access variables within functions

[Rus-Rebreanu Alin-Florin]

Hi,
I have a problem with accessing a variable using systemtap.
Let's take for example vfs_read in fs/read_write.c:
ssize_t vfs_read(file,buf,count,pos){
ssize_t ret;
........more code.....
return ret;

}

using stap i want to access "ret". Accessing the parameters of the
function works just fine with "$var".
I'm using:
stap -vvv -e 'probe kernel.function("vfs_read@fs/read_write.c:270")
{printf("%d",$ret)}'
It doesn't work. Am I missing something?

Thank you.