Hello to all, I have tried sending/getting some data to/from a bsd kernel extension using a sysctl, but when I return ENOMEM from the handler the user space got success from the sysctl(3) call. I couldn't find explanation for this case in the man page, so I made a very simple kext which registers a systl using sysctl_register_oid under _debug, which handler always returns ENOMEM. When calling this sysctl from user space I observed the following things: [1] If I call sysctlbyname with oldp set to NULL then I get an error code -1 and errno is set to ENOMEM, but [2] if I call sysctlbyname with valid oldp, in my case pointing to a stack buffer, the call to sysctlbyname returns 0. According to sysctl(3) I expect in case [2] to get ENOMEM again - "If the amount of data available is greater than the size of the buffer supplied, the call supplies as much data as fits in the buffer provided and returns with the error code ENOMEM." The system I'm testing on is 10.7.4 with Xcode 4.4.1 installed. I could also provide the source of the kext and the user space program calling the sysctl if anyone wants to test this. I tried to look through the xnu source but didn't found any place where ENOMEM is handled explicitly and changed to 0. I also debugged the command line after calling sysctl(3) and saw that till the call to syscall the execution path is the same, but if the sysctl handler returns ENOMEM the syscall returns with CF cleared and the the whole call returns success, but if the handler returns ENOATTR, then syscall returns with CF and we go on the fail path (errno is set to ENOATTR, etc). Can somebody point me whether this is well-known behavior of sysctl, is it undocumented or I'm misreading the man page? Thank you, Alex. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-kernel mailing list (Darwin-kernel@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-kernel/site_archiver%40lists.... This email sent to site_archiver@lists.apple.com