#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/sched.h>
/*
* get_vaddr_frames() - map virtual addresses to pfns
* @start: starting user address
* @nr_frames: number of pages / pfns from start to map
* @write: whether pages will be written to by the caller
* @force: whether to force write access even if user mapping is
* readonly. See description of the same argument of
get_user_pages().
* @vec: structure which receives pages / pfns of the addresses mapped.
* It should have space for at least nr_frames entries.
*
* This function maps virtual addresses from @start and fills @vec structure
* with page frame numbers or page pointers to corresponding pages (choice
* depends on the type of the vma underlying the virtual address). If @start
* belongs to a normal vma, the function grabs reference to each of the pages
* to pin them in memory. If @start belongs to VM_IO | VM_PFNMAP vma, we don't
* touch page structures and the caller must make sure pfns aren't reused for
* anything else while he is using them.
*
* The function returns number of pages mapped which may be less than
* @nr_frames. In particular we stop mapping if there are more vmas of
* different type underlying the specified range of virtual addresses.
* When the function isn't able to map a single page, it returns error.
*
* This function takes care of grabbing mmap_sem as necessary.
*/
int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
bool write, bool force, struct frame_vector *vec)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
int ret = 0;
int err;
int locked;
if (nr_frames == 0)
return 0;
if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
nr_frames = vec->nr_allocated;
down_read(&mm->mmap_sem);
locked = 1;
vma = find_vma_intersection(mm, start, start + 1);
if (!vma) {
ret = -EFAULT;
goto out;
}
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
vec->got_ref = true;
vec->is_pfns = false;
ret = get_user_pages_locked(current, mm, start, nr_frames,
write, force, (struct page **)(vec->ptrs), &locked);
goto out;
}
vec->got_ref = false;
vec->is_pfns = true;
do {
unsigned long *nums = frame_vector_pfns(vec);
while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
err = follow_pfn(vma, start, &nums[ret]);
if (err) {
if (ret == 0)
ret = err;
goto out;
}
start += PAGE_SIZE;
ret++;
}
/*
* We stop if we have enough pages or if VMA doesn't completely
* cover the tail page.
*/
if (ret >= nr_frames || start < vma->vm_end)
break;
vma = find_vma_intersection(mm, start, start + 1);
} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
out:
if (locked)
up_read(&mm->mmap_sem);
if (!ret)
ret = -EFAULT;
if (ret > 0)
vec->nr_frames = ret;
return ret;
}
EXPORT_SYMBOL(get_vaddr_frames);
/**
* put_vaddr_frames() - drop references to pages if get_vaddr_frames() acquired
* them
* @vec: frame vector to put
*
* Drop references to pages if get_vaddr_frames() acquired them. We also
* invalidate the frame vector so that it is prepared for the next call into
* get_vaddr_frames().
*/
void put_vaddr_frames(struct frame_vector *vec)
{
int i;
struct page **pages;
if (!vec->got_ref)
goto out;
pages = frame_vector_pages(vec);
/*
* frame_vector_pages() might needed to do a conversion when
* get_vaddr_frames() got pages but vec was later converted to pfns.
* But it shouldn't really fail to convert pfns back...
*/
if (WARN_ON(IS_ERR(pages)))
goto out;
for (i = 0; i < vec->nr_frames; i++)
put_page(pages[i]);
vec->got_ref = false;
out:
vec->nr_frames = 0;
}
EXPORT_SYMBOL(put_vaddr_frames);
/**
* frame_vector_to_pages - convert frame vector to contain page pointers
* @vec: frame vector to convert
*
* Convert @vec to contain array of page pointers. If the conversion is
* successful, return 0. Otherwise return an error. Note that we do not grab
* page references for the page structures.
*/
int frame_vector_to_pages(struct frame_vector *vec)
{
int i;
unsigned long *nums;
struct page **pages;
if (!vec->is_pfns)
return 0;
nums = frame_vector_pfns(vec);
for (i = 0; i < vec->nr_frames; i++)
if (!pfn_valid(nums[i]))
return -EINVAL;
pages = (struct page **)nums;
for (i = 0; i < vec->nr_frames; i++)
pages[i] = pfn_to_page(nums[i]);
vec->is_pfns = false;
return 0;
}
EXPORT_SYMBOL(frame_vector_to_pages);
/**
* frame_vector_to_pfns - convert frame vector to contain pfns
* @vec: frame vector to convert
*
* Convert @vec to contain array of pfns.
*/
void frame_vector_to_pfns(struct frame_vector *vec)
{
int i;
unsigned long *nums;
struct page **pages;
if (vec->is_pfns)
return;
pages = (struct page **)(vec->ptrs);
nums = (unsigned long *)pages;
for (i = 0; i < vec->nr_frames; i++)
nums[i] = page_to_pfn(pages[i]);
vec->is_pfns = true;
}
EXPORT_SYMBOL(frame_vector_to_pfns);
/**
* frame_vector_create() - allocate & initialize structure for pinned pfns
* @nr_frames: number of pfns slots we should reserve
*
* Allocate and initialize struct pinned_pfns to be able to hold @nr_pfns
* pfns.
*/
struct frame_vector *frame_vector_create(unsigned int nr_frames)
{
struct frame_vector *vec;
int size = sizeof(struct frame_vector) + sizeof(void *) * nr_frames;
if (WARN_ON_ONCE(nr_frames == 0))
return NULL;
/*
* This is absurdly high. It's here just to avoid strange effects when
* arithmetics overflows.
*/
if (WARN_ON_ONCE(nr_frames > INT_MAX / sizeof(void *) / 2))
return NULL;
/*
* Avoid higher order allocations, use vmalloc instead. It should
* be rare anyway.
*/
if (size <= PAGE_SIZE)
vec = kmalloc(size, GFP_KERNEL);
else
vec = vmalloc(size);
if (!vec)
return NULL;
vec->nr_allocated = nr_frames;
vec->nr_frames = 0;
return vec;
}
EXPORT_SYMBOL(frame_vector_create);
/**
* frame_vector_destroy() - free memory allocated to carry frame vector
* @vec: Frame vector to free
*
* Free structure allocated by frame_vector_create() to carry frames.
*/
void frame_vector_destroy(struct frame_vector *vec)
{
/* Make sure put_vaddr_frames() got called properly... */
VM_BUG_ON(vec->nr_frames > 0);
kvfree(vec);
}
EXPORT_SYMBOL(frame_vector_destroy);
