Thanks!
In general,
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Two nits below, after staring at some other prctl implementations.
+#define PR_SET_MEMORY_MERGE 67
+#define PR_GET_MEMORY_MERGE 68
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 495cd87d9bf4..8c2e50edeb18 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -15,6 +15,7 @@
#include <linux/highuid.h>
#include <linux/fs.h>
#include <linux/kmod.h>
+#include <linux/ksm.h>
#include <linux/perf_event.h>
#include <linux/resource.h>
#include <linux/kernel.h>
@@ -2661,6 +2662,30 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_SET_VMA:
error = prctl_set_vma(arg2, arg3, arg4, arg5);
break;
+#ifdef CONFIG_KSM
+ case PR_SET_MEMORY_MERGE:
Looking at some other code (PR_SET_NO_NEW_PRIVS/ PR_SET_THP_DISABLE) I
wonder if we also want
if (arg3 || arg4 || arg5)
return -EINVAL;
For PR_GET_MEMORY_MERGE it looks good already.
+ if (mmap_write_lock_killable(me->mm))
+ return -EINTR;
+
+ if (arg2) {
+ error = ksm_enable_merge_any(me->mm);
+ } else {
+ /*
+ * TODO: we might want disable KSM on all VMAs and
+ * trigger unsharing to completely disable KSM.
+ */
+ clear_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
+ error = 0;
+ }
+ mmap_write_unlock(me->mm);
+ break;
+ case PR_GET_MEMORY_MERGE:
+ if (arg2 || arg3 || arg4 || arg5)
+ return -EINVAL;
+
+ error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
+ break;
+#endif
default:
error = -EINVAL;
break;
[...]
+/**
+ * ksm_enable_merge_any - Add mm to mm ksm list and enable merging on all
+ * compatible VMA's
+ *
+ * @mm: Pointer to mm
+ *
+ * Returns 0 on success, otherwise error code
+ */
+int ksm_enable_merge_any(struct mm_struct *mm)
+{
+ int err;
+
+ if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+ return -EINVAL;
I'm curious, why is enabling the prctl() supposed to fail if already
enabled? (it would not fail if disabling and already disabled)
For example, PR_SET_THP_DISABLE/PR_SET_NO_NEW_PRIVS doesn't fail if
already set.
--
Thanks,
David / dhildenb
