Unable to build a working "static" 1.19.3 build under uclibc hardened

[Ed W]

Hi, I'm still trying to understand the details or figure out how to get 
a backtrace, but although I can build a working dynamically linked 
busybox 1.19.3, whenever I build the same config with "static" config 
set I get a binary which behaves very strangely, in particular dying 
whenever a sub process is used, or exiting the main executable:

# /tmp/busybox sh /tmp/test.sh
Killed (core dumped)

# cat /tmp/test.sh
#!/bin/sh
echo abcd | grep debug


The specifics of the build environment are a gentoo x86 chroot, running 
uclibc 0.9.33.1, and a hardened gcc and toolchain.  Kernel has PAX and 
grsec enabled

Running up a busybox shell with this binary and then running any command 
with a pipe (|) seems to cause the core dump message, then a second 
attempt locks up the shell and trying to kill -9 the process from 
another shell worryingly seems to take quite a significant number of 
seconds before the task dies, something like a few 10s of seconds perhaps.

I see in my log files:

[5882184.345386] PAX: From 192.168.105.65: execution attempt in: (null), 
00000000-00000000 00000000
[5882184.345391] PAX: terminating task: /tmp/busybox(busybox):20169, 
uid/euid: 0/0, PC: (nil), SP: 00000000fdba1bc4
[5882184.345393] PAX: bytes at PC: ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 
?? ?? ?? ?? ?? ?? ?? ??
[5882184.345415] PAX: bytes at SP-8: 0814ee3408138eb8 fdba1d280804faaa 
08138eb8fdba1bc0 ffffffff00000000 fdba1d28080a9805 080b4efb00000001 
0000000008138eb8 0815fdbcffffffff 0815fdac026176ba 08138eb8080a97d3 
00000018080b18d3


Same build without static works fine (I notice that toggling static 
toggles PIE - is this significant? I presume it makes no sense to have a 
PIE enabled static executable..?)

I have previously successfully built a static 1.18.3 executable, but 
foolishly can't lay my hands on the .config now... I'm just trying to 
build various previous versions to see if this is a regression in 1.19, 
but wanted to ask if there were any known regressions here, or if I'm 
overlooking some obvious build process error that would be significant 
with a hardened + static build?  I'm not even sure of a sensible way to 
get the core dump under gdb at the moment?

Thanks for any pointers

Ed W