| Nicolas Pitre | ca8b5d9 | 2017-08-25 00:54:18 -0400 | [diff] [blame] | 1 | /* |
| 2 | * XIP kernel .data segment decompressor |
| 3 | * |
| 4 | * Created by: Nicolas Pitre, August 2017 |
| 5 | * Copyright: (C) 2017 Linaro Limited |
| 6 | * |
| 7 | * This program is free software; you can redistribute it and/or modify |
| 8 | * it under the terms of the GNU General Public License version 2 as |
| 9 | * published by the Free Software Foundation. |
| 10 | */ |
| 11 | |
| 12 | #include <linux/init.h> |
| 13 | #include <linux/zutil.h> |
| 14 | |
| 15 | /* for struct inflate_state */ |
| 16 | #include "../../../lib/zlib_inflate/inftrees.h" |
| 17 | #include "../../../lib/zlib_inflate/inflate.h" |
| 18 | #include "../../../lib/zlib_inflate/infutil.h" |
| 19 | |
| 20 | extern char __data_loc[]; |
| 21 | extern char _edata_loc[]; |
| 22 | extern char _sdata[]; |
| 23 | |
| 24 | /* |
| 25 | * This code is called very early during the boot process to decompress |
| 26 | * the .data segment stored compressed in ROM. Therefore none of the global |
| 27 | * variables are valid yet, hence no kernel services such as memory |
| 28 | * allocation is available. Everything must be allocated on the stack and |
| 29 | * we must avoid any global data access. We use a temporary stack located |
| 30 | * in the .bss area. The linker script makes sure the .bss is big enough |
| 31 | * to hold our stack frame plus some room for called functions. |
| 32 | * |
| 33 | * We mimic the code in lib/decompress_inflate.c to use the smallest work |
| 34 | * area possible. And because everything is statically allocated on the |
| 35 | * stack then there is no need to clean up before returning. |
| 36 | */ |
| 37 | |
| 38 | int __init __inflate_kernel_data(void) |
| 39 | { |
| 40 | struct z_stream_s stream, *strm = &stream; |
| 41 | struct inflate_state state; |
| 42 | char *in = __data_loc; |
| 43 | int rc; |
| 44 | |
| 45 | /* Check and skip gzip header (assume no filename) */ |
| 46 | if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3) |
| 47 | return -1; |
| 48 | in += 10; |
| 49 | |
| 50 | strm->workspace = &state; |
| 51 | strm->next_in = in; |
| 52 | strm->avail_in = _edata_loc - __data_loc; /* upper bound */ |
| 53 | strm->next_out = _sdata; |
| 54 | strm->avail_out = _edata_loc - __data_loc; |
| 55 | zlib_inflateInit2(strm, -MAX_WBITS); |
| 56 | WS(strm)->inflate_state.wsize = 0; |
| 57 | WS(strm)->inflate_state.window = NULL; |
| 58 | rc = zlib_inflate(strm, Z_FINISH); |
| 59 | if (rc == Z_OK || rc == Z_STREAM_END) |
| 60 | rc = strm->avail_out; /* should be 0 */ |
| 61 | return rc; |
| 62 | } |