Fix warning caused by stringop-overflow in GCC7

Fix warning caused by stringop-overflow in GCC7

[Orlando Arias]

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Greetings,

GCC 7 introduced the -Wstringop-overflow flag to detect buffer overflows
in calls to string handling functions [1][2]. Due to the way
``empty_zero_page'' is declared in arch/sparc/include/setup.h, this
causes a warning to trigger at compile time in the function mem_init(),
which is subsequently converted to an error. The attached patch fixes
this issue and aligns the declaration of empty_zero_page to that of
other architectures. Thank you.

Cheers,
Orlando.


[1] https://gcc.gnu.org/ml/gcc-patches/2016-10/msg02308.html
[2] https://gcc.gnu.org/gcc-7/changes.html

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diff -rupN linux-4.11.1-pristine/arch/sparc/include/asm/pgtable_32.h linux-4.11.1-modified/arch/sparc/include/asm/pgtable_32.h
--- linux-4.11.1-pristine/arch/sparc/include/asm/pgtable_32.h	2017-05-14 08:06:16.000000000 -0400
+++ linux-4.11.1-modified/arch/sparc/include/asm/pgtable_32.h	2017-05-16 14:08:21.220784497 -0400
@@ -91,9 +91,9 @@ extern unsigned long pfn_base;
  * ZERO_PAGE is a global shared page that is always zero: used
  * for zero-mapped memory areas etc..
  */
-extern unsigned long empty_zero_page;
+extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
 
-#define ZERO_PAGE(vaddr) (virt_to_page(&empty_zero_page))
+#define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page))
 
 /*
  * In general all page table modifications should use the V8 atomic
diff -rupN linux-4.11.1-pristine/arch/sparc/include/asm/setup.h linux-4.11.1-modified/arch/sparc/include/asm/setup.h
--- linux-4.11.1-pristine/arch/sparc/include/asm/setup.h	2017-05-14 08:06:16.000000000 -0400
+++ linux-4.11.1-modified/arch/sparc/include/asm/setup.h	2017-05-16 14:05:31.887441581 -0400
@@ -16,7 +16,7 @@ extern char reboot_command[];
  */
 extern unsigned char boot_cpu_id;
 
-extern unsigned long empty_zero_page;
+extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)];
 
 extern int serial_console;
 static inline int con_is_present(void)
diff -rupN linux-4.11.1-pristine/arch/sparc/mm/init_32.c linux-4.11.1-modified/arch/sparc/mm/init_32.c
--- linux-4.11.1-pristine/arch/sparc/mm/init_32.c	2017-05-14 08:06:16.000000000 -0400
+++ linux-4.11.1-modified/arch/sparc/mm/init_32.c	2017-05-16 14:06:02.497443313 -0400
@@ -290,7 +290,7 @@ void __init mem_init(void)
 
 
 	/* Saves us work later. */
-	memset((void *)&empty_zero_page, 0, PAGE_SIZE);
+	memset((void *)empty_zero_page, 0, PAGE_SIZE);
 
 	i = last_valid_pfn >> ((20 - PAGE_SHIFT) + 5);
 	i += 1;

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Re: Fix warning caused by stringop-overflow in GCC7,Fix warning caused by stringop-overflow in GCC7

[David Miller]

Please post patches properly.

They must be inline.

You also must format your Subject line properly, it must be
of the following form:

	Subject: [PATCH $TREE] $SUBSYSTEM: Simplified description.

Here, $TREE would be "sparc" and also $SUBSYSTEM would be "sparc: "

Your subject line description is too lone, simplify it for the
final Subject line.

You also must provide a proper Signoff, as described in
Documentation/SubmittingPatches

Thank you.