1 files changed, 199 insertions, 1 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 308fc54..bbd9b14 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
-