[PATCH bpf-next v3 5/8] selftests/bpf: don't report arena tests as passing with an empty body
From: Vineet Gupta
Date: Mon Nov 02 2026 - 17:13:21 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 do not check theirs at all: the
address parameter of bpf_arena_{alloc,free,reserve}_pages() carries the
__ign suffix, get_kfunc_arg_type() returns ARG_IGNORE for it, and
check_func_arg() returns before any register type check. So a test
that only passes pointers to those kfuncs 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, for verifier_arena and
verifier_arena_large:
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.
arena_kfunc.c, verifier_arena_globals1.c and verifier_arena_globals2.c
have the same shape and are included here: nine more guards go, seven
more tags arrive, and seven more subtests go OK -> SKIP. arena_kfunc.c
had six of those, the most of the three.
Signed-off-by: Vineet Gupta <vineet.gupta@xxxxxxxxx>
---
.../testing/selftests/bpf/progs/arena_kfunc.c | 18 +++--------
.../selftests/bpf/progs/verifier_arena.c | 31 +++----------------
.../bpf/progs/verifier_arena_globals1.c | 6 ++--
.../bpf/progs/verifier_arena_globals2.c | 3 +-
.../bpf/progs/verifier_arena_large.c | 16 ++--------
5 files changed, 14 insertions(+), 60 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/arena_kfunc.c b/tools/testing/selftests/bpf/progs/arena_kfunc.c
index 5d1cb1a7e8ee..757aa0618571 100644
--- a/tools/testing/selftests/bpf/progs/arena_kfunc.c
+++ b/tools/testing/selftests/bpf/progs/arena_kfunc.c
@@ -29,9 +29,9 @@ SEC("syscall")
__arch_x86_64
__arch_arm64
__success __retval(0)
+__skip_without_arena
int arena_arg_forms(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
u64 ret;
@@ -59,7 +59,6 @@ int arena_arg_forms(void *ctx)
return 4;
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
-#endif
return 0;
}
@@ -75,7 +74,6 @@ __arch_arm64
__success __retval(0)
int arena_arg_rebase(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
u64 base, off;
@@ -107,7 +105,6 @@ int arena_arg_rebase(void *ctx)
return 7;
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
-#endif
return 0;
}
@@ -115,9 +112,9 @@ SEC("syscall")
__arch_x86_64
__arch_arm64
__success __retval(0)
+__skip_without_arena
int arena_args5(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
val = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
@@ -139,7 +136,6 @@ int arena_args5(void *ctx)
return 3;
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
-#endif
return 0;
}
@@ -147,9 +143,9 @@ SEC("syscall")
__arch_x86_64
__arch_arm64
__success __retval(0)
+__skip_without_arena
int arena_arg_mixed(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
val = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
@@ -166,7 +162,6 @@ int arena_arg_mixed(void *ctx)
return 3;
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
-#endif
return 0;
}
@@ -177,7 +172,6 @@ __arch_arm64
__success __retval(0)
int arena_arg_unpopulated(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
val = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
@@ -188,7 +182,6 @@ int arena_arg_unpopulated(void *ctx)
bpf_kfunc_arena_arg_test((u64 *)stash);
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
-#endif
return 0;
}
@@ -220,9 +213,9 @@ SEC("syscall")
__arch_x86_64
__arch_arm64
__success __retval(0)
+__skip_without_arena
int arena_arg_subprog(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
u64 __arena *val;
int ret;
@@ -238,9 +231,6 @@ int arena_arg_subprog(void *ctx)
bpf_arena_free_pages(&arena, (void __arena *)val, 1);
return ret;
-#else
- return 0;
-#endif
}
SEC("syscall")
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c
index 121f8cea8c25..27ffd74567ec 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;
}
@@ -780,6 +758,7 @@ 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_globals1.c b/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c
index 45d364b0bc85..31be4c944252 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_globals1.c
@@ -30,9 +30,9 @@ volatile char __arena global_data[GLOBAL_PAGES][PAGE_SIZE];
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int check_reserve1(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
const u8 magic = 0x5a;
__u8 __arena *guard, *globals;
volatile char __arena *ptr;
@@ -60,7 +60,6 @@ int check_reserve1(void *ctx)
if (*ptr != magic)
return i + 3;
}
-#endif
return 0;
}
@@ -69,9 +68,9 @@ int check_reserve1(void *ctx)
*/
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int check_relocation(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
const u8 magic = 0xfa;
u8 __arena *ptr;
@@ -80,7 +79,6 @@ int check_relocation(void *ctx)
if (*ptr != magic)
return 1;
-#endif
return 0;
}
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c b/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c
index b51594dbc005..cd48d6bd782e 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_globals2.c
@@ -30,9 +30,9 @@ char __arena global_data[ARENA_PAGES][PAGE_SIZE];
SEC("syscall")
__success __retval(0)
+__skip_without_arena
int check_reserve2(void *ctx)
{
-#if defined(__BPF_FEATURE_ADDR_SPACE_CAST)
void __arena *guard;
int ret;
@@ -42,7 +42,6 @@ int check_reserve2(void *ctx)
ret = bpf_arena_reserve_pages(&arena, guard, 1);
if (!ret)
return 1;
-#endif
return 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