Re: [PATCH v4 19/20] tools/testing/vma: add test to assert MAP_PRIVATE-/dev/zero is anon

Now we've made MAP_PRIVATE-mapped /dev/zero mappings truly anonymous, add a
VMA userland test to assert that this is the case and everything is as
we would expect for an anonymous mapping.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
 tools/testing/vma/include/dup.h |  1 +
 tools/testing/vma/tests/mmap.c  | 50 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index aee36707abdd..41203b1c2323 100644
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h

@@ -20,6 +20,7 @@ struct task_struct *get_current(void);
 
 #define MAJOR(dev)	((unsigned int) ((dev) >> MINORBITS))
 #define MINOR(dev)	((unsigned int) ((dev) & MINORMASK))
+#define MKDEV(ma, mi)	(((ma) << MINORBITS) | (mi))
 
 #define S_IFMT  00170000
 #define S_IFCHR  0020000

diff --git a/tools/testing/vma/tests/mmap.c b/tools/testing/vma/tests/mmap.c
index c85bc000d1cb..ebe01362e530 100644
--- a/tools/testing/vma/tests/mmap.c
+++ b/tools/testing/vma/tests/mmap.c

@@ -45,7 +45,57 @@ static bool test_mmap_region_basic(void)
 	return true;
 }
 
+static int dummy_mmap_prepare(struct vm_area_desc *desc)
+{
+	return 0;
+}
+
+static bool test_pure_anon_dev_zero(void)
+{