[patch] my mmu notifier sample driver

Nick Piggin
2008-02-19T08:45:01Z

Index: linux-2.6/drivers/char/mmu_notifier_skel.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/char/mmu_notifier_skel.c
@@ -0,0 +1,255 @@
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/mmu_notifier.h>
+#include <linux/radix-tree.h>
+#include <linux/seqlock.h>
+#include <asm/tlbflush.h>
+
+static DEFINE_SPINLOCK(mmn_lock);
+static RADIX_TREE(rmap_tree, GFP_ATOMIC);
+static seqcount_t rmap_seq = SEQCNT_ZERO;
+
+static int __rmap_add(unsigned long mem, unsigned long vaddr)
+{
+ int err;
+
+ err = radix_tree_insert(&rmap_tree, mem >> PAGE_SHIFT, (void *)vaddr);
+
+ return err;
+}
+
+static void __rmap_del(unsigned long mem)
+{
+ void *ret;
+
+ ret = radix_tree_delete(&rmap_tree, mem >> PAGE_SHIFT);
+ BUG_ON(!ret);
+}
+
+static unsigned long rmap_find(unsigned long mem)
+{
+ unsigned long vaddr;
+
+ rcu_read_lock();
+ vaddr = (unsigned long)radix_tree_lookup(&rmap_tree, mem >> PAGE_SHIFT);
+ rcu_read_unlock();
+
+ return vaddr;
+}
+
+static struct page *follow_page_atomic(struct mm_struct *mm, unsigned long address, int write)
+{
+ struct vm_area_struct *vma;
+
+ vma = find_vma(mm, address);
+ if (!vma || (vma->vm_start > address))
+ return NULL;
+
+ if (vma->vm_flags & (VM_IO | VM_PFNMAP))
+ return NULL;
+
+ return follow_page(vma, address, FOLL_GET|(write ? FOLL_WRITE : 0));
+}
+
+static int mmn_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long source_vaddr = (unsigned long)vmf->pgoff << PAGE_SHIFT;
+ unsigned long dest_vaddr = (unsigned long)vmf->virtual_address;
+ unsigned long pfn;
+ struct page *page;
+ pgprot_t prot;
+ int write = vmf->flags & FAULT_FLAG_WRITE;
+ int ret;
+
+ printk("mmn_vm_fault %s@vaddr=%lx sourcing from %lx\n", write ? "write" : "read", dest_vaddr, source_vaddr);
+
+ BUG_ON(mm != current->mm); /* disallow get_user_pages */
+
+again:
+ spin_lock(&mmn_lock);
+ write_seqcount_begin(&rmap_seq);
+ page = follow_page_atomic(mm, source_vaddr, write);
+ if (unlikely(!page)) {
+ write_seqcount_end(&rmap_seq);
+ spin_unlock(&mmn_lock);
+ ret = get_user_pages(current, mm, source_vaddr,
+ 1, write, 0, &page, NULL);
+ if (ret != 1)
+ goto out_err;
+ put_page(page);
+ goto again;
+ }
+
+ ret = __rmap_add(source_vaddr, dest_vaddr);
+ if (ret)
+ goto out_lock;
+
+ pfn = page_to_pfn(page);
+ prot = vma->vm_page_prot;
+ if (!write)
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags & ~(VM_WRITE|VM_MAYWRITE));
+ ret = vm_insert_pfn(vma, dest_vaddr, pfn);
+ vma->vm_page_prot = prot;
+ if (ret) {
+ if (ret == -EBUSY)
+ WARN_ON(1);
+ goto out_rmap;
+ }
+ write_seqcount_end(&rmap_seq);
+ spin_unlock(&mmn_lock);
+ put_page(page);
+
+ return VM_FAULT_NOPAGE;
+
+out_rmap:
+ __rmap_del(source_vaddr);
+out_lock:
+ write_seqcount_end(&rmap_seq);
+ spin_unlock(&mmn_lock);
+ put_page(page);
+out_err:
+ switch (ret) {
+ case -EFAULT:
+ case -EEXIST:
+ case -EBUSY:
+ return VM_FAULT_SIGBUS;
+ case -ENOMEM:
+ return VM_FAULT_OOM;
+ default:
+ BUG();
+ }
+}
+
+struct vm_operations_struct mmn_vm_ops = {
+ .fault = mmn_vm_fault,
+};
+
+static int mmu_notifier_busy;
+static struct mmu_notifier mmu_notifier;
+
+static int mmn_clear_young(struct mmu_notifier *mn, unsigned long address)
+{
+ unsigned long vaddr;
+ unsigned seq;
+ struct mm_struct *mm = mn->mm;
+ pgd_t *pgd;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *ptep, pte;
+
+ do {
+ seq = read_seqcount_begin(&rmap_seq);
+ vaddr = rmap_find(address);
+ } while (read_seqcount_retry(&rmap_seq, seq));
+
+ if (vaddr == 0)
+ return 0;
+
+ printk("mmn_clear_young@vaddr=%lx sourced from %lx\n", vaddr, address);
+
+ spin_lock(&mmn_lock);
+ pgd = pgd_offset(mm, vaddr);
+ pud = pud_offset(pgd, vaddr);
+ if (pud) {
+ pmd = pmd_offset(pud, vaddr);
+ if (pmd) {
+ ptep = pte_offset_map(pmd, vaddr);
+ if (ptep) {
+ pte = *ptep;
+ if (!pte_present(pte)) {
+ /* x86 specific, don't have a vma */
+ ptep_get_and_clear(mm, vaddr, ptep);
+ __flush_tlb_one(vaddr);
+ }
+ pte_unmap(ptep);
+ }
+ }
+ }
+ __rmap_del(address);
+ spin_unlock(&mmn_lock);
+
+ return 1;
+}
+
+static void mmn_unmap(struct mmu_notifier *mn, unsigned long address)
+{
+ mmn_clear_young(mn, address);
+}
+
+static void mmn_release(struct mmu_notifier *mn)
+{
+ mmu_notifier_busy = 0;
+}
+
+static struct mmu_notifier_operations mmn_ops = {
+ .clear_young = mmn_clear_young,
+ .unmap = mmn_unmap,
+ .release = mmn_release,
+};
+
+static int mmn_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int busy;
+
+ if ((vma->vm_flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE)
+ return -EINVAL;
+
+ spin_lock(&mmn_lock);
+ busy = mmu_notifier_busy;
+ if (!busy)
+ mmu_notifier_busy = 1;
+ spin_unlock(&mmn_lock);
+ if (busy)
+ return -EBUSY;
+
+ vma->vm_flags |= VM_PFNMAP;
+ vma->vm_ops = &mmn_vm_ops;
+
+ mmu_notifier_init(&mmu_notifier, &mmn_ops, current->mm);
+ mmu_notifier_register(&mmu_notifier);
+
+ return 0;
+}
+
+static const struct file_operations mmn_fops =
+{
+ .owner = THIS_MODULE,
+ .llseek = no_llseek,
+ .mmap = mmn_mmap,
+};
+
+static struct miscdevice mmn_miscdev =
+{
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "mmn",
+ .fops = &mmn_fops
+};
+
+static int __init mmn_init(void)
+{
+ if (misc_register(&mmn_miscdev)) {
+ printk(KERN_ERR "mmn: unable to register device\n");
+ return -EIO;
+ }
+ return 0;
+}
+
+static void __exit mmn_exit(void)
+{
+ misc_deregister(&mmn_miscdev);
+}
+
+MODULE_DESCRIPTION("mmu_notifier skeleton driver");
+MODULE_LICENSE("GPL");
+
+module_init(mmn_init);
+module_exit(mmn_exit);
+
Index: linux-2.6/drivers/char/Kconfig
===================================================================
--- linux-2.6.orig/drivers/char/Kconfig
+++ linux-2.6/drivers/char/Kconfig
@@ -4,6 +4,10 @@

menu "Character devices"

+config MMU_NOTIFIER_SKEL
+ tristate "MMU Notifier skeleton driver"
+ default n
+
config VT
bool "Virtual terminal" if EMBEDDED
depends on !S390
Index: linux-2.6/drivers/char/Makefile
===================================================================
--- linux-2.6.orig/drivers/char/Makefile
+++ linux-2.6/drivers/char/Makefile
@@ -97,6 +97,7 @@ obj-$(CONFIG_CS5535_GPIO) += cs5535_gpio
obj-$(CONFIG_GPIO_VR41XX) += vr41xx_giu.o
obj-$(CONFIG_GPIO_TB0219) += tb0219.o
obj-$(CONFIG_TELCLOCK) += tlclk.o
+obj-$(CONFIG_MMU_NOTIFIER_SKEL) += mmu_notifier_skel.o

obj-$(CONFIG_MWAVE) += mwave/
obj-$(CONFIG_AGP) += agp/