How to control location of startup code?

[Toralf Lund]

Richard Earnshaw wrote:

>>>>Is there any way to control how the default startup code ends up in
>>>>        
>>>>
>>   the output file/the virutal address it gets and/or what output
>>   section it's included in?
>>
>>I do it by putting it in a seperate segment. More specifically, I have
>>my own "crt0.s" it contains the reset vector and other IRQ like things
>>below is the relavent snippit in ARM assembly
>>
>>
>>    
>>
>>>>	.section	.vectors
>>>>        
>>>>
>[...]
>  
>
>>The *PROBLEM* with this is by default the '.vectors' segment is not
>>tagged as loadable perhaps there is a way to do this in GAS, it was
>>not obvious to me.
>>
>>    
>>
>
>You need to set the section flags when you create the section, something 
>like:
>
>	.section .vectors, code, "ax"
>
>which tells the assembler that the section contains code, has to be 
>_A_llocated at load time and is e_X_ecutable.
>
>R.
>  
>
OK. Thanks to you both.

I really think there ought to be some way to match the startup code by 
file name in the linker script, though... Also, in the meantime, I've 
started wonder if I raelly want to handle crt0 this way. The alternative 
is to keep it in the normal code section, and have something like

vectors:
	ldr	pc, Reset_Addr
	ldr	pc, Undefined_Addr	/* Undefined instructions */
	ldr	pc, SWI_Addr
	ldr	pc, Prefetch_Addr	/* Prefetch abort*/
	ldr	pc, Abort_Addr		/* Data abort */
	nop				/* Reserved vector */
	ldr	pc, IRQ_Addr
	ldr	pc, FIQ_Addr
	
[ ... ]

resetHandler:
	[ initial system setup ]
	ldr	pc, Start_Addr

	.align 0
Reset_Addr:	.word resetHandler
[ ... ]
Start_Addr:	.word _start


in a separate file, and direct the associated object code to a different 
output section (which is easy.) Actually, I'm quite sure I want to keep 
the vectors separate, the question is really whether to target vectors 
*and* crt0 for the area starting at address 0, or just the vectors.

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