+#include <stdio.h>
+
#define POLY 0x04c11db7
/* Theory of operation:
* (arm-elf-objdump -b binary -m arm -M reg-names-raw -D RSB_S2_SINGLE.bin)
+ * Addresses: 0x4c4, 0x55ae0, 0x59734
*
* 440: push {r4, r5, r6, r7, r8, r9, r10, r11, r14}
* 444: mov r11, r0
return r11_crc;
}
+
+/* Second broken algorithm:
+ *
+ * 55a30: push {r3, r4, r5, r6, r7, r8, r9, r14}
+ * 55a34: bl 0x55a3c
+ * 55a38: pop {r3, r4, r5, r6, r7, r8, r9, r15}
+ * 55a3c: mov r8, #1 ; 0x1
+ * 55a40: mov r3, #-1073741824 ; 0xc0000000
+ * 55a44: cmp r0, r3
+ * 55a48: ble 0x55ad8
+ * 55a4c: mov r3, #32 ; 0x20
+ * 55a50: ldr r4, [r3, r0]!
+ * 55a54: mov r8, #2 ; 0x2
+ * 55a58: ldr r5, [r3, #4]
+ * 55a5c: cmp r5, r2
+ * 55a60: bne 0x55ad8
+ * 55a64: mov r8, #3 ; 0x3
+ * 55a68: cmp r1, r4
+ * 55a6c: movscs r5, #0 ; 0x0
+ * 55a70: movscc r5, #1 ; 0x1
+ * 55a74: bne 0x55ad8
+ * 55a78: mov r8, #4 ; 0x4
+ * 55a7c: mov r3, r0
+ * 55a80: add r4, r0, r4
+ * 55a84: mvn r5, #0 ; 0x0
+ * 55a88: ldr r7, [pc, #80] ; 0x55ae0
+ * 55a8c: cmp r3, r4
+ * 55a90: bcs 0x55ac8
+ * 55a94: bic r9, r3, #3 ; 0x3
+ * 55a98: ldr r6, [r9]
+ * 55a9c: and r9, r3, #3 ; 0x3
+ * 55aa0: lsl r9, r9, #3
+ * 55aa4: lsr r6, r6, r9
+ * 55aa8: eor r5, r5, r6, lsl #24
+ * 55aac: mov r6, #8 ; 0x8
+ * 55ab0: lsls r5, r5, #1
+ * 55ab4: eorcs r5, r5, r7
+ * 55ab8: subs r6, r6, #1 ; 0x1
+ * 55abc: bne 0x55ab0
+ * 55ac0: add r3, r3, #1 ; 0x1
+ * 55ac4: b 0x55a8c
+ * 55ac8: mvn r5, r5
+ * 55acc: ldr r3, [r4]
+ * 55ad0: subs r3, r3, r5
+ * 55ad4: moveq r8, #0 ; 0x0
+ * 55ad8: mov r0, r8
+ * 55adc: mov r15, r14
+ * 55ae0: DATA: 0x04c11db7
+ */
+
+unsigned int rsb_crc2(unsigned char *r0_buf, unsigned int r1_buflen, unsigned int r2_magic, unsigned int *crc_out) {
+ int r8_ret = 1;
+ unsigned int r3_pos = 0xc0000000;
+ unsigned int r4_len;
+ unsigned int r5_crc;
+ unsigned int r6;
+ unsigned int r9;
+ unsigned int carry;
+
+#if 0
+ if (r0_buf <= r3_pos)
+ return 1; /* Not in RAM */
+#endif
+
+ r4_len = *(unsigned int*)(r0_buf + 0x20);
+
+ if (*((unsigned int*)(r0_buf + 0x24)) != r2_magic)
+ return 2; /* MAGIC does not match */
+
+ if (r1_buflen < r4_len)
+ return 3; /* image to small */
+
+ r8_ret = 4;
+
+ r3_pos = (unsigned int)r0_buf;
+ r4_len += r3_pos;
+
+ r5_crc = ~0x0;
+
+ while (r3_pos < r4_len) {
+ r9 = r3_pos & (~0x3);
+ r6 = *((unsigned int*)r9);
+ r9 = r3_pos & 0x3;
+ r9 = r9 << 0x3;
+ r6 = r6 >> r9;
+ r5_crc = r5_crc ^ (r6 << 24);
+ r6 = 0x8;
+
+ do {
+ carry = r5_crc & 0x80000000;
+ r5_crc = r5_crc << 1;
+ if (carry)
+ r5_crc = r5_crc ^ POLY;
+ r6--;
+ } while(r6);
+ r3_pos++;
+ }
+
+ r5_crc = ~r5_crc;
+ *crc_out = r5_crc;
+
+ r3_pos = *((unsigned int*)r4_len);
+
+ if (r3_pos == r5_crc)
+ r8_ret = 0;
+
+ return r8_ret;
+}