[PATCH bpf-next 2/2] selftests/bpf: add selftests for bpf_arena_guard_pages

[Emil Tsalapatis <emil@etsalapatis.com>]

Add selftests for the new bpf_arena_guard_pages kfunc.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
---
 .../testing/selftests/bpf/bpf_arena_common.h  |   3 +
 .../selftests/bpf/progs/verifier_arena.c      | 106 ++++++++++++++++++
 .../bpf/progs/verifier_arena_large.c          |  93 +++++++++++++++
 3 files changed, 202 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_arena_common.h b/tools/testing/selftests/bpf/bpf_arena_common.h
index 68a51dcc0669..339de1719bc7 100644
--- a/tools/testing/selftests/bpf/bpf_arena_common.h
+++ b/tools/testing/selftests/bpf/bpf_arena_common.h
@@ -46,8 +46,11 @@
 
 void __arena* bpf_arena_alloc_pages(void *map, void __arena *addr, __u32 page_cnt,
 				    int node_id, __u64 flags) __ksym __weak;
+int bpf_arena_guard_pages(void *map, void __arena *addr, __u32 page_cnt) __ksym __weak;
 void bpf_arena_free_pages(void *map, void __arena *ptr, __u32 page_cnt) __ksym __weak;
 
+#define arena_base(map) ((void __arena *)((struct bpf_arena *)(map))->user_vm_start)
+
 #else /* when compiled as user space code */
 
 #define __arena
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c
index 67509c5d3982..af175dc89a8c 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena.c
@@ -114,6 +114,112 @@ int basic_alloc3(void *ctx)
 	return 0;
 }
 
+SEC("syscall")
+__success __retval(0)
+int basic_guard1(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
+	if (!page)
+		return 1;
+
+	page += __PAGE_SIZE;
+
+	/* Guard the second page */
+	ret = bpf_arena_guard_pages(&arena, page, 1);
+	if (ret)
+		return 2;
+
+	/* Try to explicitly allocate the guarded page. */
+	page = bpf_arena_alloc_pages(&arena, page, 1, NUMA_NO_NODE, 0);
+	if (page)
+		return 3;
+
+	/* Try to implicitly allocate the page (since there's only 2 of them). */
+	page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
+	if (page)
+		return 4;
+#endif
+	return 0;
+}
+
+SEC("syscall")
+__success __retval(0)
+int basic_guard2(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	page = arena_base(&arena);
+	ret = bpf_arena_guard_pages(&arena, page, 1);
+	if (ret)
+		return 1;
+
+	page = bpf_arena_alloc_pages(&arena, page, 1, NUMA_NO_NODE, 0);
+	if ((u64)page)
+		return 2;
+#endif
+	return 0;
+}
+
+/* Guard the same page twice, should return -EALREADY. */
+SEC("syscall")
+__success __retval(0)
+int guard_twice(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	page = arena_base(&arena);
+
+	ret = bpf_arena_guard_pages(&arena, page, 1);
+	if (ret)
+		return 1;
+
+	/* Should be -EALREADY. */
+	ret = bpf_arena_guard_pages(&arena, page, 1);
+	if (ret != -114)
+		return 2;
+#endif
+	return 0;
+}
+
+/* Try to add a guard past the end of the arena. */
+SEC("syscall")
+__success __retval(0)
+int guard_invalid_region(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	/* Try a NULL pointer. */
+	ret = bpf_arena_guard_pages(&arena, NULL, 3);
+	if (ret != -22)
+		return 1;
+
+	page = arena_base(&arena);
+
+	ret = bpf_arena_guard_pages(&arena, page, 3);
+	if (ret != -22)
+		return 2;
+
+	ret = bpf_arena_guard_pages(&arena, page, 4096);
+	if (ret != -22)
+		return 3;
+
+	ret = bpf_arena_guard_pages(&arena, page, (1ULL << 32) - 1);
+	if (ret != -22)
+		return 4;
+#endif
+	return 0;
+}
+
 SEC("iter.s/bpf_map")
 __success __log_level(2)
 int iter_maps1(struct bpf_iter__bpf_map *ctx)
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_large.c b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
index f94f30cf1bb8..cf76acd72ed1 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_large.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
@@ -67,6 +67,99 @@ int big_alloc1(void *ctx)
 	return 0;
 }
 
+/* Try to access a guarded page. Behavior should be identical with accessing unallocated pages. */
+SEC("syscall")
+__success __retval(0)
+int access_guarded(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	volatile char __arena *page;
+	char __arena *base;
+	const size_t len = 4;
+	int ret, i;
+
+	/* Get a separate region of the arena. */
+	page = base = arena_base(&arena) + 16384 * PAGE_SIZE;
+
+	ret = bpf_arena_guard_pages(&arena, base, len);
+	if (ret)
+		return 1;
+
+	/* Try to dirty guarded memory. */
+	for (i = 0; i < len && can_loop; i++)
+		*page = 0x5a;
+
+	for (i = 0; i < len && can_loop; i++) {
+		page = (volatile char __arena *)(base + i * PAGE_SIZE);
+
+		/*
+		 * Error out in case either the write went through,
+		 * or the address has random garbage.
+		 */
+		if (*page == 0x5a)
+			return 2 + 2 * i;
+
+		if (*page)
+			return 2 + 2 * i + 1;
+	}
+#endif
+	return 0;
+}
+
+/* Try to allocate a region overlapping with a guard. */
+SEC("syscall")
+__success __retval(0)
+int request_partially_guarded(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	volatile char __arena *page;
+	char __arena *base;
+	int ret;
+
+	/* Add an arbitrary page offset. */
+	page = base = arena_base(&arena) + 4096 * __PAGE_SIZE;
+
+	ret = bpf_arena_guard_pages(&arena, base + 3 * __PAGE_SIZE, 4);
+	if (ret)
+		return 1;
+
+	page = bpf_arena_alloc_pages(&arena, base, 5, NUMA_NO_NODE, 0);
+	if ((u64)page != 0ULL)
+		return 2;
+#endif
+	return 0;
+}
+
+SEC("syscall")
+__success __retval(0)
+int free_guarded(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *addr;
+	char __arena *page;
+	int ret;
+
+	/* Add an arbitrary page offset. */
+	addr = arena_base(&arena) + 32768 * __PAGE_SIZE;
+
+	page = bpf_arena_alloc_pages(&arena, addr, 4, NUMA_NO_NODE, 0);
+	if (!page)
+		return 1;
+
+	ret = bpf_arena_guard_pages(&arena, addr + 4 * __PAGE_SIZE, 4);
+	if (ret)
+		return 2;
+
+	bpf_arena_free_pages(&arena, addr + 3 * __PAGE_SIZE, 2);
+
+	/* The free pages call above should have failed, so this allocation should fail too. */
+	page = bpf_arena_alloc_pages(&arena, addr + 3 * __PAGE_SIZE, 1, NUMA_NO_NODE, 0);
+	if (page)
+		return 3;
+#endif
+	return 0;
+}
+
 #if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
 #define PAGE_CNT 100
 __u8 __arena * __arena page[PAGE_CNT]; /* occupies the first page */
-- 
2.49.0