rkevingibson rkevingibson - 1 year ago 140
C++ Question

valgrind returning an unhandled instruction on Raspberry Pi

I've been trying to debug a segmentation fault recently using valgrind on my raspberry Pi (model b), running Debian GNU/Linux7.0 (wheezy). Every time I run valgrind on a compiled C++ program, I get something like the following:

disInstr(arm): unhandled instruction: 0xF1010200
cond=15(0xF) 27:20=16(0x10) 4:4=0 3:0=0(0x0)
valgrind: Unrecognized instruction at address 0x4843638.
at 0x4843638: ??? (in /usr/lib/arm-linux-gnueabihf/libconfi_rpi.so)

Then the normal valgrind stuff, causing a SIGILL and terminating my program. At first I assumed there was some memory leak in my program that was causing it to execute a piece of non-instruction memory as an instruction, but then I ran the following hello world code, and got the same result.

#include <iostream>
using namespace std;

int main() {
cout<<"Hello World"<<endl;

return 0;

There can't possibly be a memory leak/segfault in that, so why is it giving me this error?
I'm pretty new with valgrind, but I ran it with the most basic
valgrind ./a.out

Answer Source

From your code (a simple hello world), It complain about an Unrecognized instruction at address 0x4843638. My guess is:

  • Since valgrind need to intercept your malloc system call function (c standard library). This allow valgrind to check how many resource you did allocated/free which is used for memory leak detection (for example). If valgrind does not recognize your standard library environement (or the instruction language of your processor), It may does not behave as expecting, which would be the cause of your crash. You should check valgrind version and download the one fitted for your platform.



3.3. My program dies, printing a message like this along the way:

vex x86->IR: unhandled instruction bytes: 0x66 0xF 0x2E 0x5

One possibility is that your program has a bug and erroneously jumps to a non-code address, in which case you'll get a SIGILL signal. Memcheck may issue a warning just before this happens, but it might not if the jump happens to land in addressable memory.

Another possibility is that Valgrind does not handle the instruction. If you are using an older Valgrind, a newer version might handle the instruction. However, all instruction sets have some obscure, rarely used instructions. Also, on amd64 there are an almost limitless number of combinations of redundant instruction prefixes, many of them undocumented but accepted by CPUs. So Valgrind will still have decoding failures from time to time. If this happens, please file a bug report.


From wikipedia, the Raspberry Pi CPU:

  • 700 MHz ARM1176JZF-S core (ARM11 family, ARMv6 instruction set)[3]

2.11. Limitations

On ARM, essentially the entire ARMv7-A instruction set is supported, in both ARM and Thumb mode. ThumbEE and Jazelle are not supported. NEON, VFPv3 and ARMv6 media support is fairly complete.

Your program/library just happened to have some instruction which is not supported yet.

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