ksyms pseudo driver

[Kostik Belousov]

On Tue, Jul 15, 2008 at 08:14:28AM -0500, Stacey Son wrote:
> Kostik Belousov wrote:
> >>The snapshot of the consolidated symbol table is made when /dev/ksyms is
> >>opened.   The storage for the snapshot is allocated in the memory map of
> >>the calling process.  No kernel address space is used for the snapshot.
> >>     
> >Again, why this is done this way ? Why not creating snapshot when the
> >user process issues ioctl that supplies neccessary usermode memory
> >to the driver ?
> >   
> 
> The main reason it is written as a pseudo driver is so it can be used 
> with standard command-line utilities.   For example, see the ksyms 
> example in the dtrace manual 
> (http://wikis.sun.com/display/DTrace/Structs+and+Unions).   I guess it 
> could still be possible to do in the way you are suggesting but it would 
> require a special 'cat', or something, to allocate the user space buffer 
> and then pass that in driver before it starts reading the symbol table.  
> You could then pipe the output of the "special ksyms cat" to the actual 
> command-line program you wanted to use.    Of course, if you had to use 
> a "special ksyms cat" then there would be no reason to make this a 
> pseudo driver.   You could simply make it a system call and eliminate a 
> lot of code and calls into the kernel.

Would dd bs=<some large value> work as the "special cat" ? procfs'
/proc/pid/map has the similar problem, and there was a procmap program
in ports. I believe dd is enough.
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