The runtime configure commands' output is not logged anywhere. From the generated Makefile for module builds:
@if $(CHECK_BUILD) $(SYSTEMTAP_RUNTIME)/linux/autoconf-linux-sched_headers.c > /dev/null 2>&1; then echo "#define STAPCONF_LINUX_SCHED_HEADERS 1"; fi >> $@
all output is sent to /dev/null .
This made diagnosis rather harder in #25265
I suggest redirection of stdout to stderr instead, and bracketing it with an echo. Like
@echo Runtime configure test linux/autoconf-linux-sched_headers.c for STAPCONF_LINUX_SCHED_HEADERS:
@if $(CHECK_BUILD) $(SYSTEMTAP_RUNTIME)/linux/autoconf-linux-sched_headers.c 1>&2; then echo "#define STAPCONF_LINUX_SCHED_HEADERS 1"; echo "yes"; else echo "no"; fi >> $@
All the runtime autoconf results end up in a stapconf_HEXHEXHEX.h file, did you see that one? We can't transcribe dozens of check/results to systemtap's stderr, that's too chatty. Maybe with some stap --vp 0x000 level, but then this level would have to be communicated to the kbuild makefile.
Yes, it's relatively easy to find the test outcomes, but not why the test returned success or failure. That's part of why diagnosing these issues took me so long.
I was thinking it'd make sense to output the configure test results at stap -vvv or similar. So yes, probably by injecting a variable in the make command invocation.