2011/12/18 Fernando Apesteguía <fernando.apesteg...@gmail.com>: > El 18/12/2011 22:12, "Julian Elischer" <jul...@freebsd.org> escribió: >> >> On 12/18/11 12:18 PM, Fernando Apesteguía wrote: >>> >>> Hi all, >>> >>> I'm writing a small module just for fun. I would like to have two > variables: >>> >>> - "pid" of type unsigned int and RW so the user can set a pid >>> - "process_name" as a string RD that will display the process name >>> associated to that pid (or a message if the pid doesn't exist anymore) >> >> >> this is dangerous as there are some places in the kernel where processes >> are referenced by pid, so changing it may break kernel assumptions. > > Sorry, i think i didn't explain it clearly. The "pid" variable is static in > my module and it is used just to tell the module which information it > should show in the other variable.
Many sysctl handlers look for a req->newptr and leave early if it's NULL. If it's non-NULL then you can use SYSCTL_IN to fetch the data. Note that a caller of sysctl(3) API can specify both old pointer and new pointer, which is why most handlers always do a SYSCTL_OUT on the current value. Cheers, matthew >>> My problem is with the handler functions. For "process_name", as it is >>> read only, I wrote a simple handler that works fine. However, I want >>> to write another one for "pid" so I can sanitize the input (avoiding >>> pids< 0 and so). As I understand, the handler I specify with >>> SYSCTL_OID will be called for both reads and writes. But, how can I >>> tell what kind of operation is it, so I know if I have to use >>> SYSCTL_OUT or SYSCTL_IN? I tried to have a look at sysctl_handle_int >>> but I don't fully understand what is going on with the arg1 parameter. >>> What is it for? >>> >>> Thanks in advance. >>> _______________________________________________ >>> freebsd-hackers@freebsd.org mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers >>> To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org > " >>> >> > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org" _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
