x86, bts: memory accounting

Impact: move the BTS buffer accounting to the mlock bucket

Add alloc_locked_buffer() and free_locked_buffer() functions to mm/mlock.c
to kalloc a buffer and account the locked memory to current.

Account the memory for the BTS buffer to the tracer.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

mm/mlock.c

@@ -667,3 +667,48 @@ void user_shm_unlock(size_t size, struct user_struct *user)
 	spin_unlock(&shmlock_user_lock);
 	free_uid(user);
 }
+
+void *alloc_locked_buffer(size_t size)
+{
+	unsigned long rlim, vm, pgsz;
+	void *buffer = NULL;
+
+	pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+	down_write(&current->mm->mmap_sem);
+
+	rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
+	vm   = current->mm->total_vm + pgsz;
+	if (rlim < vm)
+		goto out;
+
+	rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
+	vm   = current->mm->locked_vm + pgsz;
+	if (rlim < vm)
+		goto out;
+
+	buffer = kzalloc(size, GFP_KERNEL);
+	if (!buffer)
+		goto out;
+
+	current->mm->total_vm  += pgsz;
+	current->mm->locked_vm += pgsz;
+
+ out:
+	up_write(&current->mm->mmap_sem);
+	return buffer;
+}
+
+void free_locked_buffer(void *buffer, size_t size)
+{
+	unsigned long pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+	down_write(&current->mm->mmap_sem);
+
+	current->mm->total_vm  -= pgsz;
+	current->mm->locked_vm -= pgsz;
+
+	up_write(&current->mm->mmap_sem);
+
+	kfree(buffer);
+}