Re: backtrace support

[Vincent Pelletier <subdino2004@yahoo.fr>]

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Vincent Guffens wrote:
> This is a problem because I would say that it breaks compilation for
> other architectures. I think that the other architectures should have a
> function grub_backtrace() that does nothing, or even better that really
> does print a backtrace(). However, I don't know how to do it and I can't
> test it anyway.

For sparc64-ieee1275, there is a ctrace command in open firmware which
does that work. grub_backtrace() could do a
grub_ieee1275_interpret("ctrace",NULL);
then
grub_ieee1275_exit();

To make ctrace work the ELF has to be unstripped - for now I hardcoded
it in conf/sparc64-ieee1275.rmk. To my experience, -O1 produces an
easier to understand ASM than -O0 (sparc64-ieee1275 allows to run in
step-by-step or breakpoint mode) because -O0 does really dumb things
that is very verbose in ASM line number. But I don't know in details
what -O1 does, and if it has drawbacks in optimisation (I think about
local functions).

> I hope this backtrace will be usefull, but not too much !

I have already found a use for it : I can't make vbetest work, it fails
with out of range pointer.

I hope it will be committed soon.

Oh, by the way, I'm trying to implement the OpenFirmware framebuffer
primitives - for now with no luck - so we can have it on ieee1275 ports.
There are lots of FCODE examples on Google, but all for PPC.
My current problem is how to allocate memory for the framebuffer itself,
and how to pass the address "to frame_buffer_adr" (the usual FCODE way
to store a value), if possible without using grub_ieee1275_interpret.

Vincent Pelletier
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