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mem: Don't assume guard page is returned in procfs with new kernels

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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>
This commit is contained in:
Cyrill Gorcunov 2017-06-26 23:55:29 +03:00 • committed by Andrei Vagin
parent 8a4a164f3e
commit be37925cff
3 changed files with 18 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

2
criu/include/mem.h
View file

@ -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 void prepare_cow_vmas(void);

19
criu/mem.c
View file

@ -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;
size = vma_entry_len(vma->e);
@ -686,7 +686,7 @@ static int premap_private_vma(struct pstree_item *t, struct vma_area *vma, void
*/
paddr = decode_pointer(vma->pvma->premmaped_addr);
if (vma->e->flags & MAP_GROWSDOWN)
if (vma_has_guard_gap_hidden(vma))
paddr -= PAGE_SIZE;
addr = mremap(paddr, size, 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;
}
@ -717,7 +717,8 @@ static int premap_private_vma(struct pstree_item *t, struct vma_area *vma, void
static inline bool vma_force_premap(struct vma_area *vma, struct list_head *head)
{
/*
* Growsdown VMAs always have one guard page at the
* On kernels with 4K guard pages, growsdown VMAs
* always have one guard page at the
* beginning and sometimes this page contains data.
* In case the VMA is premmaped, we premmap one page
* larger VMA. In case of in place restore we can only
@ -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(vma, VMA_PREMMAPED))
continue;

3
criu/proc_parse.c
View file

@ -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;