L4/Alpha palcodes

Sebastian Schoenberg schoenbg at sophia.inf.tu-dresden.de
Tue Jan 22 13:19:56 CET 2002


Yes, they were set to numbers which do not conflict with OSF/Linux/WinNT.

A PALcall instuction is coded as cmd (6 bits) = 0, number (26 bits).
There are two ways of calling PALcode: A direct way, where a certain address
is called, or an indirect way, which must examine the calling instruction to
jump to the right place.

All L4Alpha PALcalls are located at the end of direct-callable PALcalls,
hence they are fast and do not conflict with any other system

Seb

> -----Original Message-----
> From: Daniel Potts [mailto:danielp at cse.unsw.edu.au] 
> Sent: Dienstag, 22. Januar 2002 09:50
> To: Goswin Brederlow
> Cc: l4-hackers at os.inf.tu-dresden.de
> Subject: Re: L4/Alpha palcodes
> 
> 
> On 22 Jan 2002, Goswin Brederlow wrote:
> 
> > Hi,
> >
> > I hope this is the right place, havent read anything here for ages.
> >
> >
> > I was wondering whether the palcodes used by L4 on Alpha 
> are disjunct 
> > to the ones used by OSF / BSD / Linux.
> 
> yes they are. An exception is l4_whoami which is an 
> experimental syscall anyway. I think it maps directly to the 
> OSF whoami call.
> 
> >
> > If not could they be made disjunct?
> >
> >
> > The idea I have in mind is to make a module for linux that 
> catches the 
> > L4 syscalls and throws them back into user-space. That way a L4 
> > environment could be setup within linux.  It would be much like 
> > user-space-linux and would save a lot of reboots just to test out a 
> > few bytes of code.
> 
> heh :) That would be an interesting project. I'd be 
> interested to know how (if) you will deal with device 
> drivers, memory etc.
> 
> > On the other hand, inside L4 you could do the same with OSF / BSD / 
> > Linux syscalls and thus run their binaries under L4. (You 
> want to run 
> > Netscape under L4? Or Mathematica? Or something as simple as xemacs 
> > and gcc?)
> >
> >
> > A l4-linux for alpha would also need those changes (if any) 
> I believe.
> 
> Yes that is how we would run unmodified Linux/Alpha binaries on L4..
> 
> Cheers,
> Daniel
> 
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