efi: Make 'efi_enabled' a function to query EFI facilities

Originally 'efi_enabled' indicated whether a kernel was booted from
EFI firmware. Over time its semantics have changed, and it now
indicates whether or not we are booted on an EFI machine with
bit-native firmware, e.g. 64-bit kernel with 64-bit firmware.

The immediate motivation for this patch is the bug report at,

    https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557

which details how running a platform driver on an EFI machine that is
designed to run under BIOS can cause the machine to become
bricked. Also, the following report,

    https://bugzilla.kernel.org/show_bug.cgi?id=47121

details how running said driver can also cause Machine Check
Exceptions. Drivers need a new means of detecting whether they're
running on an EFI machine, as sadly the expression,

    if (!efi_enabled)

hasn't been a sufficient condition for quite some time.

Users actually want to query 'efi_enabled' for different reasons -
what they really want access to is the list of available EFI
facilities.

For instance, the x86 reboot code needs to know whether it can invoke
the ResetSystem() function provided by the EFI runtime services, while
the ACPI OSL code wants to know whether the EFI config tables were
mapped successfully. There are also checks in some of the platform
driver code to simply see if they're running on an EFI machine (which
would make it a bad idea to do BIOS-y things).

This patch is a prereq for the samsung-laptop fix patch.

Cc: David Airlie <airlied@linux.ie>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Peter Jones <pjones@redhat.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Steve Langasek <steve.langasek@canonical.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 15 insertions, 15 deletions

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 4e8ba39eaf0f..76fa1e9a2b39 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -584,7 +584,7 @@ static void native_machine_emergency_restart(void)
                         break;
 
                 case BOOT_EFI:
-                        if (efi_enabled)
+                        if (efi_enabled(EFI_RUNTIME_SERVICES))
                                 efi.reset_system(reboot_mode ?
                                                  EFI_RESET_WARM :
                                                  EFI_RESET_COLD,
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 00f6c1472b85..8b24289cc10c 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -807,15 +807,15 @@ void __init setup_arch(char **cmdline_p)
 #ifdef CONFIG_EFI
         if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
                      "EL32", 4)) {
-                efi_enabled = 1;
-                efi_64bit = false;
+                set_bit(EFI_BOOT, &x86_efi_facility);
         } else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
                      "EL64", 4)) {
-                efi_enabled = 1;
-                efi_64bit = true;
+                set_bit(EFI_BOOT, &x86_efi_facility);
+                set_bit(EFI_64BIT, &x86_efi_facility);
         }
-        if (efi_enabled && efi_memblock_x86_reserve_range())
-                efi_enabled = 0;
+
+        if (efi_enabled(EFI_BOOT))
+                efi_memblock_x86_reserve_range();
 #endif
 
         x86_init.oem.arch_setup();
@@ -888,7 +888,7 @@ void __init setup_arch(char **cmdline_p)
 
         finish_e820_parsing();
 
-        if (efi_enabled)
+        if (efi_enabled(EFI_BOOT))
                 efi_init();
 
         dmi_scan_machine();
@@ -971,7 +971,7 @@ void __init setup_arch(char **cmdline_p)
          * The EFI specification says that boot service code won't be called
          * after ExitBootServices(). This is, in fact, a lie.
          */
-        if (efi_enabled)
+        if (efi_enabled(EFI_MEMMAP))
                 efi_reserve_boot_services();
 
         /* preallocate 4k for mptable mpc */
@@ -1114,7 +1114,7 @@ void __init setup_arch(char **cmdline_p)
 
 #ifdef CONFIG_VT
 #if defined(CONFIG_VGA_CONSOLE)
-        if (!efi_enabled || (efi_mem_type(0xa0000) != EFI_CONVENTIONAL_MEMORY))
+        if (!efi_enabled(EFI_BOOT) || (efi_mem_type(0xa0000) != EFI_CONVENTIONAL_MEMORY))
                 conswitchp = &vga_con;
 #elif defined(CONFIG_DUMMY_CONSOLE)
         conswitchp = &dummy_con;
@@ -1131,14 +1131,14 @@ void __init setup_arch(char **cmdline_p)
         register_refined_jiffies(CLOCK_TICK_RATE);
 
 #ifdef CONFIG_EFI
-        /* Once setup is done above, disable efi_enabled on mismatched
-         * firmware/kernel archtectures since there is no support for
-         * runtime services.
+        /* Once setup is done above, unmap the EFI memory map on
+         * mismatched firmware/kernel archtectures since there is no
+         * support for runtime services.
          */
-        if (efi_enabled && IS_ENABLED(CONFIG_X86_64) != efi_64bit) {
+        if (efi_enabled(EFI_BOOT) &&
+            IS_ENABLED(CONFIG_X86_64) != efi_enabled(EFI_64BIT)) {
                 pr_info("efi: Setup done, disabling due to 32/64-bit mismatch\n");
                 efi_unmap_memmap();
-                efi_enabled = 0;
         }
 #endif
 }