1 // SPDX-License-Identifier: GPL-2.0
4  * Important notes about in-place decompression
7  * is placed to the end of the output buffer, and the decompressor overwrites
8  * most of the compressed data. There must be enough safety margin to
14  * The worst case for in-place decompression is that the beginning of
15  * the file is compressed extremely well, and the rest of the file is
16  * uncompressible. Thus, we must look for worst-case expansion when the
19  * The structure of the .zst file in case of a compressed kernel is as follows.
20  * Maximum sizes (as bytes) of the fields are in parenthesis.
29  * a 3 bytes. After the block header, there is up to 128 KB of payload.
30  * The maximum uncompressed size of the payload is 128 KB. The minimum
31  * uncompressed size of the payload is never less than the payload size
34  * The assumption, that the uncompressed size of the payload is never
38  * the worst case for this would be tricky. Instead of trying to do that,
40  * of the payload which it is currently reading.
43  *   - 22 bytes for the .zst file format headers;
44  *   - 3 bytes per every 128 KiB of uncompressed size (one block header per
46  *   - 128 KiB (biggest possible zstd block size) to make sure that the
58  * All of the source files we depend on must be #included.
63  * used for kernel decompression, instead of unzstd().
80 /* 128MB is the maximum window size supported by zstd. */
83  * Size of the input and output buffers in multi-call mode.
86  * zstd's window anyway. The larger size speeds up initramfs decompression.
103 		error("ZSTD decompressor ran out of memory");  in handle_zstd_error()
111 		error("ZSTD-compressed data is corrupt");  in handle_zstd_error()
114 		error("ZSTD-compressed data is probably corrupt");  in handle_zstd_error()
117 	return -1;  in handle_zstd_error()
122  * We can allocate less memory (no circular buffer for the sliding window),
136 		error("Out of memory while allocating zstd_dctx");  in decompress_single()
137 		err = -1;  in decompress_single()
138 		goto out;  in decompress_single()
141 	 * Find out how large the frame actually is, there may be junk at  in decompress_single()
142 	 * the end of the frame that zstd_decompress_dctx() can't handle.  in decompress_single()
147 		goto out;  in decompress_single()
153 		goto out;  in decompress_single()
159 out:  in decompress_single()
173 	zstd_out_buffer out;  in __unzstd()  local
189 		out_len = UINTPTR_MAX - (uintptr_t)out_buf;  in __unzstd()
207 			error("Out of memory while allocating input buffer");  in __unzstd()
208 			err = -1;  in __unzstd()
209 			goto out;  in __unzstd()
218 		error("ZSTD-compressed data is truncated");  in __unzstd()
219 		err = -1;  in __unzstd()
220 		goto out;  in __unzstd()
222 	/* Set the first non-empty input buffer. */  in __unzstd()
230 			error("Out of memory while allocating output buffer");  in __unzstd()
231 			err = -1;  in __unzstd()
232 			goto out;  in __unzstd()
238 	out.dst = out_buf;  in __unzstd()
239 	out.pos = 0;  in __unzstd()
240 	out.size = out_len;  in __unzstd()
243 	 * We need to know the window size to allocate the zstd_dstream.  in __unzstd()
245 	 * window. The window size varies from 1 KB to ZSTD_WINDOWSIZE_MAX  in __unzstd()
252 		goto out;  in __unzstd()
254 		error("ZSTD-compressed data has an incomplete frame header");  in __unzstd()
255 		err = -1;  in __unzstd()
256 		goto out;  in __unzstd()
259 		error("ZSTD-compressed data has too large a window size");  in __unzstd()
260 		err = -1;  in __unzstd()
261 		goto out;  in __unzstd()
272 		error("Out of memory while allocating ZSTD_DStream");  in __unzstd()
273 		err = -1;  in __unzstd()
274 		goto out;  in __unzstd()
293 			in_len = fill ? fill(in_buf, ZSTD_IOBUF_SIZE) : -1;  in __unzstd()
295 				error("ZSTD-compressed data is truncated");  in __unzstd()
296 				err = -1;  in __unzstd()
297 				goto out;  in __unzstd()
303 		ret = zstd_decompress_stream(dstream, &out, &in);  in __unzstd()
306 			goto out;  in __unzstd()
307 		/* Flush all of the data produced if using flush(). */  in __unzstd()
308 		if (flush != NULL && out.pos > 0) {  in __unzstd()
309 			if (out.pos != flush(out.dst, out.pos)) {  in __unzstd()
311 				err = -1;  in __unzstd()
312 				goto out;  in __unzstd()
314 			out.pos = 0;  in __unzstd()
322 out:  in __unzstd()