[PATCH v4 2/2] selftest/vm: add helpers to detect PAGE_SIZE and PAGE_SHIFT

["Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>]

From: Mike Rapoport <rppt@xxxxxxxxxx>

PAGE_SIZE is not 4096 in many configurations, particularly ppc64 uses
64K pages in majority of cases.

Add helpers to detect PAGE_SIZE and PAGE_SHIFT dynamically.

Without this tests are broken w.r.t reading /proc/self/pagemap

    if (pread(pagemap_fd, ent, sizeof(ent),
              (uintptr_t)ptr >> (PAGE_SHIFT - 3)) != sizeof(ent))
              err(2, "read pagemap");

Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: linux-kselftest@xxxxxxxxxxxxxxx
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
 tools/testing/selftests/vm/gup_test.c |  3 ++-
 tools/testing/selftests/vm/util.h     | 27 ++++++++++++++++++++++++---
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/vm/gup_test.c b/tools/testing/selftests/vm/gup_test.c
index fe043f67798b..cda837a14736 100644
--- a/tools/testing/selftests/vm/gup_test.c
+++ b/tools/testing/selftests/vm/gup_test.c
@@ -10,8 +10,9 @@
 #include <assert.h>
 #include "../../../../mm/gup_test.h"
 
+#include "util.h"
+
 #define MB (1UL << 20)
-#define PAGE_SIZE sysconf(_SC_PAGESIZE)
 
 /* Just the flags we need, copied from mm.h: */
 #define FOLL_WRITE	0x01	/* check pte is writable */
diff --git a/tools/testing/selftests/vm/util.h b/tools/testing/selftests/vm/util.h
index 0f0a0f345d76..b27d26199334 100644
--- a/tools/testing/selftests/vm/util.h
+++ b/tools/testing/selftests/vm/util.h
@@ -6,11 +6,32 @@
 #include <stdint.h>
 #include <sys/mman.h>
 #include <err.h>
+#include <string.h> /* ffsl() */
+#include <unistd.h> /* _SC_PAGESIZE */
 
-#define PAGE_SHIFT	12
-#define HPAGE_SHIFT	21
+static unsigned int __page_size;
+static unsigned int __page_shift;
 
-#define PAGE_SIZE (1 << PAGE_SHIFT)
+static inline unsigned int page_size(void)
+{
+	if (!__page_size)
+		__page_size = sysconf(_SC_PAGESIZE);
+	return __page_size;
+}
+
+static inline unsigned int page_shift(void)
+{
+	if (!__page_shift)
+		__page_shift = (ffsl(page_size()) - 1);
+	return __page_shift;
+}
+
+#define PAGE_SHIFT	(page_shift())
+#define PAGE_SIZE	(page_size())
+/*
+ * On ppc64 this will only work with radix 2M hugepage size
+ */
+#define HPAGE_SHIFT 21
 #define HPAGE_SIZE (1 << HPAGE_SHIFT)
 
 #define PAGEMAP_PRESENT(ent)	(((ent) & (1ull << 63)) != 0)
-- 
2.35.1