Fwd: Re: zlib-1.1.4 out - security fix

Ian Molton spyro at armlinux.org
Tue Mar 12 14:24:31 PST 2002


On a sunny Tue, 12 Mar 2002 17:05:37 -0500 (EST) Bill Maltby LFS Related
gathered a sheaf of electrons and etched in their motions the following
immortal words:

> Ah, at last! A man after my own heart. An assembly language,
> inline coder from the old IBM mainframe days!
> 
> Good to hear from you sir,
> 
> BALR 14, Save area is pointed to by GPR 13.

:-) close.

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.

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.

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 ;-)

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

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