Re: [U-Boot-Users] Side-effects when adding debug output

13 Jul 2005


      In message 2D9AB865A49FD511914700105A0EF6790252BD31@morse.smart.lfk.eads.net you wrote:
...
I want to add some extra output to the functions do_bootm and do_bootm_linux
because I have problems with the kernel parameters. So i added a few
printf's to the functions mentioned above. The things that happen now, I do
not understand:
Don't use printf for debugging here. Use a debugger.
...
Parameters of called functions (e.g. like the "int argc" parameter) suddenly
change to random values. How could that be caused? Has it something to do
with the stack (overflow or undefined behaviour when using "printf")?
Passing control to the Linux kernel invoves giving up more  and  more
function  in  U-Boot, including things like overwriting the exception
vector table or so. Adding printf() to the wrong place may have funny
effects. You better know exactly what yuou are doing.
...
Or should I use any other function for creating output? (instead of using
the BDI2k)
Use the BDI2000. That's what it was made for.
Best regards,
Wolfgang Denk
-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
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thus ``(1)''. But thereafter I could not think of anything  connected
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