new file mode 100644
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef LINUX_DECOMPRESS_UNZSTD_H
+#define LINUX_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_fn)(char *x));
+#endif
@@ -134,13 +134,16 @@ 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
@@ -219,6 +222,15 @@ 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
+ ZSTD is a compression algorithm targeting intermediate compression
+ with fast decompression speed. It will compress better than GZIP and
+ decompress around the same speed as LZO, but slower than LZ4. You
+ will need at least 192 KB RAM or more for booting.
+
config KERNEL_UNCOMPRESSED
bool "None"
depends on HAVE_KERNEL_UNCOMPRESSED
@@ -304,6 +304,10 @@ config DECOMPRESS_LZ4
select LZ4_DECOMPRESS
tristate
+config DECOMPRESS_ZSTD
+ select ZSTD_DECOMPRESS
+ tristate
+
#
# Generic allocator support is selected if needed
#
@@ -139,6 +139,7 @@ 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
@@ -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 }
};
new file mode 100644
@@ -0,0 +1,341 @@
+/*
+ * Copyright (C) 2017 Facebook
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/*
+ * Important notes about in-place decompression
+ *
+ * At least on x86, the kernel is decompressed in place: the compressed data
+ * is placed to the end of the output buffer, and the decompressor overwrites
+ * most of the compressed data. There must be enough safety margin to
+ * guarantee that the write position is always behind the read position.
+ *
+ * The safety margin for ZSTD with a 128 KB block size is calculated below.
+ * Note that the margin with ZSTD is bigger than with GZIP or XZ!
+ *
+ * The worst case for in-place decompression is that the beginning of
+ * the file is compressed extremely well, and the rest of the file is
+ * uncompressible. Thus, we must look for worst-case expansion when the
+ * compressor is encoding uncompressible data.
+ *
+ * The structure of the .zst file in case of a compresed kernel is as follows.
+ * Maximum sizes (as bytes) of the fields are in parenthesis.
+ *
+ * Frame Header: (18)
+ * Blocks: (N)
+ * Checksum: (4)
+ *
+ * The frame header and checksum overhead is at most 22 bytes.
+ *
+ * ZSTD stores the data in blocks. Each block has a header whose size is
+ * a 3 bytes. After the block header, there is up to 128 KB of payload.
+ * The maximum uncompressed size of the payload is 128 KB. The minimum
+ * uncompressed size of the payload is never less than the payload size
+ * (excluding the block header).
+ *
+ * The assumption, that the uncompressed size of the payload is never
+ * smaller than the payload itself, is valid only when talking about
+ * the payload as a whole. It is possible that the payload has parts where
+ * the decompressor consumes more input than it produces output. Calculating
+ * the worst case for this would be tricky. Instead of trying to do that,
+ * let's simply make sure that the decompressor never overwrites any bytes
+ * of the payload which it is currently reading.
+ *
+ * Now we have enough information to calculate the safety margin. We need
+ * - 22 bytes for the .zst file format headers;
+ * - 3 bytes per every 128 KiB of uncompressed size (one block header per
+ * block); and
+ * - 128 KiB (biggest possible zstd block size) to make sure that the
+ * decompressor never overwrites anything from the block it is currently
+ * reading.
+ *
+ * We get the following formula:
+ *
+ * safety_margin = 22 + uncompressed_size * 3 / 131072 + 131072
+ * <= 22 + (uncompressed_size >> 15) + 131072
+ */
+
+#ifdef STATIC
+ /* Preboot environments #include "path/to/decompress_unzstd.c".
+ * All of the source files we depend on must be #included.
+ * zstd's only source dependeny is xxhash, which has no source
+ * dependencies.
+ *
+ * zstd and xxhash both avoid declaring themselves as modules
+ * when PREBOOT is defined.
+ */
+# define PREBOOT
+# include "xxhash.c"
+# include "zstd/entropy_common.c"
+# include "zstd/fse_decompress.c"
+# include "zstd/huf_decompress.c"
+# include "zstd/zstd_common.c"
+# include "zstd/decompress.c"
+#endif
+
+#include <linux/decompress/mm.h>
+#include <linux/kernel.h>
+#include <linux/zstd.h>
+
+/* 8 MB maximum window size */
+#define ZSTD_WINDOWSIZE_MAX (1 << 23)
+/* Size of the input and output buffers in multi-call mdoe */
+#define ZSTD_IOBUF_SIZE 4096
+
+static int INIT handle_zstd_error(size_t ret, void (*error)(char *x))
+{
+ const int err = ZSTD_getErrorCode(ret);
+
+ if (!ZSTD_isError(ret))
+ return 0;
+
+ switch (err) {
+ case ZSTD_error_memory_allocation:
+ error("ZSTD decompressor ran out of memory");
+ break;
+ case ZSTD_error_prefix_unknown:
+ error("Input is not in the ZSTD format (wrong magic bytes)");
+ break;
+ case ZSTD_error_dstSize_tooSmall:
+ case ZSTD_error_corruption_detected:
+ case ZSTD_error_checksum_wrong:
+ error("ZSTD-compressed data is corrupt");
+ break;
+ default:
+ error("ZSTD-compressed data is probably corrupt");
+ break;
+ }
+ return -1;
+}
+
+/* Handle the case where we have the entire input and output in one segment.
+ * We can allocate less memory (no circular buffer for the sliding window),
+ * and avoid some memcpy() calls.
+ */
+static int INIT decompress_single(const u8 *in_buf, long in_len, u8 *out_buf,
+ long out_len, long *in_pos,
+ void (*error)(char *x))
+{
+ const size_t wksp_size = ZSTD_DCtxWorkspaceBound();
+ void *wksp = large_malloc(wksp_size);
+ ZSTD_DCtx *dctx = ZSTD_initDCtx(wksp, wksp_size);
+ int err;
+ size_t ret;
+
+ if (dctx == NULL) {
+ error("Out of memory while allocating ZSTD_DCtx");
+ err = -1;
+ goto out;
+ }
+ /* Find out how large the frame actually is, there may be junk at
+ * the end of the frame that ZSTD_decompressDCtx() can't handle.
+ */
+ ret = ZSTD_findFrameCompressedSize(in_buf, in_len);
+ err = handle_zstd_error(ret, error);
+ if (err)
+ goto out;
+ in_len = (long)ret;
+
+ ret = ZSTD_decompressDCtx(dctx, out_buf, out_len, in_buf, in_len);
+ err = handle_zstd_error(ret, error);
+ if (err)
+ goto out;
+
+ if (in_pos != NULL)
+ *in_pos = in_len;
+
+ err = 0;
+out:
+ if (wksp != NULL)
+ large_free(wksp);
+ return err;
+}
+
+static int INIT __unzstd(unsigned char *in_buf, long in_len,
+ long (*fill)(void*, unsigned long),
+ long (*flush)(void*, unsigned long),
+ unsigned char *out_buf, long out_len,
+ long *in_pos,
+ void (*error)(char *x))
+{
+ ZSTD_inBuffer in;
+ ZSTD_outBuffer out;
+ ZSTD_frameParams params;
+ void *in_allocated = NULL;
+ void *out_allocated = NULL;
+ void *wksp = NULL;
+ size_t wksp_size;
+ ZSTD_DStream *dstream;
+ int err;
+ size_t ret;
+
+ if (out_len == 0)
+ out_len = LONG_MAX; /* no limit */
+
+ if (fill == NULL && flush == NULL)
+ /* We can decompress faster and with less memory when we have a
+ * single chunk.
+ */
+ return decompress_single(in_buf, in_len, out_buf, out_len,
+ in_pos, error);
+
+ /* If in_buf is not provided, we must be using fill(), so allocate
+ * a large enough buffer. If it is provided, it must be at least
+ * ZSTD_IOBUF_SIZE large.
+ */
+ if (in_buf == NULL) {
+ in_allocated = malloc(ZSTD_IOBUF_SIZE);
+ if (in_allocated == NULL) {
+ error("Out of memory while allocating input buffer");
+ err = -1;
+ goto out;
+ }
+ in_buf = in_allocated;
+ in_len = 0;
+ }
+ /* Read the first chunk, since we need to decode the frame header */
+ if (fill != NULL)
+ in_len = fill(in_buf, ZSTD_IOBUF_SIZE);
+ if (in_len < 0) {
+ error("ZSTD-compressed data is truncated");
+ err = -1;
+ goto out;
+ }
+ /* Set the first non-empty input buffer */
+ in.src = in_buf;
+ in.pos = 0;
+ in.size = in_len;
+ /* Allocate the output buffer if we are using flush(). */
+ if (flush != NULL) {
+ out_allocated = malloc(ZSTD_IOBUF_SIZE);
+ if (out_allocated == NULL) {
+ error("Out of memory while allocating output buffer");
+ err = -1;
+ goto out;
+ }
+ out_buf = out_allocated;
+ out_len = ZSTD_IOBUF_SIZE;
+ }
+ /* Set the output buffer */
+ out.dst = out_buf;
+ out.pos = 0;
+ out.size = out_len;
+
+ /* We need to know the window size to allocate the ZSTD_DStream.
+ * Since we are streaming, we need to allocate a buffer for the sliding
+ * window. The window size varies from 1 KB to ZSTD_WINDOWSIZE_MAX
+ * (8 MB), so it is important to use the actual value so as not to
+ * waste memory when it is smaller.
+ */
+ ret = ZSTD_getFrameParams(¶ms, in.src, in.size);
+ err = handle_zstd_error(ret, error);
+ if (err)
+ goto out;
+ if (ret != 0) {
+ error("ZSTD-compressed data has an incomplete frame header");
+ err = -1;
+ goto out;
+ }
+ if (params.windowSize > ZSTD_WINDOWSIZE_MAX) {
+ error("ZSTD-compressed data has too large a window size");
+ err = -1;
+ goto out;
+ }
+
+ /* Allocate the ZSTD_DStream now that we know how much memory is
+ * required.
+ */
+ wksp_size = ZSTD_DStreamWorkspaceBound(params.windowSize);
+ wksp = large_malloc(wksp_size);
+ dstream = ZSTD_initDStream(params.windowSize, wksp, wksp_size);
+ if (dstream == NULL) {
+ error("Out of memory while allocating ZSTD_DStream");
+ err = -1;
+ goto out;
+ }
+ /* Decompression loop:
+ * Read more data if necessary (error if no more data can be read).
+ * Call the decompression function, which returns 0 when finished.
+ * Flush any data produced if using flush().
+ */
+ if (in_pos != NULL)
+ *in_pos = 0;
+ do {
+ /* If we need to reload data, either we have fill() and can
+ * try to get more data, or we don't and the input is truncated.
+ */
+ if (in.pos == in.size) {
+ if (in_pos != NULL)
+ *in_pos += in.pos;
+ in_len = fill ? fill(in_buf, ZSTD_IOBUF_SIZE) : -1;
+ if (in_len < 0) {
+ error("ZSTD-compressed data is truncated");
+ err = -1;
+ goto out;
+ }
+ in.pos = 0;
+ in.size = in_len;
+ }
+ /* Returns zero when the frame is complete */
+ ret = ZSTD_decompressStream(dstream, &out, &in);
+ err = handle_zstd_error(ret, error);
+ if (err)
+ goto out;
+ /* Flush all of the data produced if using flush() */
+ if (flush != NULL && out.pos > 0) {
+ if (out.pos != flush(out.dst, out.pos)) {
+ error("Failed to flush()");
+ err = -1;
+ goto out;
+ }
+ out.pos = 0;
+ }
+ } while (ret != 0);
+
+ if (in_pos != NULL)
+ *in_pos += in.pos;
+
+ err = 0;
+out:
+ if (in_allocated != NULL)
+ free(in_allocated);
+ if (out_allocated != NULL)
+ free(out_allocated);
+ if (wksp != NULL)
+ large_free(wksp);
+ return err;
+}
+
+#ifndef PREBOOT
+STATIC int INIT unzstd(unsigned char *buf, long len,
+ long (*fill)(void*, unsigned long),
+ long (*flush)(void*, unsigned long),
+ unsigned char *out_buf,
+ long *pos,
+ void (*error)(char *x))
+{
+ return __unzstd(buf, len, fill, flush, out_buf, 0, pos, error);
+}
+#else
+STATIC int INIT __decompress(unsigned char *buf, long len,
+ long (*fill)(void*, unsigned long),
+ long (*flush)(void*, unsigned long),
+ unsigned char *out_buf, long out_len,
+ long *pos,
+ void (*error)(char *x))
+{
+ return __unzstd(buf, len, fill, flush, out_buf, out_len, pos, error);
+}
+#endif
@@ -80,13 +80,11 @@ void xxh32_copy_state(struct xxh32_state *dst, const struct xxh32_state *src)
{
memcpy(dst, src, sizeof(*dst));
}
-EXPORT_SYMBOL(xxh32_copy_state);
void xxh64_copy_state(struct xxh64_state *dst, const struct xxh64_state *src)
{
memcpy(dst, src, sizeof(*dst));
}
-EXPORT_SYMBOL(xxh64_copy_state);
/*-***************************
* Simple Hash Functions
@@ -151,7 +149,6 @@ uint32_t xxh32(const void *input, const size_t len, const uint32_t seed)
return h32;
}
-EXPORT_SYMBOL(xxh32);
static uint64_t xxh64_round(uint64_t acc, const uint64_t input)
{
@@ -234,7 +231,6 @@ uint64_t xxh64(const void *input, const size_t len, const uint64_t seed)
return h64;
}
-EXPORT_SYMBOL(xxh64);
/*-**************************************************
* Advanced Hash Functions
@@ -251,7 +247,6 @@ void xxh32_reset(struct xxh32_state *statePtr, const uint32_t seed)
state.v4 = seed - PRIME32_1;
memcpy(statePtr, &state, sizeof(state));
}
-EXPORT_SYMBOL(xxh32_reset);
void xxh64_reset(struct xxh64_state *statePtr, const uint64_t seed)
{
@@ -265,7 +260,6 @@ void xxh64_reset(struct xxh64_state *statePtr, const uint64_t seed)
state.v4 = seed - PRIME64_1;
memcpy(statePtr, &state, sizeof(state));
}
-EXPORT_SYMBOL(xxh64_reset);
int xxh32_update(struct xxh32_state *state, const void *input, const size_t len)
{
@@ -334,7 +328,6 @@ int xxh32_update(struct xxh32_state *state, const void *input, const size_t len)
return 0;
}
-EXPORT_SYMBOL(xxh32_update);
uint32_t xxh32_digest(const struct xxh32_state *state)
{
@@ -372,7 +365,6 @@ uint32_t xxh32_digest(const struct xxh32_state *state)
return h32;
}
-EXPORT_SYMBOL(xxh32_digest);
int xxh64_update(struct xxh64_state *state, const void *input, const size_t len)
{
@@ -439,7 +431,6 @@ int xxh64_update(struct xxh64_state *state, const void *input, const size_t len)
return 0;
}
-EXPORT_SYMBOL(xxh64_update);
uint64_t xxh64_digest(const struct xxh64_state *state)
{
@@ -494,7 +485,19 @@ uint64_t xxh64_digest(const struct xxh64_state *state)
return h64;
}
+
+#ifndef PREBOOT
+EXPORT_SYMBOL(xxh32_copy_state);
+EXPORT_SYMBOL(xxh64_copy_state);
+EXPORT_SYMBOL(xxh32);
+EXPORT_SYMBOL(xxh64);
+EXPORT_SYMBOL(xxh32_reset);
+EXPORT_SYMBOL(xxh64_reset);
+EXPORT_SYMBOL(xxh32_update);
+EXPORT_SYMBOL(xxh32_digest);
+EXPORT_SYMBOL(xxh64_update);
EXPORT_SYMBOL(xxh64_digest);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("xxHash");
+#endif
@@ -2487,6 +2487,7 @@ size_t ZSTD_decompressStream(ZSTD_DStream *zds, ZSTD_outBuffer *output, ZSTD_inB
}
}
+#ifndef PREBOOT
EXPORT_SYMBOL(ZSTD_DCtxWorkspaceBound);
EXPORT_SYMBOL(ZSTD_initDCtx);
EXPORT_SYMBOL(ZSTD_decompressDCtx);
@@ -2526,3 +2527,4 @@ EXPORT_SYMBOL(ZSTD_insertBlock);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("Zstd Decompressor");
+#endif
@@ -47,6 +47,7 @@
****************************************************************/
#include "bitstream.h"
#include "fse.h"
+#include "zstd_internal.h"
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/string.h> /* memcpy, memset */
@@ -60,14 +61,6 @@
enum { FSE_static_assert = 1 / (int)(!!(c)) }; \
} /* use only *after* variable declarations */
-/* check and forward error code */
-#define CHECK_F(f) \
- { \
- size_t const e = f; \
- if (FSE_isError(e)) \
- return e; \
- }
-
/* **************************************************************
* Templates
****************************************************************/
@@ -127,7 +127,13 @@ static const U32 OF_defaultNormLog = OF_DEFAULTNORMLOG;
* Shared functions to include for inlining
*********************************************/
ZSTD_STATIC void ZSTD_copy8(void *dst, const void *src) {
- memcpy(dst, src, 8);
+ /* zstd relies heavily on gcc being able to analyze and inline this
+ * memcpy() call, since it is called in a tight loop. Preboot mode
+ * is compiled in freestanding mode, which stops gcc from analyzing
+ * memcpy(). Use __builtin_memcpy() to tell gcc to analyze this as a
+ * regular memcpy().
+ */
+ __builtin_memcpy(dst, src, 8);
}
/*! ZSTD_wildcopy() :
* custom version of memcpy(), can copy up to 7 bytes too many (8 bytes if length==0) */
@@ -137,6 +143,7 @@ ZSTD_STATIC void ZSTD_wildcopy(void *dst, const void *src, ptrdiff_t length)
const BYTE* ip = (const BYTE*)src;
BYTE* op = (BYTE*)dst;
BYTE* const oend = op + length;
+#if GCC_VERSION >= 70000 && GCC_VERSION < 70200
/* Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388.
* Avoid the bad case where the loop only runs once by handling the
* special case separately. This doesn't trigger the bug because it
@@ -144,6 +151,7 @@ ZSTD_STATIC void ZSTD_wildcopy(void *dst, const void *src, ptrdiff_t length)
*/
if (length <= 8)
return ZSTD_copy8(dst, src);
+#endif
do {
ZSTD_copy8(op, ip);
op += 8;
@@ -389,6 +389,21 @@ cmd_xzmisc = (cat $(filter-out FORCE,$^) | \
xz --check=crc32 --lzma2=dict=1MiB) > $@ || \
(rm -f $@ ; false)
+# ZSTD
+# ---------------------------------------------------------------------------
+# Appends the uncompressed size of the data using size_append. The .zst
+# format has the size information available at the beginning of the file too,
+# but it's in a more complex format and it's good to avoid changing the part
+# of the boot code that reads the uncompressed size.
+# Note that the bytes added by size_append will make the zstd tool think that
+# the file is corrupt. This is expected.
+
+quiet_cmd_zstd = ZSTD $@
+cmd_zstd = (cat $(filter-out FORCE,$^) | \
+ zstd -19 && \
+ $(call size_append, $(filter-out FORCE,$^))) > $@ || \
+ (rm -f $@ ; false)
+
# ASM offsets
# ---------------------------------------------------------------------------
@@ -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 +223,17 @@ 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
+ ZSTD is a compression algorithm targeting intermediate compression
+ with fast decompression speed. It will compress better than GZIP and
+ decompress around the same speed as LZO, but slower than LZ4.
+
+ 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 +246,12 @@ 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 ""