On 02/20/2015 03:15 AM, Rusty Russell wrote: > Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx> writes: >> On 02/19/2015 02:10 AM, Rusty Russell wrote: >>> This is not portable. Other archs don't use vmalloc, or don't use >>> (or define) MODULES_VADDR. If you really want to hook here, you'd >>> need a new flag (or maybe use PAGE_KERNEL_EXEC after an audit). >>> >> >> Well, instead of explicit (addr >= MODULES_VADDR && addr < MODULES_END) >> I could hide this into arch-specific function: 'kasan_need_to_allocate_shadow(const void *addr)' >> or make make all those functions weak and allow arch code to redefine them. > > That adds another layer of indirection. And how would the caller of > plain vmalloc() even know what to return? > I think I don't understand what do you mean here. vmalloc() callers shouldn't know anything about kasan/shadow. You were concerned that this patch is not portable, so I suggested to hide arch specific part in arch code. That's it. >>> Thus I think modifying the callers is the better choice. >>> >> >> I could suggest following (though, I still prefer 'modifying vmalloc' approach): >> * In do_init_module(), instead of call_rcu(&freeinit->rcu, do_free_init); >> use synchronyze_rcu() + module_memfree(). Of course this will be >> under CONFIG_KASAN. > > But it would be slow, and a disparate code path, which is usually a bad > idea. > >> As you said there other module_memfree() users, so what if they will decide >> to free memory in atomic context? > > Hmm, how about a hybrid: > > 1) Add kasan_module_alloc(p, size) after module alloc as your original. > 2) Hook into vfree(), and ignore it if you can't find the map. > That should work, but it looks messy IMO. > Or is the latter too expensive? > Not sure whether this will be too expensive or not, but definitely more expensive than simple (addr >= MODULES_VADDR && addr < MODULES_END) check. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>