selftests/bpf: add selftests for bpf_arena_reserve_pages

Add selftests for the new bpf_arena_reserve_pages kfunc.

Acked-by: Yonghong Song <[e-mail]>
Signed-off-by: Emil Tsalapatis <[e-mail]>
Acked-by: Kumar Kartikeya Dwivedi <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/bpf_arena_common.h

···
 
 void __arena* bpf_arena_alloc_pages(void *map, void __arena *addr, __u32 page_cnt,
 				    int node_id, __u64 flags) __ksym __weak;
+int bpf_arena_reserve_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 */
 

tools/testing/selftests/bpf/progs/verifier_arena.c

···
 
 #define BPF_NO_KFUNC_PROTOTYPES
 #include <vmlinux.h>
+#include <errno.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 #include "bpf_misc.h"
···
 	pages = bpf_arena_alloc_pages(&ar->map, NULL, ar->map.max_entries, NUMA_NO_NODE, 0);
 	if (!pages)
 		return 1;
+	return 0;
+}
+
+SEC("syscall")
+__success __retval(0)
+int basic_reserve1(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;
+
+	/* Reserve the second page */
+	ret = bpf_arena_reserve_pages(&arena, page, 1);
+	if (ret)
+		return 2;
+
+	/* Try to explicitly allocate the reserved 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_reserve2(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	page = arena_base(&arena);
+	ret = bpf_arena_reserve_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;
+}
+
+/* Reserve the same page twice, should return -EBUSY. */
+SEC("syscall")
+__success __retval(0)
+int reserve_twice(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	page = arena_base(&arena);
+
+	ret = bpf_arena_reserve_pages(&arena, page, 1);
+	if (ret)
+		return 1;
+
+	ret = bpf_arena_reserve_pages(&arena, page, 1);
+	if (ret != -EBUSY)
+		return 2;
+#endif
+	return 0;
+}
+
+/* Try to reserve past the end of the arena. */
+SEC("syscall")
+__success __retval(0)
+int reserve_invalid_region(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+	char __arena *page;
+	int ret;
+
+	/* Try a NULL pointer. */
+	ret = bpf_arena_reserve_pages(&arena, NULL, 3);
+	if (ret != -EINVAL)
+		return 1;
+
+	page = arena_base(&arena);
+
+	ret = bpf_arena_reserve_pages(&arena, page, 3);
+	if (ret != -EINVAL)
+		return 2;
+
+	ret = bpf_arena_reserve_pages(&arena, page, 4096);
+	if (ret != -EINVAL)
+		return 3;
+
+	ret = bpf_arena_reserve_pages(&arena, page, (1ULL << 32) - 1);
+	if (ret != -EINVAL)
+		return 4;
+#endif
 	return 0;
 }
 

tools/testing/selftests/bpf/progs/verifier_arena_large.c

···
 	return 0;
 }
 
+/* Try to access a reserved page. Behavior should be identical with accessing unallocated pages. */
+SEC("syscall")
+__success __retval(0)
+int access_reserved(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_reserve_pages(&arena, base, len);
+	if (ret)
+		return 1;
+
+	/* Try to dirty reserved 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 reservation. */
+SEC("syscall")
+__success __retval(0)
+int request_partially_reserved(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_reserve_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_reserved(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, 2, NUMA_NO_NODE, 0);
+	if (!page)
+		return 1;
+
+	ret = bpf_arena_reserve_pages(&arena, addr + 2 * __PAGE_SIZE, 2);
+	if (ret)
+		return 2;
+
+	/*
+	 * Reserved and allocated pages should be interchangeable for
+	 * bpf_arena_free_pages(). Free a reserved and an allocated
+	 * page with a single call.
+	 */
+	bpf_arena_free_pages(&arena, addr + __PAGE_SIZE , 2);
+
+	/* The free call above should have succeeded, so this allocation should too. */
+	page = bpf_arena_alloc_pages(&arena, addr + __PAGE_SIZE, 2, 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 */