[Devel] [RFC v14-rc2][PATCH 06/29] Dump memory address space
Oren Laadan
orenl at cs.columbia.edu
Mon Mar 30 22:28:46 PDT 2009
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[v14]:
- Revert change to pr_debug(), back to cr_debug()
- Save new field 'vdso' in mm_context
- Discard field 'h->parent'
- Check whether calls to cr_hbuf_get() fail
Changelog[v13]:
- pgprot_t is an abstract type; use the proper accessor (fix for
64-bit powerpc (Nathan Lynch <ntl at pobox.com>)
Changelog[v12]:
- Hide pgarr management inside cr_private_vma_fill_pgarr()
- Fix management of pgarr chain reset and alloc/expand: keep empty
pgarr in a pool chain
- Replace obsolete cr_debug() with pr_debug()
Changelog[v11]:
- Copy contents of 'init->fs->root' instead of pointing to them.
- Add missing test for VM_MAYSHARE when dumping memory
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 <orenl at cs.columbia.edu>
Acked-by: Serge Hallyn <serue at us.ibm.com>
Signed-off-by: Dave Hansen <dave at linux.vnet.ibm.com>
---
arch/x86/include/asm/checkpoint_hdr.h | 6 +
arch/x86/mm/checkpoint.c | 31 ++
checkpoint/Makefile | 3 +-
checkpoint/checkpoint.c | 87 +++++
checkpoint/checkpoint_arch.h | 1 +
checkpoint/checkpoint_mem.h | 41 +++
checkpoint/ckpt_mem.c | 558 +++++++++++++++++++++++++++++++++
checkpoint/sys.c | 11 +
include/linux/checkpoint.h | 13 +
include/linux/checkpoint_hdr.h | 32 ++
10 files changed, 782 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 ffdb5f5..54d3a41 100644
--- a/arch/x86/include/asm/checkpoint_hdr.h
+++ b/arch/x86/include/asm/checkpoint_hdr.h
@@ -95,4 +95,10 @@ struct cr_hdr_cpu {
/* thread_xstate contents follow (if used_math) */
} __attribute__((aligned(8)));
+struct cr_hdr_mm_context {
+ __u64 vdso;
+ __u32 ldt_entry_size;
+ __u32 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 946fac1..92926e1 100644
--- a/arch/x86/mm/checkpoint.c
+++ b/arch/x86/mm/checkpoint.c
@@ -240,3 +240,34 @@ 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)
+{
+ 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);
+
+ mutex_lock(&mm->context.lock);
+
+ hh->vdso = (unsigned long) mm->context.vdso;
+ hh->ldt_entry_size = LDT_ENTRY_SIZE;
+ hh->nldt = mm->context.size;
+
+ cr_debug("nldt %d vdso %#llx\n", hh->nldt, hh->vdso);
+
+ 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 364c326..6924ef4 100644
--- a/checkpoint/Makefile
+++ b/checkpoint/Makefile
@@ -2,4 +2,5 @@
# Makefile for linux checkpoint/restart.
#
-obj-$(CONFIG_CHECKPOINT) += sys.o checkpoint.o restart.o
+obj-$(CONFIG_CHECKPOINT) += sys.o checkpoint.o restart.o \
+ ckpt_mem.o
diff --git a/checkpoint/checkpoint.c b/checkpoint/checkpoint.c
index 422ceff..422e1a3 100644
--- a/checkpoint/checkpoint.c
+++ b/checkpoint/checkpoint.c
@@ -13,6 +13,7 @@
#include <linux/time.h>
#include <linux/fs.h>
#include <linux/file.h>
+#include <linux/fdtable.h>
#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/utsname.h>
@@ -73,6 +74,65 @@ 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;
+ 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)
{
@@ -186,6 +246,10 @@ 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)
@@ -196,10 +260,33 @@ 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)
+{
+ struct fs_struct *fs;
+
+ ctx->root_pid = pid;
+
+ /*
+ * assume checkpointer is in container's root vfs
+ * FIXME: this works for now, but will change with real containers
+ */
+
+ fs = current->fs;
+ read_lock(&fs->lock);
+ ctx->fs_mnt = fs->root;
+ path_get(&ctx->fs_mnt);
+ read_unlock(&fs->lock);
+
+ return 0;
+}
+
int do_checkpoint(struct cr_ctx *ctx, pid_t pid)
{
int ret;
+ ret = cr_ctx_checkpoint(ctx, pid);
+ if (ret < 0)
+ goto out;
ret = cr_write_head(ctx);
if (ret < 0)
goto out;
diff --git a/checkpoint/checkpoint_arch.h b/checkpoint/checkpoint_arch.h
index ada1369..5168765 100644
--- a/checkpoint/checkpoint_arch.h
+++ b/checkpoint/checkpoint_arch.h
@@ -3,6 +3,7 @@
extern int cr_write_head_arch(struct cr_ctx *ctx);
extern int cr_write_thread(struct cr_ctx *ctx, struct task_struct *t);
extern int cr_write_cpu(struct cr_ctx *ctx, struct task_struct *t);
+extern int cr_write_mm_context(struct cr_ctx *ctx, struct mm_struct *mm);
extern int cr_read_head_arch(struct cr_ctx *ctx);
extern int cr_read_thread(struct cr_ctx *ctx);
diff --git a/checkpoint/checkpoint_mem.h b/checkpoint/checkpoint_mem.h
new file mode 100644
index 0000000..3e48bc4
--- /dev/null
+++ b/checkpoint/checkpoint_mem.h
@@ -0,0 +1,41 @@
+#ifndef _CHECKPOINT_CKPT_MEM_H_
+#define _CHECKPOINT_CKPT_MEM_H_
+/*
+ * Generic container checkpoint-restart
+ *
+ * Copyright (C) 2008 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/mm_types.h>
+
+/*
+ * page-array chains: each cr_pgarr describes a set of <struct page *,vaddr>
+ * tuples (where vaddr is the virtual address of a page in a particular mm).
+ * Specifically, we use separate arrays so that all vaddrs can be written
+ * and read at once.
+ */
+
+struct cr_pgarr {
+ unsigned long *vaddrs;
+ struct page **pages;
+ unsigned int nr_used;
+ struct list_head list;
+};
+
+#define CR_PGARR_TOTAL (PAGE_SIZE / sizeof(void *))
+#define CR_PGARR_CHUNK (4 * CR_PGARR_TOTAL)
+
+extern void cr_pgarr_free(struct cr_ctx *ctx);
+extern struct cr_pgarr *cr_pgarr_current(struct cr_ctx *ctx);
+extern void cr_pgarr_reset_all(struct cr_ctx *ctx);
+
+static inline int cr_pgarr_is_full(struct cr_pgarr *pgarr)
+{
+ return (pgarr->nr_used == CR_PGARR_TOTAL);
+}
+
+#endif /* _CHECKPOINT_CKPT_MEM_H_ */
diff --git a/checkpoint/ckpt_mem.c b/checkpoint/ckpt_mem.c
new file mode 100644
index 0000000..3d3c5f5
--- /dev/null
+++ b/checkpoint/ckpt_mem.c
@@ -0,0 +1,558 @@
+/*
+ * Checkpoint memory contents
+ *
+ * Copyright (C) 2008-2009 Oren Laadan
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <linux/pagemap.h>
+#include <linux/mm_types.h>
+#include <linux/checkpoint.h>
+#include <linux/checkpoint_hdr.h>
+
+#include "checkpoint_arch.h"
+#include "checkpoint_mem.h"
+
+/*
+ * utilities to alloc, free, and handle 'struct cr_pgarr' (page-arrays)
+ * (common to ckpt_mem.c and rstr_mem.c).
+ *
+ * The checkpoint context structure has two members for page-arrays:
+ * ctx->pgarr_list: list head of populated page-array chain
+ * ctx->pgarr_pool: list head of empty page-array pool chain
+ *
+ * During checkpoint (and restart) the chain tracks the dirty pages (page
+ * pointer and virtual address) of each MM. For a particular MM, these are
+ * always added to the head of the page-array chain (ctx->pgarr_list).
+ * Before the next chunk of pages, the chain is reset (by dereferencing
+ * all pages) but not freed; instead, empty descsriptors are kept in pool.
+ *
+ * The head of the chain page-array ("current") advances as necessary. When
+ * it gets full, a new page-array descriptor is pushed in front of it. The
+ * new descriptor is taken from first empty descriptor (if one exists, for
+ * instance, after a chain reset), or allocated on-demand.
+ *
+ * When dumping the data, the chain is traversed in reverse order.
+ */
+
+/* return first page-array in the chain */
+static inline struct cr_pgarr *cr_pgarr_first(struct cr_ctx *ctx)
+{
+ if (list_empty(&ctx->pgarr_list))
+ return NULL;
+ return list_first_entry(&ctx->pgarr_list, struct cr_pgarr, list);
+}
+
+/* return (and detach) first empty page-array in the pool, if exists */
+static inline struct cr_pgarr *cr_pgarr_from_pool(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr;
+
+ if (list_empty(&ctx->pgarr_pool))
+ return NULL;
+ pgarr = list_first_entry(&ctx->pgarr_pool, struct cr_pgarr, list);
+ list_del(&pgarr->list);
+ return pgarr;
+}
+
+/* release pages referenced by a page-array */
+static void cr_pgarr_release_pages(struct cr_pgarr *pgarr)
+{
+ cr_debug("nr_used %d\n", pgarr->nr_used);
+ /*
+ * both checkpoint and restart use 'nr_used', however we only
+ * collect pages during checkpoint; in restart we simply return
+ * because pgarr->pages remains NULL.
+ */
+ if (pgarr->pages) {
+ struct page **pages = pgarr->pages;
+ int nr = pgarr->nr_used;
+
+ while (nr--)
+ page_cache_release(pages[nr]);
+ }
+
+ pgarr->nr_used = 0;
+}
+
+/* free a single page-array object */
+static void cr_pgarr_free_one(struct cr_pgarr *pgarr)
+{
+ cr_pgarr_release_pages(pgarr);
+ kfree(pgarr->pages);
+ kfree(pgarr->vaddrs);
+ kfree(pgarr);
+}
+
+/* free the chains of page-arrays (populated and empty pool) */
+void cr_pgarr_free(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr, *tmp;
+
+ list_for_each_entry_safe(pgarr, tmp, &ctx->pgarr_list, list) {
+ list_del(&pgarr->list);
+ cr_pgarr_free_one(pgarr);
+ }
+
+ list_for_each_entry_safe(pgarr, tmp, &ctx->pgarr_pool, list) {
+ list_del(&pgarr->list);
+ cr_pgarr_free_one(pgarr);
+ }
+}
+
+/* allocate a single page-array object */
+static struct cr_pgarr *cr_pgarr_alloc_one(unsigned long flags)
+{
+ struct cr_pgarr *pgarr;
+
+ pgarr = kzalloc(sizeof(*pgarr), GFP_KERNEL);
+ if (!pgarr)
+ return NULL;
+
+ pgarr->vaddrs = kmalloc(CR_PGARR_TOTAL * sizeof(unsigned long),
+ GFP_KERNEL);
+ if (!pgarr->vaddrs)
+ goto nomem;
+
+ /* pgarr->pages is needed only for checkpoint */
+ if (flags & CR_CTX_CKPT) {
+ pgarr->pages = kmalloc(CR_PGARR_TOTAL * sizeof(struct page *),
+ GFP_KERNEL);
+ if (!pgarr->pages)
+ goto nomem;
+ }
+
+ return pgarr;
+
+ nomem:
+ cr_pgarr_free_one(pgarr);
+ return NULL;
+}
+
+/* cr_pgarr_current - return the next available page-array in the chain
+ * @ctx: checkpoint context
+ *
+ * Returns the first page-array in the list that has space. Otherwise,
+ * try the next page-array after the last non-empty one, and move it to
+ * the front of the chain. Extends the list if none has space.
+ */
+struct cr_pgarr *cr_pgarr_current(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr;
+
+ pgarr = cr_pgarr_first(ctx);
+ if (pgarr && !cr_pgarr_is_full(pgarr))
+ return pgarr;
+
+ pgarr = cr_pgarr_from_pool(ctx);
+ if (!pgarr)
+ pgarr = cr_pgarr_alloc_one(ctx->flags);
+ if (!pgarr)
+ return NULL;
+
+ list_add(&pgarr->list, &ctx->pgarr_list);
+ return pgarr;
+}
+
+/* reset the page-array chain (dropping page references if necessary) */
+void cr_pgarr_reset_all(struct cr_ctx *ctx)
+{
+ struct cr_pgarr *pgarr;
+
+ list_for_each_entry(pgarr, &ctx->pgarr_list, list)
+ cr_pgarr_release_pages(pgarr);
+ list_splice_init(&ctx->pgarr_list, &ctx->pgarr_pool);
+}
+
+/*
+ * Checkpoint is outside the context of the checkpointee, so one cannot
+ * simply read pages from user-space. Instead, we scan the address space
+ * of the target to cherry-pick pages of interest. Selected pages are
+ * enlisted in a page-array chain (attached to the checkpoint context).
+ * To save their contents, each page is mapped to kernel memory and then
+ * dumped to the file descriptor.
+ */
+
+
+/**
+ * cr_private_follow_page - return page pointer for dirty pages
+ * @vma - target vma
+ * @addr - page address
+ *
+ * Looks up the page that correspond to the address in the vma, and
+ * returns the page if it was modified (and grabs a reference to it),
+ * or otherwise returns NULL (or error).
+ *
+ * This function should _only_ called for private vma's.
+ */
+static struct page *
+cr_consider_private_page(struct vm_area_struct *vma, unsigned long addr)
+{
+ struct page *page;
+
+ /*
+ * simplified version of get_user_pages(): already have vma,
+ * only need FOLL_ANON, and (for now) ignore fault stats.
+ *
+ * follow_page() will return NULL if the page is not present
+ * (swapped), ZERO_PAGE(0) if the pte wasn't allocated, and
+ * the actual page pointer otherwise.
+ *
+ * FIXME: consolidate with get_user_pages()
+ */
+
+ cond_resched();
+ while (!(page = follow_page(vma, addr, FOLL_ANON | FOLL_GET))) {
+ int ret;
+
+ /* the page is swapped out - bring it in (optimize ?) */
+ ret = handle_mm_fault(vma->vm_mm, vma, addr, 0);
+ if (ret & VM_FAULT_ERROR) {
+ if (ret & VM_FAULT_OOM)
+ return ERR_PTR(-ENOMEM);
+ else if (ret & VM_FAULT_SIGBUS)
+ return ERR_PTR(-EFAULT);
+ else
+ BUG();
+ break;
+ }
+ cond_resched();
+ }
+
+ if (IS_ERR(page))
+ return page;
+
+ /*
+ * Only care about dirty pages: either anonymous non-zero pages,
+ * or file-backed COW (copy-on-write) pages that were modified.
+ * A clean COW page is not interesting because its contents are
+ * identical to the backing file; ignore such pages.
+ * A file-backed broken COW is identified by its page_mapping()
+ * being unset (NULL) because the page will no longer be mapped
+ * to the original file after having been modified.
+ */
+ if (page == ZERO_PAGE(0)) {
+ /* this is the zero page: ignore */
+ page_cache_release(page);
+ page = NULL;
+ } else if (vma->vm_file && (page_mapping(page) != NULL)) {
+ /* file backed clean cow: ignore */
+ page_cache_release(page);
+ page = NULL;
+ }
+
+ return page;
+}
+
+/**
+ * cr_private_vma_fill_pgarr - fill a page-array with addr/page tuples
+ * @ctx - checkpoint context
+ * @vma - vma to scan
+ * @start - start address (updated)
+ *
+ * Returns the number of pages collected
+ */
+static int
+cr_private_vma_fill_pgarr(struct cr_ctx *ctx, struct vm_area_struct *vma,
+ unsigned long *start)
+{
+ unsigned long end = vma->vm_end;
+ unsigned long addr = *start;
+ struct cr_pgarr *pgarr;
+ int nr_used;
+ int cnt = 0;
+
+ /* this function is only for private memory (anon or file-mapped) */
+ BUG_ON(vma->vm_flags & (VM_SHARED | VM_MAYSHARE));
+
+ do {
+ pgarr = cr_pgarr_current(ctx);
+ if (!pgarr)
+ return -ENOMEM;
+
+ nr_used = pgarr->nr_used;
+
+ while (addr < end) {
+ struct page *page;
+
+ page = cr_consider_private_page(vma, addr);
+ if (IS_ERR(page))
+ return PTR_ERR(page);
+
+ if (page) {
+ pgarr->pages[pgarr->nr_used] = page;
+ pgarr->vaddrs[pgarr->nr_used] = addr;
+ pgarr->nr_used++;
+ }
+
+ addr += PAGE_SIZE;
+
+ if (cr_pgarr_is_full(pgarr))
+ break;
+ }
+
+ cnt += pgarr->nr_used - nr_used;
+
+ } while ((cnt < CR_PGARR_CHUNK) && (addr < end));
+
+ *start = addr;
+ return cnt;
+}
+
+/* dump contents of a pages: use kmap_atomic() to avoid TLB flush */
+static int cr_page_write(struct cr_ctx *ctx, struct page *page, char *buf)
+{
+ void *ptr;
+
+ ptr = kmap_atomic(page, KM_USER1);
+ memcpy(buf, ptr, PAGE_SIZE);
+ kunmap_atomic(ptr, KM_USER1);
+
+ return cr_kwrite(ctx, buf, PAGE_SIZE);
+}
+
+/**
+ * cr_vma_dump_pages - dump pages listed in the ctx page-array chain
+ * @ctx - checkpoint context
+ * @total - total number of pages
+ *
+ * First dump all virtual addresses, followed by the contents of all pages
+ */
+static int cr_vma_dump_pages(struct cr_ctx *ctx, int total)
+{
+ struct cr_pgarr *pgarr;
+ void *buf;
+ int i, ret = 0;
+
+ if (!total)
+ return 0;
+
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ ret = cr_kwrite(ctx, pgarr->vaddrs,
+ pgarr->nr_used * sizeof(*pgarr->vaddrs));
+ if (ret < 0)
+ return ret;
+ }
+
+ buf = (void *) __get_free_page(GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ list_for_each_entry_reverse(pgarr, &ctx->pgarr_list, list) {
+ for (i = 0; i < pgarr->nr_used; i++) {
+ ret = cr_page_write(ctx, pgarr->pages[i], buf);
+ if (ret < 0)
+ goto out;
+ }
+ }
+
+ out:
+ free_page((unsigned long) buf);
+ return ret;
+}
+
+/**
+ * cr_write_private_vma_contents - dump contents of a VMA with private memory
+ * @ctx - checkpoint context
+ * @vma - vma to scan
+ *
+ * Collect lists of pages that needs to be dumped, and corresponding
+ * virtual addresses into ctx->pgarr_list page-array chain. Then dump
+ * the addresses, followed by the page contents.
+ */
+static int
+cr_write_private_vma_contents(struct cr_ctx *ctx, struct vm_area_struct *vma)
+{
+ struct cr_hdr h;
+ struct cr_hdr_pgarr *hh;
+ unsigned long addr = vma->vm_start;
+ int cnt, ret;
+
+ /*
+ * Work iteratively, collecting and dumping at most CR_PGARR_CHUNK
+ * in each round. Each iterations is divided into two steps:
+ *
+ * (1) scan: scan through the PTEs of the vma to collect the pages
+ * to dump (later we'll also make them COW), while keeping a list
+ * of pages and their corresponding addresses on ctx->pgarr_list.
+ *
+ * (2) dump: write out a header specifying how many pages, followed
+ * by the addresses of all pages in ctx->pgarr_list, followed by
+ * the actual contents of all pages. (Then, release the references
+ * to the pages and reset the page-array chain).
+ *
+ * (This split makes the logic simpler by first counting the pages
+ * that need saving. More importantly, it allows for a future
+ * optimization that will reduce application downtime by deferring
+ * the actual write-out of the data to after the application is
+ * allowed to resume execution).
+ *
+ * After dumpting the entire contents, conclude with a header that
+ * specifies 0 pages to mark the end of the contents.
+ */
+
+ h.type = CR_HDR_PGARR;
+ h.len = sizeof(*hh);
+
+ while (addr < vma->vm_end) {
+ cnt = cr_private_vma_fill_pgarr(ctx, vma, &addr);
+ if (cnt == 0)
+ break;
+ else if (cnt < 0)
+ return cnt;
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+
+ hh->nr_pages = cnt;
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ ret = cr_vma_dump_pages(ctx, cnt);
+ if (ret < 0)
+ return ret;
+
+ cr_pgarr_reset_all(ctx);
+ }
+
+ /* mark end of contents with header saying "0" pages */
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+ hh->nr_pages = 0;
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+
+ return ret;
+}
+
+/**
+ * cr_write_vma - classify the vma and dump its contents
+ * @ctx: checkpoint context
+ * @vma: vma object
+ *
+ * (see vma subtypes in checkpoint_hdr.h)
+ */
+static int cr_write_vma(struct cr_ctx *ctx, struct vm_area_struct *vma)
+{
+ struct cr_hdr h;
+ struct cr_hdr_vma *hh;
+ int vma_type, ret;
+
+ h.type = CR_HDR_VMA;
+ h.len = sizeof(*hh);
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -EBUSY;
+
+ hh->vm_start = vma->vm_start;
+ hh->vm_end = vma->vm_end;
+ hh->vm_page_prot = pgprot_val(vma->vm_page_prot);
+ hh->vm_flags = vma->vm_flags;
+ hh->vm_pgoff = vma->vm_pgoff;
+
+#define CR_BAD_VM_FLAGS \
+ (VM_SHARED | VM_MAYSHARE | VM_IO | VM_HUGETLB | VM_NONLINEAR)
+
+ if (vma->vm_flags & CR_BAD_VM_FLAGS) {
+ pr_warning("c/r: unsupported VMA %#lx\n", vma->vm_flags);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ return -ENOSYS;
+ }
+
+ /* by default assume anon memory */
+ vma_type = CR_VMA_ANON;
+
+ /*
+ * if there is a backing file, assume private-mapped
+ * (FIXME: check if the file is unlinked)
+ */
+ if (vma->vm_file)
+ vma_type = CR_VMA_FILE;
+
+ hh->vma_type = vma_type;
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ return ret;
+
+ /* save the file name */
+ /* FIXME: files should be deposited and sought in the objhash */
+ if (vma->vm_file) {
+ ret = cr_write_fname(ctx, &vma->vm_file->f_path, &ctx->fs_mnt);
+ if (ret < 0)
+ return ret;
+ }
+
+ return cr_write_private_vma_contents(ctx, vma);
+}
+
+int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t)
+{
+ struct cr_hdr h;
+ struct cr_hdr_mm *hh;
+ struct mm_struct *mm;
+ struct vm_area_struct *vma;
+ int objref, ret;
+
+ h.type = CR_HDR_MM;
+ h.len = sizeof(*hh);
+
+ hh = cr_hbuf_get(ctx, sizeof(*hh));
+ if (!hh)
+ return -ENOMEM;
+
+ mm = get_task_mm(t);
+
+ objref = 0; /* will be meaningful with multiple processes */
+ hh->objref = objref;
+
+ down_read(&mm->mmap_sem);
+
+ hh->start_code = mm->start_code;
+ hh->end_code = mm->end_code;
+ hh->start_data = mm->start_data;
+ hh->end_data = mm->end_data;
+ hh->start_brk = mm->start_brk;
+ hh->brk = mm->brk;
+ hh->start_stack = mm->start_stack;
+ hh->arg_start = mm->arg_start;
+ hh->arg_end = mm->arg_end;
+ hh->env_start = mm->env_start;
+ hh->env_end = mm->env_end;
+
+ hh->map_count = mm->map_count;
+
+ /* FIX: need also mm->flags */
+
+ ret = cr_write_obj(ctx, &h, hh);
+ cr_hbuf_put(ctx, sizeof(*hh));
+ if (ret < 0)
+ goto out;
+
+ /* write the vma's */
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ ret = cr_write_vma(ctx, vma);
+ if (ret < 0)
+ goto out;
+ }
+
+ ret = cr_write_mm_context(ctx, mm);
+
+ out:
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ return ret;
+}
diff --git a/checkpoint/sys.c b/checkpoint/sys.c
index 337c160..d403731 100644
--- a/checkpoint/sys.c
+++ b/checkpoint/sys.c
@@ -16,6 +16,8 @@
#include <linux/capability.h>
#include <linux/checkpoint.h>
+#include "checkpoint_mem.h"
+
/*
* Helpers to write(read) from(to) kernel space to(from) the checkpoint
* image file descriptor (similar to how a core-dump is performed).
@@ -153,7 +155,13 @@ static void cr_ctx_free(struct cr_ctx *ctx)
{
if (ctx->file)
fput(ctx->file);
+
kfree(ctx->hbuf);
+
+ path_put(&ctx->fs_mnt); /* safe with NULL pointers */
+
+ cr_pgarr_free(ctx);
+
kfree(ctx);
}
@@ -168,6 +176,9 @@ static struct cr_ctx *cr_ctx_alloc(int fd, unsigned long flags)
ctx->flags = flags;
+ INIT_LIST_HEAD(&ctx->pgarr_list);
+ INIT_LIST_HEAD(&ctx->pgarr_pool);
+
err = -EBADF;
ctx->file = fget(fd);
if (!ctx->file)
diff --git a/include/linux/checkpoint.h b/include/linux/checkpoint.h
index 97f4af5..56442ab 100644
--- a/include/linux/checkpoint.h
+++ b/include/linux/checkpoint.h
@@ -10,6 +10,9 @@
* distribution for more details.
*/
+#include <linux/path.h>
+#include <linux/fs.h>
+
#define CR_VERSION 1
struct cr_ctx {
@@ -25,6 +28,11 @@ struct cr_ctx {
void *hbuf; /* temporary buffer for headers */
int hpos; /* position in headers buffer */
+
+ struct list_head pgarr_list; /* page array to dump VMA contents */
+ struct list_head pgarr_pool; /* pool of empty page arrays chain */
+
+ struct path fs_mnt; /* container root (FIXME) */
};
/* cr_ctx: flags */
@@ -42,6 +50,8 @@ struct cr_hdr;
extern int cr_write_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf);
extern int cr_write_buffer(struct cr_ctx *ctx, void *buf, int len);
extern int cr_write_string(struct cr_ctx *ctx, char *str, int len);
+extern int cr_write_fname(struct cr_ctx *ctx,
+ struct path *path, struct path *root);
extern int cr_read_obj(struct cr_ctx *ctx, struct cr_hdr *h, void *buf, int n);
extern int cr_read_obj_type(struct cr_ctx *ctx, void *buf, int len, int type);
@@ -50,7 +60,10 @@ extern int cr_read_buffer(struct cr_ctx *ctx, void *buf, int *len);
extern int cr_read_string(struct cr_ctx *ctx, char *str, int len);
extern int do_checkpoint(struct cr_ctx *ctx, pid_t pid);
+extern int cr_write_mm(struct cr_ctx *ctx, struct task_struct *t);
+
extern int do_restart(struct cr_ctx *ctx, pid_t pid);
+extern int cr_read_mm(struct cr_ctx *ctx);
#define cr_debug(fmt, args...) \
pr_debug("[%d:c/r:%s] " fmt, task_pid_vnr(current), __func__, ## args)
diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
index 0629c66..2a06a2f 100644
--- a/include/linux/checkpoint_hdr.h
+++ b/include/linux/checkpoint_hdr.h
@@ -42,6 +42,7 @@ enum {
CR_HDR_HEAD_ARCH,
CR_HDR_BUFFER,
CR_HDR_STRING,
+ CR_HDR_FNAME,
CR_HDR_TASK = 101,
CR_HDR_THREAD,
@@ -49,6 +50,7 @@ enum {
CR_HDR_MM = 201,
CR_HDR_VMA,
+ CR_HDR_PGARR,
CR_HDR_MM_CONTEXT,
CR_HDR_TAIL = 5001
@@ -91,4 +93,34 @@ struct cr_hdr_task {
__u32 task_comm_len;
} __attribute__((aligned(8)));
+struct cr_hdr_mm {
+ __s32 objref; /* identifier for shared objects */
+ __u32 map_count;
+
+ __u64 start_code, end_code, start_data, end_data;
+ __u64 start_brk, brk, start_stack;
+ __u64 arg_start, arg_end, env_start, env_end;
+} __attribute__((aligned(8)));
+
+/* vma subtypes */
+enum cr_vma_type {
+ CR_VMA_ANON = 1, /* private anonymous */
+ CR_VMA_FILE, /* private mapped file */
+};
+
+struct cr_hdr_vma {
+ __u32 vma_type;
+ __u32 _padding;
+
+ __u64 vm_start;
+ __u64 vm_end;
+ __u64 vm_page_prot;
+ __u64 vm_flags;
+ __u64 vm_pgoff;
+} __attribute__((aligned(8)));
+
+struct cr_hdr_pgarr {
+ __u64 nr_pages; /* number of pages to saved */
+} __attribute__((aligned(8)));
+
#endif /* _CHECKPOINT_CKPT_HDR_H_ */
--
1.5.4.3
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