valgrind unrecognizes memcmp instruction in raspberry Pi

Question

I'm testing my aplication in Valgrind an i can't understand why it throws error on unrecognised instruction in this here:

unsigned char *temp=SearchStartPtr;
unsigned char *NrStartPos=NULL;
unsigned char *Param=(unsigned char*)ParamName; //this is originally *char with "PAR#" inside

if(0==memcmp(temp,Param,4)) 
        {
        NrStartPos=temp;
        break;
        }       

Valgrind throws this and exits my application.

disInstr(arm): unhandled instruction: 0xF1010200
cond=15(0xF) 27:20=16(0x10) 4:4=0 3:0=0(0x0)
==7679== valgrind: Unrecognised instruction at address 0x4843588.
==7679==    at 0x4843588: ??? (in /usr/lib/arm-linux-gnueabihf/libcofi_rpi.so)
Your program just tried to execute an instruction that Valgrind
==7679== did not recognise.  There are two possible reasons for this.
==7679== 1. Your program has a bug and erroneously jumped to a non-code
==7679==    location.  If you are running Memcheck and you just saw a
==7679==    warning about a bad jump, it's probably your program's fault.
==7679== 2. The instruction is legitimate but Valgrind doesn't handle it,
==7679==    i.e. it's Valgrind's fault.  If you think this is the case or
==7679==    you are not sure, please let us know and we'll try to fix it.
==7679== Either way, Valgrind will now raise a SIGILL signal which will
==7679== probably kill your program.
==7679== 
==7679== Process terminating with default action of signal 4 (SIGILL)
==7679==  Illegal opcode at address 0x4843588
==7679==    at 0x4843588: ??? (in /usr/lib/arm-linux-gnueabihf/libcofi_rpi.so)

Normally the code works fine (however i don't know if it doesn't have some memory leaks).

I know for sure that the problem is memcmp instruction but i don't understand what is wrong.

Earlier in the code i have another instruction which did the same thing but i could just comment it away before checking:

  memcmp(ReadPtr,ToWritePtr,sizeof(struct termios)

Answer 1

You need to patch libarmmem.so to operate in little-endian-mode only. To build on @nigelharper's answer, Valgrind does not support operation in reverse endian, and so traps on the SETEND instruction. However, memcmp() can be implemented without SETEND, as done here: https://github.com/rsaxvc/arm-mem/commit/b836e465c2fd0bb006b428abce99e31607072834

@user167752 is also correct, that disabling libarmmem will also work, but this will change out all of libarmmem, not just memcmp()