pvmfw: Issue MMIO_GUARD_MAP for UART
Share the MMIO page containing the UART with the VMM.
When handling a synchronous exception, don't print to the UART if it
would cause re-entering the handler.
Bug: 237371962
Test: m pvmfw_img && flash pvmfw.img && access UART
Change-Id: Ia384f2e3a15b40b5e67cfafd50e571848fd5a126
diff --git a/pvmfw/src/helpers.rs b/pvmfw/src/helpers.rs
new file mode 100644
index 0000000..781c1ac
--- /dev/null
+++ b/pvmfw/src/helpers.rs
@@ -0,0 +1,36 @@
+// Copyright 2022, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Miscellaneous helper functions.
+
+/// Computes the address of the page containing a given address.
+pub const fn page_of(addr: u64, page_size: u64) -> u64 {
+ addr & !(page_size - 1)
+}
+
+/// Validates a page size and computes the address of the page containing a given address.
+pub const fn checked_page_of(addr: u64, page_size: u64) -> Option<u64> {
+ if page_size.is_power_of_two() {
+ Some(page_of(addr, page_size))
+ } else {
+ None
+ }
+}
+
+/// Computes the address of the 4KiB page containing a given address.
+pub const fn page_4kb_of(addr: u64) -> u64 {
+ const PAGE_SIZE: u64 = 4 << 10;
+
+ page_of(addr, PAGE_SIZE)
+}