On Tue, 24 Jun 2014, Joe Perches wrote:
> On Tue, 2014-06-24 at 07:24 +0200, Julia Lawall wrote > > On Mon, 23 Jun 2014, Joe Perches wrote: > > > > > $ cat ./scripts/coccinelle/api/alloc/pci_zalloc_consistent.cocci > > > > > /// > > > > > /// Use pci_zalloc_consistent rather than > > > > > /// pci_alloc_consistent followed by memset with 0 > > > > > /// > > > > > /// This considers some simple cases that are common and easy to > > > > > validate > > > > > /// Note in particular that there are no ...s in the rule, so all of > > > > > the > > > > > /// matched code has to be contiguous > > > > > /// > > > > > /// Blatantly cribbed from: > > > > > scripts/coccinelle/api/alloc/kzalloc-simple.cocci > > > > > > > > > > @@ > > > > > type T, T2; > > > > > expression x; > > > > > expression E1,E2,E3; > > > > > statement S; > > > > > @@ > > > > > > > > > > - x = (T)pci_alloc_consistent(E1,E2,E3); > > > > > + x = pci_zalloc_consistent(E1,E2,E3); > > > > > if ((x==NULL) || ...) S > > > > > - memset((T2)x,0,E2); > > > > > > > > I don't know much about SmPL, but wouldn't having that if statement > > > > there reduce your matches? > > > > > > No, not really. > > > > > > Almost none of the pci_alloc_consistent calls > > > do not have a test for failure immediately after > > > them. > > > Do not or do? > > Sorry, English double negative. > > As far as I know, almost every instance of pci_alloc_consistent > is followed by an if. > > Exceptions exist in: > > drivers/isdn/hardware/eicon/divasmain.c > drivers/staging/slicoss/slicoss.c > drivers/tty/synclink_gt.c > > There might be others, but I didn't look too hard. > > > The advantage of the if is that you are sure that nothing strange happens > > to x between alloc and memset. But a problem can be that sometimes people > > allocate two things, and then do error checking for both of them. Then > > you rule would not match. Or the set the return variable to an error code > > before doing the check rather than in the if branch. > > > > You could put the following between the malloc and the memset in stead of > > the if. > > > > ... when != ( f(...,x,...) | <+...x...+> = E3 ) > > when != ( while(...) S | for(...;...;...) S ) > > > > This has given reasonable results for kmalloc and memset. > > Thanks for that. > > It might be nice to add that to the kzalloc example > in scripts/coccinelle I will do that. Thanks. julia -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
