On 10/27/16 at 11:41am, Dave Anderson wrote: > > > ----- Original Message ----- > > > > > > ----- Original Message ----- > > > > > > > > That being said, my recent 4.8 and 4.9 KASLR testing has been on live > > > systems and compressed kdumps, so the old tried-and-true manner of > > > calculating the phys_base from the ELF PT_LOAD segments apparently > > > no longer works with KASLR. > > > > > > It would be so much more helpful if the VMCOREINFO data in the ELF > > > header stored the actual phys_base value instead of its symbol value: > > > > > > crash> help -D > > > ... > > > SYMBOL(phys_base)=ffffffffa740b010 > > > ... > > > > > > which is completely useless unless the phys_base value is known. > > > > > > Anyway, can you send me the makedumpfile code that calculates the > > > phys_base value? > > > > > > Dave > > > > As it turns out, the problem with the crash utility is that it has to > > calculate phys_base well before it even knows the kernel has been relocated > > by KASLR. So when it sees the __START_KERNEL_map PT_LOAD segment, it > > mistakes > > it for the kernel modules' virtual address region and skips it. > > > > The kernel has this: > > > > #if defined(CONFIG_RANDOMIZE_BASE) > > #define KERNEL_IMAGE_SIZE (1024 * 1024 * 1024) > > #else > > #define KERNEL_IMAGE_SIZE (512 * 1024 * 1024) > > #endif > > > > and then this: > > > > #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE) > > > > So with KASLR, MODULES_VADDR gets pushed up from the traditional ffffffffa0000000 > > up to ffffffffc0000000. > > > > So I'm curious as to what you use in makedumpfile to determine whether > > CONFIG_RANDOMIZE_BASE has been configured? > > > > Thanks, > > Dave > > Hey, sorry, I didn't notice that this was added upstream: > > commit 1303a27c9c32020a3b6ac89be270d2ab1f28be24 > Author: Baoquan He <bhe at redhat.com> > Date: Wed Sep 9 15:39:03 2015 -0700 > > kexec: export KERNEL_IMAGE_SIZE to vmcoreinfo > > With that in place, it will be an easy fix for the crash utility. Dave, I confirmed your fix in crash git tree works, it also works for the elf format vmcore, /proc/vmcore and makedumpfile -E created vmcore. Thanks for the quick fix.. > > Thanks, > Dave > > > > > > > > > > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec
