Revision 5f56a74cc0a6d9b9f8ba89cea29cd7c4774cb2b1 authored by Ard Biesheuvel on 20 September 2022, 15:08:23 UTC, committed by Ard Biesheuvel on 22 September 2022, 08:15:44 UTC
We currently check the MokSBState variable to decide whether we should
treat UEFI secure boot as being disabled, even if the firmware thinks
otherwise. This is used by shim to indicate that it is not checking
signatures on boot images. In the kernel, we use this to relax lockdown
policies.

However, in cases where shim is not even being used, we don't want this
variable to interfere with lockdown, given that the variable may be
non-volatile and therefore persist across a reboot. This means setting
it once will persistently disable lockdown checks on a given system.

So switch to the mirrored version of this variable, called MokSBStateRT,
which is supposed to be volatile, and this is something we can check.

Cc: <stable@vger.kernel.org> # v4.19+
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Peter Jones <pjones@redhat.com>
1 parent 63bf28c
Raw File
highmem.c
// SPDX-License-Identifier: GPL-2.0
/*
 * High memory handling common code and variables.
 *
 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
 *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
 *
 *
 * Redesigned the x86 32-bit VM architecture to deal with
 * 64-bit physical space. With current x86 CPUs this
 * means up to 64 Gigabytes physical RAM.
 *
 * Rewrote high memory support to move the page cache into
 * high memory. Implemented permanent (schedulable) kmaps
 * based on Linus' idea.
 *
 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
 */

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/highmem.h>
#include <linux/kgdb.h>
#include <asm/tlbflush.h>
#include <linux/vmalloc.h>

/*
 * Virtual_count is not a pure "count".
 *  0 means that it is not mapped, and has not been mapped
 *    since a TLB flush - it is usable.
 *  1 means that there are no users, but it has been mapped
 *    since the last TLB flush - so we can't use it.
 *  n means that there are (n-1) current users of it.
 */
#ifdef CONFIG_HIGHMEM

/*
 * Architecture with aliasing data cache may define the following family of
 * helper functions in its asm/highmem.h to control cache color of virtual
 * addresses where physical memory pages are mapped by kmap.
 */
#ifndef get_pkmap_color

/*
 * Determine color of virtual address where the page should be mapped.
 */
static inline unsigned int get_pkmap_color(struct page *page)
{
	return 0;
}
#define get_pkmap_color get_pkmap_color

/*
 * Get next index for mapping inside PKMAP region for page with given color.
 */
static inline unsigned int get_next_pkmap_nr(unsigned int color)
{
	static unsigned int last_pkmap_nr;

	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
	return last_pkmap_nr;
}

/*
 * Determine if page index inside PKMAP region (pkmap_nr) of given color
 * has wrapped around PKMAP region end. When this happens an attempt to
 * flush all unused PKMAP slots is made.
 */
static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
{
	return pkmap_nr == 0;
}

/*
 * Get the number of PKMAP entries of the given color. If no free slot is
 * found after checking that many entries, kmap will sleep waiting for
 * someone to call kunmap and free PKMAP slot.
 */
static inline int get_pkmap_entries_count(unsigned int color)
{
	return LAST_PKMAP;
}

/*
 * Get head of a wait queue for PKMAP entries of the given color.
 * Wait queues for different mapping colors should be independent to avoid
 * unnecessary wakeups caused by freeing of slots of other colors.
 */
static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
{
	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);

	return &pkmap_map_wait;
}
#endif

atomic_long_t _totalhigh_pages __read_mostly;
EXPORT_SYMBOL(_totalhigh_pages);

unsigned int __nr_free_highpages(void)
{
	struct zone *zone;
	unsigned int pages = 0;

	for_each_populated_zone(zone) {
		if (is_highmem(zone))
			pages += zone_page_state(zone, NR_FREE_PAGES);
	}

	return pages;
}

static int pkmap_count[LAST_PKMAP];
static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);

pte_t *pkmap_page_table;

/*
 * Most architectures have no use for kmap_high_get(), so let's abstract
 * the disabling of IRQ out of the locking in that case to save on a
 * potential useless overhead.
 */
#ifdef ARCH_NEEDS_KMAP_HIGH_GET
#define lock_kmap()             spin_lock_irq(&kmap_lock)
#define unlock_kmap()           spin_unlock_irq(&kmap_lock)
#define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
#define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
#else
#define lock_kmap()             spin_lock(&kmap_lock)
#define unlock_kmap()           spin_unlock(&kmap_lock)
#define lock_kmap_any(flags)    \
		do { spin_lock(&kmap_lock); (void)(flags); } while (0)
#define unlock_kmap_any(flags)  \
		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
#endif

struct page *__kmap_to_page(void *vaddr)
{
	unsigned long addr = (unsigned long)vaddr;

	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
		int i = PKMAP_NR(addr);

		return pte_page(pkmap_page_table[i]);
	}

	return virt_to_page(vaddr);
}
EXPORT_SYMBOL(__kmap_to_page);

static void flush_all_zero_pkmaps(void)
{
	int i;
	int need_flush = 0;

	flush_cache_kmaps();

	for (i = 0; i < LAST_PKMAP; i++) {
		struct page *page;

		/*
		 * zero means we don't have anything to do,
		 * >1 means that it is still in use. Only
		 * a count of 1 means that it is free but
		 * needs to be unmapped
		 */
		if (pkmap_count[i] != 1)
			continue;
		pkmap_count[i] = 0;

		/* sanity check */
		BUG_ON(pte_none(pkmap_page_table[i]));

		/*
		 * Don't need an atomic fetch-and-clear op here;
		 * no-one has the page mapped, and cannot get at
		 * its virtual address (and hence PTE) without first
		 * getting the kmap_lock (which is held here).
		 * So no dangers, even with speculative execution.
		 */
		page = pte_page(pkmap_page_table[i]);
		pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);

		set_page_address(page, NULL);
		need_flush = 1;
	}
	if (need_flush)
		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
}

void __kmap_flush_unused(void)
{
	lock_kmap();
	flush_all_zero_pkmaps();
	unlock_kmap();
}

static inline unsigned long map_new_virtual(struct page *page)
{
	unsigned long vaddr;
	int count;
	unsigned int last_pkmap_nr;
	unsigned int color = get_pkmap_color(page);

start:
	count = get_pkmap_entries_count(color);
	/* Find an empty entry */
	for (;;) {
		last_pkmap_nr = get_next_pkmap_nr(color);
		if (no_more_pkmaps(last_pkmap_nr, color)) {
			flush_all_zero_pkmaps();
			count = get_pkmap_entries_count(color);
		}
		if (!pkmap_count[last_pkmap_nr])
			break;	/* Found a usable entry */
		if (--count)
			continue;

		/*
		 * Sleep for somebody else to unmap their entries
		 */
		{
			DECLARE_WAITQUEUE(wait, current);
			wait_queue_head_t *pkmap_map_wait =
				get_pkmap_wait_queue_head(color);

			__set_current_state(TASK_UNINTERRUPTIBLE);
			add_wait_queue(pkmap_map_wait, &wait);
			unlock_kmap();
			schedule();
			remove_wait_queue(pkmap_map_wait, &wait);
			lock_kmap();

			/* Somebody else might have mapped it while we slept */
			if (page_address(page))
				return (unsigned long)page_address(page);

			/* Re-start */
			goto start;
		}
	}
	vaddr = PKMAP_ADDR(last_pkmap_nr);
	set_pte_at(&init_mm, vaddr,
		   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));

	pkmap_count[last_pkmap_nr] = 1;
	set_page_address(page, (void *)vaddr);

	return vaddr;
}

/**
 * kmap_high - map a highmem page into memory
 * @page: &struct page to map
 *
 * Returns the page's virtual memory address.
 *
 * We cannot call this from interrupts, as it may block.
 */
void *kmap_high(struct page *page)
{
	unsigned long vaddr;

	/*
	 * For highmem pages, we can't trust "virtual" until
	 * after we have the lock.
	 */
	lock_kmap();
	vaddr = (unsigned long)page_address(page);
	if (!vaddr)
		vaddr = map_new_virtual(page);
	pkmap_count[PKMAP_NR(vaddr)]++;
	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
	unlock_kmap();
	return (void *) vaddr;
}
EXPORT_SYMBOL(kmap_high);

#ifdef ARCH_NEEDS_KMAP_HIGH_GET
/**
 * kmap_high_get - pin a highmem page into memory
 * @page: &struct page to pin
 *
 * Returns the page's current virtual memory address, or NULL if no mapping
 * exists.  If and only if a non null address is returned then a
 * matching call to kunmap_high() is necessary.
 *
 * This can be called from any context.
 */
void *kmap_high_get(struct page *page)
{
	unsigned long vaddr, flags;

	lock_kmap_any(flags);
	vaddr = (unsigned long)page_address(page);
	if (vaddr) {
		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
		pkmap_count[PKMAP_NR(vaddr)]++;
	}
	unlock_kmap_any(flags);
	return (void *) vaddr;
}
#endif

/**
 * kunmap_high - unmap a highmem page into memory
 * @page: &struct page to unmap
 *
 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
 * only from user context.
 */
void kunmap_high(struct page *page)
{
	unsigned long vaddr;
	unsigned long nr;
	unsigned long flags;
	int need_wakeup;
	unsigned int color = get_pkmap_color(page);
	wait_queue_head_t *pkmap_map_wait;

	lock_kmap_any(flags);
	vaddr = (unsigned long)page_address(page);
	BUG_ON(!vaddr);
	nr = PKMAP_NR(vaddr);

	/*
	 * A count must never go down to zero
	 * without a TLB flush!
	 */
	need_wakeup = 0;
	switch (--pkmap_count[nr]) {
	case 0:
		BUG();
	case 1:
		/*
		 * Avoid an unnecessary wake_up() function call.
		 * The common case is pkmap_count[] == 1, but
		 * no waiters.
		 * The tasks queued in the wait-queue are guarded
		 * by both the lock in the wait-queue-head and by
		 * the kmap_lock.  As the kmap_lock is held here,
		 * no need for the wait-queue-head's lock.  Simply
		 * test if the queue is empty.
		 */
		pkmap_map_wait = get_pkmap_wait_queue_head(color);
		need_wakeup = waitqueue_active(pkmap_map_wait);
	}
	unlock_kmap_any(flags);

	/* do wake-up, if needed, race-free outside of the spin lock */
	if (need_wakeup)
		wake_up(pkmap_map_wait);
}
EXPORT_SYMBOL(kunmap_high);

void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
		unsigned start2, unsigned end2)
{
	unsigned int i;

	BUG_ON(end1 > page_size(page) || end2 > page_size(page));

	if (start1 >= end1)
		start1 = end1 = 0;
	if (start2 >= end2)
		start2 = end2 = 0;

	for (i = 0; i < compound_nr(page); i++) {
		void *kaddr = NULL;

		if (start1 >= PAGE_SIZE) {
			start1 -= PAGE_SIZE;
			end1 -= PAGE_SIZE;
		} else {
			unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);

			if (end1 > start1) {
				kaddr = kmap_local_page(page + i);
				memset(kaddr + start1, 0, this_end - start1);
			}
			end1 -= this_end;
			start1 = 0;
		}

		if (start2 >= PAGE_SIZE) {
			start2 -= PAGE_SIZE;
			end2 -= PAGE_SIZE;
		} else {
			unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);

			if (end2 > start2) {
				if (!kaddr)
					kaddr = kmap_local_page(page + i);
				memset(kaddr + start2, 0, this_end - start2);
			}
			end2 -= this_end;
			start2 = 0;
		}

		if (kaddr) {
			kunmap_local(kaddr);
			flush_dcache_page(page + i);
		}

		if (!end1 && !end2)
			break;
	}

	BUG_ON((start1 | start2 | end1 | end2) != 0);
}
EXPORT_SYMBOL(zero_user_segments);
#endif /* CONFIG_HIGHMEM */

#ifdef CONFIG_KMAP_LOCAL

#include <asm/kmap_size.h>

/*
 * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
 * slot is unused which acts as a guard page
 */
#ifdef CONFIG_DEBUG_KMAP_LOCAL
# define KM_INCR	2
#else
# define KM_INCR	1
#endif

static inline int kmap_local_idx_push(void)
{
	WARN_ON_ONCE(in_hardirq() && !irqs_disabled());
	current->kmap_ctrl.idx += KM_INCR;
	BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX);
	return current->kmap_ctrl.idx - 1;
}

static inline int kmap_local_idx(void)
{
	return current->kmap_ctrl.idx - 1;
}

static inline void kmap_local_idx_pop(void)
{
	current->kmap_ctrl.idx -= KM_INCR;
	BUG_ON(current->kmap_ctrl.idx < 0);
}

#ifndef arch_kmap_local_post_map
# define arch_kmap_local_post_map(vaddr, pteval)	do { } while (0)
#endif

#ifndef arch_kmap_local_pre_unmap
# define arch_kmap_local_pre_unmap(vaddr)		do { } while (0)
#endif

#ifndef arch_kmap_local_post_unmap
# define arch_kmap_local_post_unmap(vaddr)		do { } while (0)
#endif

#ifndef arch_kmap_local_map_idx
#define arch_kmap_local_map_idx(idx, pfn)	kmap_local_calc_idx(idx)
#endif

#ifndef arch_kmap_local_unmap_idx
#define arch_kmap_local_unmap_idx(idx, vaddr)	kmap_local_calc_idx(idx)
#endif

#ifndef arch_kmap_local_high_get
static inline void *arch_kmap_local_high_get(struct page *page)
{
	return NULL;
}
#endif

#ifndef arch_kmap_local_set_pte
#define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev)	\
	set_pte_at(mm, vaddr, ptep, ptev)
#endif

/* Unmap a local mapping which was obtained by kmap_high_get() */
static inline bool kmap_high_unmap_local(unsigned long vaddr)
{
#ifdef ARCH_NEEDS_KMAP_HIGH_GET
	if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
		return true;
	}
#endif
	return false;
}

static inline int kmap_local_calc_idx(int idx)
{
	return idx + KM_MAX_IDX * smp_processor_id();
}

static pte_t *__kmap_pte;

static pte_t *kmap_get_pte(unsigned long vaddr, int idx)
{
	if (IS_ENABLED(CONFIG_KMAP_LOCAL_NON_LINEAR_PTE_ARRAY))
		/*
		 * Set by the arch if __kmap_pte[-idx] does not produce
		 * the correct entry.
		 */
		return virt_to_kpte(vaddr);
	if (!__kmap_pte)
		__kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
	return &__kmap_pte[-idx];
}

void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
{
	pte_t pteval, *kmap_pte;
	unsigned long vaddr;
	int idx;

	/*
	 * Disable migration so resulting virtual address is stable
	 * across preemption.
	 */
	migrate_disable();
	preempt_disable();
	idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
	kmap_pte = kmap_get_pte(vaddr, idx);
	BUG_ON(!pte_none(*kmap_pte));
	pteval = pfn_pte(pfn, prot);
	arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte, pteval);
	arch_kmap_local_post_map(vaddr, pteval);
	current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
	preempt_enable();

	return (void *)vaddr;
}
EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);

void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
{
	void *kmap;

	/*
	 * To broaden the usage of the actual kmap_local() machinery always map
	 * pages when debugging is enabled and the architecture has no problems
	 * with alias mappings.
	 */
	if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
		return page_address(page);

	/* Try kmap_high_get() if architecture has it enabled */
	kmap = arch_kmap_local_high_get(page);
	if (kmap)
		return kmap;

	return __kmap_local_pfn_prot(page_to_pfn(page), prot);
}
EXPORT_SYMBOL(__kmap_local_page_prot);

void kunmap_local_indexed(const void *vaddr)
{
	unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
	pte_t *kmap_pte;
	int idx;

	if (addr < __fix_to_virt(FIX_KMAP_END) ||
	    addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
			/* This _should_ never happen! See above. */
			WARN_ON_ONCE(1);
			return;
		}
		/*
		 * Handle mappings which were obtained by kmap_high_get()
		 * first as the virtual address of such mappings is below
		 * PAGE_OFFSET. Warn for all other addresses which are in
		 * the user space part of the virtual address space.
		 */
		if (!kmap_high_unmap_local(addr))
			WARN_ON_ONCE(addr < PAGE_OFFSET);
		return;
	}

	preempt_disable();
	idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
	WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));

	kmap_pte = kmap_get_pte(addr, idx);
	arch_kmap_local_pre_unmap(addr);
	pte_clear(&init_mm, addr, kmap_pte);
	arch_kmap_local_post_unmap(addr);
	current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
	kmap_local_idx_pop();
	preempt_enable();
	migrate_enable();
}
EXPORT_SYMBOL(kunmap_local_indexed);

/*
 * Invoked before switch_to(). This is safe even when during or after
 * clearing the maps an interrupt which needs a kmap_local happens because
 * the task::kmap_ctrl.idx is not modified by the unmapping code so a
 * nested kmap_local will use the next unused index and restore the index
 * on unmap. The already cleared kmaps of the outgoing task are irrelevant
 * because the interrupt context does not know about them. The same applies
 * when scheduling back in for an interrupt which happens before the
 * restore is complete.
 */
void __kmap_local_sched_out(void)
{
	struct task_struct *tsk = current;
	pte_t *kmap_pte;
	int i;

	/* Clear kmaps */
	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
		pte_t pteval = tsk->kmap_ctrl.pteval[i];
		unsigned long addr;
		int idx;

		/* With debug all even slots are unmapped and act as guard */
		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
			WARN_ON_ONCE(pte_val(pteval) != 0);
			continue;
		}
		if (WARN_ON_ONCE(pte_none(pteval)))
			continue;

		/*
		 * This is a horrible hack for XTENSA to calculate the
		 * coloured PTE index. Uses the PFN encoded into the pteval
		 * and the map index calculation because the actual mapped
		 * virtual address is not stored in task::kmap_ctrl.
		 * For any sane architecture this is optimized out.
		 */
		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));

		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
		kmap_pte = kmap_get_pte(addr, idx);
		arch_kmap_local_pre_unmap(addr);
		pte_clear(&init_mm, addr, kmap_pte);
		arch_kmap_local_post_unmap(addr);
	}
}

void __kmap_local_sched_in(void)
{
	struct task_struct *tsk = current;
	pte_t *kmap_pte;
	int i;

	/* Restore kmaps */
	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
		pte_t pteval = tsk->kmap_ctrl.pteval[i];
		unsigned long addr;
		int idx;

		/* With debug all even slots are unmapped and act as guard */
		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
			WARN_ON_ONCE(pte_val(pteval) != 0);
			continue;
		}
		if (WARN_ON_ONCE(pte_none(pteval)))
			continue;

		/* See comment in __kmap_local_sched_out() */
		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
		kmap_pte = kmap_get_pte(addr, idx);
		set_pte_at(&init_mm, addr, kmap_pte, pteval);
		arch_kmap_local_post_map(addr, pteval);
	}
}

void kmap_local_fork(struct task_struct *tsk)
{
	if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
		memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
}

#endif

#if defined(HASHED_PAGE_VIRTUAL)

#define PA_HASH_ORDER	7

/*
 * Describes one page->virtual association
 */
struct page_address_map {
	struct page *page;
	void *virtual;
	struct list_head list;
};

static struct page_address_map page_address_maps[LAST_PKMAP];

/*
 * Hash table bucket
 */
static struct page_address_slot {
	struct list_head lh;			/* List of page_address_maps */
	spinlock_t lock;			/* Protect this bucket's list */
} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];

static struct page_address_slot *page_slot(const struct page *page)
{
	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
}

/**
 * page_address - get the mapped virtual address of a page
 * @page: &struct page to get the virtual address of
 *
 * Returns the page's virtual address.
 */
void *page_address(const struct page *page)
{
	unsigned long flags;
	void *ret;
	struct page_address_slot *pas;

	if (!PageHighMem(page))
		return lowmem_page_address(page);

	pas = page_slot(page);
	ret = NULL;
	spin_lock_irqsave(&pas->lock, flags);
	if (!list_empty(&pas->lh)) {
		struct page_address_map *pam;

		list_for_each_entry(pam, &pas->lh, list) {
			if (pam->page == page) {
				ret = pam->virtual;
				break;
			}
		}
	}

	spin_unlock_irqrestore(&pas->lock, flags);
	return ret;
}
EXPORT_SYMBOL(page_address);

/**
 * set_page_address - set a page's virtual address
 * @page: &struct page to set
 * @virtual: virtual address to use
 */
void set_page_address(struct page *page, void *virtual)
{
	unsigned long flags;
	struct page_address_slot *pas;
	struct page_address_map *pam;

	BUG_ON(!PageHighMem(page));

	pas = page_slot(page);
	if (virtual) {		/* Add */
		pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
		pam->page = page;
		pam->virtual = virtual;

		spin_lock_irqsave(&pas->lock, flags);
		list_add_tail(&pam->list, &pas->lh);
		spin_unlock_irqrestore(&pas->lock, flags);
	} else {		/* Remove */
		spin_lock_irqsave(&pas->lock, flags);
		list_for_each_entry(pam, &pas->lh, list) {
			if (pam->page == page) {
				list_del(&pam->list);
				break;
			}
		}
		spin_unlock_irqrestore(&pas->lock, flags);
	}

	return;
}

void __init page_address_init(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
		INIT_LIST_HEAD(&page_address_htable[i].lh);
		spin_lock_init(&page_address_htable[i].lock);
	}
}

#endif	/* defined(HASHED_PAGE_VIRTUAL) */
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