我想做的事情很简单。当我启动猫鼬服务器时,我想创建一个额外的线程来完成一些额外的工作。为了做到这一点,我想我需要LD_PRELOAD
the __libc_start_main
服务器的。
/* This is spec_hooks.cpp */
typedef int (*main_type)(int, char**, char**);
struct arg_type
{
char **argv;
int (*main_func) (int, char **, char **);
};
main_type saved_init_func = NULL;
void tern_init_func(int argc, char **argv, char **env){
dprintf("%04d: __tern_init_func() called.\n", (int) pthread_self());
if(saved_init_func)
saved_init_func(argc, argv, env);
__tern_prog_begin(); //create a new thread in this function
}
extern "C" int my_main(int argc, char **pt, char **aa)
{
int ret;
arg_type *args = (arg_type*)pt;
dprintf("%04d: __libc_start_main() called.\n", (int) pthread_self());
ret = args->main_func(argc, args->argv, aa);
return ret;
}
extern "C" int __libc_start_main(
void *func_ptr,
int argc,
char* argv[],
void (*init_func)(void),
void (*fini_func)(void),
void (*rtld_fini_func)(void),
void *stack_end)
{
typedef void (*fnptr_type)(void);
typedef int (*orig_func_type)(void *, int, char *[], fnptr_type,
fnptr_type, fnptr_type, void*);
orig_func_type orig_func;
arg_type args;
void * handle;
int ret;
// Get lib path.
Dl_info dli;
dladdr((void *)dlsym, &dli);
std::string libPath = dli.dli_fname;
libPath = dli.dli_fname;
size_t lastSlash = libPath.find_last_of("/");
libPath = libPath.substr(0, lastSlash);
libPath += "/libc.so.6";
libPath = "/lib/x86_64-linux-gnu/libc.so.6";
if(!(handle=dlopen(libPath.c_str(), RTLD_LAZY))) {
puts("dlopen error");
abort();
}
orig_func = (orig_func_type) dlsym(handle, "__libc_start_main");
if(dlerror()) {
puts("dlerror");
abort();
}
dlclose(handle);
dprintf("%04d: __libc_start_main is hooked.\n", (int) pthread_self());
args.argv = argv;
args.main_func = (main_type)func_ptr;
saved_init_func = (main_type)init_func;
saved_fini_func = (fini_type)rtld_fini_func;
ret = orig_func((void*)my_main, argc, (char**)(&args),
(fnptr_type)tern_init_func, (fnptr_type)fini_func,
rtld_fini_func, stack_end);
return ret;
}
但是,我不知道如何为此编写 Makefile。有人可以给我任何帮助吗?有什么需要注意的吗?