On Tue, May 10, 2016 at 11:24 PM, Ingo Molnar <[email protected]> wrote: > > * Kees Cook <[email protected]> wrote: > >> +/* >> + * Mapping information structure passed to kernel_ident_mapping_init(). >> + * Due to relocation, pointers must be assigned at run time not build time. >> + */ >> +static struct x86_mapping_info mapping_info = { >> + .pmd_flag = __PAGE_KERNEL_LARGE_EXEC, >> +}; > >> +void initialize_identity_maps(void) >> { >> + /* Init mapping_info with run-time function/buffer pointers. */ >> + mapping_info.alloc_pgt_page = alloc_pgt_page; >> + mapping_info.context = &pgt_data; > > Could you please outline the precise failure mode? What gets executed when, > which > pointer gets relocated and which not, and exactly when does it pose a problem, > etc.
It's the issue described at the top of misc.c: /* * WARNING!! * This code is compiled with -fPIC and it is relocated dynamically at * run time, but no relocation processing is performed. This means that * it is not safe to place pointers in static structures. */ Should this be repeated in each .c file maybe as a reminder? If the rest of the patches look good, we could clean this up as a following patch? What do you think? -Kees -- Kees Cook Chrome OS & Brillo Security
