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modifying the reset handler asm code

Ash J

question 1:
This is the original reset handler that is in the startup file (*.s)

Reset_Handler   PROC
                EXPORT  Reset_Handler             [WEAK]
                IMPORT  SystemInit
                IMPORT  __main
                LDR     R0, =SystemInit
                BLX     R0
                LDR     R0, =__main
                BX      R0
                ENDP

which i modify to

Reset_Handler   PROC
                EXPORT  Reset_Handler             [WEAK]
                IMPORT  SystemInit
                IMPORT  OSInit
                IMPORT  __main
                LDR     R0, =SystemInit
                BLX     R0
                LDR     R0, =OSInit
                BLX     R0
                LDR     R0, =__main
                BX      R0
                ENDP

Here the OSInit is a function. This works fine.

But when i modify the original to following, I get a hard fault.

Reset_Handler   PROC
                EXPORT  Reset_Handler             [WEAK]
                IMPORT  SystemInit
                IMPORT  main
                IMPORT  OSInit
                LDR     R0, =SystemInit
                BLX     R0
                LDR     R0, =main
                BLX     R0                    ;getting hardfault here
                LDR     R0, =OSInit
                BX      R0
                ENDP


Irrespective of whether the OSInit is a function or a task, i get Hardfault.

question 2:
does the '__' (two underscores) before 'main' have any significance. Because when i write __OSInit, the compiler is unable to locate OSInit function (Error L6218E: undefined symbol).
but for '__main' the function name is always 'main' and compiler locates it.

Parents
  • 0 in reply to Ash J

    Your fault is that you don't realize that main() can be the function that initializes the OS. And that main() can then call funny_end_user_stupid_main_run_only_after_os_initialized_for_thread_1() and another_funny_end_user_main_run_only_after_os_initialized_for_thread_2().

    As long as your goal is to put the donkey behind the wagon, you are going to have huge issues. The world works much better if you try to follow the normal path instead of going against the stream. Especially since you don't really have anything to gain by mucking up the startup sequence.

Reply
  • 0 in reply to Ash J

    Your fault is that you don't realize that main() can be the function that initializes the OS. And that main() can then call funny_end_user_stupid_main_run_only_after_os_initialized_for_thread_1() and another_funny_end_user_main_run_only_after_os_initialized_for_thread_2().

    As long as your goal is to put the donkey behind the wagon, you are going to have huge issues. The world works much better if you try to follow the normal path instead of going against the stream. Especially since you don't really have anything to gain by mucking up the startup sequence.

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