On Wed, May 02, 2007 at 12:51:40AM -0700, Andrew Morton wrote:
>> Thanks for the report. I can reproduce it.
>> Bisection shows that x86_64-mm-paravirt-initial-pagetable.patch caused
>> this.
>> I didn't check whether the patch actually permits us to read kernel
>> memory. Probably it does. Probably we'd prefer that it didn't ;)
On Wed, May 02, 2007 at 01:46:17AM -0700, Bill Irwin wrote:
> Brown paper bag time. I don't know how it got past me.
Brain dump before crashing for the night:
The patch refuses to clobber already-present pagetable entries of
whatever origin. There are pagetables prior to this setup covering the
address range just above PAGE_OFFSET. If this theory is correct, you
should only be able to go a few MB above PAGE_OFFSET before encountering
unreadable kernel memory. IIRC those pagetables are a statically
allocated array in assembly; altering that array to set supervisor bits
may resolve it, though it may also be freed as initmem.
-- wli
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