x/sys/unix: mkerrors.sh broken on AIX

[jtroy]

Go version

go version go1.23.1 aix/ppc64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='ppc64'
GOBIN=''
GOCACHE='/home/jtroy/.cache/go-build'
GOENV='/home/jtroy/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='ppc64'
GOHOSTOS='aix'
GOINSECURE=''
GOMODCACHE='/home/jtroy/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='aix'
GOPATH='/home/jtroy/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/jtroy/go1.23.1'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/jtroy/go1.23.1/pkg/tool/aix_ppc64'
GOVCS=''
GOVERSION='go1.23.1'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/jtroy/.config/go/telemetry'
GCCGO='gccgo'
GOPPC64='power8'
AR='ar'
CC='gcc-12'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/jtroy/src/sys/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -maix64 -pthread -mcmodel=large -fmessage-length=0 -ffile-prefix-map=/tmp/go-build4197857588=/tmp/go-build -gno-record-gcc-switches'

What did you do?

I ran mkerrors.sh in the unix directory in order to regenerate zerrors_aix_ppc64.go according to the README.

What did you see happen?

The process crashed with a segfault:

bash-5.2$ pwd
/home/jtroy/src/sys/unix
bash-5.2$ CC=gcc-12 GOOS=aix GOARCH=ppc64 ./mkerrors.sh
[lots of generated Go output omitted]

// Signal table
var signalList = [...]struct {
        num  syscall.Signal
        name string
        desc string
} {
        { 1, "SIGHUP", "hangup" },
        { 2, "SIGINT", "interrupt" },
        { 3, "SIGQUIT", "quit" },
        { 4, "SIGILL", "illegal instruction" },
        { 5, "SIGTRAP", "trace/BPT trap" },
        { 6, "SIGLOST", "IOT/Abort trap" },
        { 7, "SIGEMT", "EMT trap" },
        { 8, "SIGFPE", "floating point exception" },
        { 9, "SIGKILL", "killed" },
        { 10, "SIGBUS", "bus error" },
        { 11, "SIGSEGV", "segmentation fault" },
        { 12, "SIGSYS", "bad system call" },
        { 13, "SIGPIPE", "broken pipe" },
        { 14, "SIGALRM", "alarm clock" },
        { 15, "SIGTERM", "terminated" },
        { 16, "SIGURG", "urgent I/O condition" },
        { 17, "SIGSTOP", "stopped (signal)" },
        { 18, "SIGTSTP", "stopped" },
        { 19, "SIGCONT", "continued" },
        { 20, "SIGCLD", "child exited" },
        { 21, "SIGTTIN", "stopped (tty input)" },
        { 22, "SIGTTOU", "stopped (tty output)" },
        { 23, "SIGPTY", "I/O possible/complete" },
        { 24, "SIGXCPU", "cputime limit exceeded" },
        { 25, "SIGXFSZ", "filesize limit exceeded" },
        { 27, "SIGMSG", "input device data" },
        { 28, "SIGWINCH", "window size changes" },
        { 29, "SIGPWR", "power-failure" },
        { 30, "SIGUSR1", "user defined signal 1" },
        { 31, "SIGUSR2", "user defined signal 2" },
        { 32, "SIGPROF", "profiling timer expired" },
        { 33, "SIGDANGER", "paging space low" },
        { 34, "SIGVTALRM", "virtual timer expired" },
        { 35, "SIGMIGRATE", "signal 35" },
        { 36, "SIGPRE", "signal 36" },
        { 37, "SIGVIRT", "signal 37" },
        { 38, "SIGALRM1", "signal 38" },
        { 39, "SIGWAITING", "signal 39" },
        { 48, "SIGSYSERROR", "signal 48" },
        { 49, "SIGCAPI", "signal 49" },
        { 50, "SIGRTMIN", "signal 50" },
        { 57, "SIGRTMAX", "signal 57" },
        { 58, "SIGRECONFIG", "signal 58" },
        { 59, "SIGCPUFAIL", "CPU Failure Predicted" },
        { 60, "SIGGRANT", "monitor mode granted" },
        { 61, "SIGRETRACT", "monitor mode retracted" },
        { 62, "SIGSOUND", "sound completed" },
        { 63, "SIGMAX", "secure attention" },
./mkerrors.sh: line 793: 24052120 Segmentation fault      (core dumped) $GORUN ./_errors

What did you expect to see?

I expected mkerrors.sh to produce complete output on aix/ppc64 without crashing.

Debugging further:

bash-5.2$ CC=gcc-12 GOOS=aix GOARCH=ppc64 ./mkerrors.sh -g
[stdout omitted]
./mkerrors.sh: line 793: 20316654 Segmentation fault      (core dumped) $GORUN ./_errors
bash-5.2$ gdb _errors core
GNU gdb (GDB) 14.1
Copyright (C) 2023 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 "powerpc64-ibm-aix7.1.0.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from _errors...
Core was generated by `_errors'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x10000b54 in strncpy ()
(gdb) up
#1  0x100008e4 in main () at _errors.c:245
245                     strncpy(buf, strsignal(e), sizeof(buf) - 1);
(gdb) p e
$1 = 255
(gdb) p signals[i]
$2 = {num = 255, name = 0x10001878 <_GLOBAL__FD__errors+1564> "SIGMAX64"}

The program attempts to call strsignal() against SIGMAX64, which is not a real signal and is not a valid thing to do. Digging further, it seems the intent is to filter SIGMAX64 out with grep, but using a GNU syntax which doesn't behave the same way with AIX's grep. It looks like it may have broken in x/sys #137. The OS is AIX 7.3.

I've submitted a proposed fix in golang/sys#217

[gabyhelp]

Related Issues and Documentation

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• src/runtime/signal_unix.go:202 Normal gameplay and subsequent code execution #67874 (closed)
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• SIGSEGV: segmentation violation code=0x1 - help #49992 (closed)
• runtime: getArgInfo nil dereference #17471 (closed)

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[timothy-king]

CC @golang/runtime, @ianlancetaylor, @bradfitz, @tklauser per owners for x/sys/unix.

[gopherbot]

Change https://go.dev/cl/615755 mentions this issue: unix: fix grep syntax to work on non-GNU greps