On 7/8/25 6:57 PM, Emil Tsalapatis wrote:
Add selftests for the new bpf_arena_reserve_pages kfunc.
Signed-off-by: Emil Tsalapatis <emil@xxxxxxxxxxxxxxx>
LGTM with some nits below.
Acked-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
.../testing/selftests/bpf/bpf_arena_common.h | 3 +
.../selftests/bpf/progs/verifier_arena.c | 106 ++++++++++++++++++
.../bpf/progs/verifier_arena_large.c | 95 ++++++++++++++++
3 files changed, 204 insertions(+)
diff --git a/tools/testing/selftests/bpf/bpf_arena_common.h b/tools/testing/selftests/bpf/bpf_arena_common.h
index 68a51dcc0669..16f8ce832004 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_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 */
#define __arena
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c
index 67509c5d3982..35248b3327aa 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_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;
+
+ /* Should be -EBUSY. */
+ ret = bpf_arena_reserve_pages(&arena, page, 1);
+ if (ret != -16)
+ return 2;
Maybe do the following is better:
#define EBUSY 16
...
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 != -22)
+ return 1;
Same here.
#define EINVAL 22
...
if (ret != -EINVAL)
return 1;
and a few cases below.
+
+ page = arena_base(&arena);
+
+ ret = bpf_arena_reserve_pages(&arena, page, 3);
+ if (ret != -22)
+ return 2;
+
+ ret = bpf_arena_reserve_pages(&arena, page, 4096);
+ if (ret != -22)
+ return 3;
+
+ ret = bpf_arena_reserve_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..9eee51912280 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_large.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
@@ -67,6 +67,101 @@ int big_alloc1(void *ctx)
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, 4, NUMA_NO_NODE, 0);
+ if (!page)
+ return 1;
+
+ ret = bpf_arena_reserve_pages(&arena, addr + 4 * __PAGE_SIZE, 4);
+ if (ret)
+ return 2;
+
[...]
+ /* Freeing a reserved area, fully or partially, should succeed. */
You are not freeing a reserved area below. Actually you freeing an allocated area.
Maybe you need to add addr argument with 4 * __PAGE_SIZE?
+ bpf_arena_free_pages(&arena, addr, 2);
+ bpf_arena_free_pages(&arena, addr + 2 * __PAGE_SIZE, 2);
+
+ /* The free pages call above should have succeeded, so this allocation should 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 */
