On Sat, 14 Nov 2015, Matt Fleming wrote:
> The x86 pageattr code is confused about the data that is stored
> cpa->pfn, sometimes it's treated as a page frame number, sometimes
> it's treated as an unshifted physical address, and in one place it's
> treated as a pte.
Yuck.
> The result of this is that the mapping functions do not map the
> intended physical address.
>
> This isn't a problem in practice because most of the addresses we're
> mapping in the EFI code paths are already mapped in 'trampoline_pgd'
> and so the pageattr mappings functions don't actually do anything in
> this case. But when we move to using a separate page table for the EFI
> runtime this will be an issue.
Are you sure that this does not affect existing kernel versions?
> while (num_pages-- && start < end) {
> -
> - /* deal with the NX bit */
> - if (!(pgprot_val(pgprot) & _PAGE_NX))
> - cpa->pfn &= ~_PAGE_NX;
That should be a seperate patch because this is just bogus code and
has nothing to do with the pfn confusion.
> -
> - set_pte(pte, pfn_pte(cpa->pfn >> PAGE_SHIFT, pgprot));
> + set_pte(pte, pfn_pte(cpa->pfn, pgprot));
> diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
> index a0ac0f9c307f..c8b58ac47b77 100644
> --- a/arch/x86/platform/efi/efi_64.c
> +++ b/arch/x86/platform/efi/efi_64.c
> @@ -143,7 +143,7 @@ void efi_sync_low_kernel_mappings(void)
>
> int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> {
> - unsigned long text;
> + unsigned long pfn, text;
> struct page *page;
> unsigned npages;
> pgd_t *pgd;
> @@ -160,7 +160,8 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> * and ident-map those pages containing the map before calling
> * phys_efi_set_virtual_address_map().
> */
> - if (kernel_map_pages_in_pgd(pgd, pa_memmap, pa_memmap, num_pages, _PAGE_NX)) {
> + pfn = pa_memmap >> PAGE_SHIFT;
> + if (kernel_map_pages_in_pgd(pgd, pfn, pa_memmap, num_pages, _PAGE_NX)) {
> pr_err("Error ident-mapping new memmap (0x%lx)!\n", pa_memmap);
> return 1;
> }
> @@ -176,21 +177,29 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
> if (!IS_ENABLED(CONFIG_EFI_MIXED))
> return 0;
>
> + npages = (_end - _text) >> PAGE_SHIFT;
You really need to PFN_ALIGN _end and _text. Has been wrong in the
existing code as well.
> + text = __pa(_text);
> + pfn = text >> PAGE_SHIFT;
> +
> + if (kernel_map_pages_in_pgd(pgd, pfn, text, npages, 0)) {
> + pr_err("Failed to map kernel text 1:1\n");
> + return 1;
> + }
> +
> page = alloc_page(GFP_KERNEL|__GFP_DMA32);
> if (!page)
> panic("Unable to allocate EFI runtime stack < 4GB\n");
>
> efi_scratch.phys_stack = virt_to_phys(page_address(page));
> - efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */
> -
> - npages = (_end - _text) >> PAGE_SHIFT;
> - text = __pa(_text);
> + pfn = page_to_pfn(page);
>
> - if (kernel_map_pages_in_pgd(pgd, text >> PAGE_SHIFT, text, npages, 0)) {
> - pr_err("Failed to map kernel text 1:1\n");
> + if (kernel_map_pages_in_pgd(pgd, pfn, efi_scratch.phys_stack, 1, 0)) {
This looks like an unrelated change, hmm?
> + pr_err("Failed to map mixed mode stack\n");
> return 1;
> }
>
> + efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */
> +
> return 0;
> }
Thanks,
tglx
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