[CRIU] [PATCH 3/3] ptrace: try to get signal blocking mask via ptrace (v2)

[Andrey Vagin]

Two new commands SETSIGMASK and GETSIGMASK were added to ptrace.

It allows to execute only one parasite command for dumping threads,
so unrecoverable window become smaller and performance is improved.

v2: splite the patch in two parts

Signed-off-by: Andrey Vagin <avagin at openvz.org>
---
 parasite-syscall.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 pie/parasite.c     |  2 ++
 2 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/parasite-syscall.c b/parasite-syscall.c
index fe3241e..be6f5d1 100644
--- a/parasite-syscall.c
+++ b/parasite-syscall.c
@@ -515,18 +515,74 @@ static int dump_thread_in_two_stage(struct parasite_ctl *ctl, int id,
 	return 0;
 }
 
+static int dump_thread_in_one_stage(struct parasite_ctl *ctl, int id,
+				struct pid *tid, CoreEntry *core)
+{
+	user_regs_struct_t regs_orig;
+	pid_t pid = tid->real;
+	k_rtsigset_t maskall;
+	int ret;
+
+	ksigfillset(&maskall);
+
+	ret = ptrace(PTRACE_SETSIGMASK, pid, sizeof(k_rtsigset_t), &maskall);
+	if (ret) {
+		pr_perror("Can't get signal blocking mask for %d", pid);
+		return -1;
+	}
+
+	ret = ptrace(PTRACE_GETREGS, pid, NULL, &regs_orig);
+	if (ret) {
+		pr_perror("Can't obtain registers (pid: %d)", pid);
+		goto out;
+	}
+
+	ret = parasite_execute_trap_by_pid(PARASITE_CMD_DUMP_THREAD, ctl,
+					pid, &regs_orig,
+					ctl->r_thread_stack, false);
+	if (ret) {
+		pr_err("Can't init thread in parasite %d\n", pid);
+		goto out;
+	}
+
+	ret = get_task_regs(pid, regs_orig, core);
+	if (ret)
+		pr_err("Can't obtain regs for thread %d\n", pid);
+
+out:
+	if (ptrace(PTRACE_SETSIGMASK, pid, sizeof(k_rtsigset_t),
+					&core->thread_core->blk_sigset)) {
+		pr_perror("Can't restore signal blocking mask for %d", pid);
+		ret = -1;
+	}
+
+	return ret;
+}
+
 int parasite_dump_thread_seized(struct parasite_ctl *ctl, int id,
 				struct pid *tid, CoreEntry *core)
 {
 	struct parasite_dump_thread *args;
+	pid_t pid = tid->real;
 	int ret;
 
 	args = parasite_args(ctl, struct parasite_dump_thread);
 
 	if (id == 0)
 		ret = parasite_execute_daemon(PARASITE_CMD_DUMP_THREAD, ctl);
-	else
-		ret = dump_thread_in_two_stage(ctl, id, tid, core);
+	else {
+		ret = ptrace(PTRACE_GETSIGMASK, pid, sizeof(k_rtsigset_t),
+						&core->thread_core->blk_sigset);
+		if (ret) {
+			pr_warn("ptrace can't get signal blocking mask for %d", pid);
+			ret = dump_thread_in_two_stage(ctl, id, tid, core);
+		} else {
+			core->thread_core->has_blk_sigset = true;
+
+			ret = dump_thread_in_one_stage(ctl, id, tid, core);
+		}
+
+	}
 
 	CORE_THREAD_ARCH_INFO(core)->clear_tid_addr = encode_pointer(args->tid_addr);
 	tid->virt = args->tid;
diff --git a/pie/parasite.c b/pie/parasite.c
index e840960..6a02b9f 100644
--- a/pie/parasite.c
+++ b/pie/parasite.c
@@ -528,6 +528,8 @@ int __used parasite_service(unsigned int cmd, void *args)
 	switch (cmd) {
 	case PARASITE_CMD_INIT:
 		return init(args);
+	case PARASITE_CMD_DUMP_THREAD:
+		return dump_thread(args);
 	case PARASITE_CMD_INIT_THREAD:
 		return init_thread(args);
 	case PARASITE_CMD_FINI_THREAD:
-- 
1.8.2