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 <mingo@elte.hu>
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index 2119610..9fd1f85 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -1,6 +1,7 @@
#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.