Re: [PATCH 3/3] mini-os: mm: convert set_readonly() to use walk_pt()

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Juergen Gross, le mer. 31 juil. 2024 15:00:26 +0200, a ecrit:
> +static int set_readonly_func(unsigned long va, unsigned int lvl, bool 
> is_leaf,
> +                             pgentry_t *pte, void *par)
> +{
> +    struct set_readonly_par *ro = par;
>  
> +    mmu_updates[ro->count].ptr = virt_to_mach(pte);
> +    mmu_updates[ro->count].val = *pte & ~_PAGE_RW;
> +    ro->count++;
> +
> +    if ( (ro->count == L1_PAGETABLE_ENTRIES ||
> +          va + 2 * PAGE_SIZE > ro->etext) &&
> +         HYPERVISOR_mmu_update(mmu_updates, ro->count, NULL, DOMID_SELF) < 0 
> )
> +    {
> +        printk("ERROR: set_readonly(): PTE could not be updated\n");
> +        do_exit();
> +    }

Don't we also want to set ro->count to 0?
And assert that it is 0 after calling walk_pt in set_readonly, to make
sure the va + 2 * PAGE_SIZE > ro->etext test did work properly
(personally I would have rather made set_readonly call a last
HYPERVISOR_mmu_update in case ro->count is not 0, which looks more
robust that a quite magic-looking va + 2 * PAGE_SIZE > ro->etext test)

Samuel