What can I access in return probe

[Badari Pulavarty]

Hi,

I am wondering if I can access arguments in my return probe ?
And also, how do I access return value ?
 
Whats wrong here ?

# stap -g pagecache.stp
ERROR: pointer dereference fault near identifier 'page_cache_pages' at
pagecache.stp:8:2


Thanks,
Badari




-------------- next part --------------
#! stap

global page_cache_pages

function _(n) { return string(n) } 

probe kernel.function("add_to_page_cache").return {
	page_cache_pages[$mapping] = $mapping->nrpages
}

probe kernel.function("__remove_from_page_cache") {
	page_cache_pages[$page->mapping] = $page->mapping->nrpages
}

function report () {
  foreach (mapping in page_cache_pages) {
	print("mapping = " . hexstring(mapping) . 
		" nrpages = " . _(page_cache_pages[mapping]) . "\n")
  }
  delete page_cache_pages
}

probe end {
  report()
}