From 1c3c909303924d30145601f47b6c058fdd2cbc2e Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Tue, 16 Aug 2016 18:27:07 -0700 Subject: [PATCH] ARC: mm: fix build breakage with STRICT_MM_TYPECHECKS MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit | 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: #4.4+ Signed-off-by: Vineet Gupta --- arch/arc/include/asm/pgtable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h index 0f92d97432a2..89eeb3720051 100644 --- a/arch/arc/include/asm/pgtable.h +++ b/arch/arc/include/asm/pgtable.h @@ -280,7 +280,7 @@ static inline void pmd_set(pmd_t *pmdp, pte_t *ptep) #define pte_page(pte) pfn_to_page(pte_pfn(pte)) #define mk_pte(page, prot) pfn_pte(page_to_pfn(page), prot) -#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)) /* Don't use virt_to_pfn for macros below: could cause truncations for PAE40*/ #define pte_pfn(pte) (pte_val(pte) >> PAGE_SHIFT) -- 2.20.1