25  * - A page frame is a page-sized physical memory region in RAM. It is a
26  *   container where a data page may be placed. It is always referred to by
29  *   every page frame.
31  * - A data page is a page-sized region of data. It may exist in a page frame,
33  *   up in the CPU's page tables (or equivalent) by virtual address.
38 /* Spinlock to protect any globals in this file and serialize page table
44  * General page frame management
47 /* Database of all RAM page frames */
57 /* Add colors to page table dumps to indicate mapping type */
147  * purposes and does not otherwise affect page frame accounting or flags;
173  * | Reserved     | <- special purpose virtual page(s) of size Z_VM_RESERVED
177 /* Bitmap of virtual addresses where one bit corresponds to one page.
362  * Free page frames management
367 /* Linked list of unused and available page frames.
369  * TODO: This is very simple and treats all free page frames as being equal.
372  * may require a more complex ontology which prefers page frames in RAM banks
376  * pages. Each page frame will still just have one snode link.
380 /* Number of unused and available free page frames */
384 	__ASSERT(expr, "page frame 0x%lx: " fmt, z_page_frame_to_phys(pf), \
387 /* Get an unused page frame. don't care which one, or NULL if there are none */
404 /* Release a page frame back into the list of free pages */
408 		 "unavailable page put on free list");  in free_page_frame_list_put()
437 		  "attempted to map a reserved page frame");  in frame_mapped_set()
439 	/* We do allow multiple mappings for pinned page frames  in frame_mapped_set()
452 /* Go through page frames to find the physical address mapped
492 /* Allocate a free page frame, and map it to a specified virtual address
494  * TODO: Add optional support for copy-on-write mappings to a zero page instead
495  * of allocating, in which case page frames will be allocated lazily as
496  * the mappings to the zero page get touched. This will avoid expensive
497  * page-ins as memory is mapped and physical RAM or backing store storage will
499  * page of zeroes.
516 		__ASSERT(pf != NULL, "failed to get a page frame");  in map_anon_page()
540 	LOG_DBG("memory mapping anon page %p -> 0x%lx", addr, phys);  in map_anon_page()
544 		 * zero page, won't need this step  in map_anon_page()
590 	/* Skip over the "before" guard page in returned address. */  in k_mem_map()
599 			 * page as well.  in k_mem_map()
619 	/* Need space for the "before" guard page */  in k_mem_unmap()
638 			 "%s: cannot find preceding guard page for (%p, %zu)",  in k_mem_unmap()
646 			 "%s: cannot find succeeding guard page for (%p, %zu)",  in k_mem_unmap()
663 			 "%s: 0x%lx is not a page frame", __func__, phys);  in k_mem_unmap()
665 			/* Physical address has no corresponding page frame  in k_mem_unmap()
666 			 * description in the page frame array.  in k_mem_unmap()
672 		/* Grab the corresponding page frame from physical address */  in k_mem_unmap()
676 			 "%s: 0x%lx is not a mapped page frame", __func__, phys);  in k_mem_unmap()
678 			/* Page frame is not marked mapped.  in k_mem_unmap()
686 		/* Put the page frame back into free list */  in k_mem_unmap()
723 /* Get the default virtual region alignment, here the default MMU page size
861 	/* The actual mapped region must be page-aligned. Round down the  in k_mem_region_align()
910 	/* If some page frames are unavailable for use as memory, arch  in z_mem_manage_init()
932 		 * structures, and any code used to perform page fault  in z_mem_manage_init()
933 		 * handling, page-ins, etc.  in z_mem_manage_init()
947 	/* Pin the page frames correspondng to the pinned symbols */  in z_mem_manage_init()
959 	LOG_DBG("free page frames: %zu", z_free_page_count);  in z_mem_manage_init()
1065 /* Current implementation relies on interrupt locking to any prevent page table
1085  * Perform some preparatory steps before paging out. The provided page frame
1088  * a data page.
1090  * - Map page frame to scratch area if requested. This always is true if we're
1091  *   doing a page fault, but is only set on manual evictions if the page is
1095  *    - Update page tables with location
1096  * - Mark page frame as busy
1108 	__ASSERT(!z_page_frame_is_pinned(pf), "page frame 0x%lx is pinned",  in page_frame_prepare_locked()
1111 	/* If the backing store doesn't have a copy of the page, even if it  in page_frame_prepare_locked()
1114 	 * 1) Page has never been swapped out before, and the backing store  in page_frame_prepare_locked()
1115 	 *    wasn't pre-populated with this data page.  in page_frame_prepare_locked()
1116 	 * 2) Page was swapped out before, but the page contents were not  in page_frame_prepare_locked()
1118 	 * 3) Page contents were preserved when swapped back in, but were later  in page_frame_prepare_locked()
1140 		__ASSERT(!dirty, "un-mapped page determined to be dirty");  in page_frame_prepare_locked()
1144 	__ASSERT(!z_page_frame_is_busy(pf), "page frame 0x%lx is already busy",  in page_frame_prepare_locked()
1182 	__ASSERT(pf->addr == addr, "page frame address mismatch");  in do_mem_evict()
1188 	__ASSERT(ret == 0, "failed to prepare page frame");  in do_mem_evict()
1238 	 * data page to page-in, see comments in that function.  in z_page_frame_evict()
1250 		/* Nothing to do, free page */  in z_page_frame_evict()
1256 	__ASSERT((flags & ARCH_DATA_PAGE_LOADED) != 0, "data page not loaded");  in z_page_frame_evict()
1384 	__ASSERT(page_frames_initialized, "page fault at %p happened too early",  in do_page_fault()
1387 	LOG_DBG("page fault at %p", addr);  in do_page_fault()
1397 	 * during the page-in/out operation.  in do_page_fault()
1399 	 * We do however re-enable interrupts during the page-in/page-out  in do_page_fault()
1401 	 * in this configuration page faults in an ISR are a bug; all their  in do_page_fault()
1410 	 * but requires less pinned pages and ISRs may also take page faults.  in do_page_fault()
1417 	 * sleep on a contended page fault operation will break scheduling  in do_page_fault()
1422 	__ASSERT(!k_is_in_isr(), "ISR page faults are forbidden");  in do_page_fault()
1443 		/* This if-block is to pin the page if it is  in do_page_fault()
1457 		/* Need to evict a page frame */  in do_page_fault()
1459 		__ASSERT(pf != NULL, "failed to get a page frame");  in do_page_fault()
1466 	__ASSERT(ret == 0, "failed to prepare page frame");  in do_page_fault()
1550 		 "invalid data page at %p", addr);  in do_mem_unpin()