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From:   Matteo Croce <mcroce@linux.microsoft.com>
To:     Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        bpf@vger.kernel.org
Cc:     Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        linux-kernel@vger.kernel.org
Subject: [PATCH bpf-next v2 2/2] selftests/bpf: test maximum recursion depth for bpf_core_types_are_compat()
Date:   Wed,  2 Feb 2022 22:13:28 +0100
Message-Id: <20220202211328.176481-3-mcroce@linux.microsoft.com>
In-Reply-To: <20220202211328.176481-1-mcroce@linux.microsoft.com>
References: <20220202211328.176481-1-mcroce@linux.microsoft.com>
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From: Matteo Croce <mcroce@microsoft.com>

bpf_core_types_are_compat() was limited to 2 recursion levels, which are
enough to parse a function prototype.
Add a test which checks the existence of a function prototype, so to
test the bpf_core_types_are_compat() code path.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
---
 .../selftests/bpf/bpf_testmod/bpf_testmod.c        |  3 +++
 tools/testing/selftests/bpf/progs/core_kern.c      | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 595d32ab285a..a457071a7751 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -13,6 +13,9 @@
 #define CREATE_TRACE_POINTS
 #include "bpf_testmod-events.h"
 
+typedef int (*func_proto_typedef)(long);
+func_proto_typedef funcp = NULL;
+
 DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123;
 
 noinline void
diff --git a/tools/testing/selftests/bpf/progs/core_kern.c b/tools/testing/selftests/bpf/progs/core_kern.c
index 13499cc15c7d..bfea86b42563 100644
--- a/tools/testing/selftests/bpf/progs/core_kern.c
+++ b/tools/testing/selftests/bpf/progs/core_kern.c
@@ -101,4 +101,18 @@ int balancer_ingress(struct __sk_buff *ctx)
 	return 0;
 }
 
+typedef int (*func_proto_typedef___match)(long);
+typedef void (*func_proto_typedef___doesnt_match)(char*);
+
+int out[2];
+
+SEC("raw_tracepoint/sys_enter")
+int core_relo_recur_limit(void *ctx)
+{
+	out[0] = bpf_core_type_exists(func_proto_typedef___match);
+	out[1] = bpf_core_type_exists(func_proto_typedef___doesnt_match);
+
+	return 0;
+}
+
 char LICENSE[] SEC("license") = "GPL";
-- 
2.34.1