Red Hat Bugzilla – Bug 101500
strace confuses MTIOCTOP for SNDCTL_MIDI_MPUMODE
Last modified: 2007-03-27 00:08:38 EDT
Running strace of "mt stoptions" produces this: open("/dev/nst0", O_RDONLY|O_NONBLOCK) = 3 ioctl(3, SNDCTL_MIDI_MPUMODE, 0xbfffefc0) = 0 close(3) = 0 Or, with "-e raw=ioctl": open("/dev/nst0", O_RDONLY|O_NONBLOCK) = 3 ioctl(0x3, 0x40086d01, 0xbfffe0c0) = 0 close(3) = 0 #define MTIOCTOP _IOW('m', 1, struct mtop) /* do a mag tape op */ #define SNDCTL_MIDI_MPUMODE _SIOWR('m', 1, int) Upper bits in the ioctl command cannot be the same: sizes are different. Not a big problem as long as I can see the raw number, but FYI, in case you want to overhaul how strace matches ioctl numbers.
[zaitcev@niphredil zaitcev]$ rpm -q strace strace-4.4.95-2
AFAICT this has been broken upstream since 4.4 because of wrong assumptions in the revamp of ioctl handling done between 4.3 and 4.4. The situation is dicey, because there seems to be no law or convention that prevents multiple unrelated ioctl codes being defined for different devices using the same value. It so happens that these two do not actually collide because of the data sizes, but the overloading of the 'm' code letter for SNDCTL_* and MTIO_* codes means that new additions could easily collide. If that were to happen, strace would have no way to know which one you had in mind. I don't think I will fix this upstream before the strace-4.5 release, it will have to go on the list of known bugs.