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loading a module and enabling function tracing at the same time. He uncovered a race where the module when loaded will convert the calls to mcount into nops, and expects the module's text to be RW. But when function tracing is enabled, it will convert all kernel text (core and module) from RO to RW to convert the nops to calls to ftrace to record the function. After the convertion, it will convert all the text back from RW to RO. The issue is, it will also convert the module's text that is loading. If it converts it to RO before ftrace does its conversion, it will cause ftrace to fail and require a reboot to fix it again. This patch moves the ftrace module update that converts calls to mcount into nops to be done when the module state is still MODULE_STATE_UNFORMED. This will ignore the module when the text is being converted from RW back to RO. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAABAgAGBQJTXuHsAAoJEKQekfcNnQGuT7cIAJQhwX2fpdFr5eHwx0CyFo5c 75V0xcRhJsGeXqfgekkRhCHYEfL7v4sl6D+Bj8qzLG/0QresF9jVSMUTTZqYFpFc t7f3oDDtdCmfofD/uyS7YOQ3JhU5ijo+Drzq8qRYtWNJJ0WCqbddpevcUiW1Zbvr LAT3lcb+2I5Y1Jnyfd920+0plAnoeOw1/BPuRVJINwh8zeyvWnmp3iq9fOPdhMQQ VhCCg+C2ILBPrCPFdwC5pVrL4a/CjyNd+LqtFXjLS9sO8s5KyUGkqKkbHMlhZeot uRWlZUSNZsh/jpP4X2b+dtYGQ4Rrnp253a594Kmrzm/MPdsAV62oDqOfN0tzm7w= =K59a -----END PGP SIGNATURE----- Merge tag 'trace-fixes-v3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull ftrace bugfix from Steven Rostedt: "Takao Indoh reported that he was able to cause a ftrace bug while loading a module and enabling function tracing at the same time. He uncovered a race where the module when loaded will convert the calls to mcount into nops, and expects the module's text to be RW. But when function tracing is enabled, it will convert all kernel text (core and module) from RO to RW to convert the nops to calls to ftrace to record the function. After the convertion, it will convert all the text back from RW to RO. The issue is, it will also convert the module's text that is loading. If it converts it to RO before ftrace does its conversion, it will cause ftrace to fail and require a reboot to fix it again. This patch moves the ftrace module update that converts calls to mcount into nops to be done when the module state is still MODULE_STATE_UNFORMED. This will ignore the module when the text is being converted from RW back to RO" * tag 'trace-fixes-v3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: ftrace/module: Hardcode ftrace_module_init() call into load_module() |
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