* Ingo Molnar <[email protected]> wrote:
>
> * Linus Torvalds <[email protected]> wrote:
>
> > Your compiler generates
> >
> > movl -16(%ebp),%edx
> > movl (%edx),%edi /* this is _totally_ bogus! */
> > incl %edx
> > movl %edx,-16(%ebp)
> > movl %edi,%ecx
> > testb %cl,%cl
> > je ...
>
> ah, ok.
>
> > while I get (gcc version 4.1.2 20070925 (Red Hat 4.1.2-28)):
> >
> > movl -16(%ebp), %eax # p,
> > movzbl (%eax), %edi #, c /* not bogus! */
> > movl %edi, %edx # c,
> > testb %dl, %dl #
> > je .L64 #,
> > incl %eax #
> > movsbl %dl,%ebx #, D.12414
> > movl %eax, -16(%ebp) #, p
> >
> > where the difference (apart from doing the increment differently and
> > different register allocation) is that I have a "movzbl" (correct),
> > while you have a "movl" (pure and utter crap).
>
> i'll try with another compiler in a minute.
i just tried:
gcc version 4.1.2 20070626 (Red Hat 4.1.2-13)
and indeed the crash is gone. So you are completely right, it's a
compiler bug in 4.0.2 (it's vanilla gcc 4.0.2 built by me, not a distro
compiler). It should not affect normal kernels too much this bug needs
CONFIG_DEBUG_PAGEALLOC. (or it needs a _really_ unlucky allocation being
at the far upper end of RAM - but those are usually taken up by
boot-time allocations anyway).
i also just re-tried the other config as well - and crash is gone there
too. (not surprisingly)
Ingo
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