Quelle highmem.h Sprache: C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_HIGHMEM_H
#define _LINUX_HIGHMEM_H

#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/cacheflush.h>
#include <linux/kmsan.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>

#include "highmem-internal.h"

/**
* kmap - Map a page for long term usage
* @page: Pointer to the page to be mapped
*
* Returns: The virtual address of the mapping
*
* Can only be invoked from preemptible task context because on 32bit
* systems with CONFIG_HIGHMEM enabled this function might sleep.
*
* For systems with CONFIG_HIGHMEM=n and for pages in the low memory area
* this returns the virtual address of the direct kernel mapping.
*
* The returned virtual address is globally visible and valid up to the
* point where it is unmapped via kunmap(). The pointer can be handed to
* other contexts.
*
* For highmem pages on 32bit systems this can be slow as the mapping space
* is limited and protected by a global lock. In case that there is no
* mapping slot available the function blocks until a slot is released via
* kunmap().
*/
static inline void *kmap(struct page *page);

/**
* kunmap - Unmap the virtual address mapped by kmap()
* @page: Pointer to the page which was mapped by kmap()
*
* Counterpart to kmap(). A NOOP for CONFIG_HIGHMEM=n and for mappings of
* pages in the low memory area.
*/
static inline void kunmap(struct page *page);

/**
* kmap_to_page - Get the page for a kmap'ed address
* @addr: The address to look up
*
* Returns: The page which is mapped to @addr.
*/
static inline struct page *kmap_to_page(void *addr);

/**
* kmap_flush_unused - Flush all unused kmap mappings in order to
*        remove stray mappings
*/
static inline void kmap_flush_unused(void);

/**
* kmap_local_page - Map a page for temporary usage
* @page: Pointer to the page to be mapped
*
* Returns: The virtual address of the mapping
*
* Can be invoked from any context, including interrupts.
*
* Requires careful handling when nesting multiple mappings because the map
* management is stack based. The unmap has to be in the reverse order of
* the map operation:
*
* addr1 = kmap_local_page(page1);
* addr2 = kmap_local_page(page2);
* ...
* kunmap_local(addr2);
* kunmap_local(addr1);
*
* Unmapping addr1 before addr2 is invalid and causes malfunction.
*
* Contrary to kmap() mappings the mapping is only valid in the context of
* the caller and cannot be handed to other contexts.
*
* On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
* virtual address of the direct mapping. Only real highmem pages are
* temporarily mapped.
*
* While kmap_local_page() is significantly faster than kmap() for the highmem
* case it comes with restrictions about the pointer validity.
*
* On HIGHMEM enabled systems mapping a highmem page has the side effect of
* disabling migration in order to keep the virtual address stable across
* preemption. No caller of kmap_local_page() can rely on this side effect.
*/
static inline void *kmap_local_page(struct page *page);

/**
* kmap_local_folio - Map a page in this folio for temporary usage
* @folio: The folio containing the page.
* @offset: The byte offset within the folio which identifies the page.
*
* Requires careful handling when nesting multiple mappings because the map
* management is stack based. The unmap has to be in the reverse order of
* the map operation::
*
*   addr1 = kmap_local_folio(folio1, offset1);
*   addr2 = kmap_local_folio(folio2, offset2);
*   ...
*   kunmap_local(addr2);
*   kunmap_local(addr1);
*
* Unmapping addr1 before addr2 is invalid and causes malfunction.
*
* Contrary to kmap() mappings the mapping is only valid in the context of
* the caller and cannot be handed to other contexts.
*
* On CONFIG_HIGHMEM=n kernels and for low memory pages this returns the
* virtual address of the direct mapping. Only real highmem pages are
* temporarily mapped.
*
* While it is significantly faster than kmap() for the highmem case it
* comes with restrictions about the pointer validity.
*
* On HIGHMEM enabled systems mapping a highmem page has the side effect of
* disabling migration in order to keep the virtual address stable across
* preemption. No caller of kmap_local_folio() can rely on this side effect.
*
* Context: Can be invoked from any context.
* Return: The virtual address of @offset.
*/
static inline void *kmap_local_folio(struct folio *folio, size_t offset);

/**
* kmap_atomic - Atomically map a page for temporary usage - Deprecated!
* @page: Pointer to the page to be mapped
*
* Returns: The virtual address of the mapping
*
* In fact a wrapper around kmap_local_page() which also disables pagefaults
* and, depending on PREEMPT_RT configuration, also CPU migration and
* preemption. Therefore users should not count on the latter two side effects.
*
* Mappings should always be released by kunmap_atomic().
*
* Do not use in new code. Use kmap_local_page() instead.
*
* It is used in atomic context when code wants to access the contents of a
* page that might be allocated from high memory (see __GFP_HIGHMEM), for
* example a page in the pagecache.  The API has two functions, and they
* can be used in a manner similar to the following::
*
*   // Find the page of interest.
*   struct page *page = find_get_page(mapping, offset);
*
*   // Gain access to the contents of that page.
*   void *vaddr = kmap_atomic(page);
*
*   // Do something to the contents of that page.
*   memset(vaddr, 0, PAGE_SIZE);
*
*   // Unmap that page.
*   kunmap_atomic(vaddr);
*
* Note that the kunmap_atomic() call takes the result of the kmap_atomic()
* call, not the argument.
*
* If you need to map two pages because you want to copy from one page to
* another you need to keep the kmap_atomic calls strictly nested, like:
*
* vaddr1 = kmap_atomic(page1);
* vaddr2 = kmap_atomic(page2);
*
* memcpy(vaddr1, vaddr2, PAGE_SIZE);
*
* kunmap_atomic(vaddr2);
* kunmap_atomic(vaddr1);
*/
static inline void *kmap_atomic(struct page *page);

/* Highmem related interfaces for management code */
static inline unsigned long nr_free_highpages(void);
static inline unsigned long totalhigh_pages(void);

#ifndef ARCH_HAS_FLUSH_ANON_PAGE
static inline void flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
{
}
#endif

#ifndef ARCH_IMPLEMENTS_FLUSH_KERNEL_VMAP_RANGE
static inline void flush_kernel_vmap_range(void *vaddr, int size)
{
}
static inline void invalidate_kernel_vmap_range(void *vaddr, int size)
{
}
#endif

/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
{
void *addr = kmap_local_page(page);
clear_user_page(addr, vaddr, page);
kunmap_local(addr);
}
#endif

#ifndef vma_alloc_zeroed_movable_folio
/**
* vma_alloc_zeroed_movable_folio - Allocate a zeroed page for a VMA.
* @vma: The VMA the page is to be allocated for.
* @vaddr: The virtual address the page will be inserted into.
*
* This function will allocate a page suitable for inserting into this
* VMA at this virtual address.  It may be allocated from highmem or
* the movable zone.  An architecture may provide its own implementation.
*
* Return: A folio containing one allocated and zeroed page or NULL if
* we are out of memory.
*/
static inline
struct folio *vma_alloc_zeroed_movable_folio(struct vm_area_struct *vma,
       unsigned long vaddr)
{
struct folio *folio;

folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vaddr);
if (folio && user_alloc_needs_zeroing())
  clear_user_highpage(&folio->page, vaddr);

return folio;
}
#endif

static inline void clear_highpage(struct page *page)
{
void *kaddr = kmap_local_page(page);
clear_page(kaddr);
kunmap_local(kaddr);
}

static inline void clear_highpage_kasan_tagged(struct page *page)
{
void *kaddr = kmap_local_page(page);

clear_page(kasan_reset_tag(kaddr));
kunmap_local(kaddr);
}

#ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE

static inline void tag_clear_highpage(struct page *page)
{
}

#endif

/*
* If we pass in a base or tail page, we can zero up to PAGE_SIZE.
* If we pass in a head page, we can zero up to the size of the compound page.
*/
#ifdef CONFIG_HIGHMEM
void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
  unsigned start2, unsigned end2);
#else
static inline void zero_user_segments(struct page *page,
  unsigned start1, unsigned end1,
  unsigned start2, unsigned end2)
{
void *kaddr = kmap_local_page(page);
unsigned int i;

BUG_ON(end1 > page_size(page) || end2 > page_size(page));

if (end1 > start1)
  memset(kaddr + start1, 0, end1 - start1);

if (end2 > start2)
  memset(kaddr + start2, 0, end2 - start2);

kunmap_local(kaddr);
for (i = 0; i < compound_nr(page); i++)
  flush_dcache_page(page + i);
}
#endif

static inline void zero_user_segment(struct page *page,
unsigned start, unsigned end)
{
zero_user_segments(page, start, end, 0, 0);
}

#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE

static inline void copy_user_highpage(struct page *to, struct page *from,
unsigned long vaddr, struct vm_area_struct *vma)
{
char *vfrom, *vto;

vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
copy_user_page(vto, vfrom, vaddr, to);
kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
kunmap_local(vto);
kunmap_local(vfrom);
}

#endif

#ifndef __HAVE_ARCH_COPY_HIGHPAGE

static inline void copy_highpage(struct page *to, struct page *from)
{
char *vfrom, *vto;

vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
copy_page(vto, vfrom);
kmsan_copy_page_meta(to, from);
kunmap_local(vto);
kunmap_local(vfrom);
}

#endif

#ifdef copy_mc_to_kernel
/*
* If architecture supports machine check exception handling, define the
* #MC versions of copy_user_highpage and copy_highpage. They copy a memory
* page with #MC in source page (@from) handled, and return the number
* of bytes not copied if there was a #MC, otherwise 0 for success.
*/
static inline int copy_mc_user_highpage(struct page *to, struct page *from,
     unsigned long vaddr, struct vm_area_struct *vma)
{
unsigned long ret;
char *vfrom, *vto;

vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
if (!ret)
  kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
kunmap_local(vto);
kunmap_local(vfrom);

if (ret)
  memory_failure_queue(page_to_pfn(from), 0);

return ret;
}

static inline int copy_mc_highpage(struct page *to, struct page *from)
{
unsigned long ret;
char *vfrom, *vto;

vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
if (!ret)
  kmsan_copy_page_meta(to, from);
kunmap_local(vto);
kunmap_local(vfrom);

if (ret)
  memory_failure_queue(page_to_pfn(from), 0);

return ret;
}
#else
static inline int copy_mc_user_highpage(struct page *to, struct page *from,
     unsigned long vaddr, struct vm_area_struct *vma)
{
copy_user_highpage(to, from, vaddr, vma);
return 0;
}

static inline int copy_mc_highpage(struct page *to, struct page *from)
{
copy_highpage(to, from);
return 0;
}
#endif

static inline void memcpy_page(struct page *dst_page, size_t dst_off,
          struct page *src_page, size_t src_off,
          size_t len)
{
char *dst = kmap_local_page(dst_page);
char *src = kmap_local_page(src_page);

VM_BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);
memcpy(dst + dst_off, src + src_off, len);
kunmap_local(src);
kunmap_local(dst);
}

static inline void memcpy_folio(struct folio *dst_folio, size_t dst_off,
  struct folio *src_folio, size_t src_off, size_t len)
{
VM_BUG_ON(dst_off + len > folio_size(dst_folio));
VM_BUG_ON(src_off + len > folio_size(src_folio));

do {
  char *dst = kmap_local_folio(dst_folio, dst_off);
  const char *src = kmap_local_folio(src_folio, src_off);
  size_t chunk = len;

  if (folio_test_highmem(dst_folio) &&
      chunk > PAGE_SIZE - offset_in_page(dst_off))
   chunk = PAGE_SIZE - offset_in_page(dst_off);
  if (folio_test_highmem(src_folio) &&
      chunk > PAGE_SIZE - offset_in_page(src_off))
   chunk = PAGE_SIZE - offset_in_page(src_off);
  memcpy(dst, src, chunk);
  kunmap_local(src);
  kunmap_local(dst);

  dst_off += chunk;
  src_off += chunk;
  len -= chunk;
} while (len > 0);
}

static inline void memset_page(struct page *page, size_t offset, int val,
          size_t len)
{
char *addr = kmap_local_page(page);

VM_BUG_ON(offset + len > PAGE_SIZE);
memset(addr + offset, val, len);
kunmap_local(addr);
}

static inline void memcpy_from_page(char *to, struct page *page,
        size_t offset, size_t len)
{
char *from = kmap_local_page(page);

VM_BUG_ON(offset + len > PAGE_SIZE);
memcpy(to, from + offset, len);
kunmap_local(from);
}

static inline void memcpy_to_page(struct page *page, size_t offset,
      const char *from, size_t len)
{
char *to = kmap_local_page(page);

VM_BUG_ON(offset + len > PAGE_SIZE);
memcpy(to + offset, from, len);
flush_dcache_page(page);
kunmap_local(to);
}

static inline void memzero_page(struct page *page, size_t offset, size_t len)
{
char *addr = kmap_local_page(page);

VM_BUG_ON(offset + len > PAGE_SIZE);
memset(addr + offset, 0, len);
flush_dcache_page(page);
kunmap_local(addr);
}

/**
* memcpy_from_folio - Copy a range of bytes from a folio.
* @to: The memory to copy to.
* @folio: The folio to read from.
* @offset: The first byte in the folio to read.
* @len: The number of bytes to copy.
*/
static inline void memcpy_from_folio(char *to, struct folio *folio,
  size_t offset, size_t len)
{
VM_BUG_ON(offset + len > folio_size(folio));

do {
  const char *from = kmap_local_folio(folio, offset);
  size_t chunk = len;

  if (folio_test_partial_kmap(folio) &&
      chunk > PAGE_SIZE - offset_in_page(offset))
   chunk = PAGE_SIZE - offset_in_page(offset);
  memcpy(to, from, chunk);
  kunmap_local(from);

  to += chunk;
  offset += chunk;
  len -= chunk;
} while (len > 0);
}

/**
* memcpy_to_folio - Copy a range of bytes to a folio.
* @folio: The folio to write to.
* @offset: The first byte in the folio to store to.
* @from: The memory to copy from.
* @len: The number of bytes to copy.
*/
static inline void memcpy_to_folio(struct folio *folio, size_t offset,
  const char *from, size_t len)
{
VM_BUG_ON(offset + len > folio_size(folio));

do {
  char *to = kmap_local_folio(folio, offset);
  size_t chunk = len;

  if (folio_test_partial_kmap(folio) &&
      chunk > PAGE_SIZE - offset_in_page(offset))
   chunk = PAGE_SIZE - offset_in_page(offset);
  memcpy(to, from, chunk);
  kunmap_local(to);

  from += chunk;
  offset += chunk;
  len -= chunk;
} while (len > 0);

flush_dcache_folio(folio);
}

/**
* folio_zero_tail - Zero the tail of a folio.
* @folio: The folio to zero.
* @offset: The byte offset in the folio to start zeroing at.
* @kaddr: The address the folio is currently mapped to.
*
* If you have already used kmap_local_folio() to map a folio, written
* some data to it and now need to zero the end of the folio (and flush
* the dcache), you can use this function.  If you do not have the
* folio kmapped (eg the folio has been partially populated by DMA),
* use folio_zero_range() or folio_zero_segment() instead.
*
* Return: An address which can be passed to kunmap_local().
*/
static inline __must_check void *folio_zero_tail(struct folio *folio,
  size_t offset, void *kaddr)
{
size_t len = folio_size(folio) - offset;

if (folio_test_partial_kmap(folio)) {
  size_t max = PAGE_SIZE - offset_in_page(offset);

  while (len > max) {
   memset(kaddr, 0, max);
   kunmap_local(kaddr);
   len -= max;
   offset += max;
   max = PAGE_SIZE;
   kaddr = kmap_local_folio(folio, offset);
  }
}

memset(kaddr, 0, len);
flush_dcache_folio(folio);

return kaddr;
}

/**
* folio_fill_tail - Copy some data to a folio and pad with zeroes.
* @folio: The destination folio.
* @offset: The offset into @folio at which to start copying.
* @from: The data to copy.
* @len: How many bytes of data to copy.
*
* This function is most useful for filesystems which support inline data.
* When they want to copy data from the inode into the page cache, this
* function does everything for them.  It supports large folios even on
* HIGHMEM configurations.
*/
static inline void folio_fill_tail(struct folio *folio, size_t offset,
  const char *from, size_t len)
{
char *to = kmap_local_folio(folio, offset);

VM_BUG_ON(offset + len > folio_size(folio));

if (folio_test_partial_kmap(folio)) {
  size_t max = PAGE_SIZE - offset_in_page(offset);

  while (len > max) {
   memcpy(to, from, max);
   kunmap_local(to);
   len -= max;
   from += max;
   offset += max;
   max = PAGE_SIZE;
   to = kmap_local_folio(folio, offset);
  }
}

memcpy(to, from, len);
to = folio_zero_tail(folio, offset + len, to + len);
kunmap_local(to);
}

/**
* memcpy_from_file_folio - Copy some bytes from a file folio.
* @to: The destination buffer.
* @folio: The folio to copy from.
* @pos: The position in the file.
* @len: The maximum number of bytes to copy.
*
* Copy up to @len bytes from this folio.  This may be limited by PAGE_SIZE
* if the folio comes from HIGHMEM, and by the size of the folio.
*
* Return: The number of bytes copied from the folio.
*/
static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
  loff_t pos, size_t len)
{
size_t offset = offset_in_folio(folio, pos);
char *from = kmap_local_folio(folio, offset);

if (folio_test_partial_kmap(folio)) {
  offset = offset_in_page(offset);
  len = min_t(size_t, len, PAGE_SIZE - offset);
} else
  len = min(len, folio_size(folio) - offset);

memcpy(to, from, len);
kunmap_local(from);

return len;
}

/**
* folio_zero_segments() - Zero two byte ranges in a folio.
* @folio: The folio to write to.
* @start1: The first byte to zero.
* @xend1: One more than the last byte in the first range.
* @start2: The first byte to zero in the second range.
* @xend2: One more than the last byte in the second range.
*/
static inline void folio_zero_segments(struct folio *folio,
  size_t start1, size_t xend1, size_t start2, size_t xend2)
{
zero_user_segments(&folio->page, start1, xend1, start2, xend2);
}

/**
* folio_zero_segment() - Zero a byte range in a folio.
* @folio: The folio to write to.
* @start: The first byte to zero.
* @xend: One more than the last byte to zero.
*/
static inline void folio_zero_segment(struct folio *folio,
  size_t start, size_t xend)
{
zero_user_segments(&folio->page, start, xend, 0, 0);
}

/**
* folio_zero_range() - Zero a byte range in a folio.
* @folio: The folio to write to.
* @start: The first byte to zero.
* @length: The number of bytes to zero.
*/
static inline void folio_zero_range(struct folio *folio,
  size_t start, size_t length)
{
zero_user_segments(&folio->page, start, start + length, 0, 0);
}

/**
* folio_release_kmap - Unmap a folio and drop a refcount.
* @folio: The folio to release.
* @addr: The address previously returned by a call to kmap_local_folio().
*
* It is common, eg in directory handling to kmap a folio.  This function
* unmaps the folio and drops the refcount that was being held to keep the
* folio alive while we accessed it.
*/
static inline void folio_release_kmap(struct folio *folio, void *addr)
{
kunmap_local(addr);
folio_put(folio);
}
#endif /* _LINUX_HIGHMEM_H */

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