From 01b019dda3002075e48ebb0d5759afa9bbef975b Mon Sep 17 00:00:00 2001
From: Akira Moroo <retrage01@gmail.com>
Date: Sun, 2 May 2021 13:52:12 +0900
Subject: [PATCH] efi: Opt-out EFI variable support

On current design, RuntimeServices.set_virtual_address_map overwrites
all function pointers in the RuntimeServices to not_available function
to avoid calling original functions on runtime phase. However, the
Windows Hardware Abstraction Layer (HAL) stores the original
RuntimeServices function addresses before the phase and uses the
functions afterwards. This behavior causes invalid memory access error
because this firmware does not do self-relocation. On Windows, it to use
EFI variables on runtime phase (See issue #115).

Signed-off-by: Akira Moroo <retrage01@gmail.com>
---
 Cargo.toml     |  1 +
 src/efi/mod.rs | 20 ++++++++++++++------
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index f4edc1c2..edf25674 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ log-serial = []
 log-panic = ["log-serial"]
 integration_tests = []
 coreboot = []
+efi-var = []
 
 [dependencies]
 bitflags = "1.2.1"
diff --git a/src/efi/mod.rs b/src/efi/mod.rs
index a25ededb..81182652 100644
--- a/src/efi/mod.rs
+++ b/src/efi/mod.rs
@@ -291,9 +291,13 @@ pub extern "win64" fn get_variable(
     data_size: *mut usize,
     data: *mut c_void,
 ) -> Status {
-    VARIABLES
-        .borrow_mut()
-        .get(variable_name, vendor_guid, attributes, data_size, data)
+    if cfg!(feature = "efi-var") {
+        VARIABLES
+            .borrow_mut()
+            .get(variable_name, vendor_guid, attributes, data_size, data)
+    } else {
+        Status::NOT_FOUND
+    }
 }
 
 pub extern "win64" fn get_next_variable_name(
@@ -311,9 +315,13 @@ pub extern "win64" fn set_variable(
     data_size: usize,
     data: *mut c_void,
 ) -> Status {
-    VARIABLES
-        .borrow_mut()
-        .set(variable_name, vendor_guid, attributes, data_size, data)
+    if cfg!(feature = "efi-var") {
+        VARIABLES
+            .borrow_mut()
+            .set(variable_name, vendor_guid, attributes, data_size, data)
+    } else {
+        Status::UNSUPPORTED
+    }
 }
 
 pub extern "win64" fn get_next_high_mono_count(_: *mut u32) -> Status {