1 files changed, 84 insertions, 0 deletions
diff --git a/lib/decompress.c b/lib/decompress.c
new file mode 100644
index 000000000..ab3fc90ff
--- /dev/null
+++ b/lib/decompress.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * decompress.c
+ *
+ * Detect the decompression method based on magic number
+ */
+
+#include <linux/decompress/generic.h>
+
+#include <linux/decompress/bunzip2.h>
+#include <linux/decompress/unlzma.h>
+#include <linux/decompress/unxz.h>
+#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>
+#include <linux/init.h>
+#include <linux/printk.h>
+
+#ifndef CONFIG_DECOMPRESS_GZIP
+# define gunzip NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_BZIP2
+# define bunzip2 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZMA
+# define unlzma NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_XZ
+# define unxz NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZO
+# define unlzo NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_LZ4
+# define unlz4 NULL
+#endif
+#ifndef CONFIG_DECOMPRESS_ZSTD
+# define unzstd NULL
+#endif
+
+struct compress_format {
+	unsigned char magic[2];
+	const char *name;
+	decompress_fn decompressor;
+};
+
+static const struct compress_format compressed_formats[] __initconst = {
+	{ {0x1f, 0x8b}, "gzip", gunzip },
+	{ {0x1f, 0x9e}, "gzip", gunzip },
+	{ {0x42, 0x5a}, "bzip2", bunzip2 },
+	{ {0x5d, 0x00}, "lzma", unlzma },
+	{ {0xfd, 0x37}, "xz", unxz },
+	{ {0x89, 0x4c}, "lzo", unlzo },
+	{ {0x02, 0x21}, "lz4", unlz4 },
+	{ {0x28, 0xb5}, "zstd", unzstd },
+	{ {0, 0}, NULL, NULL }
+};
+
+decompress_fn __init decompress_method(const unsigned char *inbuf, long len,
+				const char **name)
+{
+	const struct compress_format *cf;
+
+	if (len < 2) {
+		if (name)
+			*name = NULL;
+		return NULL;	/* Need at least this much... */
+	}
+
+	pr_debug("Compressed data magic: %#.2x %#.2x\n", inbuf[0], inbuf[1]);
+
+	for (cf = compressed_formats; cf->name; cf++) {
+		if (!memcmp(inbuf, cf->magic, 2))
+			break;
+
+	}
+	if (name)
+		*name = cf->name;
+	return cf->decompressor;
+}