On Thu, Mar 18, 2021 at 10:10:55AM -0700, Sami Tolvanen wrote:
> +static void update_shadow(struct module *mod, unsigned long base_addr,
> + update_shadow_fn fn)
> +{
> + struct cfi_shadow *prev;
> + struct cfi_shadow *next;
> + unsigned long min_addr, max_addr;
> +
> + next = vmalloc(SHADOW_SIZE);
> +
> + mutex_lock(&shadow_update_lock);
> + prev = rcu_dereference_protected(cfi_shadow,
> + mutex_is_locked(&shadow_update_lock));
> +
> + if (next) {
> + next->base = base_addr >> PAGE_SHIFT;
> + prepare_next_shadow(prev, next);
> +
> + min_addr = (unsigned long)mod->core_layout.base;
> + max_addr = min_addr + mod->core_layout.text_size;
> + fn(next, mod, min_addr & PAGE_MASK, max_addr & PAGE_MASK);
> +
> + set_memory_ro((unsigned long)next, SHADOW_PAGES);
> + }
> +
> + rcu_assign_pointer(cfi_shadow, next);
> + mutex_unlock(&shadow_update_lock);
> + synchronize_rcu_expedited();
expedited is BAD(tm), why is it required and why doesn't it have a
comment?
> +
> + if (prev) {
> + set_memory_rw((unsigned long)prev, SHADOW_PAGES);
> + vfree(prev);
> + }
> +}
