EABI PowerPC - function without stack frame

[Thierry Moreau]

Frank Juergen-r58616 wrote:
>  
> Hi !!
> 
> I want to use a C function from the an exception vector (only this vector use this function). 
> For this reason I need a function without a stack frame (during this time is no memory available).
> 
> How can I do this with gcc (I use the gcc for the target eabi-powerpc ) ? 
> 
> I dig under __attribute__ but I can't find anything (possible I'm blind ;o) )

Your question is actually very specific to the powerpc model used in 
your application environment since PPC exception vectors use 
procesor-variant specific registers to save the current state. The PPC 
cache and MMU configuration define an execution environment which you 
need to comply before the C function can access memory.

The GCC run-time model in eabi-powerpc is isolated from these details. 
You have to work them in assembly-language exception vector processing, 
so that an EABI-compliant (in addition to cache and MMU-compliant) 
environment is created for your C function.

You got a great value with the GCC cross-compiler technology, with an 
adequately defined mission statement (EABI spec in this case). What it 
doesn't provide, you must make up.

As a reminder, your C function will be somehow restricted in which 
library function calls it can make (reentrancy concerns).

Have fun.

-- 

- Thierry Moreau

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