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frame2: R4_w=scalar(id=8,smin=smin3 2=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) R6_w=scalar(id=8,smin=smin3 2=0,smax=umax=smax32=umax32=255,var_off=(0x0; 0xff)) BPF: 800: (07) r4 += 7 ; frame2: R4_w=scalar(smin=umin=smin32=umin32=7,smax=umax=smax32=umax32=262,var_off=(0x0; 0x1ff)) BPF: 801: (57) r4 &= -8 ; frame2: R4_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=262,var_off=(0x0; 0x1f8)) And when checking kernel 6.5.0: BPF: 791: (bf) r4 = r6 ; frame2: R4_w=scalar(id=8,umax=255,var_off=(0x0; 0xff)) R6_w=scalar(id=8,umax=255,var_off=(0x0; 0xff)) BPF: 792: (07) r4 += 7 ; frame2: R4_w=scalar(umin=7,umax=262,var_off=(0x0; 0x1ff)) BPF: 793: (57) r4 &= -8 ; frame2: R4_w=scalar(umax=262,var_off=(0x0; 0x1f8)) And kernel 5.15.0: BPF: 799: (bf) r4 = r6 BPF: 800: frame2: R0=inv(id=11,umin_value=1,umax_value=256,var_off=(0x0; 0x1ff)) R4_w=inv(id=12,umax_value=255,var_off=(0x0; 0xff)) R6_w=inv(id=12,umax_value=255,var_off=(0x0; 0xff)) R10=fp0 fp-8=map_value fp-16=inv4774451407313060418 fp-24=map_value fp-32=map_value BPF: 800: (07) r4 += 7 BPF: 801: frame2: R0=inv(id=11,umin_value=1,umax_value=256,var_off=(0x0; 0x1ff)) R4_w=inv(id=0,umin_value=7,umax_value=262,var_off=(0x0; 0x1ff)) R6_w=inv(id=12,umax_value=255,var_off=(0x0; 0xff)) R10=fp0 fp-8=map_value fp-16=inv4774451407313060418 fp-24=map_value fp-32=map_value BPF: 801: (57) r4 &= -8 BPF: 802: frame2: R0=inv(id=11,umin_value=1,umax_value=256,var_off=(0x0; 0x1ff)) R4_w=inv(id=0,umax_value=262,var_off=(0x0; 0x1f8)) R6_w=inv(id=12,umax_value=255,var_off=(0x0; 0xff)) R10=fp0 fp-8=map_value fp-16=inv4774451407313060418 fp-24=map_value fp-32=map_value This code is supposed to round the value in %r4 up to the nearest multiple of 8. So, if %r4 is 255, one would expect this to yield 256. Yet, it does not.