使用行号和列号将 map 一个源代码变量返回到它在一个结构变量中的定义 c

Question

如果我有一个这样的 c 程序：定义了node_s和list_s结构，并且list_get_first是定义为获取其第一个元素数据的 function；

typedef struct node_s {
    void          *data;
    struct node_s *next;
    struct node_s *prev;
} Node;

struct list_s {
    size_t  size;
    Node   *head;
    Node   *tail;
};

int list_get_first(CC_List *list, void **out)
{
    if (list->size == 0)                       // list->size: 9:14
        return -1;

    *out = list->head->data;                   // list->head->data: 12:13
    return 1;
}
...
  

假设我可以在运行时获取list->size: 9:14和list->head->data: 12:13的调试信息。 有没有一种简单的方法 map 可以自动将调试信息返回到其结构名称和关联字段名称的定义？ 我正在使用 clang 和 llvm 进行编译和代码分析。

Answer 1

您可以编写一个 LLVM pass 来完成这项工作。

1. 首先，确保在 clang 中使用“-g”生成调试信息，并使用“-S -emit-llvm”发出 LLVM IR
2. 创建一个自定义的 LLVM pass，尝试找到你需要的所有变量。
3. 对于每个加载指令，您必须找到这些变量的类型定义。 尝试获取它们的调试信息。
4. 为每个变量创建一个 map 到其在结构中的定义。

以下 function 显示了您将感兴趣的信息包含在元数据中的位置。 您可以获得它们并为每个变量创建 map。

static void findStructType(Module &M) {
  LLVM_DEBUG(M.dump());
  for (auto &F : M) {
    if (F.isDeclaration()) continue;
    for (auto &BB : F) {
      for (auto &I : BB) {
        if (I.getOpcode() == Instruction::Load) {
          if (I.hasMetadata("dbg")) {
            // This will give the line number for this load
            auto* node = dyn_cast<DILocation>(I.getMetadata("dbg"));
            node->dump();
          }
          // Here has the structure information for your structure
          if (F.hasMetadata("dbg")) {
            auto* subprog = dyn_cast<DISubprogram>(F.getMetadata("dbg"));
            subprog->getType()->dumpTree();
          }

          if (I.hasMetadata("tbaa")) {
            // This use TBAA for getting the type of this load;
            auto* tbaa = dyn_cast<MDNode>(I.getMetadata("tbaa"));  
            tbaa->getOperand(0)->dump(); // the struct type
            tbaa->getOperand(1)->dump(); // what is loading
            tbaa->getOperand(2)->dump(); // offset
          }
        }
      }
    }
  }
}

这是我可以从您的示例代码中得到的（只有第一条加载指令）：

<0x55e7875d1470> = !DISubroutineType(types: <0x55e787514828>)
  <0x55e787514828> = !{<0x55e7875cfb58>, <0x55e7875d1380>, <0x55e7875d1400>}
    <0x55e7875cfb58> = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
    <0x55e7875d1380> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: <0x55e7875d0230>, size: 64)
      <0x55e7875d0230> = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "list_s", file: <0x55e7875cc850>, line: 9, size: 192, elements: <0x55e78755c878>)
        <0x55e7875cc850> = !DIFile(filename: "example/dwarf/p1.c", directory: "/home/riple/IPRA-exp", checksumkind: CSK_MD5, checksum: "b2e16825badf1eb53bc8cb87df801efe")
        <0x55e78755c878> = !{<0x55e7875147c0>, <0x55e7875d1280>, <0x55e7875d1300>}
          <0x55e7875147c0> = !DIDerivedType(tag: DW_TAG_member, name: "size", scope: <0x55e7875d0230>, file: <0x55e7875cc850>, line: 10, baseType: <0x55e7875d0800>, size: 64)
            <0x55e7875d0800> = !DIDerivedType(tag: DW_TAG_typedef, name: "size_t", file: <0x55e7875d0780>, line: 46, baseType: <0x55e7875d06c8>)
              <0x55e7875d0780> = !DIFile(filename: "install/llvm/lib/clang/16.0.0/include/stddef.h", directory: "/home/riple/IPRA-exp", checksumkind: CSK_MD5, checksum: "89af46ad12914219411a5eaafda2889f")
              <0x55e7875d06c8> = !DIBasicType(name: "unsigned long", size: 64, encoding: DW_ATE_unsigned)
          <0x55e7875d1280> = !DIDerivedType(tag: DW_TAG_member, name: "head", scope: <0x55e7875d0230>, file: <0x55e7875cc850>, line: 11, baseType: <0x55e7875d1200>, size: 64, offset: 64)
            <0x55e7875d1200> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: <0x55e7875d1180>, size: 64)
              <0x55e7875d1180> = !DIDerivedType(tag: DW_TAG_typedef, name: "Node", file: <0x55e7875cc850>, line: 7, baseType: <0x55e7875d0c70>)
                <0x55e7875d0c70> = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "node_s", file: <0x55e7875cc850>, line: 3, size: 192, elements: <0x55e787593388>)
                  <0x55e787593388> = !{<0x55e7875d0d70>, <0x55e7875d0e70>, <0x55e7875d0ef0>}
                    <0x55e7875d0d70> = !DIDerivedType(tag: DW_TAG_member, name: "data", scope: <0x55e7875d0c70>, file: <0x55e7875cc850>, line: 4, baseType: <0x55e7875d0cf0>, size: 64)
                      <0x55e7875d0cf0> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
                    <0x55e7875d0e70> = !DIDerivedType(tag: DW_TAG_member, name: "next", scope: <0x55e7875d0c70>, file: <0x55e7875cc850>, line: 5, baseType: <0x55e7875d0df0>, size: 64, offset: 64)
                      <0x55e7875d0df0> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: <0x55e7875d0c70>, size: 64)
                    <0x55e7875d0ef0> = !DIDerivedType(tag: DW_TAG_member, name: "prev", scope: <0x55e7875d0c70>, file: <0x55e7875cc850>, line: 6, baseType: <0x55e7875d0df0>, size: 64, offset: 128)
          <0x55e7875d1300> = !DIDerivedType(tag: DW_TAG_member, name: "tail", scope: <0x55e7875d0230>, file: <0x55e7875cc850>, line: 12, baseType: <0x55e7875d1200>, size: 64, offset: 128)
    <0x55e7875d1400> = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: <0x55e7875d0cf0>, size: 64)
<0x55e7875d7878> = !{!"list_s", <0x55e7875d7628>, i64 0, <0x55e7875d36d8>, i64 8, <0x55e7875d36d8>, i64 16}
<0x55e7875d7628> = !{!"long", <0x55e7875d3698>, i64 0}
i64 0