linux-kernel - [PATCH bpf-next 2/2] selftests/bpf: Add test to access const void pointer argument in tracing program

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Message-ID: <20250412170626.3638516-3-kafai.wan@hotmail.com>
Date: Sun, 13 Apr 2025 01:06:26 +0800
From: KaFai Wan <mannkafai@...il.com>
To: martin.lau@...ux.dev,
	ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	eddyz87@...il.com,
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Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
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	leon.hwang@...ux.dev
Subject: [PATCH bpf-next 2/2] selftests/bpf: Add test to access const void pointer argument in tracing program

Adding verifier test for accessing const void pointer argument in
tracing programs.

The test program loads 2nd argument of kfree tp_btf which is
const void pointer and checks that verifier allows that.

Signed-off-by: KaFai Wan <kafai.wan@...mail.com>
---
 .../selftests/bpf/progs/verifier_btf_ctx_access.c        | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c b/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
index 28b939572cda..a6cec7f73dcd 100644
--- a/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
+++ b/tools/testing/selftests/bpf/progs/verifier_btf_ctx_access.c
@@ -65,4 +65,13 @@ __naked void ctx_access_u32_pointer_reject_8(void)
 "	::: __clobber_all);
 }
 
+SEC("tp_btf/kfree")
+__description("btf_ctx_access const void pointer accept")
+int ctx_access_const_void_pointer_accept(void)
+{
+	/* load 2nd argument value (const void pointer) */
+	asm volatile ("r2 = *(u64 *)(r1 + 8); ");
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.43.0