1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * XIP kernel .data segment decompressor 4 * 5 * Created by: Nicolas Pitre, August 2017 6 * Copyright: (C) 2017 Linaro Limited 7 */ 8 9 #include <linux/init.h> 10 #include <linux/zutil.h> 11 #include "head.h" 12 13 /* for struct inflate_state */ 14 #include "../../../lib/zlib_inflate/inftrees.h" 15 #include "../../../lib/zlib_inflate/inflate.h" 16 #include "../../../lib/zlib_inflate/infutil.h" 17 18 /* 19 * This code is called very early during the boot process to decompress 20 * the .data segment stored compressed in ROM. Therefore none of the global 21 * variables are valid yet, hence no kernel services such as memory 22 * allocation is available. Everything must be allocated on the stack and 23 * we must avoid any global data access. We use a temporary stack located 24 * in the .bss area. The linker script makes sure the .bss is big enough 25 * to hold our stack frame plus some room for called functions. 26 * 27 * We mimic the code in lib/decompress_inflate.c to use the smallest work 28 * area possible. And because everything is statically allocated on the 29 * stack then there is no need to clean up before returning. 30 */ 31 32 int __init __inflate_kernel_data(void) 33 { 34 struct z_stream_s stream, *strm = &stream; 35 struct inflate_state state; 36 char *in = __data_loc; 37 int rc; 38 39 /* Check and skip gzip header (assume no filename) */ 40 if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3) 41 return -1; 42 in += 10; 43 44 strm->workspace = &state; 45 strm->next_in = in; 46 strm->avail_in = _edata_loc - __data_loc; /* upper bound */ 47 strm->next_out = _sdata; 48 strm->avail_out = _edata_loc - __data_loc; 49 zlib_inflateInit2(strm, -MAX_WBITS); 50 WS(strm)->inflate_state.wsize = 0; 51 WS(strm)->inflate_state.window = NULL; 52 rc = zlib_inflate(strm, Z_FINISH); 53 if (rc == Z_OK || rc == Z_STREAM_END) 54 rc = strm->avail_out; /* should be 0 */ 55 return rc; 56 } 57