crtools uses a parasite code for dumping processes. The parasite code is
injected into a process with help PTRACE_SEIZE.
Currently crtools blocks signals from a parasite code. If a process has
pending signals, crtools wait while a process handles these signals.
This method is not suitable for stopped tasks. A stopped task can have a
few pending signals, when we will try to execute a parasite code, we
will need to drop SIGSTOP, but all other signals must remain pending,
because a state of processes must not be changed during checkpointing.
This patch adds two ptrace commands to set/get signal-blocked mask.
I think gdb can use this commands too.
Cc: Roland McGrath <rol...@redhat.com>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Michael Kerrisk <mtk.manpa...@gmail.com>
Cc: Pavel Emelyanov <xe...@parallels.com>
Cc: Cyrill Gorcunov <gorcu...@openvz.org>
Signed-off-by: Andrey Vagin <ava...@openvz.org>
---
include/linux/signal.h | 1 +
include/uapi/linux/ptrace.h | 2 ++
kernel/ptrace.c | 36 ++++++++++++++++++++++++++++++++++++
kernel/signal.c | 2 +-
4 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/include/linux/signal.h b/include/linux/signal.h
index a2dcb94..706b88d 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -246,6 +246,7 @@ extern int do_sigtimedwait(const sigset_t *, siginfo_t *,
extern int sigprocmask(int, sigset_t *, sigset_t *);
extern void set_current_blocked(sigset_t *);
extern void __set_current_blocked(const sigset_t *);
+extern void __set_task_blocked(struct task_struct *tsk, const sigset_t
*newset);
extern int show_unhandled_signals;
extern int sigsuspend(sigset_t *);
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 52ebcc8..1527684 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -54,6 +54,8 @@
#define PTRACE_LISTEN 0x4208
#define PTRACE_PEEKSIGINFO 0x4209
+#define PTRACE_GETSIGMASK 0x420a
+#define PTRACE_SETSIGMASK 0x420b
struct ptrace_peeksiginfo_args {
__u64 off; /* from which siginfo to start */
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 17ae54d..317a737 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -841,6 +841,42 @@ int ptrace_request(struct task_struct *child, long request,
ret = ptrace_setsiginfo(child, &siginfo);
break;
+ case PTRACE_GETSIGMASK:
+ if (addr != sizeof(sigset_t)) {
+ ret = -EINVAL;
+ break;
+ }
+
+ if (copy_to_user(datavp, &child->blocked, sizeof(sigset_t)))
+ ret = -EFAULT;
+ else
+ ret = 0;
+
+ break;
+
+ case PTRACE_SETSIGMASK:
+ {
+ sigset_t new_set;
+
+ if (addr != sizeof(sigset_t)) {
+ ret = -EINVAL;
+ break;
+ }
+
+ if (copy_from_user(&new_set, datavp, sizeof(sigset_t))) {
+ ret = -EFAULT;
+ break;
+ }
+
+ sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
+
+ spin_lock_irq(&child->sighand->siglock);
+ __set_task_blocked(child, &new_set);
+ spin_unlock_irq(&child->sighand->siglock);
+
+ ret = 0;
+ break;
+ }
case PTRACE_INTERRUPT:
/*
* Stop tracee without any side-effect on signal or job
diff --git a/kernel/signal.c b/kernel/signal.c
index dd72567..d757e5b 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2522,7 +2522,7 @@ long do_no_restart_syscall(struct restart_block *param)
return -EINTR;
}
-static void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
+void __set_task_blocked(struct task_struct *tsk, const sigset_t *newset)
{
if (signal_pending(tsk) && !thread_group_empty(tsk)) {
sigset_t newblocked;
--
1.8.1.4
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