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Subject[PATCH 1/2] lib: add support for ZSTD-compressed kernel
Date
Add support for extracting ZSTD-compressed kernel images, as well as
ZSTD-compressed initramfs.

Signed-off-by: Petr Malat <oss@malat.biz>
---
include/linux/decompress/unzstd.h | 12 +++
init/Kconfig | 15 ++-
lib/Kconfig | 4 +
lib/Makefile | 1 +
lib/decompress.c | 5 +
lib/decompress_unzstd.c | 159 ++++++++++++++++++++++++++++++
lib/zstd/decompress.c | 2 +
lib/zstd/fse_decompress.c | 4 +-
scripts/Makefile.lib | 3 +
usr/Kconfig | 24 +++++
10 files changed, 227 insertions(+), 2 deletions(-)
create mode 100644 include/linux/decompress/unzstd.h
create mode 100644 lib/decompress_unzstd.c

diff --git a/include/linux/decompress/unzstd.h b/include/linux/decompress/unzstd.h
new file mode 100644
index 000000000000..dd2c49d47456
--- /dev/null
+++ b/include/linux/decompress/unzstd.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef DECOMPRESS_UNZSTD_H
+#define DECOMPRESS_UNZSTD_H
+
+int unzstd(unsigned char *inbuf, long len,
+ long (*fill)(void*, unsigned long),
+ long (*flush)(void*, unsigned long),
+ unsigned char *output,
+ long *pos,
+ void (*error)(char *x));
+#endif
+
diff --git a/init/Kconfig b/init/Kconfig
index a34064a031a5..628eb3c290a2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -172,13 +172,16 @@ config HAVE_KERNEL_LZO
config HAVE_KERNEL_LZ4
bool

+config HAVE_KERNEL_ZSTD
+ bool
+
config HAVE_KERNEL_UNCOMPRESSED
bool

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 || HAVE_KERNEL_UNCOMPRESSED
+ depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 || HAVE_KERNEL_ZSTD || HAVE_KERNEL_UNCOMPRESSED
help
The linux kernel is a kind of self-extracting executable.
Several compression algorithms are available, which differ
@@ -257,6 +260,16 @@ config KERNEL_LZ4
is about 8% bigger than LZO. But the decompression speed is
faster than LZO.

+config KERNEL_ZSTD
+ bool "ZSTD"
+ depends on HAVE_KERNEL_ZSTD
+ help
+ Its compression ratio is roughly 10% worst than xz, but the
+ decompression is 10x faster. Currently, this is one of the optimal
+ algorithms available in the kernel, as there isn't an algorithm,
+ which would provide a better compression ratio and a shorter
+ decompression time.
+
config KERNEL_UNCOMPRESSED
bool "None"
depends on HAVE_KERNEL_UNCOMPRESSED
diff --git a/lib/Kconfig b/lib/Kconfig
index 6e790dc55c5b..df301bd888d7 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -329,6 +329,10 @@ config DECOMPRESS_LZ4
select LZ4_DECOMPRESS
tristate

+config DECOMPRESS_ZSTD
+ select ZSTD_DECOMPRESS
+ tristate
+
#
# Generic allocator support is selected if needed
#
diff --git a/lib/Makefile b/lib/Makefile
index 93217d44237f..3ab9f4c31f8b 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -158,6 +158,7 @@ lib-$(CONFIG_DECOMPRESS_LZMA) += decompress_unlzma.o
lib-$(CONFIG_DECOMPRESS_XZ) += decompress_unxz.o
lib-$(CONFIG_DECOMPRESS_LZO) += decompress_unlzo.o
lib-$(CONFIG_DECOMPRESS_LZ4) += decompress_unlz4.o
+lib-$(CONFIG_DECOMPRESS_ZSTD) += decompress_unzstd.o

obj-$(CONFIG_TEXTSEARCH) += textsearch.o
obj-$(CONFIG_TEXTSEARCH_KMP) += ts_kmp.o
diff --git a/lib/decompress.c b/lib/decompress.c
index 857ab1af1ef3..ab3fc90ffc64 100644
--- a/lib/decompress.c
+++ b/lib/decompress.c
@@ -13,6 +13,7 @@
#include <linux/decompress/inflate.h>
#include <linux/decompress/unlzo.h>
#include <linux/decompress/unlz4.h>
+#include <linux/decompress/unzstd.h>

#include <linux/types.h>
#include <linux/string.h>
@@ -37,6 +38,9 @@
#ifndef CONFIG_DECOMPRESS_LZ4
# define unlz4 NULL
#endif
+#ifndef CONFIG_DECOMPRESS_ZSTD
+# define unzstd NULL
+#endif

struct compress_format {
unsigned char magic[2];
@@ -52,6 +56,7 @@ static const struct compress_format compressed_formats[] __initconst = {
{ {0xfd, 0x37}, "xz", unxz },
{ {0x89, 0x4c}, "lzo", unlzo },
{ {0x02, 0x21}, "lz4", unlz4 },
+ { {0x28, 0xb5}, "zstd", unzstd },
{ {0, 0}, NULL, NULL }
};

diff --git a/lib/decompress_unzstd.c b/lib/decompress_unzstd.c
new file mode 100644
index 000000000000..5af647a49885
--- /dev/null
+++ b/lib/decompress_unzstd.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Wrapper for decompressing ZSTD-compressed kernel, initramfs, and initrd
+ * Based on decompress_unlz4.c
+ *
+ * Copyright (C) 2020, Petr Malat <oss@malat.biz>
+ */
+
+#ifdef STATIC
+#define PREBOOT
+#include "zstd/zstd_internal.h"
+#include "zstd/huf_decompress.c"
+#include "zstd/entropy_common.c"
+#include "zstd/fse_decompress.c"
+#include "zstd/zstd_common.c"
+#include "zstd/decompress.c"
+#include "xxhash.c"
+#else
+#include <linux/decompress/unzstd.h>
+#include <linux/zstd.h>
+#endif
+#include <linux/types.h>
+#include <linux/decompress/mm.h>
+#include <linux/compiler.h>
+
+STATIC inline int INIT unzstd(u8 *input, long in_len,
+ long (*fill)(void *, unsigned long),
+ long (*flush)(void *, unsigned long),
+ u8 *output, long *posp,
+ void (*error)(char *x))
+{
+ int ret = -1, ws = 1 << ZSTD_WINDOWLOG_MAX;
+ u8 *inp, *outp;
+ ZSTD_DStream *zstd;
+ void *workspace;
+ size_t workspace_size;
+ ZSTD_outBuffer out;
+ ZSTD_inBuffer in;
+ unsigned long out_len;
+ unsigned long pos;
+
+ if (output) {
+ out_len = ULONG_MAX; // Caller knows data will fit
+ outp = output;
+ } else if (!flush) {
+ error("NULL output pointer and no flush function provided");
+ goto exit_0;
+ } else {
+ out_len = ZSTD_DStreamOutSize();
+ outp = large_malloc(out_len);
+ if (!outp) {
+ error("Could not allocate output buffer");
+ goto exit_0;
+ }
+ }
+
+ if (input && fill) {
+ error("Both input pointer and fill function provided,");
+ goto exit_1;
+ } else if (input) {
+ ZSTD_frameParams p;
+
+ inp = input;
+ if (!ZSTD_getFrameParams(&p, input, in_len))
+ ws = p.windowSize;
+ } else if (!fill) {
+ error("NULL input pointer and missing fill function");
+ goto exit_1;
+ } else {
+ in_len = ZSTD_DStreamInSize();
+ inp = large_malloc(in_len);
+ if (!inp) {
+ error("Could not allocate input buffer");
+ goto exit_1;
+ }
+ }
+
+ workspace_size = ZSTD_DStreamWorkspaceBound(ws);
+ workspace = large_malloc(workspace_size);
+ if (!workspace) {
+ error("Could not allocate workspace");
+ goto exit_2;
+ }
+
+ zstd = ZSTD_initDStream(ws, workspace, workspace_size);
+ if (!zstd) {
+ error("Could not initialize ZSTD");
+ goto exit_3;
+ }
+
+ in.src = inp;
+ in.size = in_len;
+ in.pos = 0;
+ if (posp)
+ *posp = 0;
+
+ for (;;) {
+ if (fill) {
+ in.size = fill(inp, in_len);
+ if (in.size == 0)
+ break;
+ } else if (in.size == in.pos) {
+ break;
+ }
+init: out.dst = outp;
+ out.size = out_len;
+ out.pos = 0;
+ pos = in.pos;
+
+ ret = ZSTD_decompressStream(zstd, &out, &in);
+ if (posp)
+ *posp += in.pos - pos;
+ if (ZSTD_isError(ret)) {
+ error("Decompression failed");
+ ret = -EIO;
+ goto exit_3;
+ }
+
+ if (flush && out.pos) {
+ if (flush(out.dst, out.pos) != out.pos) {
+ ret = -EIO;
+ goto exit_3;
+ }
+ goto init;
+ }
+
+ if (ret == 0) {
+ ret = ZSTD_resetDStream(zstd);
+ if (ZSTD_isError(ret)) {
+ ret = -EIO;
+ goto exit_3;
+ }
+ }
+ if (in.pos < in.size)
+ goto init_out;
+ }
+
+ ret = 0;
+
+exit_3: large_free(workspace);
+exit_2: if (!input)
+ large_free(inp);
+exit_1: if (!output)
+ large_free(outp);
+exit_0: return ret;
+}
+
+#ifdef PREBOOT
+STATIC int INIT __decompress(unsigned char *buf, long in_len,
+ long (*fill)(void*, unsigned long),
+ long (*flush)(void*, unsigned long),
+ unsigned char *output, long out_len,
+ long *posp,
+ void (*error)(char *x)
+ )
+{
+ return unzstd(buf, in_len, fill, flush, output, posp, error);
+}
+#endif
diff --git a/lib/zstd/decompress.c b/lib/zstd/decompress.c
index 269ee9a796c1..6a5e1ce22719 100644
--- a/lib/zstd/decompress.c
+++ b/lib/zstd/decompress.c
@@ -42,9 +42,11 @@
/*-*************************************
* Macros
***************************************/
+#ifndef PREBOOT
#define ZSTD_isError ERR_isError /* for inlining */
#define FSE_isError ERR_isError
#define HUF_isError ERR_isError
+#endif

/*_*******************************************************
* Memory operations
diff --git a/lib/zstd/fse_decompress.c b/lib/zstd/fse_decompress.c
index a84300e5a013..bd4e9c891d96 100644
--- a/lib/zstd/fse_decompress.c
+++ b/lib/zstd/fse_decompress.c
@@ -54,12 +54,13 @@
/* **************************************************************
* Error Management
****************************************************************/
-#define FSE_isError ERR_isError
#define FSE_STATIC_ASSERT(c) \
{ \
enum { FSE_static_assert = 1 / (int)(!!(c)) }; \
} /* use only *after* variable declarations */

+#ifndef PREBOOT
+#define FSE_isError ERR_isError
/* check and forward error code */
#define CHECK_F(f) \
{ \
@@ -67,6 +68,7 @@
if (FSE_isError(e)) \
return e; \
}
+#endif

/* **************************************************************
* Templates
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3fa32f83b2d7..1c2f2dc528dc 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -337,6 +337,9 @@ quiet_cmd_lz4 = LZ4 $@
cmd_lz4 = { cat $(real-prereqs) | lz4c -l -c1 stdin stdout; \
$(size_append); } > $@

+quiet_cmd_zstd = ZSTD $@
+ cmd_zstd = { cat $(real-prereqs) | zstd -19 --zstd=wlog=21; $(size_append); } > $@
+
# U-Boot mkimage
# ---------------------------------------------------------------------------

diff --git a/usr/Kconfig b/usr/Kconfig
index a6b68503d177..892eb15957db 100644
--- a/usr/Kconfig
+++ b/usr/Kconfig
@@ -106,6 +106,15 @@ config RD_LZ4
Support loading of a LZ4 encoded initial ramdisk or cpio buffer
If unsure, say N.

+config RD_ZSTD
+ bool "Support initial ramdisk/ramfs compressed using ZSTD"
+ default y
+ depends on BLK_DEV_INITRD
+ select DECOMPRESS_ZSTD
+ help
+ Support loading of a ZSTD encoded initial ramdisk or cpio buffer
+ If unsure, say N.
+
choice
prompt "Built-in initramfs compression mode"
depends on INITRAMFS_SOURCE!=""
@@ -214,6 +223,19 @@ config INITRAMFS_COMPRESSION_LZ4
If you choose this, keep in mind that most distros don't provide lz4
by default which could cause a build failure.

+config INITRAMFS_COMPRESSION_ZSTD
+ bool "ZSTD"
+ depends on RD_ZSTD
+ help
+ Its compression ratio is roughly 10% worst than xz, but the
+ decompression is 10x faster. Currently, this is one of the optimal
+ algorithms available in the kernel, as there isn't an algorithm,
+ which would provide a better compression ratio and a shorter
+ decompression time.
+
+ If you choose this, keep in mind that you may need to install the zstd
+ tool to be able to compress the initram.
+
endchoice

config INITRAMFS_COMPRESSION
@@ -226,10 +248,12 @@ config INITRAMFS_COMPRESSION
default ".xz" if INITRAMFS_COMPRESSION_XZ
default ".lzo" if INITRAMFS_COMPRESSION_LZO
default ".lz4" if INITRAMFS_COMPRESSION_LZ4
+ default ".zst" if INITRAMFS_COMPRESSION_ZSTD
default ".gz" if RD_GZIP
default ".lz4" if RD_LZ4
default ".lzo" if RD_LZO
default ".xz" if RD_XZ
default ".lzma" if RD_LZMA
default ".bz2" if RD_BZIP2
+ default ".zst" if RD_ZSTD
default ""
--
2.20.1
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