[PATCH v18 38/80] c/r: restore memory address space (private memory)

Oren Laadan
2009-09-24T00:37:51Z

Restoring the memory address space begins with nuking the existing one
of the current process, and then reading the vma state and contents.
Call do_mmap_pgoffset() for each vma and then read in the data.

Changelog[v17]:
- Tighten checks on supported vma to checkpoint or restart
Changelog[v17]:
- Restore mm->{flags,def_flags,saved_auxv}
- Fix bogus warning in do_restore_mm()
Changelog[v16]:
- Restore mm->exe_file
Changelog[v14]:
- Introduce per vma-type restore() function
- Merge restart code into same file as checkpoint (memory.c)
- Compare saved 'vdso' field of mm_context with current value
- Check whether calls to ckpt_hbuf_get() fail
- Discard field 'h->parent'
- Revert change to pr_debug(), back to ckpt_debug()
Changelog[v13]:
- Avoid access to hh->vma_type after the header is freed
- Test for no vma's in exit_mmap() before calling unmap_vma() (or it
may crash if restart fails after having removed all vma's)
Changelog[v12]:
- Replace obsolete ckpt_debug() with pr_debug()
Changelog[v9]:
- Introduce ckpt_ctx_checkpoint() for checkpoint-specific ctx setup
Changelog[v7]:
- Fix argument given to kunmap_atomic() in memory dump/restore
Changelog[v6]:
- Balance all calls to ckpt_hbuf_get() with matching ckpt_hbuf_put()
(even though it's not really needed)
Changelog[v5]:
- Improve memory restore code (following Dave Hansen's comments)
- Change dump format (and code) to allow chunks of <vaddrs, pages>
instead of one long list of each
- Memory restore now maps user pages explicitly to copy data into them,
instead of reading directly to user space; got rid of mprotect_fixup()
Changelog[v4]:
- Use standard list_... for ckpt_pgarr

Signed-off-by: Oren Laadan <orenl@cs.columbia.edu>
---
arch/x86/include/asm/ldt.h | 7 +
arch/x86/mm/checkpoint.c | 64 ++++++
checkpoint/memory.c | 472 ++++++++++++++++++++++++++++++++++++++++
checkpoint/objhash.c | 1 +
checkpoint/process.c | 3 +
checkpoint/restart.c | 4 +
fs/exec.c | 2 +-
include/linux/checkpoint.h | 7 +
include/linux/checkpoint_hdr.h | 2 +-
include/linux/mm.h | 13 +
mm/filemap.c | 19 ++
mm/mmap.c | 23 ++-
12 files changed, 614 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/ldt.h b/arch/x86/include/asm/ldt.h
index 46727eb..f2845f9 100644
--- a/arch/x86/include/asm/ldt.h
+++ b/arch/x86/include/asm/ldt.h
@@ -37,4 +37,11 @@ struct user_desc {
#define MODIFY_LDT_CONTENTS_CODE 2

#endif /* !__ASSEMBLY__ */
+
+#ifdef __KERNEL__
+#include <linux/linkage.h>
+asmlinkage int sys_modify_ldt(int func, void __user *ptr,
+ unsigned long bytecount);
+#endif
+
#endif /* _ASM_X86_LDT_H */
diff --git a/arch/x86/mm/checkpoint.c b/arch/x86/mm/checkpoint.c
index 83ed047..9dd8e12 100644
--- a/arch/x86/mm/checkpoint.c
+++ b/arch/x86/mm/checkpoint.c
@@ -13,6 +13,7 @@

#include <asm/desc.h>
#include <asm/i387.h>
+#include <asm/elf.h>

#include <linux/checkpoint.h>
#include <linux/checkpoint_hdr.h>
@@ -560,3 +561,66 @@ int restore_read_header_arch(struct ckpt_ctx *ctx)
ckpt_hdr_put(ctx, h);
return ret;
}
+
+int restore_mm_context(struct ckpt_ctx *ctx, struct mm_struct *mm)
+{
+ struct ckpt_hdr_mm_context *h;
+ unsigned int n;
+ int ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_MM_CONTEXT);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ckpt_debug("nldt %d vdso %#lx (%p)\n",
+ h->nldt, (unsigned long) h->vdso, mm->context.vdso);
+
+ ret = -EINVAL;
+ if (h->vdso != (unsigned long) mm->context.vdso)
+ goto out;
+ if (h->ldt_entry_size != LDT_ENTRY_SIZE)
+ goto out;
+
+ ret = _ckpt_read_obj_type(ctx, NULL,
+ h->nldt * LDT_ENTRY_SIZE,
+ CKPT_HDR_MM_CONTEXT_LDT);
+ if (ret < 0)
+ goto out;
+
+ /*
+ * to utilize the syscall modify_ldt() we first convert the data
+ * in the checkpoint image from 'struct desc_struct' to 'struct
+ * user_desc' with reverse logic of include/asm/desc.h:fill_ldt()
+ */
+ for (n = 0; n < h->nldt; n++) {
+ struct user_desc info;
+ struct desc_struct desc;
+ mm_segment_t old_fs;
+
+ ret = ckpt_kread(ctx, &desc, LDT_ENTRY_SIZE);
+ if (ret < 0)
+ break;
+
+ info.entry_number = n;
+ info.base_addr = desc.base0 | (desc.base1 << 16);
+ info.limit = desc.limit0;
+ info.seg_32bit = desc.d;
+ info.contents = desc.type >> 2;
+ info.read_exec_only = (desc.type >> 1) ^ 1;
+ info.limit_in_pages = desc.g;
+ info.seg_not_present = desc.p ^ 1;
+ info.useable = desc.avl;
+
+ old_fs = get_fs();
+ set_fs(get_ds());
+ ret = sys_modify_ldt(1, (struct user_desc __user *) &info,
+ sizeof(info));
+ set_fs(old_fs);
+
+ if (ret < 0)
+ break;
+ }
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
diff --git a/checkpoint/memory.c b/checkpoint/memory.c
index d19d627..6a0dfaf 100644
--- a/checkpoint/memory.c
+++ b/checkpoint/memory.c
@@ -15,6 +15,9 @@
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/file.h>
+#include <linux/err.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/mm_types.h>
#include <linux/proc_fs.h>
@@ -695,3 +698,472 @@ int ckpt_collect_mm(struct ckpt_ctx *ctx, struct task_struct *t)

return ret;
}
+
+/***********************************************************************
+ * Restart
+ *
+ * Unlike checkpoint, restart is executed in the context of each restarting
+ * process: vma regions are restored via a call to mmap(), and the data is
+ * read into the address space of the current process.
+ */
+
+/**
+ * read_pages_vaddrs - read addresses of pages to page-array chain
+ * @ctx - restart context
+ * @nr_pages - number of address to read
+ */
+static int read_pages_vaddrs(struct ckpt_ctx *ctx, unsigned long nr_pages)
+{
+ struct ckpt_pgarr *pgarr;
+ unsigned long *vaddrp;
+ int nr, ret;
+
+ while (nr_pages) {
+ pgarr = pgarr_current(ctx);
+ if (!pgarr)
+ return -ENOMEM;
+ nr = pgarr_nr_free(pgarr);
+ if (nr > nr_pages)
+ nr = nr_pages;
+ vaddrp = &pgarr->vaddrs[pgarr->nr_used];
+ ret = ckpt_kread(ctx, vaddrp, nr * sizeof(unsigned long));
+ if (ret < 0)
+ return ret;
+ pgarr->nr_used += nr;
+ nr_pages -= nr;
+ }
+ return 0;
+}
+
+static int restore_read_page(struct ckpt_ctx *ctx, struct page *page, void *p)
+{
+ void *ptr;
+ int ret;
+
+ ret = ckpt_kread(ctx, p, PAGE_SIZE);
+ if (ret < 0)
+ return ret;
+
+ ptr = kmap_atomic(page, KM_USER1);
+ memcpy(ptr, p, PAGE_SIZE);
+ kunmap_atomic(ptr, KM_USER1);
+
+ return 0;
+}
+
+/**
+ * read_pages_contents - read in data of pages in page-array chain
+ * @ctx - restart context
+ */
+static int read_pages_contents(struct ckpt_ctx *ctx)
+{
+ struct mm_struct *mm = current->mm;
+ struct ckpt_pgarr *pgarr;
+ unsigned long *vaddrs;
+ char *buf;
+ int i, ret = 0;
+
+ buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ down_read(&mm->mmap_sem);
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ vaddrs = pgarr->vaddrs;
+ for (i = 0; i < pgarr->nr_used; i++) {
+ struct page *page;
+
+ _ckpt_debug(CKPT_DPAGE, "got page %#lx\n", vaddrs[i]);
+ ret = get_user_pages(current, mm, vaddrs[i],
+ 1, 1, 1, &page, NULL);
+ if (ret < 0)
+ goto out;
+
+ ret = restore_read_page(ctx, page, buf);
+ page_cache_release(page);
+
+ if (ret < 0)
+ goto out;
+ }
+ }
+
+ out:
+ up_read(&mm->mmap_sem);
+ kfree(buf);
+ return 0;
+}
+
+/**
+ * restore_memory_contents - restore contents of a VMA with private memory
+ * @ctx - restart context
+ *
+ * Reads a header that specifies how many pages will follow, then reads
+ * a list of virtual addresses into ctx->pgarr_list page-array chain,
+ * followed by the actual contents of the corresponding pages. Iterates
+ * these steps until reaching a header specifying "0" pages, which marks
+ * the end of the contents.
+ */
+static int restore_memory_contents(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_pgarr *h;
+ unsigned long nr_pages;
+ int len, ret = 0;
+
+ while (1) {
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_PGARR);
+ if (IS_ERR(h))
+ break;
+
+ ckpt_debug("total pages %ld\n", (unsigned long) h->nr_pages);
+
+ nr_pages = h->nr_pages;
+ ckpt_hdr_put(ctx, h);
+
+ if (!nr_pages)
+ break;
+
+ len = nr_pages * (sizeof(unsigned long) + PAGE_SIZE);
+ ret = _ckpt_read_buffer(ctx, NULL, len);
+ if (ret < 0)
+ break;
+
+ ret = read_pages_vaddrs(ctx, nr_pages);
+ if (ret < 0)
+ break;
+ ret = read_pages_contents(ctx);
+ if (ret < 0)
+ break;
+ pgarr_reset_all(ctx);
+ }
+
+ return ret;
+}
+
+/**
+ * calc_map_prot_bits - convert vm_flags to mmap protection
+ * orig_vm_flags: source vm_flags
+ */
+static unsigned long calc_map_prot_bits(unsigned long orig_vm_flags)
+{
+ unsigned long vm_prot = 0;
+
+ if (orig_vm_flags & VM_READ)
+ vm_prot |= PROT_READ;
+ if (orig_vm_flags & VM_WRITE)
+ vm_prot |= PROT_WRITE;
+ if (orig_vm_flags & VM_EXEC)
+ vm_prot |= PROT_EXEC;
+ if (orig_vm_flags & PROT_SEM) /* only (?) with IPC-SHM */
+ vm_prot |= PROT_SEM;
+
+ return vm_prot;
+}
+
+/**
+ * calc_map_flags_bits - convert vm_flags to mmap flags
+ * orig_vm_flags: source vm_flags
+ */
+static unsigned long calc_map_flags_bits(unsigned long orig_vm_flags)
+{
+ unsigned long vm_flags = 0;
+
+ vm_flags = MAP_FIXED;
+ if (orig_vm_flags & VM_GROWSDOWN)
+ vm_flags |= MAP_GROWSDOWN;
+ if (orig_vm_flags & VM_DENYWRITE)
+ vm_flags |= MAP_DENYWRITE;
+ if (orig_vm_flags & VM_EXECUTABLE)
+ vm_flags |= MAP_EXECUTABLE;
+ if (orig_vm_flags & VM_MAYSHARE)
+ vm_flags |= MAP_SHARED;
+ else
+ vm_flags |= MAP_PRIVATE;
+
+ return vm_flags;
+}
+
+/**
+ * generic_vma_restore - restore a vma
+ * @mm - address space
+ * @file - file to map (NULL for anonymous)
+ * @h - vma header data
+ */
+static unsigned long generic_vma_restore(struct mm_struct *mm,
+ struct file *file,
+ struct ckpt_hdr_vma *h)
+{
+ unsigned long vm_size, vm_start, vm_flags, vm_prot, vm_pgoff;
+ unsigned long addr;
+
+ if (h->vm_end < h->vm_start)
+ return -EINVAL;
+ if (h->vma_objref < 0)
+ return -EINVAL;
+
+ vm_start = h->vm_start;
+ vm_pgoff = h->vm_pgoff;
+ vm_size = h->vm_end - h->vm_start;
+ vm_prot = calc_map_prot_bits(h->vm_flags);
+ vm_flags = calc_map_flags_bits(h->vm_flags);
+
+ down_write(&mm->mmap_sem);
+ addr = do_mmap_pgoff(file, vm_start, vm_size,
+ vm_prot, vm_flags, vm_pgoff);
+ up_write(&mm->mmap_sem);
+ ckpt_debug("size %#lx prot %#lx flag %#lx pgoff %#lx => %#lx\n",
+ vm_size, vm_prot, vm_flags, vm_pgoff, addr);
+
+ return addr;
+}
+
+/**
+ * private_vma_restore - read vma data, recreate it and read contents
+ * @ctx: checkpoint context
+ * @mm: memory address space
+ * @file: file to use for mapping
+ * @h - vma header data
+ */
+int private_vma_restore(struct ckpt_ctx *ctx, struct mm_struct *mm,
+ struct file *file, struct ckpt_hdr_vma *h)
+{
+ unsigned long addr;
+
+ if (h->vm_flags & (VM_SHARED | VM_MAYSHARE))
+ return -EINVAL;
+
+ addr = generic_vma_restore(mm, file, h);
+ if (IS_ERR((void *) addr))
+ return PTR_ERR((void *) addr);
+
+ return restore_memory_contents(ctx);
+}
+
+/**
+ * anon_private_restore - read vma data, recreate it and read contents
+ * @ctx: checkpoint context
+ * @mm: memory address space
+ * @h - vma header data
+ */
+static int anon_private_restore(struct ckpt_ctx *ctx,
+ struct mm_struct *mm,
+ struct ckpt_hdr_vma *h)
+{
+ /*
+ * vm_pgoff for anonymous mapping is the "global" page
+ * offset (namely from addr 0x0), so we force a zero
+ */
+ h->vm_pgoff = 0;
+
+ return private_vma_restore(ctx, mm, NULL, h);
+}
+
+/* callbacks to restore vma per its type: */
+struct restore_vma_ops {
+ char *vma_name;
+ enum vma_type vma_type;
+ int (*restore) (struct ckpt_ctx *ctx,
+ struct mm_struct *mm,
+ struct ckpt_hdr_vma *ptr);
+};
+
+static struct restore_vma_ops restore_vma_ops[] = {
+ /* ignored vma */
+ {
+ .vma_name = "IGNORE",
+ .vma_type = CKPT_VMA_IGNORE,
+ .restore = NULL,
+ },
+ /* special mapping (vdso) */
+ {
+ .vma_name = "VDSO",
+ .vma_type = CKPT_VMA_VDSO,
+ .restore = special_mapping_restore,
+ },
+ /* anonymous private */
+ {
+ .vma_name = "ANON PRIVATE",
+ .vma_type = CKPT_VMA_ANON,
+ .restore = anon_private_restore,
+ },
+ /* file-mapped private */
+ {
+ .vma_name = "FILE PRIVATE",
+ .vma_type = CKPT_VMA_FILE,
+ .restore = filemap_restore,
+ },
+};
+
+/**
+ * restore_vma - read vma data, recreate it and read contents
+ * @ctx: checkpoint context
+ * @mm: memory address space
+ */
+static int restore_vma(struct ckpt_ctx *ctx, struct mm_struct *mm)
+{
+ struct ckpt_hdr_vma *h;
+ struct restore_vma_ops *ops;
+ int ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_VMA);
+ if (IS_ERR(h))
+ return PTR_ERR(h);
+
+ ckpt_debug("vma %#lx-%#lx flags %#lx type %d vmaref %d\n",
+ (unsigned long) h->vm_start, (unsigned long) h->vm_end,
+ (unsigned long) h->vm_flags, (int) h->vma_type,
+ (int) h->vma_objref);
+
+ ret = -EINVAL;
+ if (h->vm_end < h->vm_start)
+ goto out;
+ if (h->vma_objref < 0)
+ goto out;
+ if (h->vma_type >= CKPT_VMA_MAX)
+ goto out;
+ if (h->vm_flags & CKPT_VMA_NOT_SUPPORTED)
+ return -ENOSYS;
+
+ ops = &restore_vma_ops[h->vma_type];
+
+ /* make sure we don't change this accidentally */
+ BUG_ON(ops->vma_type != h->vma_type);
+
+ if (ops->restore) {
+ ckpt_debug("vma type %s\n", ops->vma_name);
+ ret = ops->restore(ctx, mm, h);
+ } else {
+ ckpt_debug("vma ignored\n");
+ ret = 0;
+ }
+ out:
+ ckpt_hdr_put(ctx, h);
+ return ret;
+}
+
+static int destroy_mm(struct mm_struct *mm)
+{
+ struct vm_area_struct *vmnext = mm->mmap;
+ struct vm_area_struct *vma;
+ int ret;
+
+ while (vmnext) {
+ vma = vmnext;
+ vmnext = vmnext->vm_next;
+ ret = do_munmap(mm, vma->vm_start, vma->vm_end-vma->vm_start);
+ if (ret < 0) {
+ pr_warning("c/r: failed do_munmap (%d)\n", ret);
+ return ret;
+ }
+ }
+ return 0;
+}
+
+static struct mm_struct *do_restore_mm(struct ckpt_ctx *ctx)
+{
+ struct ckpt_hdr_mm *h;
+ struct mm_struct *mm = NULL;
+ struct file *file;
+ unsigned int nr;
+ int ret;
+
+ h = ckpt_read_obj_type(ctx, sizeof(*h), CKPT_HDR_MM);
+ if (IS_ERR(h))
+ return (struct mm_struct *) h;
+
+ ckpt_debug("map_count %d\n", h->map_count);
+
+ /* XXX need more sanity checks */
+
+ ret = -EINVAL;
+ if ((h->start_code > h->end_code) ||
+ (h->start_data > h->end_data))
+ goto out;
+ if (h->exe_objref < 0)
+ goto out;
+ if (h->def_flags & ~VM_LOCKED)
+ goto out;
+ if (h->flags & ~(MMF_DUMP_FILTER_MASK |
+ ((1 << MMF_DUMP_FILTER_BITS) - 1)))
+ goto out;
+
+ mm = current->mm;
+
+ /* point of no return -- destruct current mm */
+ down_write(&mm->mmap_sem);
+ ret = destroy_mm(mm);
+ if (ret < 0) {
+ up_write(&mm->mmap_sem);
+ goto out;
+ }
+
+ mm->flags = h->flags;
+ mm->def_flags = h->def_flags;
+
+ mm->start_code = h->start_code;
+ mm->end_code = h->end_code;
+ mm->start_data = h->start_data;
+ mm->end_data = h->end_data;
+ mm->start_brk = h->start_brk;
+ mm->brk = h->brk;
+ mm->start_stack = h->start_stack;
+ mm->arg_start = h->arg_start;
+ mm->arg_end = h->arg_end;
+ mm->env_start = h->env_start;
+ mm->env_end = h->env_end;
+
+ /* restore the ->exe_file */
+ if (h->exe_objref) {
+ file = ckpt_obj_fetch(ctx, h->exe_objref, CKPT_OBJ_FILE);
+ if (IS_ERR(file)) {
+ up_write(&mm->mmap_sem);
+ ret = PTR_ERR(file);
+ goto out;
+ }
+ set_mm_exe_file(mm, file);
+ }
+
+ ret = _ckpt_read_buffer(ctx, mm->saved_auxv, sizeof(mm->saved_auxv));
+ up_write(&mm->mmap_sem);
+ if (ret < 0)
+ goto out;
+
+ for (nr = h->map_count; nr; nr--) {
+ ret = restore_vma(ctx, mm);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = restore_mm_context(ctx, mm);
+ out:
+ ckpt_hdr_put(ctx, h);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ /* restore_obj() expect an extra reference */
+ atomic_inc(&mm->mm_users);
+ return mm;
+}
+
+void *restore_mm(struct ckpt_ctx *ctx)
+{
+ return (void *) do_restore_mm(ctx);
+}
+
+int restore_obj_mm(struct ckpt_ctx *ctx, int mm_objref)
+{
+ struct mm_struct *mm;
+ int ret;
+
+ mm = ckpt_obj_fetch(ctx, mm_objref, CKPT_OBJ_MM);
+ if (IS_ERR(mm))
+ return PTR_ERR(mm);
+
+ if (mm == current->mm)
+ return 0;
+
+ ret = exec_mmap(mm);
+ if (ret < 0)
+ return ret;
+
+ atomic_inc(&mm->mm_users);
+ return 0;
+}
diff --git a/checkpoint/objhash.c b/checkpoint/objhash.c
index 4c207c3..734be3a 100644
--- a/checkpoint/objhash.c
+++ b/checkpoint/objhash.c
@@ -148,6 +148,7 @@ static struct ckpt_obj_ops ckpt_obj_ops[] = {
.ref_grab = obj_mm_grab,
.ref_users = obj_mm_users,
.checkpoint = checkpoint_mm,
+ .restore = restore_mm,
},
};

diff --git a/checkpoint/process.c b/checkpoint/process.c
index 3d0eb36..1788a39 100644
--- a/checkpoint/process.c
+++ b/checkpoint/process.c
@@ -373,6 +373,9 @@ static int restore_task_objs(struct ckpt_ctx *ctx)
ret = restore_obj_file_table(ctx, h->files_objref);
ckpt_debug("file_table: ret %d (%p)\n", ret, current->files);

+ ret = restore_obj_mm(ctx, h->mm_objref);
+ ckpt_debug("mm: ret %d (%p)\n", ret, current->mm);
+
ckpt_hdr_put(ctx, h);
return ret;
}
diff --git a/checkpoint/restart.c b/checkpoint/restart.c
index 73db44a..6183074 100644
--- a/checkpoint/restart.c
+++ b/checkpoint/restart.c
@@ -373,11 +373,15 @@ int ckpt_read_consume(struct ckpt_ctx *ctx, int len, int type)
static int check_kernel_const(struct ckpt_const *h)
{
struct task_struct *tsk;
+ struct mm_struct *mm;
struct new_utsname *uts;

/* task */
if (h->task_comm_len != sizeof(tsk->comm))
return -EINVAL;
+ /* mm */
+ if (h->mm_saved_auxv_len != sizeof(mm->saved_auxv))
+ return -EINVAL;
/* uts */
if (h->uts_release_len != sizeof(uts->release))
return -EINVAL;
diff --git a/fs/exec.c b/fs/exec.c
index 172ceb6..c8436a7 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -695,7 +695,7 @@ int kernel_read(struct file *file, loff_t offset,

EXPORT_SYMBOL(kernel_read);

-static int exec_mmap(struct mm_struct *mm)
+int exec_mmap(struct mm_struct *mm)
{
struct task_struct *tsk;
struct mm_struct * old_mm, *active_mm;
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 70d9506..cb13e8f 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -136,6 +136,7 @@ extern int checkpoint_mm_context(struct ckpt_ctx *ctx, struct mm_struct *mm);
extern int restore_read_header_arch(struct ckpt_ctx *ctx);
extern int restore_thread(struct ckpt_ctx *ctx);
extern int restore_cpu(struct ckpt_ctx *ctx);
+extern int restore_mm_context(struct ckpt_ctx *ctx, struct mm_struct *mm);

extern int checkpoint_restart_block(struct ckpt_ctx *ctx,
struct task_struct *t);
@@ -176,9 +177,15 @@ extern int private_vma_checkpoint(struct ckpt_ctx *ctx,
int vma_objref);

extern int checkpoint_obj_mm(struct ckpt_ctx *ctx, struct task_struct *t);
+extern int restore_obj_mm(struct ckpt_ctx *ctx, int mm_objref);

extern int ckpt_collect_mm(struct ckpt_ctx *ctx, struct task_struct *t);
extern int checkpoint_mm(struct ckpt_ctx *ctx, void *ptr);
+extern void *restore_mm(struct ckpt_ctx *ctx);
+
+extern int private_vma_restore(struct ckpt_ctx *ctx, struct mm_struct *mm,
+ struct file *file, struct ckpt_hdr_vma *h);
+

#define CKPT_VMA_NOT_SUPPORTED \
(VM_SHARED | VM_MAYSHARE | VM_IO | VM_HUGETLB | \
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index f29f87a..097d2e2 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -250,7 +250,7 @@ struct ckpt_hdr_mm {
__u64 arg_start, arg_end, env_start, env_end;
} __attribute__((aligned(8)));

-/* vma subtypes */
+/* vma subtypes - index into restore_vma_dispatch[] */
enum vma_type {
CKPT_VMA_IGNORE = 0,
CKPT_VMA_VDSO, /* special vdso vma */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index d5f9889..0d0c46b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1148,6 +1148,9 @@ extern int do_munmap(struct mm_struct *, unsigned long, size_t);

extern unsigned long do_brk(unsigned long, unsigned long);

+/* fs/exec.c */
+extern int exec_mmap(struct mm_struct *mm);
+
/* filemap.c */
extern unsigned long page_unuse(struct page *);
extern void truncate_inode_pages(struct address_space *, loff_t);
@@ -1166,6 +1169,16 @@ extern int filemap_checkpoint(struct ckpt_ctx *, struct vm_area_struct *);
int write_one_page(struct page *page, int wait);
void task_dirty_inc(struct task_struct *tsk);

+
+/* checkpoint/restart */
+#ifdef CONFIG_CHECKPOINT
+struct ckpt_hdr_vma;
+extern int filemap_restore(struct ckpt_ctx *ctx, struct mm_struct *mm,
+ struct ckpt_hdr_vma *hh);
+extern int special_mapping_restore(struct ckpt_ctx *ctx, struct mm_struct *mm,
+ struct ckpt_hdr_vma *hh);
+#endif
+
/* readahead.c */
#define VM_MAX_READAHEAD 128 /* kbytes */
#define VM_MIN_READAHEAD 16 /* kbytes (includes current page) */
diff --git a/mm/filemap.c b/mm/filemap.c
index 72ba805..ef7205b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1668,6 +1668,25 @@ int filemap_checkpoint(struct ckpt_ctx *ctx, struct vm_area_struct *vma)

return private_vma_checkpoint(ctx, vma, CKPT_VMA_FILE, vma_objref);
}
+
+int filemap_restore(struct ckpt_ctx *ctx,
+ struct mm_struct *mm,
+ struct ckpt_hdr_vma *h)
+{
+ struct file *file;
+ int ret;
+
+ if (h->vma_type == CKPT_VMA_FILE &&
+ (h->vm_flags & (VM_SHARED | VM_MAYSHARE)))
+ return -EINVAL;
+
+ file = ckpt_obj_fetch(ctx, h->vma_objref, CKPT_OBJ_FILE);
+ if (IS_ERR(file))
+ return PTR_ERR(file);
+
+ ret = private_vma_restore(ctx, mm, file, h);
+ return ret;
+}
#endif /* CONFIG_CHECKPOINT */

struct vm_operations_struct generic_file_vm_ops = {
diff --git a/mm/mmap.c b/mm/mmap.c
index 7415a61..3be4678 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2110,7 +2110,7 @@ void exit_mmap(struct mm_struct *mm)
tlb = tlb_gather_mmu(mm, 1);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use -1 here to ensure all VMAs in the mm are unmapped */
- end = unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL);
+ end = vma ? unmap_vmas(&tlb, vma, 0, -1, &nr_accounted, NULL) : 0;
vm_unacct_memory(nr_accounted);
free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0);
tlb_finish_mmu(tlb, 0, end);
@@ -2269,6 +2269,14 @@ static void special_mapping_close(struct vm_area_struct *vma)
}

#ifdef CONFIG_CHECKPOINT
+/*
+ * FIX:
+ * - checkpoint vdso pages (once per distinct vdso is enough)
+ * - check for compatilibility between saved and current vdso
+ * - accommodate for dynamic kernel data in vdso page
+ *
+ * Current, we require COMPAT_VDSO which somewhat mitigates the issue
+ */
static int special_mapping_checkpoint(struct ckpt_ctx *ctx,
struct vm_area_struct *vma)
{
@@ -2290,6 +2298,19 @@ static int special_mapping_checkpoint(struct ckpt_ctx *ctx,

return generic_vma_checkpoint(ctx, vma, CKPT_VMA_VDSO, 0);
}
+
+int special_mapping_restore(struct ckpt_ctx *ctx,
+ struct mm_struct *mm,
+ struct ckpt_hdr_vma *h)
+{
+ /*
+ * FIX:
+ * Currently, we only handle VDSO/vsyscall special handling.
+ * Even that, is very basic - call arch_setup_additional_pages
+ * requiring the same mapping (start address) as before.
+ */
+ return arch_setup_additional_pages(NULL, h->vm_start, 0);
+}
#endif /* CONFIG_CHECKPOINT */

static struct vm_operations_struct special_mapping_vmops = {
--
1.6.0.4