-Instruction BPF_MOVSX does move operation with sign extension.
-``BPF_ALU | MOVSX`` sign extendes 8-bit and 16-bit into 32-bit and upper 32-bit are zeroed.
-``BPF_ALU64 | MOVSX`` sign extends 8-bit, 16-bit and 32-bit into 64-bit.
+For unsigned operations (``BPF_DIV`` and ``BPF_MOD``), for ``BPF_ALU``,
+'imm' is interpreted as a 32-bit unsigned value. For ``BPF_ALU64``,
+'imm' is first sign extended from 32 to 64 bits, and then interpreted as
+a 64-bit unsigned value.
+
+For signed operations (``BPF_SDIV`` and ``BPF_SMOD``), for ``BPF_ALU``,
+'imm' is interpreted as a 32-bit signed value. For ``BPF_ALU64``, 'imm'
+is first sign extended from 32 to 64 bits, and then interpreted as a
+64-bit signed value.
+
+The ``BPF_MOVSX`` instruction does a move operation with sign extension.
+``BPF_ALU | BPF_MOVSX`` sign extends 8-bit and 16-bit operands into 32
+bit operands, and zeroes the remaining upper 32 bits.
+``BPF_ALU64 | BPF_MOVSX`` sign extends 8-bit, 16-bit, and 32-bit
+operands into 64 bit operands.