On 10/11/16 at 03:41pm, Baoquan He wrote: > Hi Eric, > > Thanks a lot for your reviewing! Sorry for late reply. > > On 10/06/16 at 03:07pm, Eric W. Biederman wrote: > > Baoquan He <bhe at redhat.com> writes: > > > > > KASLR memory randomization can randomize the base of the physical memory > > > mapping (PAGE_OFFSET), vmalloc (VMALLOC_START) and vmemmap > > > (VMEMMAP_START). These need be exported to VMCOREINFO so that user space > > > utility, mainly makedumpfile can use them to identify the base of each > > > memory section. Here using VMCOREINFO_NUMBER we can reuse the existing > > > struct number_table in makedumpfile to import data easily. > > > > > > Since they are related to x86_64 only, put them into > > > arch_crash_save_vmcoreinfo. And move the exportion of KERNEL_IMAGE_SIZE > > > together since it's also for x86_64 only. > > > > *Scratches my head* I would have thought this information would have > > better fit in the ELF header. Where it actually has a field for virtual > > address. It also has a field for physical address, and a third field > > for offset in the file (which is where the kdump finds these things in > > memory aftewards). > > > > Why do we need need more magic vmcoreinfo to handle this? > > Previously in x86_64, values of PAGE_OFFSET, VMALLOC and VMEMMAP are > fixed, makedumpfile also hard codes them. > > In kexec-tools, we try to get page_offset_base from /proc/kallsyms or > search it from /proc/kcore elf header with the help of virtual address > of symbol _stext. Then we save it into p_vaddr of kernel text program > segment. In kdump kernel, we may assume kernel text has the biggest > starting virtual address and search it from vmcore elf header. But I > can't think of a way to get the starting virtual address of vmalloc and > vmemmap which are necessary for makedumpfile analysis. > > So it's necessary to add them into VMCOREINFO to let makedumpfile know. PAGE_OFFSET can be get via vaddr - paddr from elf pt_loads so only VMALLOC_BASE and VMEMMAP_BASE is necessary.. Thanks Dave
