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[138.88.31.60]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93eb9848702sm51693885a.12.2026.10.08.16.36.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Oct 2026 16:36:25 -0700 (PDT) From: David Windsor To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, yunwei356@gmail.com, David Windsor Subject: [PATCH bpf 2/2] selftests/bpf: cover bpf_loop() state pruning regression Date: Thu, 8 Oct 2026 19:36:23 -0400 Message-ID: <20261008233623.4011127-2-dwindsor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261008233623.4011127-1-dwindsor@gmail.com> References: <20261008233623.4011127-1-dwindsor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Exercise 18 independent conditional stores to dead callback stack slots, reproducing the verifier state explosion fixed by the preceding commit. Signed-off-by: David Windsor diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c index 75dd922e4e9f87ebc947ee6e621a789cad10431e..c1c3099a6a20391c8b36b39eedd9cc6ce893d996 100644 --- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c +++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c @@ -783,4 +783,62 @@ __naked void check_add_const_regsafe_off(void) : __clobber_common); } +#define DEAD_STACK_SLOT(off) \ + "call %[bpf_get_prandom_u32];" \ + "if r0 == 0 goto 1f;" \ + "*(u64 *)(r10 - " #off ") = 1;" /* dead stack store */ \ + "goto 2f;" \ + "1: *(u64 *)(r10 - " #off ") = 2;" /* dead stack store */ \ + "2:;" + +__used __naked +static void dead_stack_cb(void) +{ + asm volatile ( + DEAD_STACK_SLOT(8) + DEAD_STACK_SLOT(16) + DEAD_STACK_SLOT(24) + DEAD_STACK_SLOT(32) + DEAD_STACK_SLOT(40) + DEAD_STACK_SLOT(48) + DEAD_STACK_SLOT(56) + DEAD_STACK_SLOT(64) + DEAD_STACK_SLOT(72) + DEAD_STACK_SLOT(80) + DEAD_STACK_SLOT(88) + DEAD_STACK_SLOT(96) + DEAD_STACK_SLOT(104) + DEAD_STACK_SLOT(112) + DEAD_STACK_SLOT(120) + DEAD_STACK_SLOT(128) + DEAD_STACK_SLOT(136) + DEAD_STACK_SLOT(144) + "r0 = 0;" + "exit;" + : + : __imm(bpf_get_prandom_u32) + : __clobber_all + ); +} + +#undef DEAD_STACK_SLOT + +SEC("?raw_tp") +__success __flag(BPF_F_TEST_STATE_FREQ) __log_level(4) +__naked void callback_dead_stack(void) +{ + asm volatile ( + "r1 = 100;" + "r2 = dead_stack_cb ll;" + "r3 = 0;" + "r4 = 0;" + "call %[bpf_loop];" /* trigger state pruning */ + "r0 = 0;" + "exit;" + : + : __imm(bpf_loop) + : __clobber_all + ); +} + char _license[] SEC("license") = "GPL"; -- 2.53.0