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.
v2: Don't use __set_task_blocked with tsk != current.
recalc_sigpending() is not called here, because it will be called after
resume. retarget_shared_pending() are not called, because we suppose,
that other threads are stopped 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/uapi/linux/ptrace.h | 3 +++
kernel/ptrace.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 45 insertions(+)
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 52ebcc8..cf1019e 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -61,6 +61,9 @@ struct ptrace_peeksiginfo_args {
__s32 nr; /* how may siginfos to take */
};
+#define PTRACE_GETSIGMASK 0x420a
+#define PTRACE_SETSIGMASK 0x420b
+
/* Read signals from a shared (process wide) queue */
#define PTRACE_PEEKSIGINFO_SHARED (1 << 0)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 17ae54d..bebe67e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -841,6 +841,48 @@ 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));
+
+ /*
+ * Every thread does recalc_sigpending() after resume, so
+ * retarget_shared_pending() and recalc_sigpending() are not
+ * called here.
+ */
+ spin_lock_irq(&child->sighand->siglock);
+ child->blocked = new_set;
+ spin_unlock_irq(&child->sighand->siglock);
+
+ ret = 0;
+ break;
+ }
+
case PTRACE_INTERRUPT:
/*
* Stop tracee without any side-effect on signal or job
--
1.8.1.4
--
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