Subject: [PATCH v9 49/51] selftest/vm: sub-page allocator

From: Ram Pai <[email-masked]>
Date: Mon, 6 Nov 2017 00:57:41 -0800

introduce a new allocator that allocates 4k hardware-pages to back
64k linux-page. This allocator is only applicable on powerpc.

Signed-off-by: Ram Pai <[email-masked]>
---
 tools/testing/selftests/vm/protection_keys.c |   30 ++++++++++++++++++++++++++
 1 files changed, 30 insertions(+), 0 deletions(-)

diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
index c790bff..7b3649f 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c
@@ -765,6 +765,35 @@ void free_pkey_malloc(void *ptr)
 	return ptr;
 }
 
+void *malloc_pkey_with_mprotect_subpage(long size, int prot, u16 pkey)
+{
+#ifdef __powerpc64__
+	void *ptr;
+	int ret;
+
+	dprintf1("doing %s(size=%ld, prot=0x%x, pkey=%d)\n", __func__,
+			size, prot, pkey);
+	pkey_assert(pkey < NR_PKEYS);
+	ptr = mmap(NULL, size, prot, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+	pkey_assert(ptr != (void *)-1);
+
+	ret = syscall(__NR_subpage_prot, ptr, size, NULL);
+	if (ret) {
+		perror("subpage_perm");
+		return PTR_ERR_ENOTSUP;
+	}
+
+	ret = mprotect_pkey((void *)ptr, PAGE_SIZE, prot, pkey);
+	pkey_assert(!ret);
+	record_pkey_malloc(ptr, size);
+
+	dprintf1("%s() for pkey %d @ %p\n", __func__, pkey, ptr);
+	return ptr;
+#else /*  __powerpc64__ */
+	return PTR_ERR_ENOTSUP;
+#endif /*  __powerpc64__ */
+}
+
 void *malloc_pkey_anon_huge(long size, int prot, u16 pkey)
 {
 	int ret;
@@ -887,6 +916,7 @@ void setup_hugetlbfs(void)
 void *(*pkey_malloc[])(long size, int prot, u16 pkey) = {
 
 	malloc_pkey_with_mprotect,
+	malloc_pkey_with_mprotect_subpage,
 	malloc_pkey_anon_huge,
 	malloc_pkey_hugetlb
 /* can not do direct with the pkey_mprotect() API:
-- 
1.7.1