[PAC] Support concurrent read/write on sensitive fields and PAC fields in DFI. 支持DFI中敏感字段和PAC字段的并发读写. · Pull Request !654 · OpenHarmony/third_party_llvm-project

【任务描述 Problem Description】

当前DFI方案中存在敏感字段和其校验值的读写并发问题。
In the current DFI scheme, there is a concurrent read and write issue for sensitive data fields and their pac values.

DFI方案利用ARM AArch64的PAC特性保护结构体中的非指针类型的敏感数据字段，方法是存入敏感数据data时利用pacga指令计算其校验值pac，将data和pac值存入struct中，读取data时会再次计算pac，比较两次的pac值是否一致来判断data值是否被恶意篡改。
The DFI scheme uses the PAC feature of ARM AArch64 to protect sensitive data fields in a struct. This is done by using the pacga instruction to calculate the pac value for sensitive data, and then storing the data and pac value in the struct. When reading data, the pac value is recalculated and compared to the stored pac value to determine if the data has been maliciously tampered with.

然而data和pac值的读取和写入并非原子操作，而是读端分两次读取，写端分两次写入，这就使得在多线程场景下，读端有概率因并发写入读取到并不匹配的data和pac。
However, the reading and writing of data and pac values are not atomic operations, but rather, the read end reads the values in two parts, and the write end writes the values in two parts. This allows for the possibility in a multithreaded environment that the read end may read data and pac values that do not match due to concurrent writes.

因此，需要在DFI方案中增加新的插桩方式，集成锁的逻辑，保证并发场景下data和pac值读写的正确性。
Therefore, a new instrument method needs to be added to the DFI scheme to integrate locking logic and ensure the correctness of the data and pac value reads and writes in concurrent scenarios.

【解决方案 Solution】

为了在DFI中增加新的插桩方式并且保留原有的DFI插桩方式，需要修改LLVM前端增加新的attribute用于区别原有的插桩方法，并在中端的Pass插件中根据LLVM前端传来的需要保护的字段添加带锁逻辑的插桩代码。
To add a new instrument in DFI while preserving the original DFI instrument method, we need to modify the LLVM/clang to add a new attribute for differentiating the original instrument method, and add instrument with locking logic for fields that need to be protected in the LLVM Pass.

类型	指派人员	状态
审查		已完成 (1/1)
测试		已完成 (1/1)

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