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-rw-r--r--mm/highmem.c814
1 files changed, 814 insertions, 0 deletions
diff --git a/mm/highmem.c b/mm/highmem.c
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+++ b/mm/highmem.c
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+// 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>
+
+#ifdef CONFIG_KMAP_LOCAL
+static inline int kmap_local_calc_idx(int idx)
+{
+ return idx + KM_MAX_IDX * smp_processor_id();
+}
+
+#ifndef arch_kmap_local_map_idx
+#define arch_kmap_local_map_idx(idx, pfn) kmap_local_calc_idx(idx)
+#endif
+#endif /* CONFIG_KMAP_LOCAL */
+
+/*
+ * 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 base = (unsigned long) vaddr & PAGE_MASK;
+ struct kmap_ctrl *kctrl = &current->kmap_ctrl;
+ unsigned long addr = (unsigned long)vaddr;
+ int i;
+
+ /* kmap() mappings */
+ if (WARN_ON_ONCE(addr >= PKMAP_ADDR(0) &&
+ addr < PKMAP_ADDR(LAST_PKMAP)))
+ return pte_page(pkmap_page_table[PKMAP_NR(addr)]);
+
+ /* kmap_local_page() mappings */
+ if (WARN_ON_ONCE(base >= __fix_to_virt(FIX_KMAP_END) &&
+ base < __fix_to_virt(FIX_KMAP_BEGIN))) {
+ for (i = 0; i < kctrl->idx; i++) {
+ unsigned long base_addr;
+ int idx;
+
+ idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
+ base_addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+
+ if (base_addr == base)
+ return pte_page(kctrl->pteval[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_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 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) */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-08 12:32:06 +0000