Messages in this thread | | | Date | Wed, 2 May 2007 03:06:00 -0700 | From | Bill Irwin <> | Subject | Re: [RFC BUG?] dereference PAGE_OFFSET address (rc7-mm2) |
| |
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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |