Messages in this thread | | | Date | Sun, 24 Sep 2006 23:25:40 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 5/7] Use %gs for per-cpu sections in kernel |
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Rusty Russell wrote: > I don't think so. There's *never* address subtraction, there's > sometimes 32 bit wrap (glibc uses this to effect subtraction, sure). > But there's no wrap here. > Hm, I guess, so long as you assume the kernel data segment is always below the kernel heap.
> To test, I changed the following: > > --- smpboot.c.~8~ 2006-09-25 15:51:50.000000000 +1000 > +++ smpboot.c 2006-09-25 16:00:36.000000000 +1000 > @@ -926,8 +926,9 @@ > unsigned long per_cpu_off) > { > unsigned limit, flags; > + extern char __per_cpu_end[]; > > - limit = (1 << 20); > + limit = PAGE_ALIGN((long)__per_cpu_end) >> PAGE_SHIFT; > limit is a size, rather than the end address, so this isn't quite right.
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