ARC: mm: fix build breakage with STRICT_MM_TYPECHECKS

commit 1c3c909303924d30145601f47b6c058fdd2cbc2e upstream.

|  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

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index 3cab04255ae0a4e9db1599ae348d6f1360acd970..e5fec320f158e51ba6519dd7ee3ef71725943d8c 100644 (file)
--- 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))
 
 /*