当我使用 dl_open()
时,我能否以编程方式从共享库(仅限 Linux)中获取所有函数名称的列表?
我想要这样的东西:
std::vector<std::string> list_all_functions(void *dl) {
//... what can I do here?
}
int main() {
void * dl = dl_open("./mylib.so", RTLD_NOW);
auto functions = list_all_functions(dl);
//...
dl_close(dl);
return 0;
}
示例库(mylib.so)
标题(.h):
extern "C" {
int sum (int a, int b);
}
来源(.c):
int sum (int a, int b) { return a + b; }
我知道的肮脏技巧:使用 nm
或 objdump
实用程序
最佳答案
更新 |长话短说:
我实际上找到了更短的方法:
auto library = dlopen("/path/to/lib.so", RTLD_LAZY | RTLD_GLOBAL);
const char * libname = "lib.so";
struct link_map * map = nullptr;
dlinfo(library, RTLD_DI_LINKMAP, &map);
Elf64_Sym * symtab = nullptr;
char * strtab = nullptr;
int symentries = 0;
for (auto section = map->l_ld; section->d_tag != DT_NULL; ++section)
{
if (section->d_tag == DT_SYMTAB)
{
symtab = (Elf64_Sym *)section->d_un.d_ptr;
}
if (section->d_tag == DT_STRTAB)
{
strtab = (char*)section->d_un.d_ptr;
}
if (section->d_tag == DT_SYMENT)
{
symentries = section->d_un.d_val;
}
}
int size = strtab - (char *)symtab;
for (int k = 0; k < size / symentries; ++k)
{
auto sym = &symtab[k];
// If sym is function
if (ELF64_ST_TYPE(symtab[k].st_info) == STT_FUNC)
{
//str is name of each symbol
auto str = &strtab[sym->st_name];
printf("%s\n", str);
}
}
旧
我相信作者不再需要这个,但也许有人需要实际代码,这里是(基于之前的回答)
首先,我们需要为 dl_iterate_phdr()
回调:
static int callback(struct dl_phdr_info *info, size_t size, void *data)
{
// data is copy of 2nd arg in dl_iterate_phdr
// you can use it for your lib name as I did
const char * libname = (const char *)data;
// if current elf's name contains your lib
if (strstr(info->dlpi_name, libname))
{
printf("loaded %s from: %s\n", libname, info->dlpi_name);
for (int j = 0; j < info->dlpi_phnum; j++)
{
// we need to save dyanmic section since it contains symbolic table
if (info->dlpi_phdr[j].p_type == PT_DYNAMIC)
{
Elf64_Sym * symtab = nullptr;
char * strtab = nullptr;
int symentries = 0;
auto dyn = (Elf64_Dyn *)(info->dlpi_addr + info->dlpi_phdr[j].p_vaddr);
for (int k = 0; k < info->dlpi_phdr[j].p_memsz / sizeof(Elf64_Dyn); ++k)
{
if (dyn[k].d_tag == DT_SYMTAB)
{
symtab = (Elf64_Sym *)dyn[k].d_un.d_ptr;
}
if (dyn[k].d_tag == DT_STRTAB)
{
strtab = (char*)dyn[k].d_un.d_ptr;
}
if (dyn[k].d_tag == DT_SYMENT)
{
symentries = dyn[k].d_un.d_val;
}
}
int size = strtab - (char *)symtab;
// for each string in table
for (int k = 0; k < size / symentries; ++k)
{
auto sym = &symtab[k];
auto str = &strtab[sym->st_name];
printf("%s\n", str);
}
break;
}
}
}
return 0;
}
接下来,我们调用dl_iterate_phdr()
:
int main()
{
auto library = dlopen("/path/to/library.so", RTLD_LAZY | RTLD_GLOBAL);
const char * libname = "library.so";
dl_iterate_phdr(callback, (void*)libname);
return 0;
}
如果您需要将这些名称存储在某个地方,您可以将一个指针传递给您的容器,用强制转换恢复它并写在那里。
对于我的示例库:
#include "simple_lib.h"
#include <cstdio>
void __attribute__ ((constructor)) initLibrary(void)
{
printf("Library is initialized\n");
}
void __attribute__ ((destructor)) cleanUpLibrary(void)
{
printf("Library is exited\n");
}
void make_number()
{
printf("1\n");
}
打印这个:
Library is initialized
_ITM_deregisterTMCloneTable
puts
__gmon_start__
_ITM_registerTMCloneTable
__cxa_finalize
_Z11initLibraryv
make_number
_Z14cleanUpLibraryv
Library is exited
关于c++ - 以编程方式获取共享库中的函数名称,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/54888147/