1ERROR::PASS2(7stap) ERROR::PASS2(7stap)
2
6 error::pass2 - systemtap pass-2 errors
7
10 Errors that occur during pass 2 (elaboration) can have a variety of
11 causes. Common types include:
12 missing debuginfo
15 The script requires debuginfo to resolve a probe point, but
16 could not find any. See error::dwarf(7stap) and warning::debug‐
17 info(7stap) for more details.
18 unavailable probe point classes
21 Some types of probe points are only available on certain system
22 versions, architectures, and configurations. For example, user-
23 space process.* probes may require utrace or uprobes capability
24 in the kernel for this architecture.
25 unavailable probe points
28 Some probe points may be individually unavailable even when
29 their class is fine. For example, kprobe.function("foobar") may
30 fail if function foobar does not exist in the kernel any more.
31 Debugging or symbol data may be absent for some types of .func‐
32 tion or .statement probes; check for availability of debuginfo.
33 Try the stap-prep program to download possibly-required debug‐
34 info. Use a wildcard parameter such as stap -l 'kprobe.func‐
35 tion("*foo*")' to locate still-existing variants. Use ! or ?
36 probe point suffixes to denote optional / preferred-alterna‐
37 tives, to let the working parts of a script continue.
38 typos There might be a spelling error in the probe point name ("syc‐
41 sall" vs. "syscall"). Wildcard probes may not find a match at
42 all in the tapsets. Recheck the names using stap -l PROBEPOINT.
43 Another common mistake is to use the . operator instead of the
44 correct -> when dereferencing context variable subfields or
45 pointers: $foo->bar->baz even if in C one would say
46 foo->bar.baz.
47 unavailable context variables
50 Systemtap scripts often wish to refer to variables from the con‐
51 text of the probed programs using $variable notation. These
52 variables may not always be available, depending on versions of
53 the compiler, debugging/optimization flags used, architecture,
54 etc. Use stap -L PROBEPOINT to list available context variables
55 for given probes. Use the @defined() expression to test for the
56 resolvability of a context variable expression. Consider using
57 the stap --skip-badvars option to silently replace misbehaving
58 context variable expressions with zero. Experiment with the
59 stap --prologue-searching option.
60 module cache inconsistencies
63 Occasionally, the systemtap module cache ($HOME/.system‐
64 tap/cache) might contain obsolete information from a prior sys‐
65 tem configuration/version, and produce false results as system‐
66 tap attempts to reuse it. Retrying with stap --poison-cache ...
67 forces new information to be generated. Note: this should not
68 happen and likely represents a systemtap bug. Please report it.
69
72 Increasing the verbosity of pass-2 with an option such as --vp 02 can
73 help pinpoint the problem.
74
77 stap(1),
78 stap-prep(1),
79 stapprobes(3stap),
80 probe::*[24m(3stap),
81 error::dwarf(7stap),
82 error::inode-uprobes(7stap),
83 warning::debuginfo(7stap),
84 error::reporting(7stap)
85 ERROR::PASS2(7stap)