move seccomp from /proc to a prctl

This reduces the memory footprint and it enforces that only the current
task can enable seccomp on itself (this is a requirement for a
strightforward [modulo preempt ;) ] TIF_NOTSC implementation).

Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 17 insertions, 2 deletions

diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 52a9be41250d..e2eff9079fe9 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -59,4 +59,8 @@
 # define PR_ENDIAN_LITTLE       1       /* True little endian mode */
 # define PR_ENDIAN_PPC_LITTLE   2       /* "PowerPC" pseudo little endian */
 
+/* Get/set process seccomp mode */
+#define PR_GET_SECCOMP  21
+#define PR_SET_SECCOMP  22
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 3e8b1cf54303..d708974dbfe3 100644
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -4,8 +4,6 @@
 
 #ifdef CONFIG_SECCOMP
 
-#define NR_SECCOMP_MODES 1
-
 #include <linux/thread_info.h>
 #include <asm/seccomp.h>
 
@@ -23,6 +21,9 @@ static inline int has_secure_computing(struct thread_info *ti)
         return unlikely(test_ti_thread_flag(ti, TIF_SECCOMP));
 }
 
+extern long prctl_get_seccomp(void);
+extern long prctl_set_seccomp(unsigned long);
+
 #else /* CONFIG_SECCOMP */
 
 typedef struct { } seccomp_t;
@@ -34,6 +35,16 @@ static inline int has_secure_computing(struct thread_info *ti)
         return 0;
 }
 
+static inline long prctl_get_seccomp(void)
+{
+        return -EINVAL;
+}
+
+static inline long prctl_set_seccomp(unsigned long arg2)
+{
+        return -EINVAL;
+}
+
 #endif /* CONFIG_SECCOMP */
 
 #endif /* _LINUX_SECCOMP_H */