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Subject[PATCH v2] zstd compressed firmware loading
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Now with zstd compressed kernel & initrd upstream, we would rather
compress everything with one type of compressor, so I added support
for zstd compressed firmware loading, too.

Tested on x86-64, sparc64 and mips64.

Signed-off-by: René Rebe <rene@exactcode.de>

diff --git a/drivers/base/firmware_loader/Kconfig b/drivers/base/firmware_loader/Kconfig
index 5b24f3959255..30d440bec257 100644
--- a/drivers/base/firmware_loader/Kconfig
+++ b/drivers/base/firmware_loader/Kconfig
@@ -169,6 +169,16 @@ config FW_LOADER_COMPRESS
be compressed with either none or crc32 integrity check type (pass
"-C crc32" option to xz command).

+config FW_LOADER_COMPRESS_ZSTD
+ bool "Enable Zstd compressed firmware support"
+ select FW_LOADER_PAGED_BUF
+ select ZSTD_DECOMPRESS
+ help
+ This option enables the support for loading Zstd compressed firmware
+ files. The caller of firmware API receives the decompressed file
+ content. The compressed file is loaded as a fallback, only after
+ loading the raw file failed at first.
+
config FW_CACHE
bool "Enable firmware caching during suspend"
depends on PM_SLEEP
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 9da0c9d5f538..cd3bd6f9a64b 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -33,7 +33,9 @@
#include <linux/syscore_ops.h>
#include <linux/reboot.h>
#include <linux/security.h>
+#include <linux/decompress/mm.h>
#include <linux/xz.h>
+#include <linux/zstd.h>

#include <generated/utsrelease.h>

@@ -435,6 +437,185 @@ static int fw_decompress_xz(struct device *dev, struct fw_priv *fw_priv,
}
#endif /* CONFIG_FW_LOADER_COMPRESS */

+/*
+ * Zstd-compressed firmware support
+ */
+#ifdef CONFIG_FW_LOADER_COMPRESS_ZSTD
+/* show an error and return the standard error code */
+static int handle_zstd_error(size_t ret)
+{
+ const int err = ZSTD_getErrorCode(ret);
+
+ if (!ZSTD_isError(ret))
+ return 0;
+
+ switch (err) {
+ case ZSTD_error_memory_allocation:
+ printk("ZSTD decompressor ran out of memory");
+ break;
+ case ZSTD_error_prefix_unknown:
+ printk("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:
+ printk("ZSTD-compressed data is corrupt");
+ break;
+ default:
+ printk("ZSTD-compressed data is probably corrupt");
+ break;
+ }
+ return -1;
+}
+
+/* single-shot decompression onto the pre-allocated buffer */
+static int fw_decompress_zstd_single(struct device *dev, struct fw_priv *fw_priv,
+ size_t in_size, const void *in_buffer)
+{
+ 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) {
+ dev_warn(dev, "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_buffer, in_size);
+ err = handle_zstd_error(ret);
+ if (err)
+ goto out;
+ in_size = (long)ret;
+
+ ret = ZSTD_decompressDCtx(dctx, fw_priv->data, fw_priv->allocated_size, in_buffer, in_size);
+ err = handle_zstd_error(ret);
+ if (err)
+ goto out;
+
+ fw_priv->size = ret;
+
+out:
+ if (wksp != NULL)
+ large_free(wksp);
+ return err;
+}
+
+/* decompression on paged buffer and map it */
+static int fw_decompress_zstd_pages(struct device *dev, struct fw_priv *fw_priv,
+ size_t in_size, const void *in_buffer)
+{
+ ZSTD_inBuffer in;
+ ZSTD_outBuffer out;
+ ZSTD_frameParams params;
+ void *wksp = NULL;
+ size_t wksp_size;
+ ZSTD_DStream *dstream;
+ int err = 0;
+ size_t ret;
+
+ struct page *page;
+
+ fw_priv->is_paged_buf = true;
+ fw_priv->size = 0;
+
+ /* Set the first non-empty input buffer. */
+ in.src = in_buffer;
+ in.pos = 0;
+ in.size = in_size;
+
+ /*
+ * 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(&params, in.src, in.size);
+ err = handle_zstd_error(ret);
+ if (err)
+ goto out;
+ if (ret != 0) {
+ printk("ZSTD-compressed data has an incomplete frame header");
+ err = -1;
+ goto out;
+ }
+ if (params.windowSize > (1 << ZSTD_WINDOWLOG_MAX)) {
+ printk("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) {
+ printk("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().
+ */
+ do {
+ /* If we need to reload data the input is truncated. */
+ if (in.pos == in.size) {
+ printk("ZSTD-compressed data is truncated");
+ err = -1;
+ goto out;
+ }
+
+ /* Allocate the output buffer */
+ if (fw_grow_paged_buf(fw_priv, fw_priv->nr_pages + 1)) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ /* Decompress into the newly allocated page */
+ page = fw_priv->pages[fw_priv->nr_pages - 1];
+ out.dst = kmap(page);
+ out.pos = 0;
+ out.size = PAGE_SIZE;
+
+ /* Returns zero when the frame is complete. */
+ ret = ZSTD_decompressStream(dstream, &out, &in);
+ kunmap(page);
+ err = handle_zstd_error(ret);
+ if (err)
+ goto out;
+ fw_priv->size += out.pos;
+ } while (ret != 0);
+
+ err = fw_map_paged_buf(fw_priv);
+out:
+ if (wksp != NULL)
+ large_free(wksp);
+ return err;
+}
+
+static int fw_decompress_zstd(struct device *dev, struct fw_priv *fw_priv,
+ size_t in_size, const void *in_buffer)
+{
+ /* if the buffer is pre-allocated, we can perform in single-shot mode */
+ if (fw_priv->data)
+ return fw_decompress_zstd_single(dev, fw_priv, in_size, in_buffer);
+ else
+ return fw_decompress_zstd_pages(dev, fw_priv, in_size, in_buffer);
+}
+#endif /* CONFIG_FW_LOADER_COMPRESS_ZSTD */
+
/* direct firmware loading support */
static char fw_path_para[256];
static const char * const fw_path[] = {
@@ -773,6 +954,11 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
ret = fw_get_filesystem_firmware(device, fw->priv, ".xz",
fw_decompress_xz);
#endif
+#ifdef CONFIG_FW_LOADER_COMPRESS_ZSTD
+ if (ret == -ENOENT)
+ ret = fw_get_filesystem_firmware(device, fw->priv, ".zst",
+ fw_decompress_zstd);
+#endif

if (ret == -ENOENT)
ret = firmware_fallback_platform(fw->priv, opt_flags);

--
René Rebe, ExactCODE GmbH, Lietzenburger Str. 42, DE-10789 Berlin
https://exactcode.com | https://t2sde.org | https://rene.rebe.de
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