[PATCH RFC v2 4/4] selftests/mm: Create MAP_BELOW_HINT test

[Charlie Jenkins <charlie@rivosinc.com>]

Add a selftest for MAP_BELOW_HINT that maps until it runs out of space
below the hint address.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
---
 tools/testing/selftests/mm/Makefile         |  1 +
 tools/testing/selftests/mm/map_below_hint.c | 32 +++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index cfad627e8d94..4e2de85267b5 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -50,6 +50,7 @@ TEST_GEN_FILES += hugepage-shm
 TEST_GEN_FILES += hugepage-vmemmap
 TEST_GEN_FILES += khugepaged
 TEST_GEN_FILES += madv_populate
+TEST_GEN_FILES += map_below_hint
 TEST_GEN_FILES += map_fixed_noreplace
 TEST_GEN_FILES += map_hugetlb
 TEST_GEN_FILES += map_populate
diff --git a/tools/testing/selftests/mm/map_below_hint.c b/tools/testing/selftests/mm/map_below_hint.c
new file mode 100644
index 000000000000..55d6cbf90645
--- /dev/null
+++ b/tools/testing/selftests/mm/map_below_hint.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test the MAP_BELOW_HINT mmap flag.
+ */
+#include <sys/mman.h>
+#include <errno.h>
+#include "../kselftest.h"
+
+#define ADDR (1 << 20)
+#define LENGTH (ADDR / 10000)
+
+#define MAP_BELOW_HINT	  0x8000000	/* Not defined in all libc */
+
+/*
+ * Map memory with MAP_BELOW_HINT until no memory left. Ensure that all returned
+ * addresses are below the hint.
+ */
+int main(int argc, char **argv)
+{
+	void *addr;
+
+	do {
+		addr = mmap((void *)ADDR, LENGTH, PROT_READ | PROT_WRITE,
+			    MAP_PRIVATE | MAP_ANONYMOUS | MAP_BELOW_HINT, -1, 0);
+	} while (addr != MAP_FAILED && (unsigned long)addr <= ADDR);
+
+	if (errno == ENOMEM)
+		ksft_test_result_pass("MAP_BELOW_HINT works\n");
+	else
+		ksft_test_result_fail("mmap returned address above hint with MAP_BELOW_HINT with error: %s\n",
+				      strerror(errno));
+}

-- 
2.45.0