On Wed, 9 Jan 2013 17:32:32 +0800
Tang Chen <tangchen@xxxxxxxxxxxxxx> wrote:
> +static void __meminit
> +remove_pagetable(unsigned long start, unsigned long end, bool direct)
> +{
> + unsigned long next;
> + pgd_t *pgd;
> + pud_t *pud;
> + bool pgd_changed = false;
> +
> + for (; start < end; start = next) {
> + pgd = pgd_offset_k(start);
> + if (!pgd_present(*pgd))
> + continue;
> +
> + next = pgd_addr_end(start, end);
> +
> + pud = (pud_t *)map_low_page((pud_t *)pgd_page_vaddr(*pgd));
> + remove_pud_table(pud, start, next, direct);
> + if (free_pud_table(pud, pgd))
> + pgd_changed = true;
> + unmap_low_page(pud);
> + }
> +
> + if (pgd_changed)
> + sync_global_pgds(start, end - 1);
> +
> + flush_tlb_all();
> +}
This generates a compiler warning saying that `next' may be used
uninitialised.
The warning is correct. If we take that `continue' on the first pass
through the loop, the "start = next" will copy uninitialised data into
`start'.
Is this the correct fix?
--- a/arch/x86/mm/init_64.c~memory-hotplug-common-apis-to-support-page-tables-hot-remove-fix-fix-fix-fix-fix-fix-fix
+++ a/arch/x86/mm/init_64.c
@@ -993,12 +993,12 @@ remove_pagetable(unsigned long start, un
bool pgd_changed = false;
for (; start < end; start = next) {
+ next = pgd_addr_end(start, end);
+
pgd = pgd_offset_k(start);
if (!pgd_present(*pgd))
continue;
- next = pgd_addr_end(start, end);
-
pud = (pud_t *)pgd_page_vaddr(*pgd);
remove_pud_table(pud, start, next, direct);
if (free_pud_table(pud, pgd))
_
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