[PATCH 1/4] um: Add the pthread-based helper support

[Tiwei Bie]

Introduce a new set of utility functions that can be used to create
pthread-based helpers. Helper threads created in this way will ensure
thread safety for errno while sharing memory address space.

Signed-off-by: Tiwei Bie <tiwei.btw at antgroup.com>
---
 arch/um/include/shared/os.h |  3 ++
 arch/um/os-Linux/helper.c   | 60 +++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 5babad8c5f75..1f62e793bce3 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -225,6 +225,9 @@ extern int run_helper_thread(int (*proc)(void *), void *arg,
 			     unsigned int flags, unsigned long *stack_out);
 extern int helper_wait(int pid);
 
+int os_run_helper_thread(void *(*routine)(void *), void *arg, void **handle_out);
+void os_kill_helper_thread(void *);
+void os_fix_helper_thread_signals(void);
 
 /* umid.c */
 extern int umid_file_name(char *name, char *buf, int len);
diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
index 3cb8ac63be6e..c6a0ef8beb29 100644
--- a/arch/um/os-Linux/helper.c
+++ b/arch/um/os-Linux/helper.c
@@ -8,6 +8,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <sched.h>
+#include <pthread.h>
 #include <linux/limits.h>
 #include <sys/socket.h>
 #include <sys/wait.h>
@@ -167,3 +168,62 @@ int helper_wait(int pid)
 	} else
 		return 0;
 }
+
+int os_run_helper_thread(void *(*routine)(void *), void *arg, void **handle_out)
+{
+	pthread_t *td;
+	sigset_t sigset, oset;
+	int err, flags;
+
+	flags = __uml_cant_sleep() ? UM_GFP_ATOMIC : UM_GFP_KERNEL;
+	td = uml_kmalloc(sizeof(*td), flags);
+	if (!td)
+		return -ENOMEM;
+
+	sigfillset(&sigset);
+	if (sigprocmask(SIG_SETMASK, &sigset, &oset) < 0) {
+		err = -errno;
+		kfree(td);
+		return err;
+	}
+
+	err = pthread_create(td, NULL, routine, arg);
+
+	if (sigprocmask(SIG_SETMASK, &oset, NULL) < 0)
+		panic("Failed to restore the signal mask: %d", errno);
+
+	if (err != 0)
+		kfree(td);
+	else
+		*handle_out = td;
+
+	return -err;
+}
+
+void os_kill_helper_thread(void *handle)
+{
+	pthread_t *td = handle;
+
+	pthread_kill(*td, SIGKILL);
+	CATCH_EINTR(pthread_join(*td, NULL));
+	kfree(td);
+}
+
+void os_fix_helper_thread_signals(void)
+{
+	sigset_t sigset;
+
+	sigemptyset(&sigset);
+
+	sigaddset(&sigset, SIGWINCH);
+	sigaddset(&sigset, SIGPIPE);
+	sigaddset(&sigset, SIGPROF);
+	sigaddset(&sigset, SIGINT);
+	sigaddset(&sigset, SIGTERM);
+	sigaddset(&sigset, SIGCHLD);
+	sigaddset(&sigset, SIGALRM);
+	sigaddset(&sigset, SIGIO);
+	sigaddset(&sigset, SIGUSR1);
+
+	pthread_sigmask(SIG_SETMASK, &sigset, NULL);
+}
-- 
2.34.1