Comment # 12 on bug 1166406 from Tony Jones

For systemtap,  man 3 stapprobes breaks down what stap functions need DWARF
(i.e debuginfo) and what need symbol table (i.e stripped vmlinux). Systemtap
doesn't use /proc (like perf) for symbol-table info as it supports
cross-instrumentation.

I've never actually looked at this as I always install debuginfo but as you can
see below,  systemtap does make use of the stripped vmlinux in question (though
it needs to be manually uncompressed)

Obviously we could ship this stripped vmlinux in a separate package and have
systemtap depend on it (as we do for kernel-devel which is necessary to compile
"hello world")

whether other tools make use of the stripped vmlinux is maybe a question for
kernel list,  there may well be some I'm not aware of

------------------------------


# cat do_fork.stp 
probe kernel.function("_do_fork"){
    if (@defined($clone_flags)) 
        printf("do_fork: clone_flags=0x%lx\n", $clone_flags);
    else
        printf("do fork: no dwarf\n");
}

# ls -l /boot/vmlinux-4.12.14-197.34-default
/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug
ls: cannot access '/boot/vmlinux-4.12.14-197.34-default': No such file or
directory
ls: cannot access '/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug':
No such file or directory

# 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'

Pass 2: analysis failed.  [man error::pass2]

# ls -l /boot/vmlinux-4.12.14-197.34-default
/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug
ls: cannot access '/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug':
No such file or directory
-rw-r--r-- 1 root root 51122824 Mar 12 09:51
/boot/vmlinux-4.12.14-197.34-default

# stap --poison-cache do_fork.stp
do fork: no dwarf
^C 

# ls -l /boot/vmlinux-4.12.14-197.34-default
/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug
-rw-r--r-- 1 root root  51122824 Mar 12 09:51
/boot/vmlinux-4.12.14-197.34-default
-rw-r--r-- 2 root root 370477552 Feb 25 09:27
/usr/lib/debug/boot/vmlinux-4.12.14-197.34-default.debug
# 
# stap --poison-cache do_fork.stp
do_fork: clone_flags=0x1200011
^C