[PATCH 3/6] x86/efi: Map RAM into the identity page table for mixed mode

Matt Fleming
2015-11-12T15:40:37Z

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.

Cc: Borislav Petkov <bp@alien8.de>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
---
arch/x86/platform/efi/efi_64.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index c8b58ac47b77..634536034e32 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -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;
@@ -200,6 +201,25 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)

efi_scratch.phys_stack += PAGE_SIZE; /* stack grows down */

+ /*
+ * 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;
+ }
+ }
+
return 0;
}

--
2.6.2