Fwd: Re: zlib-1.1.4 out - security fix

Bill Maltby LFS Related lfsbill at wlmlx1.wlmcs.com
Tue Mar 12 15:26:14 PST 2002


Ian,

Just like the old Mainframes. 16 GPR, 15 is not IP, but is branch to
address in the BALR 14,15. I never fell in love with micro assem be-
cause there were so few registers and they were so restricted. Esp.
early on when haveing to pair them up for certain ops, and math was
a relative nightmare for similar reasons.

Ahhh, the good ol' 360/370 series. You could do almost any operation
to/from any combination of mem/reg. Including math, and in several
forms - native, packed, ebcidic, whatever.

And _knobs_ and _switches_. We could stop dead in their tracks,
single step, go over and spin a tape manually past a bad spot and
start that bugger up again.

Now all we can do is swear at the nasty little temperamental SOBs.

Oh, well, I could go on. I'll just say that I think I must be warped
because I remember so much of what I haven't since ... 1979?? It was
around there I discovered PWB V6/V7 and I was -*-*- in LUV!

> <snip>

> > Ah, at last! A man after my own heart. An assembly language,
> > inline coder from the old IBM mainframe days!
> ><snip>
 
> I'm actually from a backround of RISC OS - a bit of a backwater OS.
> 
> We have a branch instruction (B) and a Branch-linked insn. (BL) which have
> 26 bit scope, so they arent any use for shared libs on a 32 bit ARM.

26 bits? That's mainframe class in the old days. Burroughs, Honeywell and
several others had "mainframes" that had similar path widths.

> 
> for a 32 bit ARM we do more like
> 
> ADR Rdest, <location>
> LDR pc, [Rdest]
> 
> instead.
> 
> the 26 bit ARM does similar 'because it can' and is easier to maintain.
> 
> I have (almost) got ARM linux working on my 15 year old Acorn A410/1.

How long have you working at that "port". It sounds like an impressive
amount of dedication is needed. Fairly lonely endeavor?

> 
> It will start, init a framebuffer, and even load and run simple programs.
> however a call to fork() will kill things in short order - the child runs,
> but the parent does not ;-)

What's the prognosis, Doc? Think you'll find the cure eventaully?

> 
> I like the way that regs are so general purpose on ARM. R0-R12 are
> completely general. R13 is the stack, R14 the link register (used by BL),
> and R15 is the pc

The IBM had a separate IPC apart from the gen purp regs. But I'll tell
ya', that Acorn sound pretty good to me.

> 
> you can treat all 16 regs pretty much the same, including doing math on the
> PC :)

Oh yes! That's what a _real_ computer is - a machine that enables, not
disables the programmers.

Well, yacc atcha later,

Bill Maltby,
billm at wlmcs.com


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