Chris, Could I do something like: Mm_segment_t cur_fs = get_fs(); Set_fs(get_ds()); // which puts me in userspace Char * newbuf[required_size]; Set_fs(cur_fs); If (copy_to_user(newbuf,srcbuf,required_size); Ret = sys_write_orig(fd, newbuf,required_size); -----Original Message----- From: Chris Brannon [mailto:chris@xxxxxxxxxxxxxxxx] Sent: Friday, July 19, 2013 5:38 AM To: Speakup is a screen review system for Linux. Subject: Re: ot memory allocation question Don Raikes <don.raikes at oracle.com> writes: > My solution: > > Allocate a new larger buffer inside of the userspace and copy_to_user > into the new buffer and then when I pass control to the "real" > sys_write function point it to the new buffer. > But the problem is how do I allocate this new buffer? There's no easy way to do this. You can't just pass your kernel buffer to the system call you are intercepting, since the intercepted call expects a user-space buffer. Have a look at this link for some inspiration: http://web.cs.wpi.edu/~cs4513/b05/proj1note2.txt Also be careful about the return value of the real sys_write system call. If you're passing it a buffer larger than the n bytes passed in from userspace, its return value can be greater than n. Don't just use it unmodified as the return value for your function. -- Chris _______________________________________________ Speakup mailing list Speakup at linux-speakup.org http://linux-speakup.org/cgi-bin/mailman/listinfo/speakup
