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Boot loader v2.4, SDL lib source, updated SDL_image
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,82 @@ | ||
| /** | ||
| * DreamShell boot loader | ||
| * Descramble binary | ||
| * (c)2011-2016 SWAT <http://www.dc-swat.ru> | ||
| */ | ||
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| #include "main.h" | ||
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| #define MAXCHUNK 0x200000 | ||
| static uint seed; | ||
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| static inline void my_srand(uint n) { | ||
| seed = n & 0xffff; | ||
| } | ||
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| static inline uint my_rand(void) { | ||
| seed = (seed * 2109 + 9273) & 0x7fff; | ||
| return (seed + 0xc000) & 0xffff; | ||
| } | ||
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| static void load(uint8 *dest, uint32 size) { | ||
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| static uint8 *source; | ||
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| if (!size) { | ||
| source = dest; | ||
| return; | ||
| } | ||
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| memcpy(dest, source, size); | ||
| source += size; | ||
| } | ||
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| static inline void handle_chunk(uint8 *ptr, int sz) { | ||
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| int idx[MAXCHUNK / 32]; | ||
| int i; | ||
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| /* Convert chunk size to number of slices */ | ||
| sz /= 32; | ||
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| /* Initialize index table with unity, | ||
| so that each slice gets loaded exactly once */ | ||
| for(i = 0; i < sz; i++) | ||
| idx[i] = i; | ||
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| for(i = sz-1; i >= 0; --i) | ||
| { | ||
| /* Select a replacement index */ | ||
| int x = (my_rand() * i) >> 16; | ||
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| /* Swap */ | ||
| int tmp = idx[i]; | ||
| idx[i] = idx[x]; | ||
| idx[x] = tmp; | ||
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| /* Load resulting slice */ | ||
| load(ptr + 32 * idx[i], 32); | ||
| } | ||
| } | ||
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| void descramble(uint8 *source, uint8 *dest, uint32 size) { | ||
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| load(source, 0); | ||
| my_srand(size); | ||
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| /* Descramble 2 meg blocks for as long as possible, then | ||
| gradually reduce the window down to 32 bytes (1 slice) */ | ||
| for(uint32 chunksz = MAXCHUNK; chunksz >= 32; chunksz >>= 1) | ||
| { | ||
| while(size >= chunksz) | ||
| { | ||
| handle_chunk(dest, chunksz); | ||
| size -= chunksz; | ||
| dest += chunksz; | ||
| } | ||
| } | ||
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| /* !!! Load final incomplete slice */ | ||
| if(size) | ||
| load(dest, size); | ||
| } |
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