Workaround missing functions in other libc

Some libc implementation (bionic) is lacking some of the syscall functions
that are present in the glibc.

For those, detect at build time the they are missing and implement a minimal
syscall() wrapper that will essentially give the same result as the glibc
function.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

diff --git a/configure.ac b/configure.ac
index 51a7749bd9eb1e5b7d7e13511f88aef64577e390..d6ecc909b46cb180f1e9cb303e6d11466d678b14 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -223,6 +223,9 @@ AC_CHECK_DECLS([PR_CAPBSET_DROP], [], [], [#include <sys/prctl.h>])
 # Check for some headers
 AC_CHECK_HEADERS([sys/signalfd.h pty.h sys/capability.h sys/personality.h])
 
+# Check for some syscalls functions
+AC_CHECK_FUNCS([setns pivot_root sethostname unshare])
+
 # Check for some functions
 AC_CHECK_FUNCS([openpty])
 AC_CHECK_FUNCS([getline],

diff --git a/src/lxc/attach.c b/src/lxc/attach.c
index 9b7efbc0b7f4bb798e530af4ef3a60bd6c65a428..b86d2f46a0e5b225456b79cea376459c8d0a2133 100644 (file)
--- a/src/lxc/attach.c
+++ b/src/lxc/attach.c
@@ -47,15 +47,31 @@
 
 lxc_log_define(lxc_attach, lxc);
 
-int setns(int fd, int nstype)
+/* Define setns() if missing from the C library */
+#ifndef HAVE_SETNS
+static int setns(int fd, int nstype)
 {
-#ifndef __NR_setns
-       errno = ENOSYS;
-       return -1;
+#ifdef __NR_setns
+return syscall(__NR_setns, fd, nstype);
 #else
-       return syscall(__NR_setns, fd, nstype);
+errno = ENOSYS;
+return -1;
 #endif
 }
+#endif
+
+/* Define unshare() if missing from the C library */
+#ifndef HAVE_UNSHARE
+static int unshare(int flags)
+{
+#ifdef __NR_unshare
+return syscall(__NR_unshare, flags);
+#else
+errno = ENOSYS;
+return -1;
+#endif
+}
+#endif
 
 /* Define getline() if missing from the C library */
 #ifndef HAVE_GETLINE

diff --git a/src/lxc/conf.c b/src/lxc/conf.c
index 673048d7f3863afd9796839a8b920f9a7a76d77d..7428b0a355efec26a261be3cbcc347be8cab9511 100644 (file)
--- a/src/lxc/conf.c
+++ b/src/lxc/conf.c
@@ -31,6 +31,7 @@
 #include <mntent.h>
 #include <unistd.h>
 #include <sys/wait.h>
+#include <sys/syscall.h>
 
 #if HAVE_PTY_H
 #include <pty.h>
@@ -132,11 +133,37 @@ lxc_log_define(lxc_conf, lxc);
 #define LO_FLAGS_AUTOCLEAR 4
 #endif
 
+/* Define pivot_root() if missing from the C library */
+#ifndef HAVE_PIVOT_ROOT
+static int pivot_root(const char * new_root, const char * put_old)
+{
+#ifdef __NR_pivot_root
+return syscall(__NR_pivot_root, new_root, put_old);
+#else
+errno = ENOSYS;
+return -1;
+#endif
+}
+#else
+extern int pivot_root(const char * new_root, const char * put_old);
+#endif
+
+/* Define sethostname() if missing from the C library */
+#ifndef HAVE_SETHOSTNAME
+static int sethostname(const char * name, size_t len)
+{
+#ifdef __NR_sethostname
+return syscall(__NR_sethostname, name, len);
+#else
+errno = ENOSYS;
+return -1;
+#endif
+}
+#endif
+
 char *lxchook_names[NUM_LXC_HOOKS] = {
        "pre-start", "pre-mount", "mount", "start", "post-stop" };
 
-extern int pivot_root(const char * new_root, const char * put_old);
-
 typedef int (*instanciate_cb)(struct lxc_handler *, struct lxc_netdev *);
 
 struct mount_opt {