Commit b61a76f8 authored Nov 27, 2015 by Matt Fleming Committed by Ingo Molnar Nov 29, 2015

x86/efi: Map RAM into the identity page table for mixed mode



We are relying on the pre-existing mappings in 'trampoline_pgd'
when accessing function arguments in the EFI mixed mode thunking
code.

Instead let's map memory explicitly so that things will continue
to work when we move to a separate page table in the future.

Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1448658575-17029-4-git-send-email-matt@codeblueprint.co.uk


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent edc3b912

arch/x86/platform/efi/efi_64.c

+20 −0

Original line number	Diff line number	Diff line
		@@ -144,6 +144,7 @@ void efi_sync_low_kernel_mappings(void)
		int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
		{
		unsigned long pfn, text;
		efi_memory_desc_t *md;
		struct page *page;
		unsigned npages;
		pgd_t *pgd;
		@@ -177,6 +178,25 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
		if (!IS_ENABLED(CONFIG_EFI_MIXED))
		return 0;

		/*
		* Map all of RAM so that we can access arguments in the 1:1
		* mapping when making EFI runtime calls.
		*/
		for_each_efi_memory_desc(&memmap, md) {
		if (md->type != EFI_CONVENTIONAL_MEMORY &&
		md->type != EFI_LOADER_DATA &&
		md->type != EFI_LOADER_CODE)
		continue;

		pfn = md->phys_addr >> PAGE_SHIFT;
		npages = md->num_pages;

		if (kernel_map_pages_in_pgd(pgd, pfn, md->phys_addr, npages, 0)) {
		pr_err("Failed to map 1:1 memory\n");
		return 1;
		}
		}

		page = alloc_page(GFP_KERNEL\|__GFP_DMA32);
		if (!page)
		panic("Unable to allocate EFI runtime stack < 4GB\n");