David Hildenbrand david@redhat.com writes:

Thanks!

In general,

Acked-by: David Hildenbrand david@redhat.com

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;

I added the above check. It requires that we always specify all parameters in the test programs. I also changed them accordingly.

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)

I changed that to not return an error in that case.

For example, PR_SET_THP_DISABLE/PR_SET_NO_NEW_PRIVS doesn't fail if already set.