On Mon, 14 Mar, at 05:47:00PM, Ingo Molnar wrote: > > * Matt Fleming <[email protected]> wrote: > > > Running the attached semantic patch across arch/x86/mm yields a few > > more places where we get the data type wrong for PAE, > > Very nice! > > > * file: arch/x86/mm/mmap.c:43 shifting int '( ( - 1UL ) & STACK_RND_MASK )' > > by PAGE_SHIFT is truncated to 32-bits > > * file: arch/x86/mm/pageattr-test.c:57 shifting long 'i' by PAGE_SHIFT is > > truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr-test.c:138 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/gup.c:422 shifting int 'nr' by PAGE_SHIFT is truncated > > to 32-bits > > * file: arch/x86/mm/gup.c:303 shifting unsigned long '( unsigned long ) > > nr_pages' by PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/gup.c:370 shifting unsigned long '( unsigned long ) > > nr_pages' by PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pat.c:751 shifting unsigned long 'pfn' by PAGE_SHIFT is > > truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr-test.c:57 shifting long 'i' by PAGE_SHIFT is > > truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:947 shifting unsigned 'num_pages' by > > PAGE_SHIFT is truncated to 32-bits > > * file: arch/x86/mm/pageattr.c:1995 shifting unsigned 'numpages' by > > PAGE_SHIFT is truncated to 32-bits > > * file: arch/x86/mm/pageattr-test.c:138 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:1117 shifting unsigned long 'cpa -> > > numpages' by PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:1017 shifting unsigned long 'cpa -> > > numpages' by PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:1277 shifting unsigned long 'cpa -> pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:1318 shifting unsigned long 'cpa -> pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:986 shifting unsigned long 'cpa -> pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/pageattr.c:1059 shifting unsigned long 'cpa -> pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:197 shifting unsigned long 'end_pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:100 shifting unsigned long 'min_pfn_mapped' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:641 shifting unsigned long 'pagenr' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:111 shifting unsigned long 'pfn' by PAGE_SHIFT > > is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:121 shifting unsigned long 'pfn' by PAGE_SHIFT > > is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:111 shifting unsigned long __initdata > > 'pgt_buf_end' by PAGE_SHIFT is truncated to 32-bits > > * file: arch/x86/mm/init.c:196 shifting unsigned long 'start_pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:91 shifting unsigned long '( unsigned long ) > > num' by PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init.c:117 shifting unsigned long '( pfn + i )' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init_32.c:293 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init_32.c:301 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init_32.c:344 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init_32.c:361 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > * file: arch/x86/mm/init_32.c:471 shifting unsigned long 'pfn' by > > PAGE_SHIFT is truncated to 32-bits for PAE > > > > The coccinelle script isn't perfect, and there are a number of false > > positives. For example, the first hit is bogus and looks like a > > coccinelle bug, but the results do show some things that need to be > > investigated. > > So I checked a few random examples in your list, and the false positive rate > looks > rather low. > > The current Kbuild integration of Cocci scripts is pretty user-hostile. I'd > love > to make this Cocci check part of the regular build process in some fashion > (if a > Kconfig option is enabled), similarly to how we run objtool for example. We > could > emit the Cocci warnings as a regular compiler 'warning: ' message, so people > will > notice them as part of the build?
For this type of cocci script where architecture knowledge of bug idioms is required (you need to know shifting by "PAGE_SHIFT" is usually done to build an address or size of some kind) I think the first step would be to automatically lookup scripts to be run on a per-directory basis. For example, running make(1) in arch/x86/kernel should map to scripts/coccinelle/arch/x86/kernel, etc. And yes, I agree, turning this on via a CONFIG_* symbol would be nice. > The false positive(s) could either be worked around or annotated away. > > Obviously we'd only use Cocci scripts that are known to be reliable. Fengguang, do you run coccinelle scripts currently as part of the 0-day lkp build machinery?
