raw_syscalls: add lxc_raw_execveat()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/Makefile.am b/src/lxc/Makefile.am
index b48c7d7c931368a39383a6003ee592011f9e9e9e..1fdd91cfcf0f25febab0c408631248a075c823ce 100644 (file)
--- a/src/lxc/Makefile.am
+++ b/src/lxc/Makefile.am
@@ -23,6 +23,7 @@ noinst_HEADERS = api_extensions.h \
                 macro.h \
                 monitor.h \
                 namespace.h \
+                raw_syscalls.h \
                 start.h \
                 state.h \
                 storage/btrfs.h \
@@ -116,6 +117,7 @@ liblxc_la_SOURCES = af_unix.c af_unix.h \
                    network.c network.h \
                    monitor.c monitor.h \
                    parse.c parse.h \
+                   raw_syscalls.c raw_syscalls.h \
                    ringbuf.c ringbuf.h \
                    rtnl.c rtnl.h \
                    state.c state.h \

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 01c1e3f5d2d15a537e4563f6c867140988e0ab6f..c450cfcbee15bc884abb1e98418636f5de8d6bb9 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -70,6 +70,7 @@
 #include "namespace.h"
 #include "network.h"
 #include "parse.h"
+#include "raw_syscalls.h"
 #include "ringbuf.h"
 #include "start.h"
 #include "storage.h"
@@ -3535,21 +3536,11 @@ static bool verify_start_hooks(struct lxc_conf *conf)
 
 static bool execveat_supported(void)
 {
-#ifdef __NR_execveat
-       /*
-        * We use the syscall here, because it was introduced in kernel 3.19,
-        * while glibc got support for using the syscall much later, in 2.27.
-        * We don't want to use glibc because it falls back to /proc, and the
-        * container may not have /proc mounted depending on its configuration.
-        */
-       syscall(__NR_execveat, -1, "", NULL, NULL, AT_EMPTY_PATH);
+       lxc_raw_execveat(-1, "", NULL, NULL, AT_EMPTY_PATH);
        if (errno == ENOSYS)
                return false;
 
        return true;
-#else
-       return false;
-#endif
 }
 
 int lxc_setup(struct lxc_handler *handler)

diff --git a/src/lxc/execute.c b/src/lxc/execute.c
index cdf5bc848f7896439ef427682b6a81ca91a90330..b6e11ef68419ca83f3272df8da8ba67cc479f2c4 100644 (file)
--- a/src/lxc/execute.c
+++ b/src/lxc/execute.c
@@ -35,6 +35,7 @@
 #include "config.h"
 #include "log.h"
 #include "start.h"
+#include "raw_syscalls.h"
 #include "utils.h"
 
 lxc_log_define(execute, start);
@@ -122,11 +123,7 @@ static int execute_start(struct lxc_handler *handler, void* data)
        NOTICE("Exec'ing \"%s\"", my_args->argv[0]);
 
        if (my_args->init_fd >= 0)
-#ifdef __NR_execveat
-               syscall(__NR_execveat, my_args->init_fd, "", argv, environ, AT_EMPTY_PATH);
-#else
-               ERROR("System seems to be missing execveat syscall number");
-#endif
+               lxc_raw_execveat(my_args->init_fd, "", argv, environ, AT_EMPTY_PATH);
        else
                execvp(argv[0], argv);
        SYSERROR("Failed to exec %s", argv[0]);

diff --git a/src/lxc/raw_syscalls.c b/src/lxc/raw_syscalls.c
new file mode 100644 (file)
index 0000000..5ce23ea
--- /dev/null
+++ b/src/lxc/raw_syscalls.c
@@ -0,0 +1,21 @@
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#endif
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "config.h"
+
+int lxc_raw_execveat(int dirfd, const char *pathname, char *const argv[],
+                    char *const envp[], int flags)
+{
+#ifdef __NR_execveat
+       syscall(__NR_execveat, dirfd, pathname, argv, envp, flags);
+#else
+       errno = ENOSYS;
+       return -1;
+#endif
+}

diff --git a/src/lxc/raw_syscalls.h b/src/lxc/raw_syscalls.h
new file mode 100644 (file)
index 0000000..af953c2
--- /dev/null
+++ b/src/lxc/raw_syscalls.h
@@ -0,0 +1,32 @@
+/* liblxcapi
+ *
+ * Copyright © 2018 Christian Brauner <christian.brauner@ubuntu.com>.
+ * Copyright © 2018 Canonical Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef __LXC_RAW_SYSCALL_H
+#define __LXC_RAW_SYSCALL_H
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+
+extern int lxc_raw_execveat(int dirfd, const char *pathname, char *const argv[],
+                           char *const envp[], int flags);
+
+#endif /* __LXC_RAW_SYSCALL_H */