text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Re-map IO memory to kernel address space so that we can access it.
   * This is needed for high PCI addresses that aren't mapped in the
   * 640k-1MB IO memory area on PC's
   *
   * (C) Copyright 1995 1996 Linus Torvalds
   */
  #include <linux/vmalloc.h>
  #include <linux/mm.h>
  #include <linux/sched.h>
  #include <linux/io.h>
  #include <linux/export.h>
  #include <asm/cacheflush.h>
  #include <asm/pgtable.h>
  
  #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
  static int __read_mostly ioremap_p4d_capable;
  static int __read_mostly ioremap_pud_capable;
  static int __read_mostly ioremap_pmd_capable;
  static int __read_mostly ioremap_huge_disabled;
  
  static int __init set_nohugeiomap(char *str)
  {
  	ioremap_huge_disabled = 1;
  	return 0;
  }
  early_param("nohugeiomap", set_nohugeiomap);
  
  void __init ioremap_huge_init(void)
  {
  	if (!ioremap_huge_disabled) {
  		if (arch_ioremap_pud_supported())
  			ioremap_pud_capable = 1;
  		if (arch_ioremap_pmd_supported())
  			ioremap_pmd_capable = 1;
  	}
  }
  
  static inline int ioremap_p4d_enabled(void)
  {
  	return ioremap_p4d_capable;
  }
  
  static inline int ioremap_pud_enabled(void)
  {
  	return ioremap_pud_capable;
  }
  
  static inline int ioremap_pmd_enabled(void)
  {
  	return ioremap_pmd_capable;
  }
  
  #else	/* !CONFIG_HAVE_ARCH_HUGE_VMAP */
  static inline int ioremap_p4d_enabled(void) { return 0; }
  static inline int ioremap_pud_enabled(void) { return 0; }
  static inline int ioremap_pmd_enabled(void) { return 0; }
  #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */
  
  static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
  		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
  {
  	pte_t *pte;
  	u64 pfn;
  
  	pfn = phys_addr >> PAGE_SHIFT;
  	pte = pte_alloc_kernel(pmd, addr);
  	if (!pte)
  		return -ENOMEM;
  	do {
  		BUG_ON(!pte_none(*pte));
  		set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
  		pfn++;
  	} while (pte++, addr += PAGE_SIZE, addr != end);
  	return 0;
  }
  
  static int ioremap_try_huge_pmd(pmd_t *pmd, unsigned long addr,
  				unsigned long end, phys_addr_t phys_addr,
  				pgprot_t prot)
  {
  	if (!ioremap_pmd_enabled())
  		return 0;
  
  	if ((end - addr) != PMD_SIZE)
  		return 0;
  
  	if (!IS_ALIGNED(phys_addr, PMD_SIZE))
  		return 0;
  
  	if (pmd_present(*pmd) && !pmd_free_pte_page(pmd, addr))
  		return 0;
  
  	return pmd_set_huge(pmd, phys_addr, prot);
  }
  
  static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
  		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
  {
  	pmd_t *pmd;
  	unsigned long next;
  
  	pmd = pmd_alloc(&init_mm, pud, addr);
  	if (!pmd)
  		return -ENOMEM;
  	do {
  		next = pmd_addr_end(addr, end);
  
  		if (ioremap_try_huge_pmd(pmd, addr, next, phys_addr, prot))
  			continue;
  
  		if (ioremap_pte_range(pmd, addr, next, phys_addr, prot))
  			return -ENOMEM;
  	} while (pmd++, phys_addr += (next - addr), addr = next, addr != end);
  	return 0;
  }
  
  static int ioremap_try_huge_pud(pud_t *pud, unsigned long addr,
  				unsigned long end, phys_addr_t phys_addr,
  				pgprot_t prot)
  {
  	if (!ioremap_pud_enabled())
  		return 0;
  
  	if ((end - addr) != PUD_SIZE)
  		return 0;
  
  	if (!IS_ALIGNED(phys_addr, PUD_SIZE))
  		return 0;
  
  	if (pud_present(*pud) && !pud_free_pmd_page(pud, addr))
  		return 0;
  
  	return pud_set_huge(pud, phys_addr, prot);
  }
  
  static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
  		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
  {
  	pud_t *pud;
  	unsigned long next;
  
  	pud = pud_alloc(&init_mm, p4d, addr);
  	if (!pud)
  		return -ENOMEM;
  	do {
  		next = pud_addr_end(addr, end);
  
  		if (ioremap_try_huge_pud(pud, addr, next, phys_addr, prot))
  			continue;
  
  		if (ioremap_pmd_range(pud, addr, next, phys_addr, prot))
  			return -ENOMEM;
  	} while (pud++, phys_addr += (next - addr), addr = next, addr != end);
  	return 0;
  }
  
  static int ioremap_try_huge_p4d(p4d_t *p4d, unsigned long addr,
  				unsigned long end, phys_addr_t phys_addr,
  				pgprot_t prot)
  {
  	if (!ioremap_p4d_enabled())
  		return 0;
  
  	if ((end - addr) != P4D_SIZE)
  		return 0;
  
  	if (!IS_ALIGNED(phys_addr, P4D_SIZE))
  		return 0;
  
  	if (p4d_present(*p4d) && !p4d_free_pud_page(p4d, addr))
  		return 0;
  
  	return p4d_set_huge(p4d, phys_addr, prot);
  }
  
  static inline int ioremap_p4d_range(pgd_t *pgd, unsigned long addr,
  		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
  {
  	p4d_t *p4d;
  	unsigned long next;
  
  	p4d = p4d_alloc(&init_mm, pgd, addr);
  	if (!p4d)
  		return -ENOMEM;
  	do {
  		next = p4d_addr_end(addr, end);
  
  		if (ioremap_try_huge_p4d(p4d, addr, next, phys_addr, prot))
  			continue;
  
  		if (ioremap_pud_range(p4d, addr, next, phys_addr, prot))
  			return -ENOMEM;
  	} while (p4d++, phys_addr += (next - addr), addr = next, addr != end);
  	return 0;
  }
  
  int ioremap_page_range(unsigned long addr,
  		       unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
  {
  	pgd_t *pgd;
  	unsigned long start;
  	unsigned long next;
  	int err;
  
  	might_sleep();
  	BUG_ON(addr >= end);
  
  	start = addr;
  	pgd = pgd_offset_k(addr);
  	do {
  		next = pgd_addr_end(addr, end);
  		err = ioremap_p4d_range(pgd, addr, next, phys_addr, prot);
  		if (err)
  			break;
  	} while (pgd++, phys_addr += (next - addr), addr = next, addr != end);
  
  	flush_cache_vmap(start, end);
  
  	return err;
  }
  