... Don´t know in %, how much of c/p is done here, just followed based on the Ix190 code the hints from stubs_entry.S. 
// Stubs below should be checked. Stub not matched 100%, or difference found to current 'stubs_entry_2.S'
// Name Address Rule % Comp to stubs_entry_2.S
NHSTUB(DeleteFile_Fut ,0xff026a98) // 1 90%
NHSTUB(GetFocusLensSubjectDistanceFromLens ,0xff1d5260) // 3 90%
// ERROR: MakeDirectory_Fut is not found. //--- --- *** != 0xff027988
// ERROR: RefreshPhysicalScreen is not found. //--- --- *** != 0x00000000
// ERROR: TurnOffBackLight is not found. //--- --- *** != 0x00000000
// ERROR: TurnOnBackLight is not found. //--- --- *** != 0x00000000
// ERROR: close is not found. //--- --- *** != 0xff023e60
// ERROR: open is not found. //--- --- *** != 0xff023db0
// Check of modemap from 'platform/CAMERA/shooting.c':
// Firmware modemap table found @ff357224 -> ff6bdef8
// No problems found with modemap table.
lib.c: In function 'camera_set_led':
lib.c:45:45: warning: unused parameter 'bright' [-Wunused-parameter]
void camera_set_led(int led, int state, int bright) {
^
Compiles fine, of course no reaction from cam. Canon basic Romlog is not written/ empty.
For me here is land´s end, everything beyond was very new stuff, could continue when a volunteer makes ubasic available on this cam... 
Missed items in stubs_entry.S are defined in stubs_entry_2.S.
You can't just c / p it, you have to manually find the correct addresses in the firmware.
The ixus 180 uses DryOS r58, which means that the code in Loader / main.c is incorrect if you copy it from the ixus 190.
Ixus 190 has CreateTask located in ROM, unlike ixus180, this also needs to be fixed in boot.c and in taskhook.S
Mostly the ixus 190 is not a good reference port, the ixus 175 is much better.
