[CRIU] [PATCH 2/4] prctl: kerndat -- Add kerndat_prctl_may_use_mm_map helper

[Cyrill Gorcunov]

It tests if new prctl interface is present in the kernel
and will be used on restore and check procedures.

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
---
 include/kerndat.h |  2 ++
 kerndat.c         | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/kerndat.h b/include/kerndat.h
index 6b9947fbddd0..cef33e26de48 100644
--- a/include/kerndat.h
+++ b/include/kerndat.h
@@ -24,4 +24,6 @@ extern u64 zero_page_pfn;
 struct stat;
 extern struct stat *kerndat_get_devpts_stat(void);
 
+extern int kerndat_prctl_may_use_mm_map(void);
+
 #endif /* __CR_KERNDAT_H__ */
diff --git a/kerndat.c b/kerndat.c
index 3c87f6ceb34f..a42a7ca66c9d 100644
--- a/kerndat.c
+++ b/kerndat.c
@@ -4,6 +4,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/mman.h>
+#include <sys/prctl.h>
 #include <errno.h>
 
 #include "log.h"
@@ -13,6 +14,7 @@
 #include "mem.h"
 #include "compiler.h"
 #include "sysctl.h"
+#include "prctl.h"
 #include "asm/types.h"
 #include "cr_options.h"
 #include "util.h"
@@ -220,6 +222,22 @@ int get_last_cap(void)
 	return sysctl_op(req, CTL_READ);
 }
 
+int kerndat_prctl_may_use_mm_map(void)
+{
+	static int prctl_may_use_mm_map = -1;
+
+	if (prctl_may_use_mm_map == -1) {
+		unsigned int size = 0;
+
+		if (!prctl(PR_SET_MM, PR_SET_MM_MAP_SIZE, (unsigned long)&size, 0, 0))
+			prctl_may_use_mm_map = (size <= sizeof(struct prctl_mm_map)) ? 1 : 0;
+		else
+			prctl_may_use_mm_map = 0;
+	}
+
+	return prctl_may_use_mm_map;
+}
+
 int kerndat_init(void)
 {
 	int ret;
-- 
1.9.3