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SubjectRe: [PATCH] module/decompress: Support zstd in-kernel decompression
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Reviewed-by: Piotr Gorski <lucjan.lucjanov@gmail.com>

> Add support for zstd compressed modules to the in-kernel decompression
> code. This allows zstd compressed modules to be decompressed by the
> kernel, similar to the existing support for gzip and xz compressed
> modules.
>
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: Piotr Gorski <lucjan.lucjanov@gmail.com>
> Cc: Nick Terrell <terrelln@fb.com>
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
> kernel/module/Kconfig | 3 +-
> kernel/module/decompress.c | 92 +++++++++++++++++++++++++++++++++++++-
> 2 files changed, 92 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
> index 26ea5d04f56c..424b3bc58f3f 100644
> --- a/kernel/module/Kconfig
> +++ b/kernel/module/Kconfig
> @@ -221,9 +221,10 @@ endchoice
>
> config MODULE_DECOMPRESS
> bool "Support in-kernel module decompression"
> - depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ
> + depends on MODULE_COMPRESS_GZIP || MODULE_COMPRESS_XZ || MODULE_COMPRESS_ZSTD
> select ZLIB_INFLATE if MODULE_COMPRESS_GZIP
> select XZ_DEC if MODULE_COMPRESS_XZ
> + select ZSTD_DECOMPRESS if MODULE_COMPRESS_ZSTD
> help
>
> Support for decompressing kernel modules by the kernel itself
> diff --git a/kernel/module/decompress.c b/kernel/module/decompress.c
> index c033572d83f0..44f14643d014 100644
> --- a/kernel/module/decompress.c
> +++ b/kernel/module/decompress.c
> @@ -50,7 +50,7 @@ static struct page *module_get_next_page(struct load_info *info)
> return page;
> }
>
> -#ifdef CONFIG_MODULE_COMPRESS_GZIP
> +#if defined(CONFIG_MODULE_COMPRESS_GZIP)
> #include <linux/zlib.h>
> #define MODULE_COMPRESSION gzip
> #define MODULE_DECOMPRESS_FN module_gzip_decompress
> @@ -141,7 +141,7 @@ static ssize_t module_gzip_decompress(struct load_info *info,
> kfree(s.workspace);
> return retval;
> }
> -#elif CONFIG_MODULE_COMPRESS_XZ
> +#elif defined(CONFIG_MODULE_COMPRESS_XZ)
> #include <linux/xz.h>
> #define MODULE_COMPRESSION xz
> #define MODULE_DECOMPRESS_FN module_xz_decompress
> @@ -199,6 +199,94 @@ static ssize_t module_xz_decompress(struct load_info *info,
> xz_dec_end(xz_dec);
> return retval;
> }
> +#elif defined(CONFIG_MODULE_COMPRESS_ZSTD)
> +#include <linux/zstd.h>
> +#define MODULE_COMPRESSION zstd
> +#define MODULE_DECOMPRESS_FN module_zstd_decompress
> +
> +static ssize_t module_zstd_decompress(struct load_info *info,
> + const void *buf, size_t size)
> +{
> + static const u8 signature[] = { 0x28, 0xb5, 0x2f, 0xfd };
> + ZSTD_outBuffer zstd_dec;
> + ZSTD_inBuffer zstd_buf;
> + zstd_frame_header header;
> + size_t wksp_size;
> + void *wksp = NULL;
> + ZSTD_DStream *dstream;
> + size_t ret;
> + size_t new_size = 0;
> + int retval;
> +
> + if (size < sizeof(signature) ||
> + memcmp(buf, signature, sizeof(signature))) {
> + pr_err("not a zstd compressed module\n");
> + return -EINVAL;
> + }
> +
> + zstd_buf.src = buf;
> + zstd_buf.pos = 0;
> + zstd_buf.size = size;
> +
> + ret = zstd_get_frame_header(&header, zstd_buf.src, zstd_buf.size);
> + if (ret != 0) {
> + pr_err("ZSTD-compressed data has an incomplete frame header\n");
> + retval = -EINVAL;
> + goto out;
> + }
> + if (header.windowSize > (1 << ZSTD_WINDOWLOG_MAX)) {
> + pr_err("ZSTD-compressed data has too large a window size\n");
> + retval = -EINVAL;
> + goto out;
> + }
> +
> + wksp_size = zstd_dstream_workspace_bound(header.windowSize);
> + wksp = kmalloc(wksp_size, GFP_KERNEL);
> + if (!wksp) {
> + retval = -ENOMEM;
> + goto out;
> + }
> +
> + dstream = zstd_init_dstream(header.windowSize, wksp, wksp_size);
> + if (!dstream) {
> + pr_err("Can't initialize ZSTD stream\n");
> + retval = -ENOMEM;
> + goto out;
> + }
> +
> + do {
> + struct page *page = module_get_next_page(info);
> +
> + if (!IS_ERR(page)) {
> + retval = PTR_ERR(page);
> + goto out;
> + }
> +
> + zstd_dec.dst = kmap_local_page(page);
> + zstd_dec.pos = 0;
> + zstd_dec.size = PAGE_SIZE;
> +
> + ret = zstd_decompress_stream(dstream, &zstd_dec, &zstd_buf);
> + kunmap(page);
> + retval = zstd_get_error_code(ret);
> + if (retval)
> + break;
> +
> + new_size += zstd_dec.pos;
> + } while (zstd_dec.pos == PAGE_SIZE && ret != 0);
> +
> + if (retval) {
> + pr_err("ZSTD-decompression failed with status %d\n", retval);
> + retval = -EINVAL;
> + goto out;
> + }
> +
> + retval = new_size;
> +
> + out:
> + kfree(wksp);
> + return retval;
> +}
> #else
> #error "Unexpected configuration for CONFIG_MODULE_DECOMPRESS"
> #endif
>
> base-commit: 76dcd734eca23168cb008912c0f69ff408905235

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