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 | ||
| c8b1eccb MG |
37 | unsigned int rsb_crc(unsigned int r11_crc, unsigned char *r10_buf, unsigned int r14_len) { |
| 38 | unsigned int r6_pos = 0; | |
| 39 | unsigned int r3_data; | |
| 40 | int r5_bit; | |
| 972ac24b | 41 | |
| c8b1eccb MG |
42 | while (r6_pos < r14_len) { |
| 43 | r3_data = (*(r6_pos+r10_buf)) << 24; | |
| 44 | r11_crc = r11_crc ^ r3_data; | |
| 972ac24b | 45 | |
| c8b1eccb | 46 | r5_bit = 8; |
| 972ac24b MG |
47 | |
| 48 | do { | |
| c8b1eccb | 49 | r3_data = r11_crc & 0x80000000; |
| 972ac24b | 50 | |
| c8b1eccb MG |
51 | if (r3_data != 0) { |
| 52 | r3_data = r11_crc << 1; | |
| 53 | r11_crc = r3_data ^ POLY; | |
| 972ac24b | 54 | } else { |
| c8b1eccb | 55 | r11_crc = r11_crc << 1; |
| 972ac24b | 56 | } |
| c8b1eccb MG |
57 | r5_bit--; |
| 58 | } while (r5_bit); | |
| 972ac24b | 59 | |
| c8b1eccb | 60 | r6_pos++; |
| 972ac24b MG |
61 | } |
| 62 | ||
| c8b1eccb | 63 | return r11_crc; |
| 972ac24b | 64 | } |