• libVEX学习


    VEX IR是一种更加接近于compiler使用的中间语言/中间表示,它是不依赖于特定体系架构的。

    1. Code Blocks

    code blocks是VEX处理代码的一个单元,使用IRSB结构体表示:

    /* Code blocks, which in proper compiler terminology are superblocks
       (single entry, multiple exit code sequences) contain:
      【与Intel Pin中的概念trace是相似的】 - A table giving a type for each temp (the "type environment") - An expandable array of statements - An expression of type 32 or 64 bits, depending on the guest's word size, indicating the next destination if the block executes all the way to the end, without a side exit - An indication of any special actions (JumpKind) needed for this final jump. "IRSB" stands for "IR Super Block". */ typedef struct { IRTypeEnv* tyenv; IRStmt** stmts; Int stmts_size; Int stmts_used; IRExpr* next; IRJumpKind jumpkind; } IRSB;

      

     Each IRSB contains three things:
       - a type environment, which indicates the type of each temporary
         value present in the IRSB
       - a list of statements, which represent code
       - a jump that exits from the end the IRSB
    

     

    2. Statements and Expressions

    Statements (type 'IRStmt') represent operations with side-effects,
       eg.  guest register writes, stores, and assignments to temporaries.
       Expressions (type 'IRExpr') represent operations without
       side-effects, eg. arithmetic operations, loads, constants.
       Expressions can contain sub-expressions, forming expression trees,
       eg. (3 + (4 * load(addr1)).
    

    Statements: IRStmt

    代表着有side-effect的操作;

    Expressions: IRExpr

    代表着没有side-effect的操作;

    3. Storage of guest state

    guest state,其实就是代表目标机器寄存器的一片连续的缓存。

    在这片缓存上可以进行Put/Get操作。

    Put/Get操作需要提供两个参数:

    在代表guest state的缓存中的offset
    
    代表操作数长度的type
    
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  • 原文地址:https://www.cnblogs.com/long123king/p/3791344.html
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