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Marchesi" , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Shuah Khan , "open list:KERNEL SELFTEST FRAMEWORK" References: <20260303131453.328674-1-hbathini@linux.ibm.com> Content-Language: en-US From: Hari Bathini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: b6xLeAZj1uH1PQvLUdtUXluCJJEvEDYS X-Authority-Analysis: v=2.4 cv=Hp172kTS c=1 sm=1 tr=0 ts=69b1ae5a cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=O-nAQ4prQPj99qpvhysA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzExMDE1MiBTYWx0ZWRfXwe3iurw3vLdE xTfM6RnsooyM/wkTnmYFAtzW5rESlFWO3HKGXD/tCEcOWaS4Ma778guTv/j+09dL/ALfUsYGfar JGv4JoF2wMHcUonmgm/DiQZ8FJ8soFJQZnKBttIIRWLroiLKrgbbHdx0h/vAF7TejN1YzEBsCSd o9Wbnqhco5yZksAe5sAeugl+SPFCXE/iZKKanFMzjTh7nz3sk6TQXKcjVAOyg6eUNZ0xKJYY/UK a6Y4V2WSI9wT7RLTAcgIw0zlzK9o3fKfqc5A7OOmTqrFdmDP1Pmv277bZAVZVfpoCX1chQw7o/f pWyiTfFUwXwIMOpH3hNegHMH1XERzYbB9JrNhLVbB55N8d4GchDslHamKXwdMy9dqJoUcUIEOdP Gwph68kVk+wUD4hMamYV9sb2k7yDy8QtwvTuHVLOhG5pggvJFKSsI9IMWLXgeMKABkBdwA7BgSN kLLyfH058VytQFwpqRw== X-Proofpoint-ORIG-GUID: mYn3XE6InOnPspwkRfZvOenOhDMsAoOE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-11_02,2026-03-09_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 malwarescore=0 impostorscore=0 suspectscore=0 spamscore=0 phishscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603110152 On 11/03/26 9:32 pm, Alexei Starovoitov wrote: > On Wed, Mar 11, 2026 at 8:10 AM Hari Bathini wrote: >> >>> >>>> + >>>> + /* Check zero-extension */ >>>> + if (val != (unsigned long)a) >>>> + return 1; >>>> + /* Check no sign-extension */ >>>> + if (val < 0) >>>> + return 2; >>>> + >>>> + val = b; >>>> + if (val != (unsigned long)b) >>>> + return 3; >>>> + if (val < 0) >>>> + return 4; >>>> + >>>> + val = c; >>>> + if (val != (unsigned long)c) >>>> + return 5; >>>> + if (val < 0) >>>> + return 6; >>>> + >>>> + return 0; >>>> +} >>> >>> Overall this looks very useful. >>> I would expand with another test where a,b,c are s8,s16,s32. >> >> Slightly different approach but kfunc_call_test4/bpf_kfunc_call_test4 >> cover signed arguments already? > > Ahh. Then may be tweak it to adopt similar fine grained > error reporting as your bpf_kfunc_call_test5() I Prefer this. Does the below change to bpf_kfunc_call_test4 look fine: diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index 48dcaf93bb9f..6237c2222633 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -760,8 +760,30 @@ __bpf_kfunc struct sock *bpf_kfunc_call_test3(struct sock *sk) __bpf_kfunc long noinline bpf_kfunc_call_test4(signed char a, short b, int c, long d) { + /* + * Make val as volatile to avoid compiler optimizations. + * Verify that negative signed values remain negative after + * sign-extension (JIT must sign-extend, not zero-extend). + */ + volatile long val; + + /* val will be positive, if JIT does zero-extension instead of sign-extension */ + val = a; + if (val >= 0) + return 1; + + val = b; + if (val >= 0) + return 2; + + val = c; + if (val >= 0) + return 3; + /* Provoke the compiler to assume that the caller has sign-extended a, * b and c on platforms where this is required (e.g. s390x). + * + * Original behavior: return sum for backward compatibility */ return (long)a + (long)b + (long)c + d; } - Hari