Messages in this thread | | | Date | Tue, 6 Jan 2009 01:32:30 -0500 | From | "Mike Frysinger" <> | Subject | Re: debugfs & vfs file permission issue? |
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On Tue, Jan 6, 2009 at 01:19, Greg KH wrote: > On Tue, Jan 06, 2009 at 12:54:58AM -0500, Mike Frysinger wrote: >> On Tue, Jan 6, 2009 at 00:48, Greg KH wrote: >> > On Mon, Jan 05, 2009 at 09:57:07PM -0500, Robin Getz wrote: >> >> On 2.6.28-rc2, If I create a debugfs file with >> >> >> >> debugfs_create_x16("SPORT1_TX", 0200 , parent, 0xFFC00910); >> > >> > Um, are you are passing in a pointer to a known memory location >> > properly? Why would it be ok for the kernel to directly read that >> > location? >> >> it's a nommu system and the 0xffc00000+ addresses are always available > > Writable but not readable? Isn't hardware fun :)
yeah and we have some readable but not writable addresses too :/
>> >> Although the file shows up as write only (no read): >> >> >> >> root:/> ls -l /sys/kernel/debug/blackfin/SPORT/SPORT1_TX >> >> --w------- 1 root root 0 Jan 1 >> >> 2007 /sys/kernel/debug/blackfin/SPORT/SPORT1_TX >> >> >> >> root:/> cat /sys/kernel/debug/blackfin/SPORT/SPORT1_TX >> >> >> >> Still works - and causes the read to occur, which crashes :( >> > >> > You're root, you can do anything :) >> >> any thoughts on how to declare debugfs files that are read or write >> only ? we'll have to add new helper functions or have it be a >> parameter or declare our own debugfs file ? > > Just use debugfs_create_file() and use your own read/write functions to > prevent a read or write from happening no matter what. No new debugfs > infrastructure should be needed.
would it be useful for this to be a common function ? probably not so much considering (i'm assuming) no one else has asked so far for such a beast ... -mike
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