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restore: use a currect stack for new processes (v3)

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Why do we need a new stack? We already have one and it can be used.

We need to step a bit for executing a glibc clone()

v2: Don't lose a page from a child's stack
v3: Remove the defined constant STACK_SIZE

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Andrey Vagin 2012-08-28 23:19:28 +04:00 • committed by Pavel Emelyanov
parent d2fab85055
commit d34b9004a7
1 changed files with 4 additions and 18 deletions
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22
cr-restore.c
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@ -480,14 +480,10 @@ out:
return ret;
}
/*
* This stack size is important for the restorer
* itself only. At the final phase, we will switch
* to the original stack the program had at checkpoint
* time.
*/
#define STACK_SIZE (8 * 4096)
/* All arguments should be above stack, because it grows down */
struct cr_clone_arg {
char stack[PAGE_SIZE];
char stack_ptr[0];
struct pstree_item *item;
unsigned long clone_flags;
int fd;
@ -497,18 +493,10 @@ static inline int fork_with_pid(struct pstree_item *item, unsigned long ns_clone
{
int ret = -1;
struct cr_clone_arg ca;
void *stack;
pid_t pid = item->pid.virt;
pr_info("Forking task with %d pid (flags 0x%lx)\n", pid, ns_clone_flags);
stack = mmap(NULL, STACK_SIZE, PROT_WRITE | PROT_READ,
MAP_PRIVATE | MAP_GROWSDOWN | MAP_ANONYMOUS, -1, 0);
if (stack == MAP_FAILED) {
pr_perror("Failed to map stack for the child");
goto err;
}
ca.item = item;
ca.clone_flags = ns_clone_flags;
@ -544,7 +532,7 @@ static inline int fork_with_pid(struct pstree_item *item, unsigned long ns_clone
if (netns_pre_create())
goto err_unlock;
ret = clone(restore_task_with_children, stack + STACK_SIZE,
ret = clone(restore_task_with_children, ca.stack_ptr,
ca.clone_flags | SIGCHLD, &ca);
if (ret < 0)
@ -574,8 +562,6 @@ err_unlock:
close(ca.fd);
}
err:
if (stack != MAP_FAILED)
munmap(stack, STACK_SIZE);
return ret;
}