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 12 /* for struct inflate_state */ 13 #include "../../../lib/zlib_inflate/inftrees.h" 14 #include "../../../lib/zlib_inflate/inflate.h" 15 #include "../../../lib/zlib_inflate/infutil.h" 16 17 extern char __data_loc[]; 18 extern char _edata_loc[]; 19 extern char _sdata[]; 20 21 /* 22 * This code is called very early during the boot process to decompress 23 * the .data segment stored compressed in ROM. Therefore none of the global 24 * variables are valid yet, hence no kernel services such as memory 25 * allocation is available. Everything must be allocated on the stack and 26 * we must avoid any global data access. We use a temporary stack located 27 * in the .bss area. The linker script makes sure the .bss is big enough 28 * to hold our stack frame plus some room for called functions. 29 * 30 * We mimic the code in lib/decompress_inflate.c to use the smallest work 31 * area possible. And because everything is statically allocated on the 32 * stack then there is no need to clean up before returning. 33 */ 34 35 int __init __inflate_kernel_data(void) 36 { 37 struct z_stream_s stream, *strm = &stream; 38 struct inflate_state state; 39 char *in = __data_loc; 40 int rc; 41 42 /* Check and skip gzip header (assume no filename) */ 43 if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3) 44 return -1; 45 in += 10; 46 47 strm->workspace = &state; 48 strm->next_in = in; 49 strm->avail_in = _edata_loc - __data_loc; /* upper bound */ 50 strm->next_out = _sdata; 51 strm->avail_out = _edata_loc - __data_loc; 52 zlib_inflateInit2(strm, -MAX_WBITS); 53 WS(strm)->inflate_state.wsize = 0; 54 WS(strm)->inflate_state.window = NULL; 55 rc = zlib_inflate(strm, Z_FINISH); 56 if (rc == Z_OK || rc == Z_STREAM_END) 57 rc = strm->avail_out; /* should be 0 */ 58 return rc; 59 } 60