From a7bf0bd5e6af7fe69342dabf2a3b721f0163469a Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Wed, 28 May 2008 15:02:14 +0100 Subject: [PATCH] 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: Ingo Molnar --- arch/x86/kernel/setup64.c | 2 +- arch/x86/mm/ioremap.c | 3 +-- include/linux/linkage.h | 4 ++++ 3 files changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/setup64.c b/arch/x86/kernel/setup64.c index 631ea6cc01d..fc1a56da824 100644 --- a/arch/x86/kernel/setup64.c +++ b/arch/x86/kernel/setup64.c @@ -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); diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c index 416ea415f5c..0561fde56a5 100644 --- a/arch/x86/mm/ioremap.c +++ b/arch/x86/mm/ioremap.c @@ -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) { diff --git a/include/linux/linkage.h b/include/linux/linkage.h index 2119610b24f..9fd1f859021 100644 --- a/include/linux/linkage.h +++ b/include/linux/linkage.h @@ -1,6 +1,7 @@ #ifndef _LINUX_LINKAGE_H #define _LINUX_LINKAGE_H +#include #include #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. -- 2.41.1