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Mon, 06 Apr 2026 12:44:11 -0700 (PDT) Received: from localhost ([2a03:2880:10ff:5f::]) by smtp.gmail.com with ESMTPSA id 5614622812f47-471cdaf207dsm3329167b6e.3.2026.04.06.12.44.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Apr 2026 12:44:10 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Emil Tsalapatis , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Tejun Heo , Dan Schatzberg , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v5 3/7] selftests/bpf: Convert ctx tests from ASM to C Date: Mon, 6 Apr 2026 21:43:57 +0200 Message-ID: <20260406194403.1649608-4-memxor@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260406194403.1649608-1-memxor@gmail.com> References: <20260406194403.1649608-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4922; h=from:subject; bh=Ke/foYSh8+Qxxcvhsgf/MyBOxg9bHj6+/MrnxFpoQL0=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIfMKD9tdrYtqi7SCn261UkjUzWdQevR3oxZj3MRmG78/fsa7 dQ51lLIwiHExyIopspT838dkfKLyd6DtMm6YOaxMIEMYuDgFYCLVnYwMB0qaRX6/jpvOcKV87ZLUxZ v67V+zzwyznWzV/vLwqg15sYwMby/YbNlRIbjNc03KqQKp1jmekz+71D4OVZ10ql7mzuwmPgA= X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit Convert existing tests from ASM to C, in prep for future changes to add more comprehensive tests. Reviewed-by: Emil Tsalapatis Signed-off-by: Kumar Kartikeya Dwivedi --- .../selftests/bpf/prog_tests/verifier.c | 2 +- .../selftests/bpf/progs/verifier_ctx.c | 78 ++++++++----------- 2 files changed, 35 insertions(+), 45 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c index 1ac366fd4dae..169cf7fbf40f 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -175,7 +175,7 @@ void test_verifier_cgroup_skb(void) { RUN(verifier_cgroup_skb); } void test_verifier_cgroup_storage(void) { RUN(verifier_cgroup_storage); } void test_verifier_const(void) { RUN(verifier_const); } void test_verifier_const_or(void) { RUN(verifier_const_or); } -void test_verifier_ctx(void) { RUN(verifier_ctx); } +void test_verifier_ctx(void) { RUN_TESTS(verifier_ctx); } void test_verifier_ctx_sk_msg(void) { RUN(verifier_ctx_sk_msg); } void test_verifier_d_path(void) { RUN(verifier_d_path); } void test_verifier_default_trusted_ptr(void) { RUN_TESTS(verifier_default_trusted_ptr); } diff --git a/tools/testing/selftests/bpf/progs/verifier_ctx.c b/tools/testing/selftests/bpf/progs/verifier_ctx.c index ae756764ffba..4c285ac8fff6 100644 --- a/tools/testing/selftests/bpf/progs/verifier_ctx.c +++ b/tools/testing/selftests/bpf/progs/verifier_ctx.c @@ -295,68 +295,58 @@ padding_access("sk_reuseport", sk_reuseport_md, hash, 4); SEC("syscall") __description("syscall: write to ctx with fixed offset") __success -__naked void syscall_ctx_fixed_off_write(void) +int syscall_ctx_fixed_off_write(void *ctx) { - asm volatile (" \ - r0 = 0; \ - *(u32*)(r1 + 0) = r0; \ - r1 += 4; \ - *(u32*)(r1 + 0) = r0; \ - exit; \ -" ::: __clobber_all); + char *p = ctx; + + *(__u32 *)p = 0; + *(__u32 *)(p + 4) = 0; + return 0; } /* - * Test that program types without convert_ctx_access can dereference - * their ctx pointer after adding a fixed offset. Variable and negative - * offsets should still be rejected. + * For non-syscall program types without convert_ctx_access, direct ctx + * dereference is still allowed after adding a fixed offset, while variable + * and negative direct accesses reject. + * + * Passing ctx as a helper or kfunc memory argument is only permitted for + * syscall programs, so the helper and kfunc cases below validate rejection + * for non-syscall ctx pointers at fixed, variable, and zero-sized accesses. */ -#define no_rewrite_ctx_access(type, name, off, ld_op) \ +#define no_rewrite_ctx_access(type, name, off, load_t) \ SEC(type) \ __description(type ": read ctx at fixed offset") \ __success \ - __naked void no_rewrite_##name##_fixed(void) \ + int no_rewrite_##name##_fixed(void *ctx) \ { \ - asm volatile (" \ - r1 += %[__off]; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm_const(__off, off) \ - : __clobber_all); \ + char *p = ctx; \ + volatile load_t val; \ + \ + val = *(load_t *)(p + off); \ + (void)val; \ + return 0; \ } \ SEC(type) \ __description(type ": reject variable offset ctx access") \ __failure __msg("variable ctx access var_off=") \ - __naked void no_rewrite_##name##_var(void) \ + int no_rewrite_##name##_var(void *ctx) \ { \ - asm volatile (" \ - r6 = r1; \ - call %[bpf_get_prandom_u32]; \ - r1 = r6; \ - r0 &= 4; \ - r1 += r0; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm(bpf_get_prandom_u32) \ - : __clobber_all); \ + __u64 off_var = bpf_get_prandom_u32(); \ + char *p = ctx; \ + \ + off_var &= 4; \ + p += off_var; \ + return *(load_t *)p; \ } \ SEC(type) \ __description(type ": reject negative offset ctx access") \ - __failure __msg("negative offset ctx ptr") \ - __naked void no_rewrite_##name##_neg(void) \ + __failure __msg("invalid bpf_context access") \ + int no_rewrite_##name##_neg(void *ctx) \ { \ - asm volatile (" \ - r1 += %[__neg_off]; \ - r0 = *(" #ld_op " *)(r1 + 0); \ - r0 = 0; \ - exit;" \ - : \ - : __imm_const(__neg_off, -(off)) \ - : __clobber_all); \ + char *p = ctx; \ + \ + p -= 612; \ + return *(load_t *)p; \ } no_rewrite_ctx_access("kprobe", kprobe, 8, u64); -- 2.52.0