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b7e5ffe5d8
If I try to do "cat /sys/kernel/debug/kernel_page_tables" I end up with: BUG: unable to handle kernel paging request at ffffc7fffffff000 IP: [<ffffffff8106aa51>] ptdump_show+0x221/0x480 PGD 0 Oops: 0000 [#1] SMP CPU 0 .. snip.. RAX: 0000000000000000 RBX: ffffc00000000fff RCX: 0000000000000000 RDX: 0000800000000000 RSI: 0000000000000000 RDI: ffffc7fffffff000 which is due to the fact we are trying to access a PFN that is not accessible to us. The reason (at least in this case) was that PGD[256] is set to __HYPERVISOR_VIRT_START which was setup (by the hypervisor) to point to a read-only linear map of the MFN->PFN array. During our parsing we would get the MFN (a valid one), try to look it up in the MFN->PFN tree and find it invalid and return ~0 as PFN. Then pte_mfn_to_pfn would happilly feed that in, attach the flags and return it back to the caller. 'ptdump_show' bitshifts it and gets and invalid value that it tries to dereference. Instead of doing all of that, we detect the ~0 case and just return !_PAGE_PRESENT. This bug has been in existence .. at least until 2.6.37 (yikes!) CC: stable@kernel.org Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> |
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.. | ||
debugfs.c | ||
debugfs.h | ||
enlighten.c | ||
grant-table.c | ||
irq.c | ||
Kconfig | ||
Makefile | ||
mmu.c | ||
mmu.h | ||
multicalls.c | ||
multicalls.h | ||
p2m.c | ||
pci-swiotlb-xen.c | ||
platform-pci-unplug.c | ||
setup.c | ||
smp.c | ||
spinlock.c | ||
suspend.c | ||
time.c | ||
trace.c | ||
vdso.h | ||
vga.c | ||
xen-asm_32.S | ||
xen-asm_64.S | ||
xen-asm.h | ||
xen-asm.S | ||
xen-head.S | ||
xen-ops.h |