假设main.c使用来自共享库的符号和在中声明的局部函数main.c。
main.c
有没有一种很好的,优雅的方法来在运行时打印所有可用函数名称和符号的列表?
由于数据已加载到.code段中,因此应该可行。
.code
由于我同样需要在运行时检索所有已加载的符号名称,因此我根据R ..的答案进行了一些研究。因此,这里是ELF格式的Linux共享库的详细解决方案,该解决方案可与我的gcc 4.3.4一起使用,但也希望与新版本一起使用。
我主要使用以下资源来开发此解决方案:
这是我的代码。我使用自解释变量名并添加了详细注释以使其易于理解。如果有什么错误或遗漏,请让我知道…(编辑:我刚刚意识到问题是C的,而我的代码是C ++的。但是,如果省略向量和字符串,它也应适用于C )
#include <link.h> #include <string> #include <vector> using namespace std; /* Callback for dl_iterate_phdr. * Is called by dl_iterate_phdr for every loaded shared lib until something * else than 0 is returned by one call of this function. */ int retrieve_symbolnames(struct dl_phdr_info* info, size_t info_size, void* symbol_names_vector) { /* ElfW is a macro that creates proper typenames for the used system architecture * (e.g. on a 32 bit system, ElfW(Dyn*) becomes "Elf32_Dyn*") */ ElfW(Dyn*) dyn; ElfW(Sym*) sym; ElfW(Word*) hash; char* strtab = 0; char* sym_name = 0; ElfW(Word) sym_cnt = 0; /* the void pointer (3rd argument) should be a pointer to a vector<string> * in this example -> cast it to make it usable */ vector<string>* symbol_names = reinterpret_cast<vector<string>*>(symbol_names_vector); /* Iterate over all headers of the current shared lib * (first call is for the executable itself) */ for (size_t header_index = 0; header_index < info->dlpi_phnum; header_index++) { /* Further processing is only needed if the dynamic section is reached */ if (info->dlpi_phdr[header_index].p_type == PT_DYNAMIC) { /* Get a pointer to the first entry of the dynamic section. * It's address is the shared lib's address + the virtual address */ dyn = (ElfW(Dyn)*)(info->dlpi_addr + info->dlpi_phdr[header_index].p_vaddr); /* Iterate over all entries of the dynamic section until the * end of the symbol table is reached. This is indicated by * an entry with d_tag == DT_NULL. * * Only the following entries need to be processed to find the * symbol names: * - DT_HASH -> second word of the hash is the number of symbols * - DT_STRTAB -> pointer to the beginning of a string table that * contains the symbol names * - DT_SYMTAB -> pointer to the beginning of the symbols table */ while(dyn->d_tag != DT_NULL) { if (dyn->d_tag == DT_HASH) { /* Get a pointer to the hash */ hash = (ElfW(Word*))dyn->d_un.d_ptr; /* The 2nd word is the number of symbols */ sym_cnt = hash[1]; } else if (dyn->d_tag == DT_STRTAB) { /* Get the pointer to the string table */ strtab = (char*)dyn->d_un.d_ptr; } else if (dyn->d_tag == DT_SYMTAB) { /* Get the pointer to the first entry of the symbol table */ sym = (ElfW(Sym*))dyn->d_un.d_ptr; /* Iterate over the symbol table */ for (ElfW(Word) sym_index = 0; sym_index < sym_cnt; sym_index++) { /* get the name of the i-th symbol. * This is located at the address of st_name * relative to the beginning of the string table. */ sym_name = &strtab[sym[sym_index].st_name]; symbol_names->push_back(string(sym_name)); } } /* move pointer to the next entry */ dyn++; } } } /* Returning something != 0 stops further iterations, * since only the first entry, which is the executable itself, is needed * 1 is returned after processing the first entry. * * If the symbols of all loaded dynamic libs shall be found, * the return value has to be changed to 0. */ return 1; } int main() { vector<string> symbolNames; dl_iterate_phdr(retrieve_symbolnames, &symbolNames); return 0; }