initial implementation of posix_spawn

file actions are not yet implemented, but everything else should be
mostly complete and roughly correct.

src/process/posix_spawn.c

@@ -0,0 +1,65 @@
+#include <spawn.h>
+#include <unistd.h>
+#include <signal.h>
+#include <stdint.h>
+#include "syscall.h"
+
+extern char **environ;
+
+int __posix_spawnx(pid_t *res, const char *path,
+	int (*exec)(const char *, char *const *),
+	const posix_spawn_file_actions_t *fa,
+	const posix_spawnattr_t *attr, char **argv, char **envp)
+{
+	pid_t pid;
+	sigset_t oldmask;
+	int i;
+	posix_spawnattr_t dummy_attr = { 0 };
+
+	if (!attr) attr = &dummy_attr;
+
+	sigprocmask(SIG_BLOCK, (void *)(uint64_t []){-1}, &oldmask);
+	pid = __syscall(SYS_fork);
+
+	if (pid) {
+		sigprocmask(SIG_SETMASK, &oldmask, 0);
+		if (pid < 0) return -pid;
+		*res = pid;
+		return 0;
+	}
+
+	for (i=1; i<=64; i++) {
+		struct sigaction sa;
+		sigaction(i, 0, &sa);
+		if (sa.sa_handler!=SIG_IGN || sigismember(&attr->__def, i)) {
+			sa.sa_handler = SIG_DFL;
+			sigaction(i, &sa, 0);
+		}
+	}
+
+	if ((attr->__flags&POSIX_SPAWN_SETPGROUP) && setpgid(0, attr->__pgrp))
+		_exit(127);
+
+	/* Use syscalls directly because pthread state is not consistent
+	 * for making calls to the library wrappers... */
+	if ((attr->__flags&POSIX_SPAWN_RESETIDS) && (
+		__syscall(SYS_setgid, __syscall(SYS_getgid)) ||
+		__syscall(SYS_setuid, __syscall(SYS_getuid)) ))
+		_exit(127);
+
+	sigprocmask(SIG_SETMASK, (attr->__flags & POSIX_SPAWN_SETSIGMASK)
+		? &attr->__mask : &oldmask, 0);
+
+	if (envp) environ = envp;
+	exec(path, argv);
+	_exit(127);
+
+	return 0;
+}
+
+int posix_spawn(pid_t *res, const char *path,
+	const posix_spawn_file_actions_t *fa,
+	const posix_spawnattr_t *attr, char **argv, char **envp)
+{
+	return __posix_spawnx(res, path, execv, fa, attr, argv, envp);
+}