C function Logos directives

[uroboro]

Added %hookf and %origf directives for hooking C functions while supporting groups and using a variant of %orig.
%hookf takes a variadic number of arguments: the function return type, the function name, the function argument list. It generates the original function function pointer from these values and the current group.
%hookf takes a variadic number to pass to the original function, which is calculated from saving the current function name in %hookf and the current group.

[uroboro]

Example code:

#import <notify.h>

%hook NSNotificationCenter
- (void)postNotification:(NSNotification *)notification {
        %orig;
}
%end

// notify_*
%hookf(uint32_t, notify_post, const char *name) {
        uint32_t r = %origf(name);
        return r;
}

%group gNSNotificationCenter

%hook NSNotificationCenter
- (void)postNotification:(NSNotification *)notification {
        %orig;
}
%end

// notify_*
%hookf(uint32_t, notify_post, const char *name) {
        uint32_t r = %origf(name);
        return r;
}

%end /* gNSNotificationCenter */


%ctor {
        if (someCondition) {
                %init(gNSNotificationCenter);
        } else {
                %init();
        }
}

[DHowett]

This is substrate-only, unfortunately. It should be in Logos::Generator::MobileSubstrate. Maybe Logos::Generator::internal::Function should throw an error.

[uroboro]

New example code to test newer additions:

%config(generator=MobileSubstrate);
//%config(generator=internal); //uncomment to break everything

%group _regrouped
%hookf(int, cool, int n, int(*(*fp)(int x))(int (*y)(int m)), const char *name, int sizes[10], struct {int x;} (*fp1)(struct{int y;} w), int(*fp2[10])(void)) {
        otherfp = &%orig;
        return %orig(0, fp, "int(*(*fp)(int x))(int (*y)(int m))", NULL, NULL);
}
%end
%hookf(int, cool, int n, int(*(*fp)(int x))(int (*y)(int m)), const char *name, int sizes[10], struct {int x;} (*fp1)(struct{int y;} w), int(*fp2[10])(void)) {
        return %orig();
}

%ctor {
        if (someCondition) {
                %init(_regrouped);
        } else {
                %init();
        }
}

[tyilo]

Maybe add support for other functions than MSHookFunction? (eg. rd_route, mach_override)

Both of the functions they provide takes the same arguments in the same order as MSHookFunction, so you could just use #define MSHookFunction rd_route.
Maybe add a config option instead: %config(hookf=rd_route)?

[ryanb93]

Would be great to see this merged soon.

[ahyattdev]

Why has this not been merged? Is there another way to hook C functions or something?

[youmingtaiziback]

Cool feature