2.18 Hardware initialization

In general, it is beneficial to separate all system initialization code from the main application. However, some components of system initialization, for example, enabling of caches and interrupts, must occur after executing C library initialization code.

Note

This does not apply to ARMv6-M and ARMv7-M profiles.

Use of $Sub and $Super

You can make use of the $Sub and $Super function wrapper symbols to insert a routine that is executed immediately before entering the main application. This mechanism enables you to extend functions without altering the source code.
This example shows how $Sub and $Super can be used in this way:
extern void $Super$$main(void);
void $Sub$$main(void)
{
    cache_enable();    // enables caches
    int_enable();      // enables interrupts 
    $Super$$main();    // calls original main()
}
The linker replaces the function call to main() with a call to $Sub$$main(). From there you can call a routine that enables caches and another to enable interrupts.
The code branches to the real main() by calling $Super$$main().
Related information
About using $Super$$ and $Sub$$ to patch symbol definitions
Non-ConfidentialPDF file icon PDF versionARM DUI0471K
Copyright © 2010-2014 ARM. All rights reserved.