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Developers would say they put a trace_printk() before and after the trace event but when they enable it (and the trace event said it was enabled) they would see the trace_printks but not the trace event. I was not able to reproduce this, but that's because I wasn't looking at the right location. Recently, another bug came up that showed the issue. If your kernel supports signed modules but allows for non-signed modules to be loaded, then when one is, the kernel will silently set the MODULE_FORCED taint on the module. Although, this taint happens without the need for insmod --force or anything of the kind, it labels the module with that taint anyway. If this tainted module has tracepoints, the tracepoints will be ignored because of the MODULE_FORCED taint. But no error message will be displayed. Worse yet, the event infrastructure will still be created letting users enable the trace event represented by the tracepoint, although that event will never actually be enabled. This is because the tracepoint infrastructure allows for non-existing tracepoints to be enabled for new modules to arrive and have their tracepoints set. Although there are several things wrong with the above, this change only addresses the creation of the trace event files for tracepoints that are not created when a module is loaded and is tainted. This change will print an error message about the module being tainted and not the trace events will not be created, and it does not create the trace event infrastructure. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAABAgAGBQJTFnMPAAoJEKQekfcNnQGuPPwH/Rtwy/siM+ltvlLnEbRjS4RL 9aF5mfJUazmfCaOBMSaMUo92uCbciIVif6icX843JmCdCOR5Hk5SZryBbt2A/dF9 TcMloKNbIn/ad7yZ0O75BJlPnRJ5RZ42edQfW1lkdeWo644C8Kj399fVPt7KU5SH 1KTWyShT05E2fYjp2lMrb+FOFfKerlzkXtgGwJKXnd/7hrbdmKEH/OO8YkMrlVZp SURPyzNMMVKoUFY797b6FrFRqV04C210BtNcNrd4S3/V9VE4IPS/8YSLfvVaGkD0 e2kVAvIOkwPnYzMZg70jf2R8NlGS2mwaVC+NenBHz3KlpFdaeRu1hFw7/n8h2/s= =YbJd -----END PGP SIGNATURE----- Merge tag 'trace-fixes-v3.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fix from Steven Rostedt: "In the past, I've had lots of reports about trace events not working. Developers would say they put a trace_printk() before and after the trace event but when they enable it (and the trace event said it was enabled) they would see the trace_printks but not the trace event. I was not able to reproduce this, but that's because I wasn't looking at the right location. Recently, another bug came up that showed the issue. If your kernel supports signed modules but allows for non-signed modules to be loaded, then when one is, the kernel will silently set the MODULE_FORCED taint on the module. Although, this taint happens without the need for insmod --force or anything of the kind, it labels the module with that taint anyway. If this tainted module has tracepoints, the tracepoints will be ignored because of the MODULE_FORCED taint. But no error message will be displayed. Worse yet, the event infrastructure will still be created letting users enable the trace event represented by the tracepoint, although that event will never actually be enabled. This is because the tracepoint infrastructure allows for non-existing tracepoints to be enabled for new modules to arrive and have their tracepoints set. Although there are several things wrong with the above, this change only addresses the creation of the trace event files for tracepoints that are not created when a module is loaded and is tainted. This change will print an error message about the module being tainted and not the trace events will not be created, and it does not create the trace event infrastructure" * tag 'trace-fixes-v3.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Do not add event files for modules that fail tracepoints |
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