This is a note to let you know that I've just added the patch titled
ARC: mm: fix build breakage with STRICT_MM_TYPECHECKS
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arc-mm-fix-build-breakage-with-strict_mm_typechecks.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1c3c909303924d30145601f47b6c058fdd2cbc2e Mon Sep 17 00:00:00 2001
From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Date: Tue, 16 Aug 2016 18:27:07 -0700
Subject: ARC: mm: fix build breakage with STRICT_MM_TYPECHECKS
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From: Vineet Gupta <vgupta@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arc/include/asm/pgtable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- 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,
#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)
Patches currently in stable-queue which might be from vgupta@xxxxxxxxxxxx are
queue-4.7/arc-elide-redundant-setup-of-dma-callbacks.patch
queue-4.7/arc-mm-fix-build-breakage-with-strict_mm_typechecks.patch
queue-4.7/arc-call-trace_hardirqs_on-before-enabling-irqs.patch
queue-4.7/arc-use-correct-offset-in-pt_regs-for-saving-restoring-user-mode-r25.patch
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