Comment # 17 on bug 1166406 from Jiri Slaby

(In reply to Tony Jones from comment #12)
> # stap do_fork.stp
> semantic error: while resolving probe point: identifier 'kernel' at
> /home/tonyj/stap/do_fork.stp:1:7
>         source: probe kernel.function("_do_fork"){
>                       ^
> 
> semantic error: missing x86_64 kernel/module debuginfo [man
> warning::debuginfo] under '/lib/modules/4.12.14-197.34-default/build'

Hmm, I don't see this:
# ll /boot/vmlinux*
-rw-r--r-- 1 root root 10030200 Mar  9 14:20 /boot/vmlinux-5.5.7-1-default.xz
# strace -fo bubak -e trace=%file stap -v b.stap 
Pass 1: parsed user script and 476 library scripts using
97296virt/88352res/6588shr/81884data kb, in 280usr/90sys/559real ms.
Pass 2: analyzed script: 1 probe, 0 functions, 0 embeds, 0 globals using
119936virt/112752res/8172shr/104524data kb, in 1110usr/100sys/1225real ms.
Pass 3: translated to C into
"/tmp/stapcPCpg1/stap_81ae959f3a822f58c54b6ac1ed4df3ae_916_src.c" using
119936virt/113000res/8420shr/104524data kb, in 990usr/60sys/1066real ms.
Pass 4: compiled C into "stap_81ae959f3a822f58c54b6ac1ed4df3ae_916.ko" in
16370usr/8760sys/37761real ms.
Pass 5: starting run.
do fork: no dwarf 
do fork: no dwarf 
^Cdo fork: no dwarf 
Pass 5: run completed in 20usr/200sys/50435real ms.
# grep '"/boot' bubak
24675 openat(AT_FDCWD, "/boot/System.map-5.5.7-1-default", O_RDONLY) = 3
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default", O_RDONLY) = -1 ENOENT
(No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.debug", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/.debug/vmlinux-5.5.7-1-default.debug", O_RDONLY)
= -1 ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/.debug/vmlinux-5.5.7-1-default", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.debug", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default", O_RDONLY) = -1 ENOENT
(No such file or directory)
24675 openat(AT_FDCWD, "/boot/build/vmlinux-5.5.7-1-default.debug", O_RDONLY) =
-1 ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/build/vmlinux-5.5.7-1-default", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.debug", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default", O_RDONLY) = -1 ENOENT
(No such file or directory)
24675 lstat("/boot", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
24675 lstat("/boot/vmlinux-5.5.7-1-default", 0x7ffc1e6778e0) = -1 ENOENT (No
such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.gz", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.bz2", O_RDONLY) = -1
ENOENT (No such file or directory)
24675 openat(AT_FDCWD, "/boot/vmlinux-5.5.7-1-default.xz", O_RDONLY) = 3

So it can and does open .xz. Tony, do you have some old version of systemtap?