0x7000
-#else
-#define BOOT_HEAP_SIZE  0x4000
-#endif
+#define BOOT_HEAP_SIZE  0x8000
 
 #endif /* !CONFIG_KERNEL_BZIP2 */