3 files changed, 204 insertions, 2 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1bd646d3fe9a..9004db04efa0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -783,7 +783,7 @@ out_no_task:
 }
 #endif
 
-static loff_t mem_lseek(struct file * file, loff_t offset, int orig)
+loff_t mem_lseek(struct file *file, loff_t offset, int orig)
 {
         switch (orig) {
         case 0:
@@ -2252,6 +2252,7 @@ static const struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_MMU
         REG("clear_refs", S_IWUSR, clear_refs),
         REG("smaps",      S_IRUGO, smaps),
+        REG("pagemap",    S_IRUSR, pagemap),
 #endif
 #ifdef CONFIG_SECURITY
         DIR("attr",       S_IRUGO|S_IXUGO, attr_dir),
@@ -2580,6 +2581,7 @@ static const struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_MMU
         REG("clear_refs", S_IWUSR, clear_refs),
         REG("smaps",     S_IRUGO, smaps),
+        REG("pagemap",    S_IRUSR, pagemap),
 #endif
 #ifdef CONFIG_SECURITY
         DIR("attr",      S_IRUGO|S_IXUGO, attr_dir),
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index ddfaeec37492..7d57e8069924 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -52,11 +52,13 @@ extern int proc_tid_stat(struct task_struct *,  char *);
 extern int proc_tgid_stat(struct task_struct *, char *);
 extern int proc_pid_status(struct task_struct *, char *);
 extern int proc_pid_statm(struct task_struct *, char *);
+extern loff_t mem_lseek(struct file *file, loff_t offset, int orig);
 
 extern const struct file_operations proc_maps_operations;
 extern const struct file_operations proc_numa_maps_operations;
 extern const struct file_operations proc_smaps_operations;
 extern const struct file_operations proc_clear_refs_operations;
+extern const struct file_operations proc_pagemap_operations;
 
 void free_proc_entry(struct proc_dir_entry *de);
 
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 308fc5451e43..bbd9b145051d 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -5,7 +5,10 @@
 #include <linux/highmem.h>
 #include <linux/ptrace.h>
 #include <linux/pagemap.h>
+#include <linux/ptrace.h>
 #include <linux/mempolicy.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
 
 #include <asm/elf.h>
 #include <asm/uaccess.h>
@@ -519,6 +522,202 @@ const struct file_operations proc_clear_refs_operations = {
         .write          = clear_refs_write,
 };
 
+struct pagemapread {
+        char __user *out, *end;
+};
+
+#define PM_ENTRY_BYTES sizeof(u64)
+#define PM_RESERVED_BITS    3
+#define PM_RESERVED_OFFSET  (64 - PM_RESERVED_BITS)
+#define PM_RESERVED_MASK    (((1LL<<PM_RESERVED_BITS)-1) << PM_RESERVED_OFFSET)
+#define PM_SPECIAL(nr)      (((nr) << PM_RESERVED_OFFSET) | PM_RESERVED_MASK)
+#define PM_NOT_PRESENT      PM_SPECIAL(1LL)
+#define PM_SWAP             PM_SPECIAL(2LL)
+#define PM_END_OF_BUFFER    1
+
+static int add_to_pagemap(unsigned long addr, u64 pfn,
+                          struct pagemapread *pm)
+{
+        /*
+         * Make sure there's room in the buffer for an
+         * entire entry.  Otherwise, only copy part of
+         * the pfn.
+         */
+        if (pm->out + PM_ENTRY_BYTES >= pm->end) {
+                if (copy_to_user(pm->out, &pfn, pm->end - pm->out))
+                        return -EFAULT;
+                pm->out = pm->end;
+                return PM_END_OF_BUFFER;
+        }
+
+        if (put_user(pfn, pm->out))
+                return -EFAULT;
+        pm->out += PM_ENTRY_BYTES;
+        return 0;
+}
+
+static int pagemap_pte_hole(unsigned long start, unsigned long end,
+                                void *private)
+{
+        struct pagemapread *pm = private;
+        unsigned long addr;
+        int err = 0;
+        for (addr = start; addr < end; addr += PAGE_SIZE) {
+                err = add_to_pagemap(addr, PM_NOT_PRESENT, pm);
+                if (err)
+                        break;
+        }
+        return err;
+}
+
+u64 swap_pte_to_pagemap_entry(pte_t pte)
+{
+        swp_entry_t e = pte_to_swp_entry(pte);
+        return PM_SWAP | swp_type(e) | (swp_offset(e) << MAX_SWAPFILES_SHIFT);
+}
+
+static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
+                             void *private)
+{
+        struct pagemapread *pm = private;
+        pte_t *pte;
+        int err = 0;
+
+        for (; addr != end; addr += PAGE_SIZE) {
+                u64 pfn = PM_NOT_PRESENT;
+                pte = pte_offset_map(pmd, addr);
+                if (is_swap_pte(*pte))
+                        pfn = swap_pte_to_pagemap_entry(*pte);
+                else if (pte_present(*pte))
+                        pfn = pte_pfn(*pte);
+                /* unmap so we're not in atomic when we copy to userspace */
+                pte_unmap(pte);
+                err = add_to_pagemap(addr, pfn, pm);
+                if (err)
+                        return err;
+        }
+
+        cond_resched();
+
+        return err;
+}
+
+static struct mm_walk pagemap_walk = {
+        .pmd_entry = pagemap_pte_range,
+        .pte_hole = pagemap_pte_hole
+};
+
+/*
+ * /proc/pid/pagemap - an array mapping virtual pages to pfns
+ *
+ * For each page in the address space, this file contains one 64-bit
+ * entry representing the corresponding physical page frame number
+ * (PFN) if the page is present. If there is a swap entry for the
+ * physical page, then an encoding of the swap file number and the
+ * page's offset into the swap file are returned. If no page is
+ * present at all, PM_NOT_PRESENT is returned. This allows determining
+ * precisely which pages are mapped (or in swap) and comparing mapped
+ * pages between processes.
+ *
+ * Efficient users of this interface will use /proc/pid/maps to
+ * determine which areas of memory are actually mapped and llseek to
+ * skip over unmapped regions.
+ */
+static ssize_t pagemap_read(struct file *file, char __user *buf,
+                            size_t count, loff_t *ppos)
+{
+        struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
+        struct page **pages, *page;
+        unsigned long uaddr, uend;
+        struct mm_struct *mm;
+        struct pagemapread pm;
+        int pagecount;
+        int ret = -ESRCH;
+
+        if (!task)
+                goto out;
+
+        ret = -EACCES;
+        if (!ptrace_may_attach(task))
+                goto out;
+
+        ret = -EINVAL;
+        /* file position must be aligned */
+        if (*ppos % PM_ENTRY_BYTES)
+                goto out;
+
+        ret = 0;
+        mm = get_task_mm(task);
+        if (!mm)
+                goto out;
+
+        ret = -ENOMEM;
+        uaddr = (unsigned long)buf & PAGE_MASK;
+        uend = (unsigned long)(buf + count);
+        pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
+        pages = kmalloc(pagecount * sizeof(struct page *), GFP_KERNEL);
+        if (!pages)
+                goto out_task;
+
+        down_read(&current->mm->mmap_sem);
+        ret = get_user_pages(current, current->mm, uaddr, pagecount,
+                             1, 0, pages, NULL);
+        up_read(&current->mm->mmap_sem);
+
+        if (ret < 0)
+                goto out_free;
+
+        pm.out = buf;
+        pm.end = buf + count;
+
+        if (!ptrace_may_attach(task)) {
+                ret = -EIO;
+        } else {
+                unsigned long src = *ppos;
+                unsigned long svpfn = src / PM_ENTRY_BYTES;
+                unsigned long start_vaddr = svpfn << PAGE_SHIFT;
+                unsigned long end_vaddr = TASK_SIZE_OF(task);
+
+                /* watch out for wraparound */
+                if (svpfn > TASK_SIZE_OF(task) >> PAGE_SHIFT)
+                        start_vaddr = end_vaddr;
+
+                /*
+                 * The odds are that this will stop walking way
+                 * before end_vaddr, because the length of the
+                 * user buffer is tracked in "pm", and the walk
+                 * will stop when we hit the end of the buffer.
+                 */
+                ret = walk_page_range(mm, start_vaddr, end_vaddr,
+                                        &pagemap_walk, &pm);
+                if (ret == PM_END_OF_BUFFER)
+                        ret = 0;
+                /* don't need mmap_sem for these, but this looks cleaner */
+                *ppos += pm.out - buf;
+                if (!ret)
+                        ret = pm.out - buf;
+        }
+
+        for (; pagecount; pagecount--) {
+                page = pages[pagecount-1];
+                if (!PageReserved(page))
+                        SetPageDirty(page);
+                page_cache_release(page);
+        }
+        mmput(mm);
+out_free:
+        kfree(pages);
+out_task:
+        put_task_struct(task);
+out:
+        return ret;
+}
+
+const struct file_operations proc_pagemap_operations = {
+        .llseek         = mem_lseek, /* borrow this */
+        .read           = pagemap_read,
+};
+
 #ifdef CONFIG_NUMA
 extern int show_numa_map(struct seq_file *m, void *v);
 
@@ -552,4 +751,3 @@ const struct file_operations proc_numa_maps_operations = {
         .release        = seq_release_private,
 };
 #endif
-