Skip to main content
  • Home
  • Development
  • Documentation
  • Donate
  • Operational login
  • Browse the archive

swh logo
SoftwareHeritage
Software
Heritage
Archive
Features
  • Search

  • Downloads

  • Save code now

  • Add forge now

  • Help

  • 7c8c5e3
  • /
  • arch
  • /
  • arm64
  • /
  • mm
  • /
  • pageattr.c
Raw File Download
Permalinks

To reference or cite the objects present in the Software Heritage archive, permalinks based on SoftWare Hash IDentifiers (SWHIDs) must be used.
Select below a type of object currently browsed in order to display its associated SWHID and permalink.

  • content
  • directory
content badge Iframe embedding
swh:1:cnt:a682a0a2a0fa4d5db9175256e78100b1afde344a
directory badge Iframe embedding
swh:1:dir:62120b4b29f806d1eed65699e76cb2176aa21746
Citations

This interface enables to generate software citations, provided that the root directory of browsed objects contains a citation.cff or codemeta.json file.
Select below a type of object currently browsed in order to generate citations for them.

  • content
  • directory
Generate software citation in BibTex format (requires biblatex-software package)
Generating citation ...
Generate software citation in BibTex format (requires biblatex-software package)
Generating citation ...
pageattr.c
/*
 * Copyright (c) 2014, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/vmalloc.h>

#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/tlbflush.h>

struct page_change_data {
	pgprot_t set_mask;
	pgprot_t clear_mask;
};

static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
			void *data)
{
	struct page_change_data *cdata = data;
	pte_t pte = *ptep;

	pte = clear_pte_bit(pte, cdata->clear_mask);
	pte = set_pte_bit(pte, cdata->set_mask);

	set_pte(ptep, pte);
	return 0;
}

/*
 * This function assumes that the range is mapped with PAGE_SIZE pages.
 */
static int __change_memory_common(unsigned long start, unsigned long size,
				pgprot_t set_mask, pgprot_t clear_mask)
{
	struct page_change_data data;
	int ret;

	data.set_mask = set_mask;
	data.clear_mask = clear_mask;

	ret = apply_to_page_range(&init_mm, start, size, change_page_range,
					&data);

	flush_tlb_kernel_range(start, start + size);
	return ret;
}

static int change_memory_common(unsigned long addr, int numpages,
				pgprot_t set_mask, pgprot_t clear_mask)
{
	unsigned long start = addr;
	unsigned long size = PAGE_SIZE*numpages;
	unsigned long end = start + size;
	struct vm_struct *area;

	if (!PAGE_ALIGNED(addr)) {
		start &= PAGE_MASK;
		end = start + size;
		WARN_ON_ONCE(1);
	}

	/*
	 * Kernel VA mappings are always live, and splitting live section
	 * mappings into page mappings may cause TLB conflicts. This means
	 * we have to ensure that changing the permission bits of the range
	 * we are operating on does not result in such splitting.
	 *
	 * Let's restrict ourselves to mappings created by vmalloc (or vmap).
	 * Those are guaranteed to consist entirely of page mappings, and
	 * splitting is never needed.
	 *
	 * So check whether the [addr, addr + size) interval is entirely
	 * covered by precisely one VM area that has the VM_ALLOC flag set.
	 */
	area = find_vm_area((void *)addr);
	if (!area ||
	    end > (unsigned long)area->addr + area->size ||
	    !(area->flags & VM_ALLOC))
		return -EINVAL;

	if (!numpages)
		return 0;

	return __change_memory_common(start, size, set_mask, clear_mask);
}

int set_memory_ro(unsigned long addr, int numpages)
{
	return change_memory_common(addr, numpages,
					__pgprot(PTE_RDONLY),
					__pgprot(PTE_WRITE));
}

int set_memory_rw(unsigned long addr, int numpages)
{
	return change_memory_common(addr, numpages,
					__pgprot(PTE_WRITE),
					__pgprot(PTE_RDONLY));
}

int set_memory_nx(unsigned long addr, int numpages)
{
	return change_memory_common(addr, numpages,
					__pgprot(PTE_PXN),
					__pgprot(0));
}
EXPORT_SYMBOL_GPL(set_memory_nx);

int set_memory_x(unsigned long addr, int numpages)
{
	return change_memory_common(addr, numpages,
					__pgprot(0),
					__pgprot(PTE_PXN));
}
EXPORT_SYMBOL_GPL(set_memory_x);

int set_memory_valid(unsigned long addr, int numpages, int enable)
{
	if (enable)
		return __change_memory_common(addr, PAGE_SIZE * numpages,
					__pgprot(PTE_VALID),
					__pgprot(0));
	else
		return __change_memory_common(addr, PAGE_SIZE * numpages,
					__pgprot(0),
					__pgprot(PTE_VALID));
}

#ifdef CONFIG_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
	set_memory_valid((unsigned long)page_address(page), numpages, enable);
}
#ifdef CONFIG_HIBERNATION
/*
 * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function
 * is used to determine if a linear map page has been marked as not-valid by
 * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.
 * This is based on kern_addr_valid(), which almost does what we need.
 *
 * Because this is only called on the kernel linear map,  p?d_sect() implies
 * p?d_present(). When debug_pagealloc is enabled, sections mappings are
 * disabled.
 */
bool kernel_page_present(struct page *page)
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	unsigned long addr = (unsigned long)page_address(page);

	pgd = pgd_offset_k(addr);
	if (pgd_none(*pgd))
		return false;

	pud = pud_offset(pgd, addr);
	if (pud_none(*pud))
		return false;
	if (pud_sect(*pud))
		return true;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(*pmd))
		return false;
	if (pmd_sect(*pmd))
		return true;

	pte = pte_offset_kernel(pmd, addr);
	return pte_valid(*pte);
}
#endif /* CONFIG_HIBERNATION */
#endif /* CONFIG_DEBUG_PAGEALLOC */

back to top

Software Heritage — Copyright (C) 2015–2025, The Software Heritage developers. License: GNU AGPLv3+.
The source code of Software Heritage itself is available on our development forge.
The source code files archived by Software Heritage are available under their own copyright and licenses.
Terms of use: Archive access, API— Contact— JavaScript license information— Web API