From patchwork Mon Jul 8 15:46:34 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yonghong Song X-Patchwork-Id: 13726758 X-Patchwork-Delegate: bpf@iogearbox.net Received: from 69-171-232-181.mail-mxout.facebook.com (69-171-232-181.mail-mxout.facebook.com [69.171.232.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 93D64139568 for ; Mon, 8 Jul 2024 15:46:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=69.171.232.181 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720453610; cv=none; b=JhxE3FZ2k6CUCbwBEingC8O2aa4/3WtZxhUNpznATENZ8EWWLsPYeXEodxmDDU9v0BQWe/xozlwqYfVF+aMgQ6fVaJprUnxRsoteYCA+WsHKmU573InsNrXCOhUrI5eOn1gKrLZU3kBO1I3TKbs4QX2hiWbCrAdnNLUkG8HXnBg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720453610; c=relaxed/simple; bh=+la4gNJoiWD3Y44qBTJL2jWBnscbfH6CrHnJ4EYkL/Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Lf4gaGgZZWHC06pOdmoy58N+YakBJUmjacs3pEAZIZCXqs/rJ+BB0pyHgoPOZXaVaWEs0lUSfwhKPWtCcVdACU0Y5cURyvorV03MqJJa8tlW7qAm1y6lTIdtTdzjVqz0H+KAYCtHccGiPkimfeM5IWNzXomfwPBZrzg8ftl+T5w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=fail smtp.mailfrom=linux.dev; arc=none smtp.client-ip=69.171.232.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=linux.dev Received: by devbig309.ftw3.facebook.com (Postfix, from userid 128203) id 2921965B78CB; Mon, 8 Jul 2024 08:46:34 -0700 (PDT) From: Yonghong Song To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau Subject: [PATCH bpf-next] selftests/bpf: Workaround iters/iter_arr_with_actual_elem_count failure when -mcpu=cpuv4 Date: Mon, 8 Jul 2024 08:46:34 -0700 Message-ID: <20240708154634.283426-1-yonghong.song@linux.dev> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net With latest llvm19, the selftest iters/iter_arr_with_actual_elem_count failed with -mcpu=v4. The following are the details: 0: R1=ctx() R10=fp0 ; int iter_arr_with_actual_elem_count(const void *ctx) @ iters.c:1420 0: (b4) w7 = 0 ; R7_w=0 ; int i, n = loop_data.n, sum = 0; @ iters.c:1422 1: (18) r1 = 0xffffc90000191478 ; R1_w=map_value(map=iters.bss,ks=4,vs=1280,off=1144) 3: (61) r6 = *(u32 *)(r1 +128) ; R1_w=map_value(map=iters.bss,ks=4,vs=1280,off=1144) R6_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) ; if (n > ARRAY_SIZE(loop_data.data)) @ iters.c:1424 4: (26) if w6 > 0x20 goto pc+27 ; R6_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) 5: (bf) r8 = r10 ; R8_w=fp0 R10=fp0 6: (07) r8 += -8 ; R8_w=fp-8 ; bpf_for(i, 0, n) { @ iters.c:1427 7: (bf) r1 = r8 ; R1_w=fp-8 R8_w=fp-8 8: (b4) w2 = 0 ; R2_w=0 9: (bc) w3 = w6 ; R3_w=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) R6_w=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) 10: (85) call bpf_iter_num_new#45179 ; R0=scalar() fp-8=iter_num(ref_id=2,state=active,depth=0) refs=2 11: (bf) r1 = r8 ; R1=fp-8 R8=fp-8 refs=2 12: (85) call bpf_iter_num_next#45181 13: R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R6=scalar(id=1,smin=smin32=0,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) R7=0 R8=fp-8 R10=fp0 fp-8=iter_num(ref_id=2,state=active,depth=1) refs=2 ; bpf_for(i, 0, n) { @ iters.c:1427 13: (15) if r0 == 0x0 goto pc+2 ; R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) refs=2 14: (81) r1 = *(s32 *)(r0 +0) ; R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R1_w=scalar(smin=0xffffffff80000000,smax=0x7fffffff) refs=2 15: (ae) if w1 < w6 goto pc+4 20: R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R1=scalar(smin=0xffffffff80000000,smax=smax32=umax32=31,umax=0xffffffff0000001f,smin32=0,var_off=(0x0; 0xffffffff0000001f)) R6=scalar(id=1,smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) R7=0 R8=fp-8 R10=fp0 fp-8=iter_num(ref_id=2,state=active,depth=1) refs=2 ; sum += loop_data.data[i]; @ iters.c:1429 20: (67) r1 <<= 2 ; R1_w=scalar(smax=0x7ffffffc0000007c,umax=0xfffffffc0000007c,smin32=0,smax32=umax32=124,var_off=(0x0; 0xfffffffc0000007c)) refs=2 21: (18) r2 = 0xffffc90000191478 ; R2_w=map_value(map=iters.bss,ks=4,vs=1280,off=1144) refs=2 23: (0f) r2 += r1 math between map_value pointer and register with unbounded min value is not allowed The source code: int iter_arr_with_actual_elem_count(const void *ctx) { int i, n = loop_data.n, sum = 0; if (n > ARRAY_SIZE(loop_data.data)) return 0; bpf_for(i, 0, n) { /* no rechecking of i against ARRAY_SIZE(loop_data.n) */ sum += loop_data.data[i]; } return sum; } The insn #14 is a sign-extenstion load which is related to 'int i'. The insn #15 did a subreg comparision. Note that smin=0xffffffff80000000 and this caused later insn #23 failed verification due to unbounded min value. Actually insn #15 smin range can be better. Since after comparison, we know smin32=0 and smax32=32. With insn #14 being a sign-extension load. We will know top 32bits should be 0 as well. Current verifier is not able to handle this, and this patch is a workaround to fix test failure by changing variable 'i' type from 'int' to 'unsigned' which will give proper range during comparison. ; bpf_for(i, 0, n) { @ iters.c:1428 13: (15) if r0 == 0x0 goto pc+2 ; R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) refs=2 14: (61) r1 = *(u32 *)(r0 +0) ; R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R1_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) refs=2 ... from 15 to 20: R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R1=scalar(smin=smin32=0,smax=umax=smax32=umax32=31,var_off=(0x0; 0x1f)) R6=scalar(id=1,smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) R7=0 R8=fp-8 R10=fp0 fp-8=iter_num(ref_id=2,state=active,depth=1) refs=2 20: R0=rdonly_mem(id=3,ref_obj_id=2,sz=4) R1=scalar(smin=smin32=0,smax=umax=smax32=umax32=31,var_off=(0x0; 0x1f)) R6=scalar(id=1,smin=umin=smin32=umin32=1,smax=umax=smax32=umax32=32,var_off=(0x0; 0x3f)) R7=0 R8=fp-8 R10=fp0 fp-8=iter_num(ref_id=2,state=active,depth=1) refs=2 ; sum += loop_data.data[i]; @ iters.c:1430 20: (67) r1 <<= 2 ; R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=124,var_off=(0x0; 0x7c)) refs=2 21: (18) r2 = 0xffffc90000185478 ; R2_w=map_value(map=iters.bss,ks=4,vs=1280,off=1144) refs=2 23: (0f) r2 += r1 mark_precise: frame0: last_idx 23 first_idx 20 subseq_idx -1 ... Signed-off-by: Yonghong Song --- tools/testing/selftests/bpf/progs/iters.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/iters.c b/tools/testing/selftests/bpf/progs/iters.c index 16bdc3e25591..d1801d151a12 100644 --- a/tools/testing/selftests/bpf/progs/iters.c +++ b/tools/testing/selftests/bpf/progs/iters.c @@ -1419,7 +1419,8 @@ SEC("raw_tp") __success int iter_arr_with_actual_elem_count(const void *ctx) { - int i, n = loop_data.n, sum = 0; + unsigned i; + int n = loop_data.n, sum = 0; if (n > ARRAY_SIZE(loop_data.data)) return 0;