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Commit a7bf0bd5 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
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build: add __page_aligned_data and __page_aligned_bss 



Making a variable page-aligned by using
__attribute__((section(".data.page_aligned"))) is fragile because if
sizeof(variable) is not also a multiple of page size, it leaves
variables in the remainder of the section unaligned.

This patch introduces two new qualifiers, __page_aligned_data and
__page_aligned_bss to set the section *and* the alignment of
variables.  This makes page-aligned variables more robust because the
linker will make sure they're aligned properly.  Unfortunately it
requires *all* page-aligned data to use these macros...

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1ecd2765

arch/x86/kernel/setup64.c

+1 −1
Original line number Diff line number Diff line
@@ -40,7 +40,7 @@ EXPORT_SYMBOL(_cpu_pda); 


struct desc_ptr idt_descr = { 256 * 16 - 1, (unsigned long) idt_table };



char boot_cpu_stack[IRQSTACKSIZE] __attribute__((section(".bss.page_aligned")));

char boot_cpu_stack[IRQSTACKSIZE] __page_aligned_bss;



unsigned long __supported_pte_mask __read_mostly = ~0UL;

EXPORT_SYMBOL_GPL(__supported_pte_mask);

arch/x86/mm/ioremap.c

+1 −2
Original line number Diff line number Diff line
@@ -394,8 +394,7 @@ static int __init early_ioremap_debug_setup(char *str) 
early_param("early_ioremap_debug", early_ioremap_debug_setup);



static __initdata int after_paging_init;

static pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)]

		__section(.bss.page_aligned);

static pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)] __page_aligned_bss;



static inline pmd_t * __init early_ioremap_pmd(unsigned long addr)

{

include/linux/linkage.h

+4 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_LINKAGE_H

#define _LINUX_LINKAGE_H



#include <linux/compiler.h>

#include <asm/linkage.h>



#ifdef __cplusplus
@@ -17,6 +18,9 @@ 
# define asmregparm

#endif



#define __page_aligned_data	__section(.data.page_aligned) __aligned(PAGE_SIZE)

#define __page_aligned_bss	__section(.bss.page_aligned) __aligned(PAGE_SIZE)



/*

 * This is used by architectures to keep arguments on the stack

 * untouched by the compiler by keeping them live until the end.