diff options
Diffstat (limited to 'include/linux/highmem.h')
| -rw-r--r-- | include/linux/highmem.h | 86 |
1 files changed, 56 insertions, 30 deletions
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 39bb9b47fa9c..e9912da5441b 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -6,6 +6,7 @@ #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> @@ -37,7 +38,7 @@ static inline void *kmap(struct page *page); /** * kunmap - Unmap the virtual address mapped by kmap() - * @addr: Virtual address to be unmapped + * @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. @@ -60,11 +61,11 @@ static inline void kmap_flush_unused(void); /** * kmap_local_page - Map a page for temporary usage - * @page: Pointer to the page to be mapped + * @page: Pointer to the page to be mapped * * Returns: The virtual address of the mapping * - * Can be invoked from any context. + * 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 @@ -86,8 +87,7 @@ static inline void kmap_flush_unused(void); * temporarily mapped. * * While it is significantly faster than kmap() for the higmem case it - * comes with restrictions about the pointer validity. Only use when really - * necessary. + * 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 @@ -138,23 +138,46 @@ static inline void *kmap_local_folio(struct folio *folio, size_t offset); * * Returns: The virtual address of the mapping * - * Effectively a wrapper around kmap_local_page() which disables pagefaults - * and preemption. + * 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. - */ -static inline void *kmap_atomic(struct page *page); - -/** - * kunmap_atomic - Unmap the virtual address mapped by kmap_atomic() - * @addr: Virtual address to be unmapped * - * Counterpart to kmap_atomic(). + * 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); * - * Effectively a wrapper around kunmap_local() which additionally undoes - * the side effects of kmap_atomic(), i.e. reenabling pagefaults and - * preemption. + * // 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 int nr_free_highpages(void); @@ -191,6 +214,8 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr) * @vma: The VMA the page is to be allocated for * @vaddr: The virtual address the page will be inserted into * + * Returns: The allocated and zeroed HIGHMEM page + * * This function will allocate a page for a VMA that the caller knows will * be able to migrate in the future using move_pages() or reclaimed * @@ -218,6 +243,16 @@ static inline void clear_highpage(struct page *page) kunmap_local(kaddr); } +static inline void clear_highpage_kasan_tagged(struct page *page) +{ + u8 tag; + + tag = page_kasan_tag(page); + page_kasan_tag_reset(page); + clear_highpage(page); + page_kasan_tag_set(page, tag); +} + #ifndef __HAVE_ARCH_TAG_CLEAR_HIGHPAGE static inline void tag_clear_highpage(struct page *page) @@ -277,6 +312,7 @@ static inline void copy_user_highpage(struct page *to, struct page *from, 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); } @@ -292,6 +328,7 @@ static inline void copy_highpage(struct page *to, struct page *from) 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); } @@ -311,19 +348,6 @@ static inline void memcpy_page(struct page *dst_page, size_t dst_off, kunmap_local(dst); } -static inline void memmove_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); - memmove(dst + dst_off, src + src_off, len); - kunmap_local(src); - kunmap_local(dst); -} - static inline void memset_page(struct page *page, size_t offset, int val, size_t len) { @@ -358,6 +382,8 @@ static inline void memcpy_to_page(struct page *page, size_t offset, 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); |