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clone_noasan: Allow to create CLONE_VM|CLONE_VFORK processes

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Picked from patch "[PATCH RFC] namespaces: use CLONE_VFORK
with CLONE_VM when it is possible" by Andrew Vagin.

Currenly parent touches child's stack, as in moment of clone() call
its stack pointer is above the child's (we allocate char stack[128]
on parent's stack). This prevents to create CLONE_VM|CLONE_VFORK
processes, because the child uses stack addresses occupied by parent.

The patch changes clone_noasan() behaviour and allows to do that
with the same memory consumption. We give a child memory, which
is not used by parent clone(), so parent's and child's stacks
have no tntersection.

This allows to create CLONE_VM|CLONE_VFORK processes.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
This commit is contained in:
Kirill Tkhai 2017-05-17 17:37:05 +03:00 • committed by Andrei Vagin
parent badf42caa4
commit ef65d98a78
1 changed files with 7 additions and 9 deletions
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16
criu/clone-noasan.c
View file

@ -1,5 +1,7 @@
#include <sched.h>
#include "common/compiler.h"
#include "log.h"
#include "common/bug.h"
/*
* ASan doesn't play nicely with clone if we use current stack for
@ -19,15 +21,11 @@
*/
int clone_noasan(int (*fn)(void *), int flags, void *arg)
{
void *stack_ptr = (void *)round_down((unsigned long)&stack_ptr - 256, 16);
BUG_ON((flags & CLONE_VM) && !(flags & CLONE_VFORK));
/*
* Reserve some space for clone() to locate arguments
* and retcode in this place
* Reserve some bytes for clone() internal needs
* and use as stack the address above this area.
*/
char stack[128] __stack_aligned__;
char *stack_ptr = &stack[sizeof(stack)];
int ret;
ret = clone(fn, stack_ptr, flags, arg);
return ret;
return clone(fn, stack_ptr, flags, arg);
}