How do I call the origianl function?

[Tousif Osman]

The last parameter is a void ** pointer which holds the original address. How do I call the original function?

[Michio Mada]

void (*orig_printf)(const char*);
xhook_register(".so library", "printf", my_printf, (void*)&orig_printf);

To call it use:
orig_printf(...);

[qingyu]

void (*orig_printf)(const char*);
xhook_register(".so library", "printf", my_printf, (void*)&orig_printf);

To call it use:
orig_printf(...);

Hello, I want to hook an open function, but its last parameter is an indefinite parameter, how can I hook it?

int open(const char* __path, int __flags, ...)

[moonoiza]

void (*orig_printf)(const char*);
xhook_register(".so library", "printf", my_printf, (void*)&orig_printf);

To call it use:
orig_printf(...);

Hello, I want to hook an open function, but its last parameter is an indefinite parameter, how can I hook it?

int open(const char* __path, int __flags, ...)

You gotta use var monitor. Here is an example:

int my_open(const char *file, int flags, ...)
{
int ret;
va_list args;
va_start(args, flags); //fetch all args after 'flags'
ret = open(file, flags, args); //pass args to open();
va_end(args); //stop monitoring
return ret;
}

[qingyu]

void (*orig_printf)(const char*);
xhook_register(".so library", "printf", my_printf, (void*)&orig_printf);

To call it use:
orig_printf(...);

Hello, I want to hook an open function, but its last parameter is an indefinite parameter, how can I hook it?
int open(const char* __path, int __flags, ...)

You gotta use var monitor. Here is an example:

int my_open(const char *file, int flags, ...)
{
int ret;
va_list args;
va_start(args, flags); //fetch all args after 'flags'
ret = open(file, flags, args); //pass args to open();
va_end(args); //stop monitoring
return ret;
}

I also wrote this, but the program can not enter, this is my code:

typedef void *xhook_func;

extern "C" char *__origin_path = NULL;
extern "C" char *__hook_path = NULL;

int new_open(const char *__path, int __flags, ...) {
va_list args;
va_start(args, __flags);

int r;

if (strcmp(__origin_path, __path) == 0) {
    r = open(__hook_path, __flags, args);
} else {
    r = open(__path, __flags, args);
}

return r;

}

extern "C" JNIEXPORT void JNICALL Java_com_qingyu_hook_Hooker_hookOpen(
JNIEnv *env, jclass type, jstring origin, jstring replace) {
__origin_path = (char )env->GetStringUTFChars(origin, 0);
__hook_path = (char )env->GetStringUTFChars(replace, 0);
//LOGW("%s",p_origin);
xhook_register( ".\.so$", "open", (xhook_func)&new_open, NULL);
xhook_register(".\.so$", "open64", (xhook_func)&new_open64, NULL);

xhook_refresh(0);

}

Please help me check, I was just getting started C language, thank you very much!

[moonoiza]

Don't you have any logcat to trace the exception ?

[qingyu]

Don't you have any logcat to trace the exception ?

Xhook will appear with these logs.
screenshot

[qingyu]

Don't you have any logcat to trace the exception ?

I got a instance here, has been successful hook, thank you for your help!