[U-Boot-Users] Re: The i386 patch
wd at denx.de
Wed Nov 20 15:06:47 CET 2002
In message <200211201114.gAKBEss01326 at dagobert.svc.sysgo.de> you wrote:
> > What do you mean with "stack to copy"?
> The standard method for the x86 to implement a syscall is through a
> "gate", which is also a mechanism to switch to a higher protection level.
> Since caller and callee run at different protection levels, they use
But this is not what U-Boot needs.
> Does that mean that the caller always runs at the same protection level as
> If so, then I think that a syscall mechanism for the x86 through gates would
> be overkill. But then, OTOH, why use syscalls at all ? A simple jump table
> could do the same thing, and do it portably.
You may remember that we used a jump table attached to the global
data in early versions of PPCBoot. I didn't like this. The nice thing
about the syscall trap on PPC is that you can easily put a "jump
table" at a well-known location, so that a standalone application can
access certain services (those explicitely exported by U-Boot using
the syscall interface) without depending on a special software
I have to admit that I did not think about other architectures at the
time we implemented this.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
Remember that Beethoven wrote his first symphony in C ...
More information about the U-Boot