getunmappedarea.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 84 行

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/shm.h>
#include <asm/mman.h>

#define COLOUR_ALIGN(addr,pgoff)		\
	((((addr)+SHMLBA-1)&~(SHMLBA-1)) +	\
	 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))

unsigned long
arch_get_unmapped_area(struct file *filp, unsigned long addr,
		unsigned long len, unsigned long pgoff, unsigned long flags)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long start_addr;
#if SHMLBA > 4096
	int do_align = filp || flags & MAP_SHARED;
#else
#define do_align 0
#endif

	if (len > TASK_SIZE)
		return -ENOMEM;

#if SHMLBA > 4096
	if (flags & MAP_FIXED) {
		/*
		 * Do not accept a shared mapping if it would
		 * violate the cache aliasing constraints.
		 */
		if ((flags & MAP_SHARED) && (addr & (SHMLBA - 1)))
			return -EINVAL;
		return addr;
	}
#endif

	if (addr) {
		if (do_align)
			addr = COLOUR_ALIGN(addr, pgoff);
		else
			addr = PAGE_ALIGN(addr);

		vma = find_vma(mm, addr);
		if (TASK_SIZE - len >= addr &&
		    (!vma || addr + len <= vma->vm_start))
			return addr;
	}
	start_addr = addr = mm->free_area_cache;

full_search:
	if (do_align)
		addr = COLOUR_ALIGN(addr, pgoff);
	else
		addr = PAGE_ALIGN(addr);

	for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
		/* At this point:  (!vma || addr < vma->vm_end). */
		if (TASK_SIZE - len < addr) {
			/*
			 * Start a new search - just in case we missed
			 * some holes.
			 */
			if (start_addr != TASK_UNMAPPED_BASE) {
				start_addr = addr = TASK_UNMAPPED_BASE;
				goto full_search;
			}
			return -ENOMEM;
		}
		if (!vma || addr + len <= vma->vm_start) {
			/*
			 * Remember the place where we stopped the search:
			 */
			mm->free_area_cache = addr + len;
			return addr;
		}
		addr = vma->vm_end;
		if (do_align)
			addr = COLOUR_ALIGN(addr, pgoff);
	}
}