Re: [PATCH] C undefined behavior fix

From: Geert Uytterhoeven (
Date: Thu Jan 03 2002 - 05:03:49 EST

On Thu, 3 Jan 2002, Paul Mackerras wrote:
> Richard Henderson writes:
> > Ignore strcpy. Yes, that's what visibly causing a failure here,
> > but the bug is in the funny pointer arithmetic. Leave that in
> > there and the compiler _will_ bite your ass sooner or later.
> I look forward to seeing your patch to remove all uses of
> virt_to_phys, phys_to_virt, __pa, __va, etc. from arch/alpha... :)

Isn't this why we use `unsigned long' to represent physical addresses, and
`void *' to represent kernel virtual addresses? Not only helps it against a
user dereferencing a physical address `pointer', but also against gcc trying to
be (too) smart.

Of course this also implies we have to change the pointer argument in readb()
and friends, since it's not a real pointer but a magic cookie. But we already
had that discussion last year...

[ and the conclusion was: keep the pointer, so we can do readl(&base->field) ]



Geert Uytterhoeven -- There's lots of Linux beyond ia32 --

In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds

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