From be37925cff8aaf43f14866bd0a60dca6068a8d97 Mon Sep 17 00:00:00 2001

From: Cyrill Gorcunov <gorcunov@openvz.org>

Date: Mon, 26 Jun 2017 23:55:29 +0300

Subject: [PATCH 2/2] mem: Don't assume guard page is returned in procfs with

 new kernels

If the guard page is not reported in show_map_vma we should

not ajust vma address neither we should call unmap_guard_pages

in restorer.

https://github.com/xemul/criu/issues/322

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

---

 criu/include/mem.h |  2 ++

 criu/mem.c         | 19 ++++++++++++++-----

 criu/proc_parse.c  |  3 ++-

 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/criu/include/mem.h b/criu/include/mem.h

index 2fae797c6..2fc8e1e0e 100644

--- a/criu/include/mem.h

+++ b/criu/include/mem.h

@@ -9,11 +9,13 @@ struct parasite_ctl;

 struct vm_area_list;

 struct page_pipe;

 struct pstree_item;

+struct vma_area;

 struct mem_dump_ctl {

 	bool	pre_dump;

 };

+extern bool vma_has_guard_gap_hidden(struct vma_area *vma);

 extern bool page_in_parent(bool dirty);

 extern int prepare_mm_pid(struct pstree_item *i);

 extern int do_task_reset_dirty_track(int pid);

diff --git a/criu/mem.c b/criu/mem.c

index 2c4323d8c..cd41829b2 100644

--- a/criu/mem.c

+++ b/criu/mem.c

@@ -499,7 +499,7 @@ int prepare_mm_pid(struct pstree_item *i)

 		if (vma_area_is_private(vma, kdat.task_size)) {

 			ri->vmas.priv_size += vma_area_len(vma);

-			if (vma->e->flags & MAP_GROWSDOWN)

+			if (vma_has_guard_gap_hidden(vma))

 				ri->vmas.priv_size += PAGE_SIZE;

 		}

@@ -634,7 +634,7 @@ static int premap_private_vma(struct pstree_item *t, struct vma_area *vma, void

 	 * A grow-down VMA has a guard page, which protect a VMA below it.

 	 * So one more page is mapped here to restore content of the first page

 	 */

-	if (vma->e->flags & MAP_GROWSDOWN) {

+	if (vma_has_guard_gap_hidden(vma)) {

 		vma->e->start -= PAGE_SIZE;

 		if (paddr)

 			paddr -= PAGE_SIZE;

@@ -702,7 +702,7 @@ static int premap_private_vma(struct pstree_item *t, struct vma_area *vma, void

 	pr_debug("\tpremap %#016"PRIx64"-%#016"PRIx64" -> %016lx\n",

 		vma->e->start, vma->e->end, (unsigned long)addr);

-	if (vma->e->flags & MAP_GROWSDOWN) { /* Skip gurad page */

+	if (vma_has_guard_gap_hidden(vma)) { /* Skip gurad page */

 		vma->e->start += PAGE_SIZE;

 		vma->premmaped_addr += PAGE_SIZE;

 	}

@@ -1046,6 +1047,11 @@ out:

 	return ret;

 }

+bool vma_has_guard_gap_hidden(struct vma_area *vma)

+{

+	return kdat.stack_guard_gap_hidden && (vma->e->flags & MAP_GROWSDOWN);

+}

+

 /*

  * A gard page must be unmapped after restoring content and

  * forking children to restore COW memory.

@@ -1055,6 +1061,9 @@ int unmap_guard_pages(struct pstree_item *t)

 	struct vma_area *vma;

 	struct list_head *vmas = &rsti(t)->vmas.h;

+	if (!kdat.stack_guard_gap_hidden)

+		return 0;

+

 	list_for_each_entry(vma, vmas, list) {

 		if (!vma_area_is_private(vma, kdat.task_size))

 			continue;

diff --git a/criu/proc_parse.c b/criu/proc_parse.c

index f1237cf9f..5e36db540 100644

--- a/criu/proc_parse.c

+++ b/criu/proc_parse.c

@@ -25,6 +25,7 @@

 #include "kerndat.h"

 #include "vdso.h"

 #include "vma.h"

+#include "mem.h"

 #include "bfd.h"

 #include "proc_parse.h"

 #include "fdinfo.h"

@@ -637,7 +638,7 @@ static int vma_list_add(struct vma_area *vma_area,

 	}

 	/* Add a guard page only if here is enough space for it */

-	if ((vma_area->e->flags & MAP_GROWSDOWN) &&

+	if (vma_has_guard_gap_hidden(vma_area) &&

 	    *prev_end < vma_area->e->start)

 		vma_area->e->start -= PAGE_SIZE; /* Guard page */

 	*prev_end = vma_area->e->end;

-- 

2.13.0