[PATCH bpf-next v1 5/7] selftests/bpf: don't report arena tests as passing with an empty body
From: Vineet Gupta
Date: Tue Oct 27 2026 - 20:07:11 EST
Some arena tests put the __BPF_FEATURE_ADDR_SPACE_CAST guard inside the
function rather than around it, so without arena support the program
still exists, its body is empty, and __success __retval(0) is met by
doing nothing. A reader sees
#584/1 verifier_arena/basic_alloc1_nosleep:OK
and concludes arena works. That is worse than the tests which vanish
entirely, since nothing hints anything is missing.
The guard was never needed to compile those bodies: without the
feature __arena is still btf_type_tag("arena"), which every compiler
accepts. What it avoided was the load failure that follows from no
addr_space_cast being emitted — but only for a body that dereferences
an arena pointer. The arena kfuncs take one as a plain scalar:
static const struct bpf_reg_types arena_types = {
.types = { PTR_TO_ARENA, SCALAR_VALUE }
so a test that only passes pointers to bpf_arena_{alloc,free,reserve}_pages()
needs no cast and runs fine.
test_loader checks skip_reason before it opens anything, so the body no
longer has to be empty to stay loadable: drop all 19 in-body guards.
They do not all need a tag in their place, which is why 19 guards go
and 7 tags arrive:
6 dereference, so they get __skip_without_arena and report SKIP:
basic_alloc1{,_nosleep}, basic_alloc2{,_nosleep}, big_alloc1,
access_reserved
11 never dereference, so they get no tag and run for real instead
of reporting a vacuous OK
2 big_alloc3 and big_alloc4, already inside the file's outer
whole-program guard, so the in-body one was redundant
The 7th tag goes on check_arena_arg_ret(), which has no guard at all
and is the one verifier_arena subtest that really fails under a stock
GCC.
Measured on bpf-next with a stock bpf-gcc, test_progs before and after:
verifier_arena/basic_alloc1 OK -> SKIP
verifier_arena/basic_alloc1_nosleep OK -> SKIP
verifier_arena/basic_alloc2 OK -> SKIP
verifier_arena/basic_alloc2_nosleep OK -> SKIP
verifier_arena_large/big_alloc1 OK -> SKIP
verifier_arena_large/access_reserved OK -> SKIP
verifier_arena/check_arena_arg_ret FAIL -> SKIP
the six that dereference stop claiming to pass, and check_arena_arg_ret
stops failing. The eleven that do not dereference stay OK, having gone
from an empty body to actually running.
Removing the guards exposes the arena_base() calls they were hiding.
The previous patch made that macro opaque to GCC's -Warray-bounds, so
nothing is needed here beyond the guards going away.
Signed-off-by: Vineet Gupta <vineet.gupta@xxxxxxxxx>
---
.../selftests/bpf/progs/verifier_arena.c | 31 +++----------------
.../bpf/progs/verifier_arena_large.c | 16 ++--------
2 files changed, 7 insertions(+), 40 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c
index 3b3410802825..21b66d51c61e 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena.c
@@ -27,9 +27,9 @@ struct {
SEC("socket")
__success __retval(0)
+__skip_without_arena
int basic_alloc1_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile int __arena *page1, *page2, *no_page;
page1 = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
@@ -52,15 +52,14 @@ int basic_alloc1_nosleep(void *ctx)
return 6;
if (*page2 != 0 && *page2 != 2) /* use-after-free should return 0 or the stored value */
return 7;
-#endif
return 0;
}
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int basic_alloc1(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile int __arena *page1, *page2, *no_page, *page3;
page1 = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
@@ -91,7 +90,6 @@ int basic_alloc1(void *ctx)
return 9;
if (*page1 != 1)
return 10;
-#endif
return 0;
}
@@ -125,9 +123,9 @@ int free_scalar_below_arena(void *ctx)
SEC("socket")
__success __retval(0)
+__skip_without_arena
int basic_alloc2_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile char __arena *page1, *page2, *page3, *page4;
page1 = bpf_arena_alloc_pages(&arena, NULL, 2, NUMA_NO_NODE, 0);
@@ -157,15 +155,14 @@ int basic_alloc2_nosleep(void *ctx)
return 7;
if (*page4 != 0)
return 8;
-#endif
return 0;
}
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int basic_alloc2(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile char __arena *page1, *page2, *page3, *page4;
page1 = bpf_arena_alloc_pages(&arena, NULL, 2, NUMA_NO_NODE, 0);
@@ -195,7 +192,6 @@ int basic_alloc2(void *ctx)
return 7;
if (*page4 != 0)
return 8;
-#endif
return 0;
}
@@ -233,7 +229,6 @@ SEC("socket")
__success __retval(0)
int basic_reserve1_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -257,7 +252,6 @@ int basic_reserve1_nosleep(void *ctx)
page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
if (page)
return 4;
-#endif
return 0;
}
@@ -265,7 +259,6 @@ SEC("syscall")
__success __retval(0)
int basic_reserve1(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -289,7 +282,6 @@ int basic_reserve1(void *ctx)
page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
if (page)
return 4;
-#endif
return 0;
}
@@ -297,7 +289,6 @@ SEC("socket")
__success __retval(0)
int basic_reserve2_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -309,7 +300,6 @@ int basic_reserve2_nosleep(void *ctx)
page = bpf_arena_alloc_pages(&arena, page, 1, NUMA_NO_NODE, 0);
if ((u64)page)
return 2;
-#endif
return 0;
}
@@ -317,7 +307,6 @@ SEC("syscall")
__success __retval(0)
int basic_reserve2(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -329,7 +318,6 @@ int basic_reserve2(void *ctx)
page = bpf_arena_alloc_pages(&arena, page, 1, NUMA_NO_NODE, 0);
if ((u64)page)
return 2;
-#endif
return 0;
}
@@ -338,7 +326,6 @@ SEC("socket")
__success __retval(0)
int reserve_twice_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -351,7 +338,6 @@ int reserve_twice_nosleep(void *ctx)
ret = bpf_arena_reserve_pages(&arena, page, 1);
if (ret != -EBUSY)
return 2;
-#endif
return 0;
}
@@ -359,7 +345,6 @@ SEC("syscall")
__success __retval(0)
int reserve_twice(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -372,7 +357,6 @@ int reserve_twice(void *ctx)
ret = bpf_arena_reserve_pages(&arena, page, 1);
if (ret != -EBUSY)
return 2;
-#endif
return 0;
}
@@ -381,7 +365,6 @@ SEC("socket")
__success __retval(0)
int reserve_invalid_region_nosleep(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -403,7 +386,6 @@ int reserve_invalid_region_nosleep(void *ctx)
ret = bpf_arena_reserve_pages(&arena, page, (1ULL << 32) - 1);
if (ret != -EINVAL)
return 4;
-#endif
return 0;
}
@@ -411,7 +393,6 @@ SEC("syscall")
__success __retval(0)
int reserve_invalid_region(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -433,7 +414,6 @@ int reserve_invalid_region(void *ctx)
ret = bpf_arena_reserve_pages(&arena, page, (1ULL << 32) - 1);
if (ret != -EINVAL)
return 4;
-#endif
return 0;
}
@@ -478,7 +458,6 @@ SEC("syscall")
__success __retval(0)
int arena_kfuncs_under_bpf_lock(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *page;
int ret;
@@ -503,7 +482,6 @@ int arena_kfuncs_under_bpf_lock(void *ctx)
bpf_arena_free_pages(&arena, page, 1);
bpf_spin_unlock(&arena_bpf_test_lock);
-#endif
return 0;
}
@@ -765,6 +743,7 @@ u32 __arena volatile *check_arena_arg_quals2(u32 volatile __arena *arg1, u32 __a
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int check_arena_arg_ret(void *ctx)
{
u32 __arena *page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_large.c b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
index 34f0a0f88e12..6ef99793cac1 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_large.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
@@ -22,9 +22,9 @@ struct {
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int big_alloc1(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile char __arena *page1, *page2, *no_page, *page3;
u64 base;
@@ -79,16 +79,15 @@ int big_alloc1(void *ctx)
return 13;
if (*(page2 - PAGE_SIZE) != 0)
return 14;
-#endif
return 0;
}
/* Try to access a reserved page. Behavior should be identical with accessing unallocated pages. */
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int access_reserved(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
volatile char __arena *page;
char __arena *base;
const size_t len = 4;
@@ -118,7 +117,6 @@ int access_reserved(void *ctx)
if (*page)
return 2 + 2 * i + 1;
}
-#endif
return 0;
}
@@ -127,7 +125,6 @@ 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;
@@ -142,7 +139,6 @@ int request_partially_reserved(void *ctx)
page = bpf_arena_alloc_pages(&arena, base, 5, NUMA_NO_NODE, 0);
if ((u64)page != 0ULL)
return 2;
-#endif
return 0;
}
@@ -150,7 +146,6 @@ 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;
@@ -177,7 +172,6 @@ int free_reserved(void *ctx)
page = bpf_arena_alloc_pages(&arena, addr + __PAGE_SIZE, 2, NUMA_NO_NODE, 0);
if (!page)
return 3;
-#endif
return 0;
}
@@ -292,7 +286,6 @@ SEC("socket")
__success __retval(0)
int big_alloc3(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *pages;
u64 i;
int err = 0;
@@ -314,8 +307,6 @@ int big_alloc3(void *ctx)
bpf_arena_free_pages(&arena, pages, LARGE_PAGE_CNT);
return err;
-#endif
- return 0;
}
/* SYSCALL programs are always sleepable. */
@@ -323,7 +314,6 @@ SEC("syscall")
__success __retval(0)
int big_alloc4(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
char __arena *pages;
u64 i;
int err = 0;
@@ -345,8 +335,6 @@ int big_alloc4(void *ctx)
bpf_arena_free_pages(&arena, pages, LARGE_PAGE_CNT);
return err;
-#endif
- return 0;
}
#else
--
2.53.0-Meta