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restore: catch task on the exit from sigreturn (v4)

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A task is stopped here for unmaping restorer blob and restoring a state.

The method is the same as for parasite. CRIU attaches to processes via
ptrace and start to trace all syscalls.

v2: don't use a software breakpoint
v3: stop all thread on the exit from sigreturn
v4: attach to each thread
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrey Vagin
2013-09-23 14:33:34 +04:00
committed by Pavel Emelyanov
parent f43ac0643e
commit 66f21e6b71
1 changed files with 85 additions and 0 deletions
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85
cr-restore.c
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@@ -64,6 +64,8 @@
#include "stats.h"
#include "tun.h"
#include "parasite-syscall.h"
#include "protobuf.h"
#include "protobuf/sa.pb-c.h"
#include "protobuf/timer.pb-c.h"
@@ -1314,6 +1316,78 @@ static int restore_switch_stage(int next_stage)
return restore_wait_inprogress_tasks();
}
static int attach_to_tasks()
{
struct pstree_item *item;
for_each_pstree_item(item) {
pid_t pid = item->pid.real;
int status, i;
if (item->state == TASK_DEAD)
continue;
if (item->state == TASK_HELPER)
continue;
if (parse_threads(item->pid.real, &item->threads, &item->nr_threads))
return -1;
for (i = 0; i < item->nr_threads; i++) {
pid = item->threads[i].real;
if (ptrace(PTRACE_ATTACH, pid, 0, 0)) {
pr_perror("Can't attach to %d", pid);
return -1;
}
if (wait4(pid, &status, __WALL, NULL) != pid) {
pr_perror("waitpid() failed");
return -1;
}
if (ptrace(PTRACE_SYSCALL, pid, NULL, NULL)) {
pr_perror("Unable to start %d", pid);
return -1;
}
}
}
return 0;
}
static void finalize_restore(int status)
{
struct pstree_item *item;
for_each_pstree_item(item) {
pid_t pid = item->pid.real;
int i;
if (item->state == TASK_DEAD)
continue;
if (item->state == TASK_HELPER)
continue;
if (status < 0)
goto detach;
/* TODO Unmap the restorer blob and restore the process state */
detach:
for (i = 0; i < item->nr_threads; i++) {
pid = item->threads[i].real;
if (pid < 0) {
BUG_ON(status >= 0);
break;
}
if (ptrace(PTRACE_DETACH, pid, NULL, 0))
pr_perror("Unable to execute %d", pid);
}
}
}
static int restore_root_task(struct pstree_item *init)
{
int ret, fd;
@@ -1423,9 +1497,20 @@ static int restore_root_task(struct pstree_item *init)
timing_stop(TIME_RESTORE);
ret = attach_to_tasks();
pr_info("Restore finished successfully. Resuming tasks.\n");
futex_set_and_wake(&task_entries->start, CR_STATE_COMPLETE);
if (ret == 0)
ret = parasite_stop_on_syscall(task_entries->nr_threads, __NR_rt_sigreturn);
/*
* finalize_restore() always detaches from processes and
* they continue run through sigreturn.
*/
finalize_restore(ret);
write_stats(RESTORE_STATS);
if (!opts.restore_detach)