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Re: [avr-gcc-list] Not naked but "topless" functions?

From: Kang Tin LAI
Subject: Re: [avr-gcc-list] Not naked but "topless" functions?
Date: Wed, 16 Oct 2002 22:07:17 +0800

As my understanding, you are the fourth one for this question of "naked"
attribute. Everyone playing avr-gcc with kernel have to face this

If this is a "address" operation in your function, it is also a trouble
regardless how many local you using.

If you are using linux, I may send you my patch for "naked" which
generates a proper stack frame setup. But you need to have your source
codes of gcc, binutils and compilation system working for recompiling
the avr-gcc.

Kang Tin LAI <address@hidden>

"Tvrtko A. Ursulin" wrote:
> Hello everyone!
> More questions...
> I need to write functions that dont push/pop registers on stack. But if I use
> __attribute__((naked)) then compiler omits code that adjusts stack pointer
> also. That is ok if my function uses less than available registers, but if
> not... trouble.
> My functions should adjust stack like this:
>  14e:   cd b7           in      r28, 0x3d       ; 61
>  150:   de b7           in      r29, 0x3e       ; 62
>  152:   25 97           sbiw    r28, 0x05       ; 5
>  154:   0f b6           in      r0, 0x3f        ; 63
>  156:   f8 94           cli
>  158:   de bf           out     0x3e, r29       ; 62
>  15a:   0f be           out     0x3f, r0        ; 63
>  15c:   cd bf           out     0x3d, r28       ; 61
> This is taken from function which uses 5 stack variables, hence sbiw r28,0x05.
> Btw, what does in/cli/out of SREG in default function prolog do? If it is
> supposed to ensure no interrupt occurs while manipulating SP, why "out
> 0x3f,r0" (enable interrupts right?) is not the last instruction?
> Thanks!
> avr-gcc-list at http://avr1.org
avr-gcc-list at http://avr1.org

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