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[Xen-devel] [PATCH v2 2/2] libxl: fix build (missing CLONE_NEWIPC) on astonishingly old systems

CLONE_NEWIPC was introduced in Linux 2.6.19, on the 29th of November
2006, which was 12 years, 1 month, and 14 days ago.

Nevertheless apparently some people are trying to build Xen on systems
whose kernel headers are that old.  Placate these people by providing
a fallback #define for CLONE_NEWIPC.

The actual binary value will of course remain constant, because of the
kernel API promise, so this is and will be correct on all platforms
where the CLONE_NEWIPC is supported.  (Even if for some reason we miss
the right #includes.)

Of course at runtime this value will not work on older kernels.  It
will be rejected as unknown.  However on those kernels we do not want
to support dm_restrict, and an attempt to use it will fail.  It is OK
for the failure to be a messy EINVAL syscall failure.  (The IPC
namespace unshare is necessary to avoid a suborned deprivileged qemu
from causing trouble with shm, sem, etc.)

CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Juergen Gross <jgross@xxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

v2: Get rid of spurious X
 tools/libxl/libxl_linux.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/libxl/libxl_linux.c b/tools/libxl/libxl_linux.c
index 6475cca64b..59dd945bc1 100644
--- a/tools/libxl/libxl_linux.c
+++ b/tools/libxl/libxl_linux.c
@@ -18,6 +18,14 @@
 #include <sys/resource.h>
 #include "libxl_internal.h"
+/* Workarounds for Linux-specific lacks can go here: */
+#ifndef CLONE_NEWIPC /* Available as of Linux 2.6.19 / glibc 2.8 */
+# define CLONE_NEWIPC 0x08000000
 int libxl__try_phy_backend(mode_t st_mode)
     if (S_ISBLK(st_mode) || S_ISREG(st_mode)) {

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