On Mon, Sep 12, 2016 at 09:32:55AM -0700, Vineet Gupta wrote: > | CC mm/memory.o > | In file included from ../mm/memory.c:53:0: > | ../include/linux/pfn_t.h: In function ‘pfn_t_pte’: > | ../include/linux/pfn_t.h:78:2: error: conversion to non-scalar type requested > | return pfn_pte(pfn_t_to_pfn(pfn), pgprot); > > With STRICT_MM_TYPECHECKS pte_t is a struct and the offending code > forces a cast which ends up shifting a struct and hence the gcc warning. > > Note that in recent past some of the arches (aarch64, s390) made > STRICT_MM_TYPECHECKS default, but we don't for ARC as this leads to slightly > worse generated code, given ARC ABI definition of returning structs > (which pte_t would become) > > Quoting from ARC ABI... > > "Results of type struct are returned in a caller-supplied temporary > variable whose address is passed in r0. > For such functions, the arguments are shifted so that they are > passed in r1 and up." > > So > - struct to be returned would be allocated on stack requiring extra > code at call sites > - callee updates stack memory to facilitate the return (vs. simple > MOV into return reg r0) > > Hence STRICT_MM_TYPECHECKS is not enabled by default for ARC > > Cc: <stable@xxxxxxxxxxxxxxx> #4.4+ > Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> > --- > arch/arc/include/asm/pgtable.h | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h > index 3cab04255ae0..e5fec320f158 100644 > --- a/arch/arc/include/asm/pgtable.h > +++ b/arch/arc/include/asm/pgtable.h > @@ -277,8 +277,7 @@ static inline void pmd_set(pmd_t *pmdp, pte_t *ptep) > > #define mk_pte(page, prot) pfn_pte(page_to_pfn(page), prot) > #define pte_pfn(pte) (pte_val(pte) >> PAGE_SHIFT) > -#define pfn_pte(pfn, prot) (__pte(((pte_t)(pfn) << PAGE_SHIFT) | \ > - pgprot_val(prot))) > +#define pfn_pte(pfn, prot) (__pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot))) > #define __pte_index(addr) (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) > > /* > -- > 2.7.4 Whitespace is correct this time, thanks. You can't cut-and-paste in a web email client... But, you forgot to say what the git commit id is for this patch :( Can you resend it with that info? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html