Messages in this thread Patch in this message | | | Date | Mon, 4 Feb 2013 15:04:17 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH v6 08/15] memory-hotplug: Common APIs to support page tables hot-remove |
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On Wed, 9 Jan 2013 17:32:32 +0800 Tang Chen <tangchen@cn.fujitsu.com> 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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