SIGFPE in s6-rc-init 3.0.0 etc,...

From: Stefan Nilsson <>
Date: Thu, 14 Dec 2017 22:35:52 +0100

Hey Laurent,

I have been using s6 for some time now to bring up and monitor services
in a custom embedded system. The system is built using buildroot and
(due to customer requirements) built with glibc 2.26.

When using buildroot 2017.08 (containing s6-rc, skalibs
and s6, I ran into the problem that one of my one-shot services
was _occasionally_ not successfully started. The "up" script looked like

/bin/sh -c "
ko=/lib/modules/$(uname -r)/extra/co80.ko
echo insmod $ko
insmod $ko
echo Done!

I noticed in the kernel log that the module was in fact correctly
loaded, but s6 was stuck waiting for something (I noticed this process
when doing a "ps"):

  1213 root s6-ipcserverd -1 -- s6-ipcserver-access -v0 -E -l0 -i
data/rules -- s6-sudod -t 2000 -- /usr/libexec/s6-rc-oneshot-run -l ../.. --

Around 1/10 boots, it got stuck here, the rest of them booted up just fine.

When buildroot 2017.11 was released, I was thrilled to see new versions
of s6 in it (s6-rc, skalibs and s6, but when
booting up I immediately got a SIGFPE in s6-rc-init,... I ran it through
strace and the result can be seen here:

It crashes at the exact same place if I re-run it, and it crashes every

So what to do,... I found:
and decided to update to this version in my buildroot system instead,
but then I got a build error:

make[1]: Entering directory '/home/stefan/buildroot/output/build/s6-'
exec /home/stefan/buildroot/output/host/bin/i586-buildroot-linux-gnu-gcc
-D_POSIX_C_SOURCE=200809L -D_XOPEN_SOURCE=700 -iquote src/include-local
-Isrc/include -Werror=implicit-function-declaration -Werror=implicit-int
-Werror=pointer-sign -Werror=pointer-arith
-Wall -std=c99 -fno-exceptions -fno-unwind-tables
-fno-asynchronous-unwind-tables -Wa,--noexecstack -ffunction-sections
-fdata-sections -O2 -fomit-frame-pointer -fno-stack-protector
-c -o src/daemontools-extras/s6-applyuidgid.o
src/daemontools-extras/s6-applyuidgid.c: In function 'main':
src/daemontools-extras/s6-applyuidgid.c:57:29: error: implicit
declaration of function 'setgroups_and_gid'
    if (gidn != (size_t)-1 && setgroups_and_gid(gid ? gid : getegid(),
gidn, gids) < 0)
cc1: some warnings being treated as errors

Oh happy days,... Any suggestions on any of the three different issues
and how to overcome? :o)

Best Regards
Stefan Nilsson
Received on Thu Dec 14 2017 - 21:35:52 UTC

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