Commit fb46d057 authored by Nick Terrell's avatar Nick Terrell Committed by Ingo Molnar
Browse files

x86: Add support for ZSTD compressed kernel 



- Add support for zstd compressed kernel

- Define __DISABLE_EXPORTS in Makefile

- Remove __DISABLE_EXPORTS definition from kaslr.c

- Bump the heap size for zstd.

- Update the documentation.

Integrates the ZSTD decompression code to the x86 pre-boot code.

Zstandard requires slightly more memory during the kernel decompression
on x86 (192 KB vs 64 KB), and the memory usage is independent of the
window size.

__DISABLE_EXPORTS is now defined in the Makefile, which covers both
the existing use in kaslr.c, and the use needed by the zstd decompressor
in misc.c.

This patch has been boot tested with both a zstd and gzip compressed
kernel on i386 and x86_64 using buildroot and QEMU.

Additionally, this has been tested in production on x86_64 devices.
We saw a 2 second boot time reduction by switching kernel compression
from xz to zstd.

Signed-off-by: default avatarNick Terrell <terrelln@fb.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200730190841.2071656-7-nickrterrell@gmail.com
parent 0fe4f4ef

Documentation/x86/boot.rst

+3 −3
Original line number Diff line number Diff line
@@ -782,9 +782,9 @@ Protocol: 2.08+ 
  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), LZMA

  (magic number 5D 00), XZ (magic number FD 37), and LZ4 (magic number

  02 21).  The uncompressed payload is currently always ELF (magic

  number 7F 45 4C 46).

  (magic number 5D 00), XZ (magic number FD 37), LZ4 (magic number

  02 21) and ZSTD (magic number 28 B5). The uncompressed payload is

  currently always ELF (magic number 7F 45 4C 46).



============	==============

Field name:	payload_length

arch/x86/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -188,6 +188,7 @@ config X86 
	select HAVE_KERNEL_LZMA

	select HAVE_KERNEL_LZO

	select HAVE_KERNEL_XZ

	select HAVE_KERNEL_ZSTD

	select HAVE_KPROBES

	select HAVE_KPROBES_ON_FTRACE

	select HAVE_FUNCTION_ERROR_INJECTION

arch/x86/boot/compressed/Makefile

+5 −1
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ OBJECT_FILES_NON_STANDARD := y 
KCOV_INSTRUMENT		:= n



targets := vmlinux vmlinux.bin vmlinux.bin.gz vmlinux.bin.bz2 vmlinux.bin.lzma \

	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4

	vmlinux.bin.xz vmlinux.bin.lzo vmlinux.bin.lz4 vmlinux.bin.zst



KBUILD_CFLAGS := -m$(BITS) -O2

KBUILD_CFLAGS += -fno-strict-aliasing $(call cc-option, -fPIE, -fPIC)
@@ -42,6 +42,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, gnu) 
KBUILD_CFLAGS += -Wno-pointer-sign

KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=)

KBUILD_CFLAGS += -fno-asynchronous-unwind-tables

KBUILD_CFLAGS += -D__DISABLE_EXPORTS



KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__

GCOV_PROFILE := n
@@ -145,6 +146,8 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE 
	$(call if_changed,lzo)

$(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE

	$(call if_changed,lz4)

$(obj)/vmlinux.bin.zst: $(vmlinux.bin.all-y) FORCE

	$(call if_changed,zstd22)



suffix-$(CONFIG_KERNEL_GZIP)	:= gz

suffix-$(CONFIG_KERNEL_BZIP2)	:= bz2
@@ -152,6 +155,7 @@ suffix-$(CONFIG_KERNEL_LZMA) := lzma 
suffix-$(CONFIG_KERNEL_XZ)	:= xz

suffix-$(CONFIG_KERNEL_LZO) 	:= lzo

suffix-$(CONFIG_KERNEL_LZ4) 	:= lz4

suffix-$(CONFIG_KERNEL_ZSTD)	:= zst



quiet_cmd_mkpiggy = MKPIGGY $@

      cmd_mkpiggy = $(obj)/mkpiggy $< > $@

arch/x86/boot/compressed/kaslr.c

+0 −7
Original line number Diff line number Diff line
@@ -19,13 +19,6 @@ 
 */

#define BOOT_CTYPE_H



/*

 * _ctype[] in lib/ctype.c is needed by isspace() of linux/ctype.h.

 * While both lib/ctype.c and lib/cmdline.c will bring EXPORT_SYMBOL

 * which is meaningless and will cause compiling error in some cases.

 */

#define __DISABLE_EXPORTS



#include "misc.h"

#include "error.h"

#include "../string.h"

arch/x86/boot/compressed/misc.c

+4 −0
Original line number Diff line number Diff line
@@ -77,6 +77,10 @@ static int lines, cols; 
#ifdef CONFIG_KERNEL_LZ4

#include "../../../../lib/decompress_unlz4.c"

#endif



#ifdef CONFIG_KERNEL_ZSTD

#include "../../../../lib/decompress_unzstd.c"

#endif

/*

 * NOTE: When adding a new decompressor, please update the analysis in

 * ../header.S.

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