x86/efi: Consolidate region mapping logic

EFI regions are currently mapped in two separate places. The bulk of
the work is done in efi_map_regions() but when CONFIG_EFI_MIXED is
enabled the additional regions that are required when operating in
mixed mode are mapping in efi_setup_page_tables().

Pull everything into efi_map_regions() and refactor the test for
which regions should be mapped into a should_map_region() function.
Generously sprinkle comments to clarify the different cases.

Acked-by: Borislav Petkov <bp@suse.de>
Tested-by: Dave Young <dyoung@redhat.com> [kexec/kdump]
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [arm]
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

1 files changed, 43 insertions, 7 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 1fbb408e2e72..625ec729b4e8 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -745,6 +745,46 @@ static void *efi_map_next_entry(void *entry)
 	return entry;
 }
 
+static bool should_map_region(efi_memory_desc_t *md)
+{
+	/*
+	 * Runtime regions always require runtime mappings (obviously).
+	 */
+	if (md->attribute & EFI_MEMORY_RUNTIME)
+		return true;
+
+	/*
+	 * 32-bit EFI doesn't suffer from the bug that requires us to
+	 * reserve boot services regions, and mixed mode support
+	 * doesn't exist for 32-bit kernels.
+	 */
+	if (IS_ENABLED(CONFIG_X86_32))
+		return false;
+
+	/*
+	 * Map all of RAM so that we can access arguments in the 1:1
+	 * mapping when making EFI runtime calls.
+	 */
+	if (IS_ENABLED(CONFIG_EFI_MIXED) && !efi_is_native()) {
+		if (md->type == EFI_CONVENTIONAL_MEMORY ||
+		    md->type == EFI_LOADER_DATA ||
+		    md->type == EFI_LOADER_CODE)
+			return true;
+	}
+
+	/*
+	 * Map boot services regions as a workaround for buggy
+	 * firmware that accesses them even when they shouldn't.
+	 *
+	 * See efi_{reserve,free}_boot_services().
+	 */
+	if (md->type == EFI_BOOT_SERVICES_CODE ||
+	    md->type == EFI_BOOT_SERVICES_DATA)
+		return true;
+
+	return false;
+}
+
 /*
  * Map the efi memory ranges of the runtime services and update new_mmap with
  * virtual addresses.
@@ -761,13 +801,9 @@ static void * __init efi_map_regions(int *count, int *pg_shift)
 	p = NULL;
 	while ((p = efi_map_next_entry(p))) {
 		md = p;
-		if (!(md->attribute & EFI_MEMORY_RUNTIME)) {
-#ifdef CONFIG_X86_64
-			if (md->type != EFI_BOOT_SERVICES_CODE &&
-			    md->type != EFI_BOOT_SERVICES_DATA)
-#endif
-				continue;
-		}
+
+		if (!should_map_region(md))
+			continue;
 
 		efi_map_region(md);
 		get_systab_virt_addr(md);