selftests/bpf: Add tests for the arena offset of globals

Add tests for the new libbpf globals arena offset logic. The
tests cover the case of globals being as large as the arena
itself, and being smaller than the arena. In that case, the
data is placed at the end of the arena, and the beginning
of the arena is free.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251216173325.98465-6-emil@etsalapatis.com

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 4b4b081b46ccc8ccf1498d4940c0f4a7da41346e..5829ffd70f8f2a5c8d798c0aead7307700ee60aa 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -6,6 +6,8 @@
 #include "verifier_and.skel.h"
 #include "verifier_arena.skel.h"
 #include "verifier_arena_large.skel.h"
+#include "verifier_arena_globals1.skel.h"
+#include "verifier_arena_globals2.skel.h"
 #include "verifier_array_access.skel.h"
 #include "verifier_async_cb_context.skel.h"
 #include "verifier_basic_stack.skel.h"
@@ -147,6 +149,8 @@ static void run_tests_aux(const char *skel_name,
 void test_verifier_and(void)                  { RUN(verifier_and); }
 void test_verifier_arena(void)                { RUN(verifier_arena); }
 void test_verifier_arena_large(void)          { RUN(verifier_arena_large); }
+void test_verifier_arena_globals1(void)       { RUN(verifier_arena_globals1); }
+void test_verifier_arena_globals2(void)       { RUN(verifier_arena_globals2); }
 void test_verifier_basic_stack(void)          { RUN(verifier_basic_stack); }
 void test_verifier_bitfield_write(void)       { RUN(verifier_bitfield_write); }
 void test_verifier_bounds(void)               { RUN(verifier_bounds); }

diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c b/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c
new file mode 100644 (file)
index 0000000..14afef3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+
+#define BPF_NO_KFUNC_PROTOTYPES
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_experimental.h"
+#include "bpf_arena_common.h"
+#include "bpf_misc.h"
+
+#define ARENA_PAGES (1UL<< (32 - 12))
+#define GLOBAL_PAGES (16)
+
+struct {
+       __uint(type, BPF_MAP_TYPE_ARENA);
+       __uint(map_flags, BPF_F_MMAPABLE);
+       __uint(max_entries, ARENA_PAGES);
+#ifdef __TARGET_ARCH_arm64
+       __ulong(map_extra, (1ull << 32) | (~0u - __PAGE_SIZE * ARENA_PAGES + 1));
+#else
+       __ulong(map_extra, (1ull << 44) | (~0u - __PAGE_SIZE * ARENA_PAGES + 1));
+#endif
+} arena SEC(".maps");
+
+/*
+ * Global data, to be placed at the end of the arena.
+ */
+volatile char __arena global_data[GLOBAL_PAGES][PAGE_SIZE];
+
+SEC("syscall")
+__success __retval(0)
+int check_reserve1(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+       const u8 magic = 0x5a;
+       __u8 __arena *guard, *globals;
+       volatile char __arena *ptr;
+       int i;
+       int ret;
+
+       guard = (void __arena *)arena_base(&arena);
+       globals = (void __arena *)(arena_base(&arena) + (ARENA_PAGES - GLOBAL_PAGES) * PAGE_SIZE);
+
+       /* Reserve the region we've offset the globals by. */
+       ret = bpf_arena_reserve_pages(&arena, guard, ARENA_PAGES - GLOBAL_PAGES);
+       if (ret)
+               return 1;
+
+       /* Make sure the globals are in the expected offset. */
+       ret = bpf_arena_reserve_pages(&arena, globals, 1);
+       if (!ret)
+               return 2;
+
+       /* Verify globals are properly mapped in by libbpf. */
+       for (i = 0; i < GLOBAL_PAGES; i++) {
+               ptr = &global_data[i][PAGE_SIZE / 2];
+
+               *ptr = magic;
+               if (*ptr != magic)
+                       return i + 3;
+       }
+#endif
+       return 0;
+}
+
+/*
+ * Relocation check by reading directly into the global data w/o using symbols.
+ */
+SEC("syscall")
+__success __retval(0)
+int check_relocation(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+       const u8 magic = 0xfa;
+       u8 __arena *ptr;
+
+       global_data[GLOBAL_PAGES - 1][PAGE_SIZE / 2] = magic;
+       ptr = (u8 __arena *)((u64)(ARENA_PAGES * PAGE_SIZE - PAGE_SIZE / 2));
+       if (*ptr != magic)
+               return 1;
+
+#endif
+       return 0;
+}
+
+char _license[] SEC("license") = "GPL";

diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c b/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c
new file mode 100644 (file)
index 0000000..e6bd7b6
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
+
+#define BPF_NO_KFUNC_PROTOTYPES
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include "bpf_misc.h"
+#include "bpf_experimental.h"
+#include "bpf_arena_common.h"
+
+#define ARENA_PAGES (32)
+
+struct {
+       __uint(type, BPF_MAP_TYPE_ARENA);
+       __uint(map_flags, BPF_F_MMAPABLE);
+       __uint(max_entries, ARENA_PAGES);
+#ifdef __TARGET_ARCH_arm64
+       __ulong(map_extra, (1ull << 32) | (~0u - __PAGE_SIZE * ARENA_PAGES + 1));
+#else
+       __ulong(map_extra, (1ull << 44) | (~0u - __PAGE_SIZE * ARENA_PAGES + 1));
+#endif
+} arena SEC(".maps");
+
+/*
+ * Fill the entire arena with global data.
+ * The offset into the arena should be 0.
+ */
+char __arena global_data[ARENA_PAGES][PAGE_SIZE];
+
+SEC("syscall")
+__success __retval(0)
+int check_reserve2(void *ctx)
+{
+#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
+       void __arena *guard;
+       int ret;
+
+       guard = (void __arena *)arena_base(&arena);
+
+       /* Make sure the data at offset 0 case is properly handled. */
+       ret = bpf_arena_reserve_pages(&arena, guard, 1);
+       if (!ret)
+               return 1;
+#endif
+       return 0;
+}
+
+char _license[] SEC("license") = "GPL";