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Marchesi" Cc: 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: t_4kJIpTzNz-lzettM23PJ-KXu-uhYzd X-Authority-Analysis: v=2.4 cv=Hp172kTS c=1 sm=1 tr=0 ts=69b185eb cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=STsw3Vc2TD3qxPjF4oIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzExMDEyNyBTYWx0ZWRfXwT8P/YKmFHIw mllH/UYbV4BKUFgCtAlpPKRdeymea9abOD2iapMNLR8d58DbP9KAWyqqBXyZs5Z2qP7GMEgNAaI HZ2R19W4ZWjhT5EjMX0d77ToBc5n1sw9keSFt9Spl+OzC7EySpAH24CWvCekK2NiB5mvETjpcu0 nWb7RNzDO+qXITGUSVfTukCM41AhJUx/79lfAOajrcdt7a8l87J/SUskIFJ/HG06mjv47XaCD+E I8bwNoue2J7/l1FmP4anpZIAiuj9FLuobjmVCkPxcQq3UqUuDOsmFjBYndEeAmren5v+yCUtGBG WR7Fy0TDFWD/CT8iHNJLThhtyEHbFysDhPZx5utb6xJz3U2U+ACfGd41CoDnVTIMtuaQifGR1wt 52VE6k6pmFQza1vXBylW/Uida2Epu1PrlLV6HHVtpMIi3US2nJCYjpPuqaz4jySBJ98JF26a1oW 8I3qUy2s/mX+OOb4K4A== X-Proofpoint-ORIG-GUID: 5QnvErwvkBK5pN4Dm8u-Ff4ZW6G7zuFh 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=1011 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-2603110127 Hi Alexei, Thanks for the review. On 09/03/26 10:37 pm, Alexei Starovoitov wrote: > On Tue, Mar 3, 2026 at 5:15 AM Hari Bathini wrote: >> >> >> +SEC("tc") >> +int kfunc_call_test5(struct __sk_buff *skb) >> +{ >> + struct bpf_sock *sk = skb->sk; >> + int ret; >> + u32 val32; >> + u16 val16; >> + u8 val8; >> + >> + if (!sk) >> + return -1; >> + >> + sk = bpf_sk_fullsock(sk); >> + if (!sk) >> + return -1; >> + >> + ret = bpf_kfunc_call_test5(0xFF, 0xFFFF, 0xFFFFFFFF); > > maybe add a comment with bpf asm to highlight what this is ? > > Also 0xFFFFffffULL ? > 8 "F"s in a row is harder on the eyes. > and ULL to make it explicit ? True. Will do that. >> + if (ret) >> + return ret; >> + >> + val32 = bpf_get_prandom_u32(); >> + val16 = val32 & 0xFFFF; >> + val8 = val32 & 0xFF; >> + ret = bpf_kfunc_call_test5(val8, val16, val32); >> + if (ret) >> + return ret; >> + >> + ret = bpf_kfunc_call_test5(val8 * 0xFF, val16 * 0xFFFF, val32 * 0xFFFFFFFF); > > I'm struggling to decipher it. Pls add a comment with asm to explain. > I think the last multiplication is still done in 32-bit domain ? > or not? 0xFFFFFFFF is a 64-bit constant in C. I think... Sure. Let me add comments to convey the intention of the bpf programs to avoid ambiguity.. > > Also we have 4 ISA versions. test_progs-no_alu32 and test_progs > compile it differently. > Maybe let's add another version of this test but fully in asm ? > Keep the C version too. > >> + if (ret) >> + return ret; >> + >> + return 0; >> +} >> + >> SEC("tc") >> int kfunc_call_test4(struct __sk_buff *skb) >> { >> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> index e62c6b78657f..de4897ddcff1 100644 >> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> @@ -766,6 +766,33 @@ __bpf_kfunc long noinline bpf_kfunc_call_test4(signed char a, short b, int c, lo >> return (long)a + (long)b + (long)c + d; >> } >> >> +__bpf_kfunc int bpf_kfunc_call_test5(u8 a, u16 b, u32 c) >> +{ >> + /* Make val as volatile to avoid compiler optimizations on the below checks */ >> + volatile long val = a; > > Pls add a comment that this is zero extended in C. > >> + >> + /* 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? > Please resend with [PATCH bpf-next] in the subject, so that CIs > can pick it up correctly. My bad. Will add the suffix while sending v2.. - Hari