pageattr.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2024 Loongson Technology Corporation Limited
 */

#include <linux/memblock.h>
#include <linux/pagewalk.h>
#include <linux/pgtable.h>
#include <asm/set_memory.h>
#include <asm/tlbflush.h>

struct pageattr_masks {
	pgprot_t set_mask;
	pgprot_t clear_mask;
};

static unsigned long set_pageattr_masks(unsigned long val, struct mm_walk *walk)
{
	unsigned long new_val = val;
	struct pageattr_masks *masks = walk->private;

	new_val &= ~(pgprot_val(masks->clear_mask));
	new_val |= (pgprot_val(masks->set_mask));

	return new_val;
}

static int pageattr_pgd_entry(pgd_t *pgd, unsigned long addr,
			      unsigned long next, struct mm_walk *walk)
{
	pgd_t val = pgdp_get(pgd);

	if (pgd_leaf(val)) {
		val = __pgd(set_pageattr_masks(pgd_val(val), walk));
		set_pgd(pgd, val);
	}

	return 0;
}

static int pageattr_p4d_entry(p4d_t *p4d, unsigned long addr,
			      unsigned long next, struct mm_walk *walk)
{
	p4d_t val = p4dp_get(p4d);

	if (p4d_leaf(val)) {
		val = __p4d(set_pageattr_masks(p4d_val(val), walk));
		set_p4d(p4d, val);
	}

	return 0;
}

static int pageattr_pud_entry(pud_t *pud, unsigned long addr,
			      unsigned long next, struct mm_walk *walk)
{
	pud_t val = pudp_get(pud);

	if (pud_leaf(val)) {
		val = __pud(set_pageattr_masks(pud_val(val), walk));
		set_pud(pud, val);
	}

	return 0;
}

static int pageattr_pmd_entry(pmd_t *pmd, unsigned long addr,
			      unsigned long next, struct mm_walk *walk)
{
	pmd_t val = pmdp_get(pmd);

	if (pmd_leaf(val)) {
		val = __pmd(set_pageattr_masks(pmd_val(val), walk));
		set_pmd(pmd, val);
	}

	return 0;
}

static int pageattr_pte_entry(pte_t *pte, unsigned long addr,
			      unsigned long next, struct mm_walk *walk)
{
	pte_t val = ptep_get(pte);

	val = __pte(set_pageattr_masks(pte_val(val), walk));
	set_pte(pte, val);

	return 0;
}

static int pageattr_pte_hole(unsigned long addr, unsigned long next,
			     int depth, struct mm_walk *walk)
{
	return 0;
}

static const struct mm_walk_ops pageattr_ops = {
	.pgd_entry = pageattr_pgd_entry,
	.p4d_entry = pageattr_p4d_entry,
	.pud_entry = pageattr_pud_entry,
	.pmd_entry = pageattr_pmd_entry,
	.pte_entry = pageattr_pte_entry,
	.pte_hole = pageattr_pte_hole,
	.walk_lock = PGWALK_RDLOCK,
};

static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask, pgprot_t clear_mask)
{
	int ret;
	unsigned long start = addr;
	unsigned long end = start + PAGE_SIZE * numpages;
	struct pageattr_masks masks = {
		.set_mask = set_mask,
		.clear_mask = clear_mask
	};

	if (!numpages)
		return 0;

	mmap_write_lock(&init_mm);
	ret = walk_kernel_page_table_range(start, end, &pageattr_ops, NULL, &masks);
	mmap_write_unlock(&init_mm);

	flush_tlb_kernel_range(start, end);

	return ret;
}

int set_memory_x(unsigned long addr, int numpages)
{
	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, numpages, __pgprot(0), __pgprot(_PAGE_NO_EXEC));
}

int set_memory_nx(unsigned long addr, int numpages)
{
	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, numpages, __pgprot(_PAGE_NO_EXEC), __pgprot(0));
}

int set_memory_ro(unsigned long addr, int numpages)
{
	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, numpages, __pgprot(0), __pgprot(_PAGE_WRITE | _PAGE_DIRTY));
}

int set_memory_rw(unsigned long addr, int numpages)
{
	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, numpages, __pgprot(_PAGE_WRITE | _PAGE_DIRTY), __pgprot(0));
}

bool kernel_page_present(struct page *page)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	unsigned long addr = (unsigned long)page_address(page);

	if (addr < vm_map_base)
		return memblock_is_memory(__pa(addr));

	pgd = pgd_offset_k(addr);
	if (pgd_none(pgdp_get(pgd)))
		return false;
	if (pgd_leaf(pgdp_get(pgd)))
		return true;

	p4d = p4d_offset(pgd, addr);
	if (p4d_none(p4dp_get(p4d)))
		return false;
	if (p4d_leaf(p4dp_get(p4d)))
		return true;

	pud = pud_offset(p4d, addr);
	if (pud_none(pudp_get(pud)))
		return false;
	if (pud_leaf(pudp_get(pud)))
		return true;

	pmd = pmd_offset(pud, addr);
	if (pmd_none(pmdp_get(pmd)))
		return false;
	if (pmd_leaf(pmdp_get(pmd)))
		return true;

	pte = pte_offset_kernel(pmd, addr);
	return pte_present(ptep_get(pte));
}

int set_direct_map_default_noflush(struct page *page)
{
	unsigned long addr = (unsigned long)page_address(page);

	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, 1, PAGE_KERNEL, __pgprot(0));
}

int set_direct_map_invalid_noflush(struct page *page)
{
	unsigned long addr = (unsigned long)page_address(page);

	if (addr < vm_map_base)
		return 0;

	return __set_memory(addr, 1, __pgprot(0), __pgprot(_PAGE_PRESENT | _PAGE_VALID));
}

int set_direct_map_valid_noflush(struct page *page, unsigned nr, bool valid)
{
	unsigned long addr = (unsigned long)page_address(page);
	pgprot_t set, clear;

	if (addr < vm_map_base)
		return 0;

	if (valid) {
		set = PAGE_KERNEL;
		clear = __pgprot(0);
	} else {
		set = __pgprot(0);
		clear = __pgprot(_PAGE_PRESENT | _PAGE_VALID);
	}

	return __set_memory(addr, 1, set, clear);
}