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authorRich Felker <dalias@aerifal.cx>2012-10-18 15:58:23 -0400
committerRich Felker <dalias@aerifal.cx>2012-10-18 15:58:23 -0400
commit44eb4d8b9b7b3b539bcd4e311e9d7c8e2acf8d80 (patch)
tree2511cd52cd02e8dbfc28b1ab231926ea9e429e6b /src/unistd
parentf1e7a5e5f62945d99bf5277fe574d2cf3983413a (diff)
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overhaul system() and popen() to use vfork; fix various related bugs
since we target systems without overcommit, special care should be
taken that system() and popen(), like posix_spawn(), do not fail in
processes whose commit charges are too high to allow ordinary forking.

this in turn requires special precautions to ensure that the parent
process's signal handlers do not end up running in the shared-memory
child, where they could corrupt the state of the parent process.

popen has also been updated to use pipe2, so it does not have a
fd-leak race in multi-threaded programs. since pipe2 is missing on
older kernels, (non-atomic) emulation has been added.

some silly bugs in the old code should be gone too.
Diffstat (limited to 'src/unistd')
-rw-r--r--src/unistd/pipe2.c20
1 files changed, 17 insertions, 3 deletions
diff --git a/src/unistd/pipe2.c b/src/unistd/pipe2.c
index 83282bb9..04e0c128 100644
--- a/src/unistd/pipe2.c
+++ b/src/unistd/pipe2.c
@@ -1,8 +1,22 @@
-#define _GNU_SOURCE
 #include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
 #include "syscall.h"
 
-int pipe2(int fd[2], int flg)
+int pipe2(int fd[2], int flag)
 {
-	return syscall(SYS_pipe2, fd, flg);
+	if (!flag) return syscall(SYS_pipe, fd);
+	int ret = __syscall(SYS_pipe2, fd, flag);
+	if (ret != -ENOSYS) return __syscall_ret(ret);
+	ret = syscall(SYS_pipe, fd);
+	if (ret) return __syscall_ret(ret);
+	if (flag & O_CLOEXEC) {
+		fcntl(fd[0], F_SETFD, FD_CLOEXEC);
+		fcntl(fd[1], F_SETFD, FD_CLOEXEC);
+	}
+	if (flag & O_NONBLOCK) {
+		fcntl(fd[0], F_SETFL, fcntl(fd[0], F_GETFL) | O_NONBLOCK);
+		fcntl(fd[1], F_SETFL, fcntl(fd[1], F_GETFL) | O_NONBLOCK);
+	}
+	return 0;
 }