[PATCH v2] x86/boot: Support uncompressed kernel

[Chao Peng <chao.p.peng@linux.intel.com>]

Compressed kernel has its own drawback: decompressing takes time. Even
though the time is short enough to ignore for most cases but for cases when
time is critical decompressing time still matters.

The patch adds a 'CONFIG_KERNEL_RAW' configure choice so the built binary
can have no decompressing at all. The experiment shows:

    kernel               kernel size    time in decompress_kernel
    compressed (gzip)    3.3M           53ms
    compressed (lz4)     4.5M           16ms
    uncompressed         14M            2ms

Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
---
v2:
  * add HAVE_KERNEL_RAW
  * decode ELF kernel in place instead of getting another copy
  * minor comment fix
---
 arch/x86/Kconfig                  |  1 +
 arch/x86/boot/compressed/Makefile |  3 +++
 arch/x86/boot/compressed/misc.c   | 18 +++++++++++++-----
 init/Kconfig                      | 13 ++++++++++++-
 scripts/Makefile.lib              |  8 ++++++++
 5 files changed, 37 insertions(+), 6 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc98d5a..207695c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -142,6 +142,7 @@ config X86
 	select HAVE_KERNEL_LZ4
 	select HAVE_KERNEL_LZMA
 	select HAVE_KERNEL_LZO
+	select HAVE_KERNEL_RAW
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES
 	select HAVE_KPROBES_ON_FTRACE
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 44163e8..ed366e1 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -120,6 +120,8 @@ $(obj)/vmlinux.relocs: vmlinux FORCE
 vmlinux.bin.all-y := $(obj)/vmlinux.bin
 vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs
 
+$(obj)/vmlinux.bin.raw: $(vmlinux.bin.all-y) FORCE
+	$(call if_changed,raw)
 $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,gzip)
 $(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE
@@ -133,6 +135,7 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE
 $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE
 	$(call if_changed,lz4)
 
+suffix-$(CONFIG_KERNEL_RAW)	:= raw
 suffix-$(CONFIG_KERNEL_GZIP)	:= gz
 suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
 suffix-$(CONFIG_KERNEL_LZMA)	:= lzma
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index b3c5a5f0..9791ca9 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -51,6 +51,10 @@
 static int vidport;
 static int lines, cols;
 
+#ifdef CONFIG_KERNEL_RAW
+#include <linux/decompress/mm.h>
+#endif
+
 #ifdef CONFIG_KERNEL_GZIP
 #include "../../../../lib/decompress_inflate.c"
 #endif
@@ -265,7 +269,7 @@ static inline void handle_relocations(void *output, unsigned long output_len,
 { }
 #endif
 
-static void parse_elf(void *output)
+static void parse_elf(void* buf, void *output)
 {
 #ifdef CONFIG_X86_64
 	Elf64_Ehdr ehdr;
@@ -277,7 +281,7 @@ static void parse_elf(void *output)
 	void *dest;
 	int i;
 
-	memcpy(&ehdr, output, sizeof(ehdr));
+	memcpy(&ehdr, buf, sizeof(ehdr));
 	if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
 	   ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
 	   ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
@@ -292,7 +296,7 @@ static void parse_elf(void *output)
 	if (!phdrs)
 		error("Failed to allocate space for phdrs");
 
-	memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
+	memcpy(phdrs, buf + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
 
 	for (i = 0; i < ehdr.e_phnum; i++) {
 		phdr = &phdrs[i];
@@ -305,7 +309,7 @@ static void parse_elf(void *output)
 #else
 			dest = (void *)(phdr->p_paddr);
 #endif
-			memmove(dest, output + phdr->p_offset, phdr->p_filesz);
+			memmove(dest, buf + phdr->p_offset, phdr->p_filesz);
 			break;
 		default: /* Ignore other PT_* */ break;
 		}
@@ -401,10 +405,14 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 		error("Destination virtual address changed when not relocatable");
 #endif
 
+#ifdef CONFIG_KERNEL_RAW
+	parse_elf(input_data, output);
+#else
 	debug_putstr("\nDecompressing Linux... ");
 	__decompress(input_data, input_len, NULL, NULL, output, output_len,
 			NULL, error);
-	parse_elf(output);
+	parse_elf(output, output);
+#endif
 	handle_relocations(output, output_len, virt_addr);
 	debug_putstr("done.\nBooting the kernel.\n");
 	return output;
diff --git a/init/Kconfig b/init/Kconfig
index a92f27d..b8926bb 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -109,6 +109,9 @@ config LOCALVERSION_AUTO
 
 	  which is done within the script "scripts/setlocalversion".)
 
+config HAVE_KERNEL_RAW
+	bool
+
 config HAVE_KERNEL_GZIP
 	bool
 
@@ -130,7 +133,7 @@ config HAVE_KERNEL_LZ4
 choice
 	prompt "Kernel compression mode"
 	default KERNEL_GZIP
-	depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
+	depends on HAVE_KERNEL_RAW || HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
 	help
 	  The linux kernel is a kind of self-extracting executable.
 	  Several compression algorithms are available, which differ
@@ -149,6 +152,14 @@ choice
 
 	  If in doubt, select 'gzip'
 
+config KERNEL_RAW
+	bool "RAW"
+	depends on HAVE_KERNEL_RAW
+	help
+	  No compression. It creates much bigger kernel and uses much more
+	  space (disk/memory) than other choices. It can be useful when
+	  decompression speed is the most concern while space matters less.
+
 config KERNEL_GZIP
 	bool "Gzip"
 	depends on HAVE_KERNEL_GZIP
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 0a07f90..8a8f9a9 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -357,6 +357,14 @@ cmd_lz4 = (cat $(filter-out FORCE,$^) | \
 	lz4c -l -c1 stdin stdout && $(call size_append, $(filter-out FORCE,$^))) > $@ || \
 	(rm -f $@ ; false)
 
+# RAW
+# ---------------------------------------------------------------------------
+quiet_cmd_raw = RAW     $@
+cmd_raw = (cat $(filter-out FORCE,$^) && \
+	$(call size_append, $(filter-out FORCE,$^))) > $@ || \
+	(rm -f $@ ; false)
+
+
 # U-Boot mkimage
 # ---------------------------------------------------------------------------
 
-- 
1.8.3.1