On Thu, Mar 20, 2014 at 01:46:08PM +0800, WANG Chao wrote: > [CC Simon] > > On 03/19/14 at 09:33am, Vivek Goyal wrote: > > On Wed, Mar 19, 2014 at 03:05:51PM +0800, WANG Chao wrote: > > > On 03/17/14 at 08:56am, Vivek Goyal wrote: > > > > On Fri, Mar 14, 2014 at 04:20:18PM +0800, WANG Chao wrote: > > > > > With kASLR enabled (CONFIG_RANDOMIZED_BASE=y), kernel virtual address > > > > > base is PAGE_OFFSET plus a randomized offset from 0 to 1G. > > > > > > > > > > Current kexec-tools gets kernel vaddr and size from /proc/kcore. It > > > > > assumes kernel vaddr start/end is within the range [0,512M). If kaslr > > > > > enabled, kernel vaddr start/end will stay at [0+offset, 512M+offset). > > > > > > NACK this patch myself. > > > > > > There are several mistakes I made. I misunderstood some concepts. Then I > > > realize this kASLR issue is not trivial to fix. > > > > > > I think if kexec-tools needs to get kernel text mapping from kcore in > > > kALSR case, the max base offset (CONFIG_RANDOMIZE_MAX_BASE_OFFSET) of > > > the kernel text area must be exposed to userspace some where. We can use > > > that value to determine which area is for kernel text mapping and which > > > is for modules text mapping. > > > > How about looking at /proc/kallsyms and look at address of one of the > > symbols say _text. And search for the ELF header in kcore which contains > > _text address and that's ELF header representing kernel text mapping. > > Cool. I'd like to go with _stext. _text presents in /proc/kallsyms only > when CONFIG_KALLSYMS_ALL=y. What do you think? That's fine. Though looks like _stext will also work only if CONFIG_KALLSYMS=y. So that's not a perfect solution either for those who have built kernel using CONFIG_KALLSYMS=n. Thanks Vivek
