V8 SIGILL on v0.12 on Raspberry Pi

[sxa]

I believe this is different from the issue mentioned in #8549 so I'm raising this separately.
There are two issues with the 0.12 build on ARM at the moment that prevent it from running correctly (although it builds without issues)

Firstly, there is a crash that is introduced when vfpv3 is used as arm_fpu (this is the default in the 0.12 configure because apparently V8 doesn't support vfpv2 which is the default in 0.10). However if I compile with it set to something else like "fpu" or "vfpv2" it does compile and start, although that's likely not the best fix ... The comment about V8 not supporting v2 is here in configure:

o['variables']['arm_fpu'] = 'vfpv3' # V8 3.18 no longer supports VFP2.

Second issue is that while it does compile or start with the above change on older kernel versions, for more recent ones (anything "current") it fails because V8 is doing CPU detection based on /proc/cpuinfo which changed as a result of this delta in the Linux kernel:
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/arch/arm/kernel/setup.c?id=b4b8f770eb10a1bccaf8aa0ec1956e2dd7ed1e0a

The change modified the line on which (v6l) shows up from "Processor" to "model name". Here is the output on my "old" kernel 3.2.27+:

sxa@raspberrypi ~ $ head -2 /proc/cpuinfo
Processor : ARMv6-compatible processor rev 7 (v6l)
BogoMIPS : 697.95

Here it is on a newer one (3.12.22+)

sxa@pi ~ $ head -2 /proc/cpuinfo
processor : 0
model name : ARMv6-compatible processor rev 7 (v6l)

Line 370 of https://github.com/joyent/node/blob/master/deps/v8/src/cpu.cc is scanning for the line prefixed "Processor" to be able to set the CPU flags correctly. Modifying the code to check for both options allows Node to execute on both old and new kernels:

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

EDIT: There is a V8 report describing the second issue at https://code.google.com/p/v8/issues/detail?id=3112 although it hasn't had any activity since February

[peerchemist]

In latest 0.12 deps/v8/src/cpu.cc was replaced with https://github.com/joyent/node/blob/v0.12/deps/v8/src/cpu-profiler.cc.
However it still does not work properly.

[leecade]

:+1

[wilson0x4d]

The cpu.cc source was not replaced with cpu-profiler.cc, but instead it has been relocated into the /base/ folder.

Specifically the offending code is currently located here: https://github.com/joyent/node/blob/master/deps/v8/src/base/cpu.cc#L373-L380

Or, within the v8 repo itself, here: https://github.com/v8/v8/blob/master/src/base/cpu.cc#L430-L436

Additionally, @sxa555's proposed edits have not yet been made to official source, applying his edits directly resolves my problem (in addition to specifying --without-checkpoint configure options.)

Since a potential fix has been identified and has been confirmed by a third party is there any hope of getting this resolved? Not everyone has the technical chops to hunt down and fix this on a per-incident basis.

If necessary I'll fork and submit a pull request, it's not hard. I just don't know what kind of process is sitting around node development that would make such an effort (all of 15 minutes I imagine) a waste of my time.

Thanks.

[magic890]

Here is the official patch from V8 team: https://github.com/v8/v8-git-mirror/blob/master/src/base/cpu.cc#L483-L499

I have created a pull request to solve this issue: #25625