From 68622a02adfa7ebd3a195667d3fbf8e1f10ca93f Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Thu, 15 Apr 2021 07:43:13 +0200
Subject: util: introduce safe versions of read & write that handle interrupted
 systems calls.

---
 bar.c   |  2 +-
 spawn.c | 11 ++++-------
 util.c  | 20 ++++++++++++++++++++
 util.h  | 10 ++++++++++
 4 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/bar.c b/bar.c
index e1e2857..67f5d6e 100644
--- a/bar.c
+++ b/bar.c
@@ -60,7 +60,7 @@ static int ass_puts(int fd, const char *str) {
 	size_t len = strlen(str);
 
 	while (len > 0) {
-		ssize_t ret = write(fd, str, len);
+		ssize_t ret = safe_write(fd, str, len);
 		if (ret <= 0) {
 			return -1;
 		}
diff --git a/spawn.c b/spawn.c
index 66f5f5e..5878122 100644
--- a/spawn.c
+++ b/spawn.c
@@ -189,12 +189,9 @@ static void bfs_spawn_exec(const char *exe, const struct bfs_spawn *ctx, char **
 fail:
 	error = errno;
 
-	while (write(pipefd[1], &error, sizeof(error)) < 0) {
-		if (errno != EINTR) {
-			// Parent will still see that we exited unsuccessfully, but won't know why
-			break;
-		}
-	}
+	// In case of write error parent will still see that we exited
+	// unsuccessfully, but won't know why.
+	safe_write(pipefd[1], &error, sizeof(error));
 
 	close(pipefd[1]);
 	_Exit(127);
@@ -224,7 +221,7 @@ pid_t bfs_spawn(const char *exe, const struct bfs_spawn *ctx, char **argv, char
 	// Parent
 	close(pipefd[1]);
 
-	ssize_t nbytes = read(pipefd[0], &error, sizeof(error));
+	ssize_t nbytes = safe_read(pipefd[0], &error, sizeof(error));
 	close(pipefd[0]);
 	if (nbytes == sizeof(error)) {
 		int wstatus;
diff --git a/util.c b/util.c
index 42e3d98..611d4b5 100644
--- a/util.c
+++ b/util.c
@@ -368,3 +368,23 @@ int bfs_minor(dev_t dev) {
 	return dev & 0xFF;
 #endif
 }
+
+ssize_t safe_read(int fd, void *buf, size_t nbytes) {
+	for (;;) {
+		ssize_t ret = read(fd, buf, nbytes);
+		if (ret < 0 && errno == EINTR) {
+			continue;
+		}
+		return ret;
+	}
+}
+
+ssize_t safe_write(int fd, const void *buf, size_t nbytes) {
+	for (;;) {
+		ssize_t ret = write(fd, buf, nbytes);
+		if (ret < 0 && errno == EINTR) {
+			continue;
+		}
+		return ret;
+	}
+}
diff --git a/util.h b/util.h
index ca90494..ef67566 100644
--- a/util.h
+++ b/util.h
@@ -225,4 +225,14 @@ int bfs_major(dev_t dev);
  */
 int bfs_minor(dev_t dev);
 
+/**
+ * A safe version of read() that handles interrupted system calls.
+ */
+ssize_t safe_read(int fd, void *buf, size_t nbytes);
+
+/**
+ * A safe version of write() that handles interrupted system calls.
+ */
+ssize_t safe_write(int fd, const void *buf, size_t nbytes);
+
 #endif // BFS_UTIL_H
-- 
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