trace, tplist, argdist: UDST probe miscellaneous fixes #909
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4ast
requested changes
Jan 17, 2017
| @@ -258,7 +258,7 @@ def _generate_streq_function(self, string): | |||
| char needle[] = %s; | |||
| char haystack[sizeof(needle)]; | |||
| bpf_probe_read(&haystack, sizeof(haystack), (void *)str); | |||
| for (int i = 0; i < sizeof(needle); ++i) { | |||
| for (int i = 0; i < sizeof(needle)-1; ++i) { | |||
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coding style nit: should be space before and after '-'
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Thanks, there's actually a couple of places in the Python script that I did the same. Will fix and force-push.
The `trace` and `argdist` tools expect location and argument indices to start at 1 -- the first argument is arg1, and so on. The `tplist` tool now prints UDST argument indices (and location indices, for consistency) as 1-based as well.
Oftentimes we want to use the STRCMP helper to compare strings that are not null-terminated, e.g. in USDT probes this often happens. Ignore the null terminator (i.e. loop until the last character excluding the null terminator).
`trace` would use the incorrect argument index for USDT probes when filtering specifically, e.g. `trace u:lib:tp (arg1 != 0) ...` would actually use the type of the 2nd argument, and not the 1st argument for the type of the filter variable in the generated program. This could cause compilation errors or subtle bugs where the data would be either extended or contracted to fit the wrong argument's type. Additionally, `trace` would use the pid (thread id, `-L`) filter with the `attach_uprobe` API, which expects a tgid (process id). As a result, incorrect filtering would happen.
goldshtn
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Also rebased and force-pushed to enable auto-merge. |
4ast
approved these changes
Jan 17, 2017
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This patchset is a collection of fixes around USDT probes and filters in trace, argdist, and tplist.