For each VMA, there is a 'struct cr_vma'; if the VMA is file-mapped,
it will be followed by the file name. Then comes the actual contents,
in one or more chunk: each chunk begins with a header that specifies
how many pages it holds, then the virtual addresses of all the dumped
pages in that chunk, followed by the actual contents of all dumped
pages. A header with zero number of pages marks the end of the contents.
Then comes the next VMA and so on.

Changelog[v10]:
  - Acquire dcache_lock around call to __d_path() in cr_fill_name()

Changelog[v9]:
  - Introduce cr_ctx_checkpoint() for checkpoint-specific ctx setup
  - Test if __d_path() changes mnt/dentry (when crossing filesystem
    namespace boundary). for now cr_fill_fname() fails the checkpoint.

Changelog[v7]:
  - Fix argument given to kunmap_atomic() in memory dump/restore

Changelog[v6]:
  - Balance all calls to cr_hbuf_get() with matching cr_hbuf_put()
    (even though it's not really needed)

Changelog[v5]:
  - Improve memory dump code (following Dave Hansen's comments)
  - Change dump format (and code) to allow chunks of <vaddrs, pages>
    instead of one long list of each
  - Fix use of follow_page() to avoid faulting in non-present pages

Changelog[v4]:
  - Use standard list_... for cr_pgarr

Signed-off-by: Oren Laadan <redacted>
Acked-by: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Dave Hansen <redacted>
---
 arch/x86/include/asm/checkpoint_hdr.h |    5 +
 arch/x86/mm/checkpoint.c              |   31 ++
 checkpoint/Makefile                   |    3 +-
 checkpoint/checkpoint.c               |   81 ++++++
 checkpoint/checkpoint_arch.h          |    2 +
 checkpoint/checkpoint_mem.h           |   41 +++
 checkpoint/ckpt_mem.c                 |  500 +++++++++++++++++++++++++++++++++
 checkpoint/sys.c                      |   11 +
 include/linux/checkpoint.h            |   12 +
 include/linux/checkpoint_hdr.h        |   32 ++
 10 files changed, 717 insertions(+), 1 deletions(-)
 create mode 100644 checkpoint/checkpoint_mem.h
 create mode 100644 checkpoint/ckpt_mem.c

diff --git a/arch/x86/include/asm/checkpoint_hdr.h b/arch/x86/include/asm/checkpoint_hdr.h
index 6325062..33f4c70 100644
--- a/arch/x86/include/asm/checkpoint_hdr.h
+++ b/arch/x86/include/asm/checkpoint_hdr.h

@@ -82,4 +82,9 @@ struct cr_hdr_cpu {
 	/* thread_xstate contents follow (if used_math) */
 } __attribute__((aligned(8)));
 
+struct cr_hdr_mm_context {
+	__s16 ldt_entry_size;
+	__s16 nldt;
+} __attribute__((aligned(8)));
+
 #endif /* __ASM_X86_CKPT_HDR__H */

diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
index 8dd6d2d..757936e 100644
--- a/arch/x86/mm/checkpoint.c
+++ b/arch/x86/mm/checkpoint.c

@@ -221,3 +221,34 @@ int cr_write_head_arch(struct cr_ctx *ctx)
 
 	return ret;
 }
+
+/* dump the mm->context state */
+int cr_write_mm_context(struct cr_ctx *ctx, struct mm_struct *mm, int parent)
+{
+	struct cr_hdr h;
+	struct cr_hdr_mm_context *hh = cr_hbuf_get(ctx, sizeof(*hh));
+	int ret;
+
+	h.type = CR_HDR_MM_CONTEXT;
+	h.len = sizeof(*hh);
+	h.parent = parent;
+
+	mutex_lock(&mm->context.lock);
+
+	hh->ldt_entry_size = LDT_ENTRY_SIZE;
+	hh->nldt = mm->context.size;
+
+	cr_debug("nldt %d\n", hh->nldt);
+
+	ret = cr_write_obj(ctx, &h, hh);
+	cr_hbuf_put(ctx, sizeof(*hh));
+	if (ret < 0)
+		goto out;
+
+	ret = cr_kwrite(ctx, mm->context.ldt,
+			mm->context.size * LDT_ENTRY_SIZE);
+
+ out:
+	mutex_unlock(&mm->context.lock);
+	return ret;
+}

diff --git a/checkpoint/Makefile b/checkpoint/Makefile
index d2df68c..3a0df6d 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile

@@ -2,4 +2,5 @@
 # Makefile for linux checkpoint/restart.
 #
 
-obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o
+obj-$(CONFIG_CHECKPOINT_RESTART) += sys.o checkpoint.o restart.o \
+		ckpt_mem.o

diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 17cc8d2..6a8f810 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c

@@ -75,6 +75,66 @@ int cr_write_string(struct cr_ctx *ctx, char *str, int len)
 	return cr_write_obj(ctx, &h, str);
 }
 
+/**
+ * cr_fill_fname - return pathname of a given file
+ * @path: path name
+ * @root: relative root
+ * @buf: buffer for pathname
+ * @n: buffer length (in) and pathname length (out)
+ */
+static char *
+cr_fill_fname(struct path *path, struct path *root, char *buf, int *n)
+{
+	struct path tmp = *root;
+	char *fname;
+
+	BUG_ON(!buf);
+	spin_lock(&dcache_lock);
+	fname = __d_path(path, &tmp, buf, *n);
+	spin_unlock(&dcache_lock);
+	if (!IS_ERR(fname))
+		*n = (buf + (*n) - fname);
+	/*
+	 * FIXME: if __d_path() changed these, it must have stepped out of
+	 * init's namespace. Since currently we require a unified namespace
+	 * within the container: simply fail.
+	 */
+	if (tmp.mnt != root->mnt || tmp.dentry != root->dentry)
+		fname = ERR_PTR(-EBADF);
+
+	return fname;
+}
+
+/**
+ * cr_write_fname - write a file name
+ * @ctx: checkpoint context
+ * @path: path name
+ * @root: relative root
+ */
+int cr_write_fname(struct cr_ctx *ctx, struct path *path, struct path *root)
+{
+	struct cr_hdr h;
+	char *buf, *fname;
+	int ret, flen;
+
+	flen = PATH_MAX;
+	buf = kmalloc(flen, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	fname = cr_fill_fname(path, root, buf, &flen);
+	if (!IS_ERR(fname)) {
+		h.type = CR_HDR_FNAME;
+		h.len = flen;
+		h.parent = 0;
+		ret = cr_write_obj(ctx, &h, fname);
+	} else
+		ret = PTR_ERR(fname);
+
+	kfree(buf);
+	return ret;
+}
+
 /* write the checkpoint header */
 static int cr_write_head(struct cr_ctx *ctx)
 {

@@ -168,6 +228,10 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
 	cr_debug("task_struct: ret %d\n", ret);
 	if (ret < 0)
 		goto out;
+	ret = cr_write_mm(ctx, t);
+	cr_debug("memory: ret %d\n", ret);
+	if (ret < 0)
+		goto out;
 	ret = cr_write_thread(ctx, t);
 	cr_debug("thread: ret %d\n", ret);
 	if (ret < 0)

@@ -178,10 +242,27 @@ static int cr_write_task(struct cr_ctx *ctx, struct task_struct *t)
 	return ret;
 }
 
+static int cr_ctx_checkpoint(struct cr_ctx *ctx, pid_t pid)
+{
+	ctx->root_pid = pid;
+
+	/*
+	 * assume checkpointer is in container's root vfs
+	 * FIXME: this works for now, but will change with real containers
+	 */
+	ctx->vfsroot = &current->fs->root;
+	path_get(ctx->vfsroot);