On Jul 22, 2014, at 2:40 PM, Alexander Nasonov <al...@yandex.ru> wrote:
> Matt Thomas wrote: >> >> On Jul 22, 2014, at 2:27 PM, Alexander Nasonov <al...@yandex.ru> wrote: >>> I allocate with the X flag and it seems to work: >>> >>> /* in sljitExecAllocator.c */ >>> return (void *)uvm_km_alloc(module_map, size, >>> PAGE_SIZE, UVM_KMF_WIRED | UVM_KMF_ZERO | UVM_KMF_EXEC); >> >> ok. Then you need don't a hook for cache flushing >> >> pmap_protect(vm_map_pamp(module_map), va, size) will do that for you. >> At least for arm/mips/ppc/vax. (e.g. changing a writeable exec page >> to read-only automatically causes it exec cleaned). > > sljit allocates 64K exec chucks which are managed by a special allocator. > You need to run pmap_protect for each chunk. I think it's cheaper to > flush icache. Maybe. But I'd prefer executable code to be in read-only pages so that malicious code can't be placed in them and executed. I think trading space for security is a valid tradeoff.
