[PATCH bpf-next v2 3/8] selftests/bpf: report SKIP for arena tests a compiler cannot build

[Vineet Gupta <vineet.gupta@linux.dev>]

Tests guarded by __BPF_FEATURE_ADDR_SPACE_CAST don't have a dummy fall back
when the compiler doesn't support the feature: so they are absent from such
a report entirely.
Every subtest inside one of those guards is invisible: 24 across seven
files, plus the five in stream_arena_fault_address, which has no guard
and fails to load instead (addressed separately, later in this series).

Give each guard an #else with a dummy marked __skip(), so the skip gap is
reported rather than invisible.  Add __skip_without_arena for it, which
expands to __skip() with a fixed reason when the compiler cannot do arena.

Measured on bpf-next with a stock bpf-gcc, test_progs before and after:
seven subtests appear that were previously absent from the report
altogether, and arena_kfunc_jit goes OK -> SKIP because every subtest
it has is now one of them.

  arena_kfunc_jit/arena_unsupported          SKIP
  compute_live_registers/arena_unsupported   SKIP
  jit_insns/arena_unsupported                SKIP
  verifier_arena/arena_unsupported           SKIP
  verifier_arena_large/arena_unsupported     SKIP
  verifier_ldsx/arena_unsupported            SKIP
  verifier_zext/arena_unsupported            SKIP
jit_insns_arena.c needs the same treatment and is easy to miss: both
of its programs are inside the guard, so without arena support the
object has none at all and RUN_TESTS(jit_insns_arena) runs zero
subtests without saying so.

Signed-off-by: Vineet Gupta <vineet.gupta@linux.dev>
---
 .../testing/selftests/bpf/progs/arena_kfunc_jit.c  |  9 +++++++++
 tools/testing/selftests/bpf/progs/bpf_misc.h       | 14 ++++++++++++++
 .../selftests/bpf/progs/compute_live_registers.c   | 10 ++++++++++
 .../testing/selftests/bpf/progs/jit_insns_arena.c  | 10 ++++++++++
 tools/testing/selftests/bpf/progs/verifier_arena.c |  9 +++++++++
 .../selftests/bpf/progs/verifier_arena_large.c     | 10 ++++++++++
 tools/testing/selftests/bpf/progs/verifier_ldsx.c  |  9 +++++++++
 tools/testing/selftests/bpf/progs/verifier_zext.c  |  9 +++++++++
 8 files changed, 80 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
index b5a01cbc33a7..97912a7b6b5e 100644
--- a/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
+++ b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
@@ -112,6 +112,15 @@ int arena_arg_jit_args5(void *ctx)
 				   (u64 *)&val[4]);
 	return 0;
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
 
 #endif /* __BPF_FEATURE_ADDR_SPACE_CAST */
 
diff --git a/tools/testing/selftests/bpf/progs/bpf_misc.h b/tools/testing/selftests/bpf/progs/bpf_misc.h
index 1b264480e128..ed1ed1b5bd09 100644
--- a/tools/testing/selftests/bpf/progs/bpf_misc.h
+++ b/tools/testing/selftests/bpf/progs/bpf_misc.h
@@ -116,6 +116,10 @@
  *                   feature the toolchain or JIT cannot provide, so a run does
  *                   not report OK for coverage it never executed.
  *
+ * __skip_without_arena
+ *                   __skip() with a fixed reason when the compiler cannot do
+ *                   the arena address space, nothing otherwise.
+ *
  * __log_level       Log level to use for the program, numeric value expected.
  *
  * __flag            Adds one flag use for the program, the following values are valid:
@@ -156,6 +160,16 @@
 #define __success		__test_tag("test_expect_success")
 #define __description(desc)	__test_tag("test_description=" desc)
 #define __skip(reason)		__test_tag("test_skip=" reason)
+
+/*
+ * Without compiler arena support, report the test as SKIP rather than let it
+ * pass vacuously or fail to load.
+ */
+#ifdef __BPF_FEATURE_ADDR_SPACE_CAST
+#define __skip_without_arena
+#else
+#define __skip_without_arena	__skip("compiler does not support the arena address space")
+#endif
 #define __msg_unpriv(msg)	__test_tag("test_expect_msg_unpriv=" msg)
 #define __not_msg_unpriv(msg)	__test_tag("test_expect_not_msg_unpriv=" msg)
 #define __msg_next_unpriv(msg)	__test_tag("test_expect_msg_next_unpriv=" msg)
diff --git a/tools/testing/selftests/bpf/progs/compute_live_registers.c b/tools/testing/selftests/bpf/progs/compute_live_registers.c
index 1ff24bbc7beb..e05431600358 100644
--- a/tools/testing/selftests/bpf/progs/compute_live_registers.c
+++ b/tools/testing/selftests/bpf/progs/compute_live_registers.c
@@ -403,6 +403,16 @@ __naked void addr_space_cast(void)
 		  __imm_addr(arena)
 		: __clobber_all);
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
+
 #endif
 
 static __used __naked int aux1(void)
diff --git a/tools/testing/selftests/bpf/progs/jit_insns_arena.c b/tools/testing/selftests/bpf/progs/jit_insns_arena.c
index 95736eae2a58..ccda60e96524 100644
--- a/tools/testing/selftests/bpf/progs/jit_insns_arena.c
+++ b/tools/testing/selftests/bpf/progs/jit_insns_arena.c
@@ -106,6 +106,16 @@ int cast_to_user(void *ctx)
 	: "r1", "r2", "r7", "r9");
 	return res != 0;
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
+
 #endif
 
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c
index 1ce9c4b78481..3b3410802825 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena.c
@@ -713,6 +713,15 @@ __naked void mixed_arena_stack_atomic(void)
 	  __imm(bpf_get_prandom_u32)
 	: __clobber_all);
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
 
 #endif /* defined(__BPF_FEATURE_ADDR_SPACE_CAST) */
 
diff --git a/tools/testing/selftests/bpf/progs/verifier_arena_large.c b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
index dbdea14ca76f..34f0a0f88e12 100644
--- a/tools/testing/selftests/bpf/progs/verifier_arena_large.c
+++ b/tools/testing/selftests/bpf/progs/verifier_arena_large.c
@@ -348,5 +348,15 @@ int big_alloc4(void *ctx)
 #endif
 	return 0;
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
+
 #endif
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_ldsx.c b/tools/testing/selftests/bpf/progs/verifier_ldsx.c
index 49e8cd4bb4f9..35b20d0796db 100644
--- a/tools/testing/selftests/bpf/progs/verifier_ldsx.c
+++ b/tools/testing/selftests/bpf/progs/verifier_ldsx.c
@@ -450,6 +450,15 @@ void kfunc_root(void)
 {
 	bpf_arena_alloc_pages(0, 0, 0, 0, 0);
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
 
 #endif /* __BPF_FEATURE_ADDR_SPACE_CAST */
 
diff --git a/tools/testing/selftests/bpf/progs/verifier_zext.c b/tools/testing/selftests/bpf/progs/verifier_zext.c
index 572017fe28fb..dbfeeea4cf9f 100644
--- a/tools/testing/selftests/bpf/progs/verifier_zext.c
+++ b/tools/testing/selftests/bpf/progs/verifier_zext.c
@@ -381,6 +381,15 @@ __naked void zext_arena_cmpxchg32(void)
 		     BPF_ATOMIC_OP(BPF_W, BPF_CMPXCHG, BPF_REG_1, BPF_REG_2, 0))
 	: __clobber_all);
 }
+#else
+
+SEC("socket")
+__skip_without_arena
+__success
+int arena_unsupported(void)
+{
+	return 0;
+}
 
 #endif
 
-- 
2.53.0-Meta