On 7/8/06, Jim Gifford <[EMAIL PROTECTED]> wrote:
The best example and most noticeable is from page.h, PAGE_SHIFT is set
by a variable from the configuration file used to create the kernel.
Here is an unsanitized version. The same holds true with all
architectures in various different files.
/*
* PAGE_SHIFT determines the page size
*/
#ifdef CONFIG_PAGE_SIZE_4KB
#define PAGE_SHIFT 12
#endif
#ifdef CONFIG_PAGE_SIZE_8KB
#define PAGE_SHIFT 13
#endif
#ifdef CONFIG_PAGE_SIZE_16KB
#define PAGE_SHIFT 14
#endif
#ifdef CONFIG_PAGE_SIZE_64KB
#define PAGE_SHIFT 16
#endif
#define PAGE_SIZE (1UL << PAGE_SHIFT)
#define PAGE_MASK (~((1 << PAGE_SHIFT) - 1))
Here is a santized version
#define PAGE_SIZE (getpagesize())
static __inline__ int getpageshift()
{
int pagesize = getpagesize();
return (__builtin_clz(pagesize) ^ 31);
}
Interesting. I'd take another look. There is more sanitization in the
kernel build now. If you're talking about asm/page.h, here's what I
get on i386.
#ifndef _I386_PAGE_H
#define _I386_PAGE_H
#include <unistd.h>
#define PAGE_SIZE (getpagesize())
static __inline__ int getpageshift()
{
int pagesize = getpagesize();
#if (__GNUC__ >= 4) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))
return (__builtin_clz(pagesize) ^ 31);
#else
register int pageshift = -1;
while (pagesize) { pagesize >>= 1; pageshift++; }
return pageshift;
#endif
}
#define PAGE_SHIFT (getpageshift())
#define PAGE_MASK (~(PAGE_SIZE-1))
#endif /* _I386_PAGE_H */
--
Dan
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