kvmem.h

Linux共享内存share memory通信机制的内核实现

/*
 *  Copyright (C) 1999 Tomasz Motylewski <[e-mail]>
 *
 *  The general driver layout borrowed from BIOS FLASH driver:
 * Copyright (C) 1998 Stefan Reinauer <[e-mail]>
 *
 * routines for vmalloc'ed area remapping from bttv.c linux 2.1 driver.
 *
 * (EDITED IN MY SO CALLED "TYPING STYLE", + A FEW CHANGES (Paolo Mantegazza))
 */


/* convert virtual user memory address to physical address */
/*  (virt_to_phys only works for kmalloced kernel memory)  */

static inline unsigned long uvirt_to_phys(unsigned long adr)
{
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t  pte;
  
	if (!pgd_none(*(pgd = pgd_offset(current->mm, adr)))) {
		if (!pmd_none(*(pmd = pmd_offset(pgd, adr)))) {
			if (pte_present((pte = *pte_offset(pmd, adr)))) {
				return virt_to_phys((void *)(pte_page(pte) | 
							(adr & (PAGE_SIZE-1))));
			}
		}
	}
	return 0;
}

static inline unsigned long uvirt_to_bus(unsigned long adr) 
{
	return virt_to_bus(phys_to_virt(uvirt_to_phys(adr)));
}

/* convert virtual kernel memory address to physical address */
/*   (virt_to_phys only works for kmalloced kernel memory)   */

static inline unsigned long kvirt_to_phys(unsigned long adr) 
{
	return uvirt_to_phys(VMALLOC_VMADDR(adr));
}

static inline unsigned long kvirt_to_bus(unsigned long adr) 
{
	return uvirt_to_bus(VMALLOC_VMADDR(adr));
}

/* allocate user space mmapable block of memory in the kernel space */

static void *rvmalloc(unsigned long size)
{
	void *vadr;
	unsigned long adr;
        
	if ((vadr = vmalloc(size))) {
	        adr = (unsigned long)vadr;
		while (size > 0) {
			mem_map_reserve(MAP_NR(phys_to_virt(kvirt_to_phys(adr))));
			adr  += PAGE_SIZE;
			size -= PAGE_SIZE;
		}
	}
	return vadr;
}

/* freee user space mmapable block of memory in the kernel space */

static void rvfree(void *vadr, unsigned long size)
{
        unsigned long adr;
        
	if (vadr) {
	        adr = (unsigned long)vadr;
		while (size > 0) {
			mem_map_unreserve(MAP_NR(phys_to_virt(kvirt_to_phys(adr))));
			adr  += PAGE_SIZE;
			size -= PAGE_SIZE;
		}
		vfree(vadr);
	}
}

/* this function will map rvmalloc'ed memory area to user space */
/*   it is not time critical code, so we check the arguments    */
/*      vma->vm_offset HAS to be checked (and is checked)       */

static int rvmmap(void *vadr, unsigned size, struct vm_area_struct *vma) 
{
	unsigned long adr, start;

	adr = (unsigned long)vadr + vma->vm_offset;
	start = vma->vm_start;
	if (vma->vm_offset < 0 || (vma->vm_end - vma->vm_start) > size ||
		adr%PAGE_SIZE || start%PAGE_SIZE || size%PAGE_SIZE) {
		return -EFAULT;
	}
	while (size > 0) {
		if (remap_page_range(start, kvirt_to_phys(adr), PAGE_SIZE, vma->vm_page_prot)) {
			return -EFAULT;
		}
		adr   += PAGE_SIZE;
		start += PAGE_SIZE;
		size  -= PAGE_SIZE;
	}
	return 0;
}