linux/lib/decompress_unxz.c

2  * Wrapper for decompressing XZ-compressed kernel, initramfs, and initrd
11  * Important notes about in-place decompression
21  * The worst case for in-place decompression is that the beginning of
23  * incompressible. Thus, we must look for worst-case expansion when the
30  *    Block Header:
31  *      Block Header (8-12)
33  *      Block Padding (0-3)
35  *    Index (8-20)
38  * Normally there is exactly one Block, but let's assume that there are
39  * 2-4 Blocks just in case. Because Stream Header and also Block Header
40  * of the first Block don't make the decompressor produce any uncompressed
41  * data, we can ignore them from our calculations. Block Headers of possible
74  *   - 128 bytes for the .xz file format headers;
75  *   - 8 bytes per every 32 KiB of uncompressed size (one LZMA2 chunk header
77  *   - 64 KiB (biggest possible LZMA2 chunk payload size) to make sure that
91  * Thus, when updating Deflate-only in-place kernel decompressor to
98  * decompression (pre-boot code). <linux/decompress/mm.h> will define
152  * when XZ_DYNALLOC is used, but the pre-boot free() doesn't support it.
165  * FIXME: Not all basic memory functions are provided in architecture-specific
170  * is fast enough. memcpy/memmove speed matters in multi-call mode, but
171  * the kernel image is decompressed in single-call mode, in which only
217 		while (i-- > 0)  in memmove()
242 /* Size of the input and output buffers in multi-call mode */
248  * This wrapper will automatically choose single-call or multi-call mode
249  * of the native XZ decoder API. The single-call mode can be used only when
274 		s = xz_dec_init(XZ_DYNALLOC, (uint32_t)-1);  in unxz()
281 		b.out_size = (size_t)-1;  in unxz()
358 		/* This can occur only in multi-call mode. */  in unxz()
373 		error("XZ-compressed data is corrupt");  in unxz()
381 	return -1;  in unxz()
392 	return -1;  in unxz()
396  * This macro is used by architecture-specific files to decompress