| Summary: | stap misses functions with the same name in one CU | ||
|---|---|---|---|
| Product: | systemtap | Reporter: | Josh Stone <jistone> |
| Component: | tapsets | Assignee: | Josh Stone <jistone> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | ||
| Priority: | P2 | ||
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Host: | Target: | ||
| Build: | Last reconfirmed: | ||
| Bug Depends on: | |||
| Bug Blocks: | 10461 | ||
I found cases of this in the kernel as well, so this isn't just a C++ issue. It
usually occurs where a function is both inlined and has concrete instances. For
example, on 2.6.29.6-217.2.16.fc11.x86_64, these are the DIEs related to
"acpi_battery_units":
(at the top level of the CU)
[2359b7f] subprogram
external
name "acpi_battery_units"
decl_file 1
decl_line 260
prototyped
type [234db21]
inline declared_inlined (3)
sibling [2359b9f]
(...)
[2359d83] subprogram
abstract_origin [2359b7f]
low_pc 0xffffffff8120f207 <acpi_battery_units>
high_pc 0xffffffff8120f22b <sysfs_remove_battery>
frame_base location list [49f943]
sibling [2359da8]
(... later, nested in other subprograms ...)
[235a69b] inlined_subroutine
abstract_origin [2359b7f]
entry_pc 0xffffffff8120fb72
<acpi_battery_print_alarm+0x5c>
ranges range list [ ab210]
call_file 1
call_line 646
(...)
[235a717] inlined_subroutine
abstract_origin [2359b7f]
entry_pc 0xffffffff8120fcaa
<acpi_battery_print_state+0xf6>
ranges range list [ ab240]
call_file 1
call_line 611
sibling [235a735]
(etc.)
Currently, through dwarf_getfuncs our code will first encounter [2359b7f] and
write it into the cache. Later we will see [2359d83], which will overwrite the
first one in the cache. Thus, we never even look for the inline instances
associated with [2359b7f].
commit b7478964 |
stap doesn't probe all possible functions when some have the same name in a single CU. This can happen in C++ if the functions have overloaded parameters, or if the functions are from different namespace/class scopes. For example: $ stap -l 'process("/usr/bin/stap").function("visit_target_symbol")' process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/staptree.cxx:2636") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/elaborate.cxx:2807") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/translate.cxx:3513") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/tapsets.cxx:2167") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/tapset-procfs.cxx:353") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/tapset-perfmon.cxx:46") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/tapset-mark.cxx:187") process("/usr/bin/stap").function("visit_target_symbol@/usr/src/debug/systemtap-0.9.9/tapset-utrace.cxx:543") That's 8 probes, but stap actually has 15 visit_target_symbol functions. You can see that there's only one function per selected CU, but should be multiple functions found in elaborate.cxx, staptree.cxx, and tapsets.cxx.