runtime: exit with useful message on ARM OABI

[lupino3]

What steps will reproduce the problem?
1. Set up a Debian Lenny ARM VM under QEMU using the image and instructions available at
http://people.debian.org/~aurel32/qemu/arm/

The emulated processor is an ARM9 (according to
http://en.wikipedia.org/wiki/List_of_ARM_microprocessor_cores):

debian-arm:~/go/src/pkg/syscall# grep Processor /proc/cpuinfo
Processor       : ARM926EJ-S rev 5 (v5l)

2. Follow the instructions at http://golang.org/doc/install.html until the hg clone
command.

3. Compile go with the following commands 
debian-arm:~/go/src# GOOS=linux GOARCH=arm GOARM=9 ./make.bash
(I have also done the same with GOARM=5)

4. Run gofmt

What is the expected output?
no output, gofmt should wait for input on stdin

What do you see instead?
Illegal instruction

Which compiler are you using (5g, 6g, 8g, gccgo)?
5g (but I don't directly use any compiler)

Which operating system are you using?
Debian GNU/Linux Lenny for ARM

Which revision are you using?  (hg identify)
c1702f36df03 (release-branch.r60) release/release.r60.3

[bradfitz]

Comment 1:

You shouldn't need GOOS=linux or GOARCH=arm if you're within a fully emulated system. 
Those will be detected.
Do other binaries fail, or just gofmt?
You've checked that the gofmt you're running is the one you just built?

[rsc]

Comment 2:

Can you please try
6nm $(which gofmt) | grep sfloat
If it does not print anything, then the GOARM=5 did not take.
On the system you are using you definitely need the GOARM=5.

[lupino3]

Comment 3:

Hello,
Brad: I tried without GOOS and GOARCH and the result is the same. I am not adding the
bin directory to PATH, so I am quite sure that I am running the one I just built.
Russ: which won't find gofmt as it is not in the PATH. Both give me just the output
"Illegal instruction".
FYI:
debian-arm:~# ls -l {go-noenv,go-linux-5}/bin/gofmt
-rwxr-xr-x 1 root root 1847596 2011-12-06 22:35 go-linux-5/bin/gofmt
-rwxr-xr-x 1 root root 1843500 2011-12-07 11:03 go-noenv/bin/gofmt
debian-arm:~# ./go-noenv/bin/gofmt
Illegal instruction
debian-arm:~# ./go-linux-5/bin/gofmt
Illegal instruction
In go-noenv I ran make.bash without specifying any environment variable; In go-linux-5 I
ran GOOS=linux GOARCH=arm GOARM=5 ./make bash.
Thanks,
Andrea

[rsc]

Comment 4:

Thanks for the information.  It sounds like the ARM 5 build
has regressed.  I have yet to find an ARM 5 system with
storage that can withstand the beating that the Go builder
puts it through.  We need to set one up again.
Russ

[rsc]

Comment 5:

Labels changed: added priority-later, removed priority-medium.

[davecheney]

Comment 6:

Hello, 
I think this may be another manifestation of 
https://golang.org/issue/2321
Can you have a look at dmesg and the contents of /proc/cpu/alignment. I have to run with
the value set to mixup (2), mainly because python generates tonnes of unaligned
accesses, but also something in the tree in the last three months is generating
unaligned memory accesses.

[lupino3]

Comment 7:

Hello,
I followed your suggestions, to no avail. dmesg does not change after I execute gofmt.
Here is /proc/alignment:
User:           0
System:         0
Skipped:        0
Half:           0
Word:           0
DWord:          0
Multi:          0
User faults:    0 (ignored)
I set it to 2:
User:           0
System:         0
Skipped:        0
Half:           0
Word:           0
DWord:          0
Multi:          0
User faults:    2 (fixup)
And I have the same error (Illegal Instruction) when executing gofmt (both the one
compiled for linux-arm-5 and the other for which no environment variables were specified
t compilation time.
I can give this VM to any developer, if needed.
Thanks,
Andrea

[davecheney]

Comment 8:

Are you able to upload the arm5 version to this issue for me to in on my system?

[lupino3]

Comment 9:

Hello,
yes, I can do that if you give me a place where I should put it.
Thanks,
Andrea

[davecheney]

Comment 10:

You should be able to add it to the issue using attach file.

[lupino3]

Comment 11:

The maximum attachment file size is 10MB, while the VM size is 1.8GB..

[davecheney]

Comment 12:

Sorry my mistake. I only need the arm5 gofmt binary that faults.

[lupino3]

Comment 13:

Sorry for the misunderstanding :)
Please find attached the version of gofmt compiled with GOOS=linux GOARCH=arm GOARM=5,
called gofmt5, and the version compiled without specifying any environment version,
called gofmt-noenv.
Thanks,
Andrea

Attachments:

1. gofmt5 (1847596 bytes)
2. gofmt-noenv (1843500 bytes)

[davecheney]

Comment 14:

gofmt5 runs perfectly on arm5, gofmt-noenv does not (not unexpected), it blows up on the
first arm6 instruction in math.init
Program received signal SIGILL, Illegal instruction.
0x000377c0 in math.init·1 ()
(gdb) x/i 0x000377c0
=> 0x377c0 <math.init·1+40>:   vmov.f64        d0, #112        ; 0x70

[lupino3]

Comment 15:

My doubt is whether the CPU emulated by QEMU is ARM5 or not.. I supposed it was ARM9.
Here is my /proc/cpuinfo:
Processor       : ARM926EJ-S rev 5 (v5l)
BogoMIPS        : 537.39
Features        : swp half thumb fastmult vfp edsp java 
CPU implementer : 0x41
CPU architecture: 5TEJ
CPU variant     : 0x0
CPU part        : 0x926
CPU revision    : 5
Cache type      : write-through
Cache clean     : not required
Cache lockdown  : not supported
Cache format    : Harvard
I size          : 4096
I assoc         : 4
I line length   : 32
I sets          : 32
D size          : 65536
D assoc         : 4
D line length   : 32
D sets          : 512
Hardware        : ARM-Versatile PB
Revision        : 0000
Serial          : 0000000000000000