rework SystemExec - use vfork wrapper (and lots of related stuff)

libs/vfork/exec_wrapper.c

@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <signal.h>
+
+#ifndef STDIN_FILENO
+#define STDIN_FILENO 0
+#endif
+#ifndef STDOUT_FILENO
+#define STDOUT_FILENO 1
+#endif
+#ifndef STDERR_FILENO
+#define STDERR_FILENO 2
+#endif
+
+extern char **environ;
+static void close_fd (int *fd) { if ((*fd) >= 0) close (*fd); *fd = -1; }
+
+int main(int argc, char *argv[]) {
+	if (argc < 10) {
+		// TODO: if argv > 3, assume pok[] is given, notifify parent.
+		// usage() and a man-page (help2man) would not be bad, either :)
+		return -1;
+	}
+
+	int pok[2];
+	int pin[2];
+	int pout[2];
+
+	pok[0]  = atoi(argv[1]);
+	pok[1]  = atoi(argv[2]);
+	pin[0]  = atoi(argv[3]);
+	pin[1]  = atoi(argv[4]);
+	pout[0] = atoi(argv[5]);
+	pout[1] = atoi(argv[6]);
+
+	int stderr_mode = atoi(argv[7]);
+	int nicelevel = atoi(argv[8]);
+
+	/* vfork()ed child process - exec external process */
+	close_fd(&pok[0]);
+	fcntl(pok[1], F_SETFD, FD_CLOEXEC);
+
+	close_fd(&pin[1]);
+	if (pin[0] != STDIN_FILENO) {
+		dup2(pin[0], STDIN_FILENO);
+	}
+	close_fd(&pin[0]);
+	close_fd(&pout[0]);
+	if (pout[1] != STDOUT_FILENO) {
+		dup2(pout[1], STDOUT_FILENO);
+	}
+
+	if (stderr_mode == 2) {
+		/* merge STDERR into output */
+		if (pout[1] != STDERR_FILENO) {
+			dup2(pout[1], STDERR_FILENO);
+		}
+	} else if (stderr_mode == 1) {
+		/* ignore STDERR */
+		close(STDERR_FILENO);
+	} else {
+		/* keep STDERR */
+	}
+
+	if (pout[1] != STDOUT_FILENO && pout[1] != STDERR_FILENO) {
+		close_fd(&pout[1]);
+	}
+
+	if (nicelevel !=0) {
+		nice(nicelevel);
+	}
+
+	/* copy current environment */
+	char **envp = NULL;
+	int i=0;
+	envp = (char **) calloc(1, sizeof(char*));
+	for (i=0;environ[i];++i) {
+		envp[i] = strdup(environ[i]);
+		envp = (char **) realloc(envp, (i+2) * sizeof(char*));
+	}
+	envp[i] = 0;
+
+#ifdef HAVE_SIGSET
+	sigset(SIGPIPE, SIG_DFL);
+#else
+	signal(SIGPIPE, SIG_DFL);
+#endif
+
+	/* all systems go */
+	execve(argv[9], &argv[9], envp);
+
+	/* if we reach here something went wrong.. */
+	char buf = 0;
+	(void) write(pok[1], &buf, 1 );
+	close_fd(&pok[1]);
+	exit(-1);
+	return -1;
+}