text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * This file contains the routines setting up the linux page tables.
   *  -- paulus
   *
   *  Derived from arch/ppc/mm/init.c:
   *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   *
   *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
   *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
   *    Copyright (C) 1996 Paul Mackerras
   *
   *  Derived from "arch/i386/mm/init.c"
   *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/mm.h>
  #include <linux/vmalloc.h>
  #include <linux/init.h>
  #include <linux/highmem.h>
  #include <linux/memblock.h>
  #include <linux/slab.h>
  
  #include <asm/pgtable.h>
  #include <asm/pgalloc.h>
  #include <asm/fixmap.h>
  #include <asm/io.h>
  #include <asm/setup.h>
  #include <asm/sections.h>
  
  #include <mm/mmu_decl.h>
  
  unsigned long ioremap_bot;
  EXPORT_SYMBOL(ioremap_bot);	/* aka VMALLOC_END */
  
  extern char etext[], _stext[], _sinittext[], _einittext[];
  
  void __iomem *
  ioremap(phys_addr_t addr, unsigned long size)
  {
  	pgprot_t prot = pgprot_noncached(PAGE_KERNEL);
  
  	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
  }
  EXPORT_SYMBOL(ioremap);
  
  void __iomem *
  ioremap_wc(phys_addr_t addr, unsigned long size)
  {
  	pgprot_t prot = pgprot_noncached_wc(PAGE_KERNEL);
  
  	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
  }
  EXPORT_SYMBOL(ioremap_wc);
  
  void __iomem *
  ioremap_wt(phys_addr_t addr, unsigned long size)
  {
  	pgprot_t prot = pgprot_cached_wthru(PAGE_KERNEL);
  
  	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
  }
  EXPORT_SYMBOL(ioremap_wt);
  
  void __iomem *
  ioremap_coherent(phys_addr_t addr, unsigned long size)
  {
  	pgprot_t prot = pgprot_cached(PAGE_KERNEL);
  
  	return __ioremap_caller(addr, size, prot, __builtin_return_address(0));
  }
  EXPORT_SYMBOL(ioremap_coherent);
  
  void __iomem *
  ioremap_prot(phys_addr_t addr, unsigned long size, unsigned long flags)
  {
  	pte_t pte = __pte(flags);
  
  	/* writeable implies dirty for kernel addresses */
  	if (pte_write(pte))
  		pte = pte_mkdirty(pte);
  
  	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
  	pte = pte_exprotect(pte);
  	pte = pte_mkprivileged(pte);
  
  	return __ioremap_caller(addr, size, pte_pgprot(pte), __builtin_return_address(0));
  }
  EXPORT_SYMBOL(ioremap_prot);
  
  void __iomem *
  __ioremap(phys_addr_t addr, unsigned long size, unsigned long flags)
  {
  	return __ioremap_caller(addr, size, __pgprot(flags), __builtin_return_address(0));
  }
  
  void __iomem *
  __ioremap_caller(phys_addr_t addr, unsigned long size, pgprot_t prot, void *caller)
  {
  	unsigned long v, i;
  	phys_addr_t p;
  	int err;
  
  	/*
  	 * Choose an address to map it to.
  	 * Once the vmalloc system is running, we use it.
  	 * Before then, we use space going down from IOREMAP_TOP
  	 * (ioremap_bot records where we're up to).
  	 */
  	p = addr & PAGE_MASK;
  	size = PAGE_ALIGN(addr + size) - p;
  
  	/*
  	 * If the address lies within the first 16 MB, assume it's in ISA
  	 * memory space
  	 */
  	if (p < 16*1024*1024)
  		p += _ISA_MEM_BASE;
  
  #ifndef CONFIG_CRASH_DUMP
  	/*
  	 * Don't allow anybody to remap normal RAM that we're using.
  	 * mem_init() sets high_memory so only do the check after that.
  	 */
  	if (slab_is_available() && p <= virt_to_phys(high_memory - 1) &&
  	    page_is_ram(__phys_to_pfn(p))) {
  		printk("__ioremap(): phys addr 0x%llx is RAM lr %ps\n",
  		       (unsigned long long)p, __builtin_return_address(0));
  		return NULL;
  	}
  #endif
  
  	if (size == 0)
  		return NULL;
  
  	/*
  	 * Is it already mapped?  Perhaps overlapped by a previous
  	 * mapping.
  	 */
  	v = p_block_mapped(p);
  	if (v)
  		goto out;
  
  	if (slab_is_available()) {
  		struct vm_struct *area;
  		area = get_vm_area_caller(size, VM_IOREMAP, caller);
  		if (area == 0)
  			return NULL;
  		area->phys_addr = p;
  		v = (unsigned long) area->addr;
  	} else {
  		v = (ioremap_bot -= size);
  	}
  
  	/*
  	 * Should check if it is a candidate for a BAT mapping
  	 */
  
  	err = 0;
  	for (i = 0; i < size && err == 0; i += PAGE_SIZE)
  		err = map_kernel_page(v + i, p + i, prot);
  	if (err) {
  		if (slab_is_available())
  			vunmap((void *)v);
  		return NULL;
  	}
  
  out:
  	return (void __iomem *) (v + ((unsigned long)addr & ~PAGE_MASK));
  }
  EXPORT_SYMBOL(__ioremap);
  
  void iounmap(volatile void __iomem *addr)
  {
  	/*
  	 * If mapped by BATs then there is nothing to do.
  	 * Calling vfree() generates a benign warning.
  	 */
  	if (v_block_mapped((unsigned long)addr))
  		return;
  
  	if (addr > high_memory && (unsigned long) addr < ioremap_bot)
  		vunmap((void *) (PAGE_MASK & (unsigned long)addr));
  }
  EXPORT_SYMBOL(iounmap);
  
  static void __init *early_alloc_pgtable(unsigned long size)
  {
  	void *ptr = memblock_alloc(size, size);
  
  	if (!ptr)
  		panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
  		      __func__, size, size);
  
  	return ptr;
  }
  
  static pte_t __init *early_pte_alloc_kernel(pmd_t *pmdp, unsigned long va)
  {
  	if (pmd_none(*pmdp)) {
  		pte_t *ptep = early_alloc_pgtable(PTE_FRAG_SIZE);
  
  		pmd_populate_kernel(&init_mm, pmdp, ptep);
  	}
  	return pte_offset_kernel(pmdp, va);
  }
  
  
  int __ref map_kernel_page(unsigned long va, phys_addr_t pa, pgprot_t prot)
  {
  	pmd_t *pd;
  	pte_t *pg;
  	int err = -ENOMEM;
  
  	/* Use upper 10 bits of VA to index the first level map */
  	pd = pmd_offset(pud_offset(pgd_offset_k(va), va), va);
  	/* Use middle 10 bits of VA to index the second-level map */
  	if (likely(slab_is_available()))
  		pg = pte_alloc_kernel(pd, va);
  	else
  		pg = early_pte_alloc_kernel(pd, va);
  	if (pg != 0) {
  		err = 0;
  		/* The PTE should never be already set nor present in the
  		 * hash table
  		 */
  		BUG_ON((pte_present(*pg) | pte_hashpte(*pg)) && pgprot_val(prot));
  		set_pte_at(&init_mm, va, pg, pfn_pte(pa >> PAGE_SHIFT, prot));
  	}
  	smp_wmb();
  	return err;
  }
  
  /*
   * Map in a chunk of physical memory starting at start.
   */
  static void __init __mapin_ram_chunk(unsigned long offset, unsigned long top)
  {
  	unsigned long v, s;
  	phys_addr_t p;
  	int ktext;
  
  	s = offset;
  	v = PAGE_OFFSET + s;
  	p = memstart_addr + s;
  	for (; s < top; s += PAGE_SIZE) {
  		ktext = ((char *)v >= _stext && (char *)v < etext) ||
  			((char *)v >= _sinittext && (char *)v < _einittext);
  		map_kernel_page(v, p, ktext ? PAGE_KERNEL_TEXT : PAGE_KERNEL);
  #ifdef CONFIG_PPC_BOOK3S_32
  		if (ktext)
  			hash_preload(&init_mm, v, false, 0x300);
  #endif
  		v += PAGE_SIZE;
  		p += PAGE_SIZE;
  	}
  }
  
  void __init mapin_ram(void)
  {
  	struct memblock_region *reg;
  
  	for_each_memblock(memory, reg) {
  		phys_addr_t base = reg->base;
  		phys_addr_t top = min(base + reg->size, total_lowmem);
  
  		if (base >= top)
  			continue;
  		base = mmu_mapin_ram(base, top);
  		if (IS_ENABLED(CONFIG_BDI_SWITCH))
  			__mapin_ram_chunk(reg->base, top);
  		else
  			__mapin_ram_chunk(base, top);
  	}
  }
  
  /* Scan the real Linux page tables and return a PTE pointer for
   * a virtual address in a context.
   * Returns true (1) if PTE was found, zero otherwise.  The pointer to
   * the PTE pointer is unmodified if PTE is not found.
   */
  static int
  get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
  {
          pgd_t	*pgd;
  	pud_t	*pud;
          pmd_t	*pmd;
          pte_t	*pte;
          int     retval = 0;
  
          pgd = pgd_offset(mm, addr & PAGE_MASK);
          if (pgd) {
  		pud = pud_offset(pgd, addr & PAGE_MASK);
  		if (pud && pud_present(*pud)) {
  			pmd = pmd_offset(pud, addr & PAGE_MASK);
  			if (pmd_present(*pmd)) {
  				pte = pte_offset_map(pmd, addr & PAGE_MASK);
  				if (pte) {
  					retval = 1;
  					*ptep = pte;
  					if (pmdp)
  						*pmdp = pmd;
  					/* XXX caller needs to do pte_unmap, yuck */
  				}
  			}
  		}
          }
          return(retval);
  }
  
  static int __change_page_attr_noflush(struct page *page, pgprot_t prot)
  {
  	pte_t *kpte;
  	pmd_t *kpmd;
  	unsigned long address;
  
  	BUG_ON(PageHighMem(page));
  	address = (unsigned long)page_address(page);
  
  	if (v_block_mapped(address))
  		return 0;
  	if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
  		return -EINVAL;
  	__set_pte_at(&init_mm, address, kpte, mk_pte(page, prot), 0);
  	pte_unmap(kpte);
  
  	return 0;
  }
  
  /*
   * Change the page attributes of an page in the linear mapping.
   *
   * THIS DOES NOTHING WITH BAT MAPPINGS, DEBUG USE ONLY
   */
  static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
  {
  	int i, err = 0;
  	unsigned long flags;
  	struct page *start = page;
  
  	local_irq_save(flags);
  	for (i = 0; i < numpages; i++, page++) {
  		err = __change_page_attr_noflush(page, prot);
  		if (err)
  			break;
  	}
  	wmb();
  	local_irq_restore(flags);
  	flush_tlb_kernel_range((unsigned long)page_address(start),
  			       (unsigned long)page_address(page));
  	return err;
  }
  
  void mark_initmem_nx(void)
  {
  	struct page *page = virt_to_page(_sinittext);
  	unsigned long numpages = PFN_UP((unsigned long)_einittext) -
  				 PFN_DOWN((unsigned long)_sinittext);
  
  	if (v_block_mapped((unsigned long)_stext + 1))
  		mmu_mark_initmem_nx();
  	else
  		change_page_attr(page, numpages, PAGE_KERNEL);
  }
  
  #ifdef CONFIG_STRICT_KERNEL_RWX
  void mark_rodata_ro(void)
  {
  	struct page *page;
  	unsigned long numpages;
  
  	if (v_block_mapped((unsigned long)_sinittext)) {
  		mmu_mark_rodata_ro();
  		return;
  	}
  
  	page = virt_to_page(_stext);
  	numpages = PFN_UP((unsigned long)_etext) -
  		   PFN_DOWN((unsigned long)_stext);
  
  	change_page_attr(page, numpages, PAGE_KERNEL_ROX);
  	/*
  	 * mark .rodata as read only. Use __init_begin rather than __end_rodata
  	 * to cover NOTES and EXCEPTION_TABLE.
  	 */
  	page = virt_to_page(__start_rodata);
  	numpages = PFN_UP((unsigned long)__init_begin) -
  		   PFN_DOWN((unsigned long)__start_rodata);
  
  	change_page_attr(page, numpages, PAGE_KERNEL_RO);
  
  	// mark_initmem_nx() should have already run by now
  	ptdump_check_wx();
  }
  #endif
  
  #ifdef CONFIG_DEBUG_PAGEALLOC
  void __kernel_map_pages(struct page *page, int numpages, int enable)
  {
  	if (PageHighMem(page))
  		return;
  
  	change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
  }
  #endif /* CONFIG_DEBUG_PAGEALLOC */
  