关键词: 固件代码，区间分析，不确定位，位运算

Abstract: The variable intervals analysis plays an important role in program data-flow analysis. There are two different operations, word-level and bit level. For the traditional iterative algorithm is inefficient to analyze the result intervals of bitwise operations if the variable has a large range, a quick bitwise operation method was proposed, which turns variables into the uncertainty bit form, and then makes the bitwise operators. When the uncertainty bit form of a variable needs to do word-level operation, the interval generated algorithm proposed can convert the form to the intervals. The experimental results show that the proposed method is time-consuming stability and more efficient than iterative algorithm with variable range large, and has a downward trend when the variable range expands.

Key words: Firmware code, Interval analysis, Uncertainty bit, Bit operation