1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       armthumb.c
4 /// \brief      Filter for ARM-Thumb binaries
5 ///
6 //  Authors:    Igor Pavlov
7 //              Lasse Collin
8 //
9 //  This file has been put into the public domain.
10 //  You can do whatever you want with this file.
11 //
12 ///////////////////////////////////////////////////////////////////////////////
13 
14 #include "simple_private.h"
15 
16 
17 static size_t
18 armthumb_code(void *simple lzma_attribute((__unused__)),
19 		uint32_t now_pos, bool is_encoder,
20 		uint8_t *buffer, size_t size)
21 {
22 	size_t i;
23 	for (i = 0; i + 4 <= size; i += 2) {
24 		if ((buffer[i + 1] & 0xF8) == 0xF0
25 				&& (buffer[i + 3] & 0xF8) == 0xF8) {
26 			uint32_t src = (((uint32_t)(buffer[i + 1]) & 7) << 19)
27 				| ((uint32_t)(buffer[i + 0]) << 11)
28 				| (((uint32_t)(buffer[i + 3]) & 7) << 8)
29 				| (uint32_t)(buffer[i + 2]);
30 
31 			src <<= 1;
32 
33 			uint32_t dest;
34 			if (is_encoder)
35 				dest = now_pos + (uint32_t)(i) + 4 + src;
36 			else
37 				dest = src - (now_pos + (uint32_t)(i) + 4);
38 
39 			dest >>= 1;
40 			buffer[i + 1] = 0xF0 | ((dest >> 19) & 0x7);
41 			buffer[i + 0] = (dest >> 11);
42 			buffer[i + 3] = 0xF8 | ((dest >> 8) & 0x7);
43 			buffer[i + 2] = (dest);
44 			i += 2;
45 		}
46 	}
47 
48 	return i;
49 }
50 
51 
52 static lzma_ret
53 armthumb_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
54 		const lzma_filter_info *filters, bool is_encoder)
55 {
56 	return lzma_simple_coder_init(next, allocator, filters,
57 			&armthumb_code, 0, 4, 2, is_encoder);
58 }
59 
60 
61 extern lzma_ret
62 lzma_simple_armthumb_encoder_init(lzma_next_coder *next,
63 		const lzma_allocator *allocator,
64 		const lzma_filter_info *filters)
65 {
66 	return armthumb_coder_init(next, allocator, filters, true);
67 }
68 
69 
70 extern lzma_ret
71 lzma_simple_armthumb_decoder_init(lzma_next_coder *next,
72 		const lzma_allocator *allocator,
73 		const lzma_filter_info *filters)
74 {
75 	return armthumb_coder_init(next, allocator, filters, false);
76 }
77