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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 | ||