projects / rsbs2 / blame
| Commit | Line | Data |
|---|---|---|
| 972ac24b MG |
1 | #define POLY 0x04c11db7 |
| 2 | ||
| 3 | /* Theory of operation: | |
| 4 | * (arm-elf-objdump -b binary -m arm -M reg-names-raw -D RSB_S2_SINGLE.bin) | |
| 5 | * | |
| 6 | * 440: push {r4, r5, r6, r7, r8, r9, r10, r11, r14} | |
| 7 | * 444: mov r11, r0 | |
| 8 | * 448: mov r10, r1 | |
| 9 | * 44c: mov r14, r2 | |
| 10 | * 450: mov r6, #0 ; 0x0 | |
| 11 | * 454: b 0x4a0 | |
| 12 | * 458: add r3, r6, r10 | |
| 13 | * 45c: ldrb r3, [r3] | |
| 14 | * 460: lsl r3, r3, #24 | |
| 15 | * 464: eor r11, r11, r3 | |
| 16 | * 468: mov r5, #8 ; 0x8 | |
| 17 | * 46c: and r3, r11, #-2147483648 ; 0x80000000 | |
| 18 | * 470: cmp r3, #0 ; 0x0 | |
| 19 | * 474: beq 0x48c | |
| 20 | * 478: lsl r3, r11, #1 | |
| 21 | * 47c: ldr r12, [pc, #64] ; 0x4c4 | |
| 22 | * 480: eor r0, r3, r12 | |
| 23 | * 484: mov r11, r0 | |
| 24 | * 488: b 0x490 | |
| 25 | * 48c: lsl r11, r11, #1 | |
| 26 | * 490: sub r5, r5, #1 ; 0x1 | |
| 27 | * 494: cmp r5, #0 ; 0x0 | |
| 28 | * 498: bne 0x46c | |
| 29 | * 49c: add r6, r6, #1 ; 0x1 | |
| 30 | * 4a0: cmp r6, r14 | |
| 31 | * 4a4: blt 0x458 | |
| 32 | * 4a8: mov r0, r11 | |
| 33 | * 4ac: pop {r4, r5, r6, r7, r8, r9, r10, r11, r15} | |
| 34 | * 4c4: DATA: 0x04c11db7 | |
| 35 | */ | |
| 36 | ||
| 37 | unsigned int rsb_crc(unsigned int r11, unsigned char *r10, unsigned int r14) { | |
| 38 | unsigned int r6 = 0; | |
| 39 | unsigned int r3; | |
| 40 | int r5; | |
| 41 | ||
| 42 | while (r6 < r14) { | |
| 43 | r3 = (*(r6+r10)) << 24; | |
| 44 | r11 = r11 ^ r3; | |
| 45 | ||
| 46 | r5 = 8; | |
| 47 | ||
| 48 | do { | |
| 49 | r3 = r11 & 0x80000000; | |
| 50 | ||
| 51 | if (r3 != 0) { | |
| 52 | r3 = r11 << 1; | |
| 53 | r11 = r3 ^ POLY; | |
| 54 | } else { | |
| 55 | r11 = r11 << 1; | |
| 56 | } | |
| 57 | r5--; | |
| 58 | } while (r5); | |
| 59 | ||
| 60 | r6++; | |
| 61 | } | |
| 62 | ||
| 63 | return r11; | |
| 64 | } |