Getting 'illegal instruction' error on armv6

[Cydox]

I built io.js with the change #282 on armv6.
When running io.js i get an 'Illegal instruction' error. g++ and gcc are on version 4.8.3.
There where no errors while building. I don´t know what other information i could give you.
Just ask me for the information you need and i´ll post it.

[bnoordhuis]

There was an rpi thread on v8-users recently. I don't know if you were involved but it lists a few things you can try. If nothing else, can you post the output of backtrace and disassemble from gdb?

[Cydox]

I saw another thread. I´m trying command line arguments from that one. But this will take some time since the Pi is slow(probably will take till tomorrow morning). When it works should I do a PR so it will print an error message if people don't use these options and add it to #282 ?

[bnoordhuis]

Yes, that would be great.

[bnoordhuis]

@Cydox How did it work?

[fivdi]

I remember having the 'illegal instruction' error on the Raspberry Pi after successfully compiling node v0.11.8 or v0.11.9 on the Pi itself. I think the issue may be related to the following code (from deps/v8/src/base/cpu.cc):

    // Unfortunately, it seems that certain ARMv6-based CPUs
    // report an incorrect architecture number of 7!
    //
    // See http://code.google.com/p/android/issues/detail?id=10812
    //
    // We try to correct this by looking at the 'elf_format'
    // field reported by the 'Processor' field, which is of the
    // form of "(v7l)" for an ARMv7-based CPU, and "(v6l)" for
    // an ARMv6-one. For example, the Raspberry Pi is one popular
    // ARMv6 device that reports architecture 7.
    if (architecture_ == 7) {
      char* processor = cpu_info.ExtractField("Processor");
      if (HasListItem(processor, "(v6l)")) {
        architecture_ = 6;
      }
      delete[] processor;
    }

This code looks at the Processor field in file /proc/cpuinfo to see if it can find "(v6l)"

Everything works correctly on older versions of Raspbian with the following /proc/cpuinfo as the Processor field contains "(v6l)":

Processor   : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS    : 697.95
Features    : swp half thumb fastmult vfp edsp java tls 
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part    : 0xb76
CPU revision    : 7

Hardware    : BCM2708
Revision    : 0002
Serial      : 000000008a51a472

However, on newer versions of Raspbian "(v6l)" has been moved to the model name field, V8 doesn't find it, and assumes that the Pi has an ARMv7 processor:

processor   : 0
model name  : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS    : 2.00
Features    : swp half thumb fastmult vfp edsp java tls 
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part    : 0xb76
CPU revision    : 7

Hardware    : BCM2708
Revision    : 0002
Serial      : 000000008a51a472

Related issues:
nodejs/node-v0.x-archive#7222
https://code.google.com/p/v8/issues/detail?id=3112

[Cydox]

This is really getting crazy now. An hour ago it the build on my Pi worked, but now i was giving it a second test but this time it gives me 'illegal instruction'. Runnig iojs --v8-options gives me

target arm v6 vfp3 hard ARMv7=1 VFP3=1 VFP32DREGS=1 NEON=0 SUDIV=0 UNALIGNED_ACCESSES=1 MOVW_MOVT_IMMEDIATE_LOADS=0 COHERENT_CACHE=0 USE_EABI_HARDFLOAT=1

so it is detecting armv7 again.
@bnoordhuis should we try to change the code in cpu.cc? Or is it a problem because it is in v8?

[Cydox]

i think the reason why it didnt work is that
(as stated in https://code.google.com/p/v8/issues/detail?id=3112) the option arm-version=6
I was using is not in this version of v8 but in a newer one. And in
https://code.google.com/p/v8/issues/detail?id=3112 at the end there is a patch that
looks like it should work(obviously I dont have enough experience with a code working on
mutiple platforms). I´m gonna test the patch on my Pi and tell you wther it worked or not(and i´ll
try more then once now before saying it works).

[Cydox]

I added this change to the Code:

if (architecture_ == 7) {
       std::cout << "7" << std::endl;
       char* processor;
       processor = cpu_info.ExtractField("Processor");
       if (HasListItem(processor, "(v6l)")) {
         architecture_ = 6;
       }
       processor = cpu_info.ExtractField("model name");
      if (HasListItem(processor, "(v6l)")) {
        std::cout << "6" << std::endl;
        architecture_ = 6;
      }
      delete[] processor;
    }
  }

I included iostream obviously and added the 'print' statements to see wether thoughs if statements
got called('not the best debugging probably'). Both if statements were called. ´So the architectue_
should have been set to 6 just like it needs to. But the output is just:

# ./iojs
7
6
Illegal instruction

I only did a short make so i didn´t need to compile the whole thing again. Could this have an
impact? I can´t think of anything else. iojs --v8-options returned that it is armv7 again.

[Cydox]

gdb backtrace and disassemble:

gdb ./iojs
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "arm-linux-gnueabihf".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/pi/io.js/iojs...done.
(gdb) run
Starting program: /home/pi/io.js/iojs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".

Program received signal SIGILL, Illegal instruction.
0x00378a60 in _armv7_neon_probe ()
(gdb) backtrace
#0  0x00378a60 in _armv7_neon_probe ()
#1  0x00232cc0 in OPENSSL_cpuid_setup ()
#2  0x008a71d4 in __libc_csu_init ()
#3  0xb6cc5228 in __libc_start_main () from /lib/arm-linux-gnueabihf/libc.so.6
#4  0x00233068 in _start ()
(gdb) dissasemble
Undefined command: "dissasemble".  Try "help".
(gdb) disassemble
Dump of assembler code for function _armv7_neon_probe:
=> 0x00378a60 <+0>:     vorr    q15, q15, q15
   0x00378a64 <+4>:     bx      lr
End of assembler dump.

[indutny]

@Cydox please type c and hit Enter key after seeing this openssl thing. It is the way the OpenSSL detects platform. It sets SIGILL handler and executes the assembly code.

Again, this could be ignored, please hit the c after it.

[Cydox]

like that?

(gdb) run
Starting program: /home/pi/io.js/iojs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".

Program received signal SIGILL, Illegal instruction.
0x00378a60 in _armv7_neon_probe ()
(gdb) backtrace
#0  0x00378a60 in _armv7_neon_probe ()
#1  0x00232cc0 in OPENSSL_cpuid_setup ()
#2  0x008a71d4 in __libc_csu_init ()
#3  0xb6cc5228 in __libc_start_main () from /lib/arm-linux-gnueabihf/libc.so.6
#4  0x00233068 in _start ()
(gdb) c
Continuing.

Program received signal SIGILL, Illegal instruction.
0x00378a68 in _armv7_tick ()

[indutny]

What if you'll hit c again? ;)

[Cydox]

here are a bunch of ´em :D

 c
Continuing.

Program received signal SIGILL, Illegal instruction.
0x00378a68 in _armv7_tick ()
(gdb) c
Continuing.
[New Thread 0xb6cab450 (LWP 26581)]
[New Thread 0xb64ab450 (LWP 26582)]
[New Thread 0xb5cab450 (LWP 26583)]
[New Thread 0xb54ab450 (LWP 26584)]
7
6

Program received signal SIGILL, Illegal instruction.
0x539242c0 in ?? ()
(gdb) c
Continuing.
[Thread 0xb54ab450 (LWP 26584) exited]
[Thread 0xb5cab450 (LWP 26583) exited]
[Thread 0xb64ab450 (LWP 26582) exited]
[Thread 0xb6cab450 (LWP 26581) exited]

Program terminated with signal SIGILL, Illegal instruction.
The program no longer exists.

[Cydox]

Any new ideas on what fails here?