Tough problem - trying to reverse engineer a CANBUS controller for which I can download firmware (as far as I can tell, binary image, not ELF) but I dont know what MCU it uses. binwalk, r2 dont give me anything useful. Binwalk opcodes match mipsel but function signatures is garbage.
What can I do to determine MCU from firmware?
It does appear to be MIPS 32-bit little-endian machine code.
First, the file was converted from .hex to binary via
$ objcopy --input-target=ihex --output-target=binary FORD_P5_STEER_RevA_v1.2.0.hex FORD_P5_STEER_RevA_v1.2.0.bin
After looking at a binwalk entropy plot and a hex dump, I sliced out the first 0x00021330 bytes, because nearly everything after is just 0x00 bytes.
000212f0 5f 50 35 20 53 74 65 65 72 00 00 00 20 24 00 00 |_P5 Steer... $..|
00021300 00 04 08 10 14 18 00 00 08 00 e0 03 00 60 62 41 |.............`bA|
00021310 08 00 e0 03 20 60 62 41 08 00 e0 03 00 00 00 00 |.... `bA........|
00021320 08 00 e0 03 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00021330 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| <--\
* |-- Huge gap
00071e40 01 00 00 00 02 00 00 00 00 00 00 00 46 4f 52 44 |............FORD| <--/
00071e50 20 50 35 20 53 74 65 65 72 69 6e 67 20 45 6d 75 | P5 Steering Emu|
00071e60 6c 61 74 6f 72 20 28 46 4f 52 44 5f 50 35 5f 53 |lator (FORD_P5_S|
00071e70 54 45 45 52 29 20 52 65 76 41 00 00 00 00 00 00 |TEER) RevA......|
00071e80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
02bf9e80 00 9d 1f 3c 70 79 ff 37 08 00 e0 03 00 00 00 00 |...<py.7........|
02bf9e90 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
02bfce70 ff ff ff 3e d9 79 f9 ff 5b 0e 66 ff ff ff ff 7f |...>.y..[.f.....|
02bfce80
ISAdetect results:
{
"prediction": {
"wordsize": 32,
"endianness": "little",
"architecture": "mips"
},
"prediction_probability": 0.81
}
To confirm, I extracted the machine code from the slice and compared it to a reference:
The byte value distributions closely match.
It is indeed valid MIPS litte-endian code:
seg000:1D0121F0 A8 FF BD 27 addiu $sp, -0x58
seg000:1D0121F4 04 00 A1 AF sw $at, 0x58+var_54($sp)
seg000:1D0121F8 08 00 A2 AF sw $v0, 0x58+var_50($sp)
seg000:1D0121FC 0C 00 A3 AF sw $v1, 0x58+var_4C($sp)
seg000:1D012200 10 00 A4 AF sw $a0, 0x58+var_48($sp)
seg000:1D012204 14 00 A5 AF sw $a1, 0x58+var_44($sp)
seg000:1D012208 18 00 A6 AF sw $a2, 0x58+var_40($sp)
seg000:1D01220C 1C 00 A7 AF sw $a3, 0x58+var_3C($sp)
seg000:1D012210 20 00 A8 AF sw $t0, 0x58+var_38($sp)
seg000:1D012214 24 00 A9 AF sw $t1, 0x58+var_34($sp)
seg000:1D012218 28 00 AA AF sw $t2, 0x58+var_30($sp)
seg000:1D01221C 2C 00 AB AF sw $t3, 0x58+var_2C($sp)
seg000:1D012220 30 00 AC AF sw $t4, 0x58+var_28($sp)
seg000:1D012224 34 00 AD AF sw $t5, 0x58+var_24($sp)
seg000:1D012228 38 00 AE AF sw $t6, 0x58+var_20($sp)
seg000:1D01222C 3C 00 AF AF sw $t7, 0x58+var_1C($sp)
seg000:1D012230 40 00 B8 AF sw $t8, 0x58+var_18($sp)
seg000:1D012234 44 00 B9 AF sw $t9, 0x58+var_14($sp)
seg000:1D012238 48 00 BF AF sw $ra, 0x58+var_10($sp)
seg000:1D01223C 12 40 00 00 mflo $t0
seg000:1D012240 4C 00 A8 AF sw $t0, 0x58+var_C($sp)
seg000:1D012244 10 40 00 00 mfhi $t0
seg000:1D012248 50 00 A8 AF sw $t0, 0x58+var_8($sp)
seg000:1D01224C 01 9D 1A 3C+ li $k0, 0x9D012CA4
seg000:1D01224C A4 2C 5A 27
seg000:1D012254 00 00 00 00 nop
seg000:1D012258 00 68 04 40 mfc0 $a0, Cause # Cause of last exception
seg000:1D01225C 00 60 05 40 mfc0 $a1, SR # Status register
seg000:1D012260 09 F8 40 03 jalr $k0
seg000:1D012264 00 00 00 00 nop
I suspect the device is using something from the Microchip's PIC32 series.
