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restore: support SYSV IPC vma

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This patch introduces the following changes:
1) writing of shmid value into vma_area->fd instead of
   waiting for shared memory region is open by parent,
   reopen it and dump fd.
2) new syscall support: sys_shmat
3) use sys_shmat() to map memory region in restorer's
   mapping function if vma flag VMA_AREA_SYSVIPC is set.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
This commit is contained in:
Kinsbursky Stanislav 2012-02-14 20:20:10 +03:00 • committed by Cyrill Gorcunov
parent e967566565
commit 574302bf8d
4 changed files with 23 additions and 3 deletions
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16
cr-restore.c
View file

@ -17,6 +17,7 @@
#include <sys/user.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <sys/shm.h>
#include <sched.h>
@ -530,6 +531,7 @@ static int try_fixup_shared_map(int pid, struct vma_entry *vi, int fd)
{
struct shmem_info *si;
struct shmem_id *shmid;
int sh_fd;
shmid = find_shmem_id(vi->start);
if (!shmid)
@ -543,9 +545,17 @@ static int try_fixup_shared_map(int pid, struct vma_entry *vi, int fd)
return -1;
}
if (si->pid != pid) {
int sh_fd;
if (vma_entry_is(vi, VMA_AREA_SYSVIPC)) {
/*
* SYSV IPC shared memory region was created already. We don't
* need to wait. But we have to pass shmid to restorer. Let's
* use vma_entry->fd for it.
*/
sh_fd = si->shmid;
goto write_fd;
}
if (si->pid != pid) {
sh_fd = shmem_wait_and_open(pid, si);
pr_info("%d: Fixing %lx vma to %lx/%d shmem -> %d\n",
pid, vi->start, si->shmid, si->pid, sh_fd);
@ -553,7 +563,7 @@ static int try_fixup_shared_map(int pid, struct vma_entry *vi, int fd)
pr_perror("%d: Can't open shmem", pid);
return -1;
}
write_fd:
lseek(fd, -sizeof(*vi), SEEK_CUR);
vi->fd = sh_fd;
pr_info("%d: Fixed %lx vma %lx/%d shmem -> %d\n",

1
include/syscall-codes.h
View file

@ -15,6 +15,7 @@
#define __NR_rt_sigaction 13
#define __NR_rt_sigreturn 15
#define __NR_mincore 27
#define __NR_shmat 30
#define __NR_dup 32
#define __NR_dup2 33
#define __NR_pause 34

4
include/syscall.h
View file

@ -136,6 +136,10 @@ static always_inline unsigned long sys_pause(void)
return syscall0(__NR_pause);
}
static always_inline unsigned long sys_shmat(int shmid, void *shmaddr, int shmflag)
{
return syscall3(__NR_shmat, shmid, (unsigned long)shmaddr, shmflag);
}
static always_inline unsigned long sys_mmap(void *addr, unsigned long len, unsigned long prot,
unsigned long flags, unsigned long fd, unsigned long offset)
{

5
restorer.c
View file

@ -7,6 +7,7 @@
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/shm.h>
#include <fcntl.h>
#include <unistd.h>
#include <sched.h>
@ -290,6 +291,10 @@ static u64 restore_mapping(const struct vma_entry *vma_entry)
{
int prot;
if (vma_entry_is(vma_entry, VMA_AREA_SYSVIPC))
return sys_shmat(vma_entry->fd, (void *)vma_entry->start,
(vma_entry->prot & PROT_WRITE) ? 0 : SHM_RDONLY);
prot = vma_entry->prot;
/* A mapping of file with MAP_SHARED is up to date */