First commit

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 200 insertions, 0 deletions

diff --git a/libexec_exec.c b/libexec_exec.c
new file mode 100644
index 0000000..3f306d0
--- /dev/null
+++ b/libexec_exec.c
@@ -0,0 +1,200 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+#ifndef TEST
+
+
+static char *
+which(const char *name, char *path, char **end_colon_out)
+{
+	size_t namelen_nul, dirlen, maxlen;
+	char *p, *q, *buf;
+	int eacces_encountered = 0;
+
+	if (!path || !*path)
+		goto enoent;
+
+	maxlen = 0;
+	for (p = path; p; p = q) {
+		q = strchr(p, ':');
+		if (q)
+			dirlen = (size_t)(q++ - p);
+		else
+			dirlen = strlen(p);
+		if (dirlen > maxlen)
+			dirlen = maxlen;
+	}
+
+	namelen_nul = strlen(name) + 1;
+
+	buf = NULL;
+	if (maxlen) {
+		buf = malloc(maxlen + 1 + namelen_nul);
+		if (!buf)
+			return NULL;
+	}
+
+	for (; path; path = q) {
+		q = strchr(p, ':');
+		if (q)
+			dirlen = (size_t)(q++ - path);
+		else
+			dirlen = strlen(path);
+		p = buf;
+		if (dirlen) {
+			memcpy(p, path, dirlen);
+			p = &p[dirlen];
+			*p++ = '/';
+		}
+		memcpy(p, name, namelen_nul);
+		if (!faccessat(AT_FDCWD, buf, X_OK, AT_EACCESS)) {
+			*end_colon_out = q;
+			return buf;
+		}
+		if (errno == EACCES)
+			eacces_encountered = 1;
+	}
+
+	free(buf);
+
+	if (eacces_encountered) {
+		errno = EACCES;
+		return NULL;
+	}
+
+enoent:
+	errno = ENOENT;
+	return NULL;
+}
+
+
+static void
+exec_path(struct libexec_command *cmd)
+{
+	const char *file = cmd->executable ? cmd->executable : cmd->arguments[0];
+	execve(file, cmd->arguments, cmd->environ ? cmd->environ : environ);
+}
+
+
+static void
+exec_name(struct libexec_command *cmd)
+{
+	/* execvpe is non-standard */
+	const char *file = cmd->executable ? cmd->executable : cmd->arguments[0];
+	char *end_colon = NULL, *file_free = NULL;
+	if (!strchr(file, '/')) {
+		file = file_free = which(file, getenv("PATH"), &end_colon);
+		if (!file)
+			return;
+	}
+	execve(file, cmd->arguments, cmd->environ ? cmd->environ : environ);
+	free(file_free);
+	if (end_colon)
+		*end_colon = ':';
+}
+
+
+static void
+exec_fd(struct libexec_command *cmd)
+{
+	fexecve(cmd->exec_fd, cmd->arguments, cmd->environ ? cmd->environ : environ);
+}
+
+
+static void
+exec_at(struct libexec_command *cmd)
+{
+	const char *file = cmd->executable ? cmd->executable : cmd->arguments[0];
+	execveat(cmd->exec_fd, file, cmd->arguments, cmd->environ ? cmd->environ : environ, 0);
+}
+
+
+int
+libexec_exec(struct libexec_command *cmd)
+{
+	void (*exec_function)(struct libexec_command *cmd);
+	size_t i;
+	int fd;
+
+	if (!cmd)
+		goto einval;
+
+	if (cmd->library_version > LIBEXEC_VERSION)
+		abort();
+
+	if (!cmd->narguments)
+		goto einval;
+
+	if (cmd->exec_how == LIBEXEC_REQUIRE_PATH)
+		exec_function = &exec_path;
+	else if (cmd->exec_how == LIBEXEC_ALLOW_NAME)
+		exec_function = &exec_name;
+	else if (cmd->exec_how == LIBEXEC_EXEC_FD)
+		exec_function = &exec_fd;
+	else if (cmd->exec_how == LIBEXEC_EXEC_AT)
+		exec_function = &exec_at;
+	else
+		goto einval;
+
+	for (i = 0; i < cmd->nplumings; i++) {
+		switch (cmd->plumings[i].type) {
+		case LIBEXEC_PLUMING_CLOSE:
+			if (cmd->plumings[i].fd >= 0) {
+				close(cmd->plumings[i].fd);
+				cmd->plumings[i].fd = -1;
+			}
+			break;
+
+#if defined(__linux__)
+		case LIBEXEC_PLUMING_OPENAT2:
+			fd = (int)syscall(SYS_openat2,
+			                  cmd->plumings[i].target.dirfd, cmd->plumings[i].target.file,
+			                  cmd->plumings[i].target.how, cmd->plumings[i].target.how_size);
+			if (fd < 0)
+				return -1;
+			free(cmd->plumings[i].target.file);
+			free(cmd->plumings[i].target.how);
+			goto openned_fd;
+#endif
+
+		case LIBEXEC_PLUMING_OPENAT:
+			fd = openat(cmd->plumings[i].target.dirfd, cmd->plumings[i].target.file,
+			            cmd->plumings[i].target.flags, cmd->plumings[i].target.mode);
+			if (fd < 0)
+				return -1;
+			free(cmd->plumings[i].target.file);
+#if defined(__linux__)
+		openned_fd:
+#endif
+			cmd->plumings[i].type = LIBEXEC_PLUMING_PIPE;
+			cmd->plumings[i].target.fd = fd;
+			/* fall through */
+
+		case LIBEXEC_PLUMING_DUP2:
+		case LIBEXEC_PLUMING_PIPE:
+			if (cmd->plumings[i].fd == cmd->plumings[i].target.fd)
+				break;
+			if (dup2(cmd->plumings[i].target.fd, cmd->plumings[i].fd) == -1)
+				return -1;
+			if (cmd->plumings[i].type == LIBEXEC_PLUMING_PIPE)
+				close(cmd->plumings[i].target.fd);
+			cmd->plumings[i].target.fd = cmd->plumings[i].fd;
+			break;
+
+		default:
+		case LIBEXEC_PLUMING_DOCUMENT:
+			goto einval;
+		}
+	}
+
+	(*exec_function)(cmd);
+	return -1;
+
+einval:
+	errno = EINVAL;
+	return -1;
+}
+
+
+#else
+LIBEXEC_CONST__ int main(void) {return 0;} /* TODO test */
+#endif