// SPDX-License-Identifier: GPL-2.0

  /*
   * Virtual Memory Map support
   *

   * (C) 2007 sgi. Christoph Lameter.

   *
   * Virtual memory maps allow VM primitives pfn_to_page, page_to_pfn,
   * virt_to_page, page_address() to be implemented as a base offset
   * calculation without memory access.
   *
   * However, virtual mappings need a page table and TLBs. Many Linux
   * architectures already map their physical space using 1-1 mappings

   * via TLBs. For those arches the virtual memory map is essentially

   * for free if we use the same page size as the 1-1 mappings. In that
   * case the overhead consists of a few additional pages that are
   * allocated to create a view of memory for vmemmap.
   *

   * The architecture is expected to provide a vmemmap_populate() function
   * to instantiate the mapping.

   */
  #include <linux/mm.h>
  #include <linux/mmzone.h>

  #include <linux/memblock.h>

  #include <linux/memremap.h>

  #include <linux/highmem.h>

  #include <linux/slab.h>

  #include <linux/spinlock.h>
  #include <linux/vmalloc.h>

  #include <linux/sched.h>

  #include <linux/pgtable.h>
  #include <linux/bootmem_info.h>

  #include <asm/dma.h>
  #include <asm/pgalloc.h>

  #include <asm/tlbflush.h>
  
  /**
   * struct vmemmap_remap_walk - walk vmemmap page table
   *
   * @remap_pte:		called for each lowest-level entry (PTE).

   * @nr_walked:		the number of walked pte.

   * @reuse_page:		the page which is reused for the tail vmemmap pages.
   * @reuse_addr:		the virtual address of the @reuse_page page.

   * @vmemmap_pages:	the list head of the vmemmap pages that can be freed
   *			or is mapped from.

   */
  struct vmemmap_remap_walk {
  	void (*remap_pte)(pte_t *pte, unsigned long addr,
  			  struct vmemmap_remap_walk *walk);

  	unsigned long nr_walked;

  	struct page *reuse_page;
  	unsigned long reuse_addr;
  	struct list_head *vmemmap_pages;
  };

  static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start,
  				  struct vmemmap_remap_walk *walk)
  {
  	pmd_t __pmd;
  	int i;
  	unsigned long addr = start;
  	struct page *page = pmd_page(*pmd);
  	pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
  
  	if (!pgtable)
  		return -ENOMEM;
  
  	pmd_populate_kernel(&init_mm, &__pmd, pgtable);
  
  	for (i = 0; i < PMD_SIZE / PAGE_SIZE; i++, addr += PAGE_SIZE) {
  		pte_t entry, *pte;
  		pgprot_t pgprot = PAGE_KERNEL;
  
  		entry = mk_pte(page + i, pgprot);
  		pte = pte_offset_kernel(&__pmd, addr);
  		set_pte_at(&init_mm, addr, pte, entry);
  	}
  
  	/* Make pte visible before pmd. See comment in __pte_alloc(). */
  	smp_wmb();
  	pmd_populate_kernel(&init_mm, pmd, pgtable);
  
  	flush_tlb_kernel_range(start, start + PMD_SIZE);
  
  	return 0;
  }

  static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
  			      unsigned long end,
  			      struct vmemmap_remap_walk *walk)
  {
  	pte_t *pte = pte_offset_kernel(pmd, addr);
  
  	/*
  	 * The reuse_page is found 'first' in table walk before we start
  	 * remapping (which is calling @walk->remap_pte).
  	 */
  	if (!walk->reuse_page) {
  		walk->reuse_page = pte_page(*pte);
  		/*
  		 * Because the reuse address is part of the range that we are
  		 * walking, skip the reuse address range.
  		 */
  		addr += PAGE_SIZE;
  		pte++;

  		walk->nr_walked++;

  	}

  	for (; addr != end; addr += PAGE_SIZE, pte++) {

  		walk->remap_pte(pte, addr, walk);

  		walk->nr_walked++;
  	}

  }

  static int vmemmap_pmd_range(pud_t *pud, unsigned long addr,
  			     unsigned long end,
  			     struct vmemmap_remap_walk *walk)

  {
  	pmd_t *pmd;
  	unsigned long next;
  
  	pmd = pmd_offset(pud, addr);
  	do {

  		if (pmd_leaf(*pmd)) {
  			int ret;

  			ret = split_vmemmap_huge_pmd(pmd, addr & PMD_MASK, walk);
  			if (ret)
  				return ret;
  		}

  		next = pmd_addr_end(addr, end);
  		vmemmap_pte_range(pmd, addr, next, walk);
  	} while (pmd++, addr = next, addr != end);

  
  	return 0;

  }

  static int vmemmap_pud_range(p4d_t *p4d, unsigned long addr,
  			     unsigned long end,
  			     struct vmemmap_remap_walk *walk)

  {
  	pud_t *pud;
  	unsigned long next;
  
  	pud = pud_offset(p4d, addr);
  	do {

  		int ret;

  		next = pud_addr_end(addr, end);

  		ret = vmemmap_pmd_range(pud, addr, next, walk);
  		if (ret)
  			return ret;

  	} while (pud++, addr = next, addr != end);

  
  	return 0;

  }

  static int vmemmap_p4d_range(pgd_t *pgd, unsigned long addr,
  			     unsigned long end,
  			     struct vmemmap_remap_walk *walk)

  {
  	p4d_t *p4d;
  	unsigned long next;
  
  	p4d = p4d_offset(pgd, addr);
  	do {

  		int ret;

  		next = p4d_addr_end(addr, end);

  		ret = vmemmap_pud_range(p4d, addr, next, walk);
  		if (ret)
  			return ret;

  	} while (p4d++, addr = next, addr != end);

  
  	return 0;

  }

  static int vmemmap_remap_range(unsigned long start, unsigned long end,
  			       struct vmemmap_remap_walk *walk)

  {
  	unsigned long addr = start;
  	unsigned long next;
  	pgd_t *pgd;
  
  	VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE));
  	VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE));
  
  	pgd = pgd_offset_k(addr);
  	do {

  		int ret;

  		next = pgd_addr_end(addr, end);

  		ret = vmemmap_p4d_range(pgd, addr, next, walk);
  		if (ret)
  			return ret;

  	} while (pgd++, addr = next, addr != end);
  
  	/*
  	 * We only change the mapping of the vmemmap virtual address range
  	 * [@start + PAGE_SIZE, end), so we only need to flush the TLB which
  	 * belongs to the range.
  	 */
  	flush_tlb_kernel_range(start + PAGE_SIZE, end);

  
  	return 0;

  }
  
  /*
   * Free a vmemmap page. A vmemmap page can be allocated from the memblock
   * allocator or buddy allocator. If the PG_reserved flag is set, it means
   * that it allocated from the memblock allocator, just free it via the
   * free_bootmem_page(). Otherwise, use __free_page().
   */
  static inline void free_vmemmap_page(struct page *page)
  {
  	if (PageReserved(page))
  		free_bootmem_page(page);
  	else
  		__free_page(page);
  }
  
  /* Free a list of the vmemmap pages */
  static void free_vmemmap_page_list(struct list_head *list)
  {
  	struct page *page, *next;
  
  	list_for_each_entry_safe(page, next, list, lru) {
  		list_del(&page->lru);
  		free_vmemmap_page(page);
  	}
  }
  
  static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
  			      struct vmemmap_remap_walk *walk)
  {
  	/*
  	 * Remap the tail pages as read-only to catch illegal write operation
  	 * to the tail pages.
  	 */
  	pgprot_t pgprot = PAGE_KERNEL_RO;
  	pte_t entry = mk_pte(walk->reuse_page, pgprot);
  	struct page *page = pte_page(*pte);

  	list_add_tail(&page->lru, walk->vmemmap_pages);

  	set_pte_at(&init_mm, addr, pte, entry);
  }

  static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
  				struct vmemmap_remap_walk *walk)
  {
  	pgprot_t pgprot = PAGE_KERNEL;
  	struct page *page;
  	void *to;
  
  	BUG_ON(pte_page(*pte) != walk->reuse_page);
  
  	page = list_first_entry(walk->vmemmap_pages, struct page, lru);
  	list_del(&page->lru);
  	to = page_to_virt(page);
  	copy_page(to, (void *)walk->reuse_addr);
  
  	set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
  }

  /**
   * vmemmap_remap_free - remap the vmemmap virtual address range [@start, @end)
   *			to the page which @reuse is mapped to, then free vmemmap
   *			which the range are mapped to.
   * @start:	start address of the vmemmap virtual address range that we want
   *		to remap.
   * @end:	end address of the vmemmap virtual address range that we want to
   *		remap.
   * @reuse:	reuse address.
   *

   * Return: %0 on success, negative error code otherwise.

   */

  int vmemmap_remap_free(unsigned long start, unsigned long end,
  		       unsigned long reuse)

  {

  	int ret;

  	LIST_HEAD(vmemmap_pages);
  	struct vmemmap_remap_walk walk = {
  		.remap_pte	= vmemmap_remap_pte,
  		.reuse_addr	= reuse,
  		.vmemmap_pages	= &vmemmap_pages,
  	};
  
  	/*
  	 * In order to make remapping routine most efficient for the huge pages,
  	 * the routine of vmemmap page table walking has the following rules
  	 * (see more details from the vmemmap_pte_range()):
  	 *
  	 * - The range [@start, @end) and the range [@reuse, @reuse + PAGE_SIZE)
  	 *   should be continuous.
  	 * - The @reuse address is part of the range [@reuse, @end) that we are
  	 *   walking which is passed to vmemmap_remap_range().
  	 * - The @reuse address is the first in the complete range.
  	 *
  	 * So we need to make sure that @start and @reuse meet the above rules.
  	 */
  	BUG_ON(start - reuse != PAGE_SIZE);

  	mmap_write_lock(&init_mm);
  	ret = vmemmap_remap_range(reuse, end, &walk);
  	mmap_write_downgrade(&init_mm);

  	if (ret && walk.nr_walked) {
  		end = reuse + walk.nr_walked * PAGE_SIZE;
  		/*
  		 * vmemmap_pages contains pages from the previous
  		 * vmemmap_remap_range call which failed.  These
  		 * are pages which were removed from the vmemmap.
  		 * They will be restored in the following call.
  		 */
  		walk = (struct vmemmap_remap_walk) {
  			.remap_pte	= vmemmap_restore_pte,
  			.reuse_addr	= reuse,
  			.vmemmap_pages	= &vmemmap_pages,
  		};

  		vmemmap_remap_range(reuse, end, &walk);
  	}
  	mmap_read_unlock(&init_mm);

  	free_vmemmap_page_list(&vmemmap_pages);

  	return ret;

  }
  
  static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
  				   gfp_t gfp_mask, struct list_head *list)
  {
  	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
  	int nid = page_to_nid((struct page *)start);
  	struct page *page, *next;
  
  	while (nr_pages--) {
  		page = alloc_pages_node(nid, gfp_mask, 0);
  		if (!page)
  			goto out;
  		list_add_tail(&page->lru, list);
  	}
  
  	return 0;
  out:
  	list_for_each_entry_safe(page, next, list, lru)
  		__free_pages(page, 0);
  	return -ENOMEM;
  }
  
  /**
   * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
   *			 to the page which is from the @vmemmap_pages
   *			 respectively.
   * @start:	start address of the vmemmap virtual address range that we want
   *		to remap.
   * @end:	end address of the vmemmap virtual address range that we want to
   *		remap.
   * @reuse:	reuse address.
   * @gfp_mask:	GFP flag for allocating vmemmap pages.

   *
   * Return: %0 on success, negative error code otherwise.

   */
  int vmemmap_remap_alloc(unsigned long start, unsigned long end,
  			unsigned long reuse, gfp_t gfp_mask)
  {
  	LIST_HEAD(vmemmap_pages);
  	struct vmemmap_remap_walk walk = {
  		.remap_pte	= vmemmap_restore_pte,
  		.reuse_addr	= reuse,
  		.vmemmap_pages	= &vmemmap_pages,
  	};
  
  	/* See the comment in the vmemmap_remap_free(). */
  	BUG_ON(start - reuse != PAGE_SIZE);

  	if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
  		return -ENOMEM;

  	mmap_read_lock(&init_mm);

  	vmemmap_remap_range(reuse, end, &walk);

  	mmap_read_unlock(&init_mm);

  
  	return 0;
  }

  /*
   * Allocate a block of memory to be used to back the virtual memory map
   * or to back the page tables that are used to create the mapping.
   * Uses the main allocators if they are available, else bootmem.
   */

  static void * __ref __earlyonly_bootmem_alloc(int node,

  				unsigned long size,
  				unsigned long align,
  				unsigned long goal)
  {

  	return memblock_alloc_try_nid_raw(size, align, goal,

  					       MEMBLOCK_ALLOC_ACCESSIBLE, node);

  }

  void * __meminit vmemmap_alloc_block(unsigned long size, int node)
  {
  	/* If the main allocator is up use that, fallback to bootmem. */
  	if (slab_is_available()) {

  		gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
  		int order = get_order(size);
  		static bool warned;

  		struct page *page;

  		page = alloc_pages_node(node, gfp_mask, order);

  		if (page)
  			return page_address(page);

  
  		if (!warned) {
  			warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
  				   "vmemmap alloc failure: order:%u", order);
  			warned = true;
  		}

  		return NULL;
  	} else

  		return __earlyonly_bootmem_alloc(node, size, size,

  				__pa(MAX_DMA_ADDRESS));
  }

  static void * __meminit altmap_alloc_block_buf(unsigned long size,
  					       struct vmem_altmap *altmap);

  /* need to make sure size is all the same during early stage */

  void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node,
  					 struct vmem_altmap *altmap)

  {

  	void *ptr;
  
  	if (altmap)
  		return altmap_alloc_block_buf(size, altmap);

  	ptr = sparse_buffer_alloc(size);

  	if (!ptr)
  		ptr = vmemmap_alloc_block(size, node);

  	return ptr;
  }

  static unsigned long __meminit vmem_altmap_next_pfn(struct vmem_altmap *altmap)
  {
  	return altmap->base_pfn + altmap->reserve + altmap->alloc
  		+ altmap->align;
  }
  
  static unsigned long __meminit vmem_altmap_nr_free(struct vmem_altmap *altmap)
  {
  	unsigned long allocated = altmap->alloc + altmap->align;
  
  	if (altmap->free > allocated)
  		return altmap->free - allocated;
  	return 0;
  }

  static void * __meminit altmap_alloc_block_buf(unsigned long size,
  					       struct vmem_altmap *altmap)

  {

  	unsigned long pfn, nr_pfns, nr_align;

  
  	if (size & ~PAGE_MASK) {
  		pr_warn_once("%s: allocations must be multiple of PAGE_SIZE (%ld)
  ",
  				__func__, size);
  		return NULL;
  	}

  	pfn = vmem_altmap_next_pfn(altmap);

  	nr_pfns = size >> PAGE_SHIFT;

  	nr_align = 1UL << find_first_bit(&nr_pfns, BITS_PER_LONG);
  	nr_align = ALIGN(pfn, nr_align) - pfn;
  	if (nr_pfns + nr_align > vmem_altmap_nr_free(altmap))
  		return NULL;
  
  	altmap->alloc += nr_pfns;
  	altmap->align += nr_align;
  	pfn += nr_align;

  	pr_debug("%s: pfn: %#lx alloc: %ld align: %ld nr: %#lx
  ",
  			__func__, pfn, altmap->alloc, altmap->align, nr_pfns);

  	return __va(__pfn_to_phys(pfn));

  }

  void __meminit vmemmap_verify(pte_t *pte, int node,
  				unsigned long start, unsigned long end)
  {
  	unsigned long pfn = pte_pfn(*pte);
  	int actual_node = early_pfn_to_nid(pfn);

  	if (node_distance(actual_node, node) > LOCAL_DISTANCE)

  		pr_warn("[%lx-%lx] potential offnode page_structs
  ",
  			start, end - 1);

  }

  pte_t * __meminit vmemmap_pte_populate(pmd_t *pmd, unsigned long addr, int node,
  				       struct vmem_altmap *altmap)

  {

  	pte_t *pte = pte_offset_kernel(pmd, addr);
  	if (pte_none(*pte)) {
  		pte_t entry;

  		void *p;

  		p = vmemmap_alloc_block_buf(PAGE_SIZE, node, altmap);

  		if (!p)

  			return NULL;

  		entry = pfn_pte(__pa(p) >> PAGE_SHIFT, PAGE_KERNEL);
  		set_pte_at(&init_mm, addr, pte, entry);
  	}
  	return pte;

  }

  static void * __meminit vmemmap_alloc_block_zero(unsigned long size, int node)
  {
  	void *p = vmemmap_alloc_block(size, node);
  
  	if (!p)
  		return NULL;
  	memset(p, 0, size);
  
  	return p;
  }

  pmd_t * __meminit vmemmap_pmd_populate(pud_t *pud, unsigned long addr, int node)

  {

  	pmd_t *pmd = pmd_offset(pud, addr);
  	if (pmd_none(*pmd)) {

  		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);

  		if (!p)

  			return NULL;

  		pmd_populate_kernel(&init_mm, pmd, p);

  	}

  	return pmd;

  }

  pud_t * __meminit vmemmap_pud_populate(p4d_t *p4d, unsigned long addr, int node)

  {

  	pud_t *pud = pud_offset(p4d, addr);

  	if (pud_none(*pud)) {

  		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);

  		if (!p)

  			return NULL;

  		pud_populate(&init_mm, pud, p);
  	}
  	return pud;
  }

  p4d_t * __meminit vmemmap_p4d_populate(pgd_t *pgd, unsigned long addr, int node)
  {
  	p4d_t *p4d = p4d_offset(pgd, addr);
  	if (p4d_none(*p4d)) {

  		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);

  		if (!p)
  			return NULL;
  		p4d_populate(&init_mm, p4d, p);
  	}
  	return p4d;
  }

  pgd_t * __meminit vmemmap_pgd_populate(unsigned long addr, int node)
  {
  	pgd_t *pgd = pgd_offset_k(addr);
  	if (pgd_none(*pgd)) {

  		void *p = vmemmap_alloc_block_zero(PAGE_SIZE, node);

  		if (!p)

  			return NULL;

  		pgd_populate(&init_mm, pgd, p);

  	}

  	return pgd;

  }

  int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end,
  					 int node, struct vmem_altmap *altmap)

  {

  	unsigned long addr = start;

  	pgd_t *pgd;

  	p4d_t *p4d;

  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *pte;

  	for (; addr < end; addr += PAGE_SIZE) {
  		pgd = vmemmap_pgd_populate(addr, node);
  		if (!pgd)
  			return -ENOMEM;

  		p4d = vmemmap_p4d_populate(pgd, addr, node);
  		if (!p4d)
  			return -ENOMEM;
  		pud = vmemmap_pud_populate(p4d, addr, node);

  		if (!pud)
  			return -ENOMEM;
  		pmd = vmemmap_pmd_populate(pud, addr, node);
  		if (!pmd)
  			return -ENOMEM;

  		pte = vmemmap_pte_populate(pmd, addr, node, altmap);

  		if (!pte)
  			return -ENOMEM;
  		vmemmap_verify(pte, node, addr, addr + PAGE_SIZE);

  	}

  
  	return 0;

  }

  struct page * __meminit __populate_section_memmap(unsigned long pfn,
  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)

  {

  	unsigned long start = (unsigned long) pfn_to_page(pfn);
  	unsigned long end = start + nr_pages * sizeof(struct page);
  
  	if (WARN_ON_ONCE(!IS_ALIGNED(pfn, PAGES_PER_SUBSECTION) ||
  		!IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION)))
  		return NULL;

  	if (vmemmap_populate(start, end, nid, altmap))

  		return NULL;

  	return pfn_to_page(pfn);

  }