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Fri, 10 Apr 2026 09:30:59 -0700 (PDT) Received: from krios.corp.tfbnw.net ([2620:10d:c090:600::6eaf]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2d55f5c69d5sm5642619eec.3.2026.04.10.09.30.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Apr 2026 09:30:58 -0700 (PDT) From: Emil Tsalapatis To: bpf@vger.kernel.org Cc: ast@kernel.org, andrii@kernel.org, memxor@gmail.com, daniel@iogearbox.net, eddyz87@gmail.com, song@kernel.org, Emil Tsalapatis Subject: [PATCH bpf-next v5 2/9] selftests/bpf: Add test for scalar/arena pointer addition Date: Fri, 10 Apr 2026 12:30:34 -0400 Message-ID: <20260410163041.8063-3-emil@etsalapatis.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260410163041.8063-1-emil@etsalapatis.com> References: <20260410163041.8063-1-emil@etsalapatis.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add a selftest that ensures scalar += ptr_to_arena instructions are accepted by the verifier. Signed-off-by: Emil Tsalapatis Acked-by: Song Liu --- .../selftests/bpf/progs/verifier_arena.c | 85 +++++++++++++++++++ 1 file changed, 85 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_arena.c b/tools/testing/selftests/bpf/progs/verifier_arena.c index c4b8daac4388..df5632ea777f 100644 --- a/tools/testing/selftests/bpf/progs/verifier_arena.c +++ b/tools/testing/selftests/bpf/progs/verifier_arena.c @@ -477,4 +477,89 @@ int arena_kfuncs_under_bpf_lock(void *ctx) return 0; } + +#if defined(__BPF_FEATURE_ADDR_SPACE_CAST) + +/* + * Test that scalar += PTR_TO_ARENA correctly upgrades the + * destination register to a PTR_TO_ARENA. + */ +SEC("syscall") +__success __retval(0) +int scalar_add_arena_ptr(void *ctx) +{ + int __arena *scalar, *arena_ptr; + + volatile char __arena *base = arena_base(&arena); + + asm volatile ( + "%[arena_ptr] = 8192;" + "%[arena_ptr] = addr_space_cast(%[arena_ptr], 0x0, 0x1);" + "%[scalar] = 12;" + "%[scalar] += %[arena_ptr];" + : [scalar] "=r"(scalar), + [arena_ptr] "=&r"(arena_ptr) + : "r"(base) + : + ); + return 0; +} + +/* + * Test that PTR_TO_ARENA + PTR_TO_ARENA is allowed. + */ +SEC("syscall") +__success __retval(0) +int arena_ptr_add_arena_ptr(void *ctx) +{ + int __arena *arena_ptr2, *arena_ptr1; + + /* Needed for the verifier to link the arena to the subprog. */ + volatile char __arena *base = arena_base(&arena); + + asm volatile ( + "%[arena_ptr1] = 8192;" + "%[arena_ptr1] = addr_space_cast(%[arena_ptr1], 0x0, 0x1);" + "%[arena_ptr2] = 4096;" + "%[arena_ptr2] = addr_space_cast(%[arena_ptr2], 0x0, 0x1);" + "%[arena_ptr2] += %[arena_ptr1];" + : [arena_ptr2] "=r"(arena_ptr2), + [arena_ptr1] "=&r"(arena_ptr1) + : "r"(base) + : + ); + return 0; +} + +/* + * Test that PTR_TO_ARENA + non-arena pointer is rejected. + */ +SEC("syscall") +__failure __msg("R4 += R3: Invalid operation between bpf_reg_state types") +int arena_ptr_add_to_non_arena_ptr(void *ctx) +{ + register int __arena *arena_ptr asm("r3"); + register void *dst asm("r4"); + + /* Needed for the verifier to link the arena to the subprog. */ + volatile char __arena *base = arena_base(&arena); + + asm volatile ( + "%[arena_ptr] = 8192;" + "%[arena_ptr] = addr_space_cast(%[arena_ptr], 0x0, 0x1);" + "%[dst] = %[ctx];" + "%[dst] += %[arena_ptr];" + : [arena_ptr] "=&r"(arena_ptr), + [dst] "=&r"(dst) + : [ctx] "r"(ctx), "r"(base) + : + ); + + (void)ctx; + + return 0; +} + +#endif + char _license[] SEC("license") = "GPL"; -- 2.53.0