[pvmfw] Extract smccc into a separate library for reuse

Test: m pvmfw_img
Bug: 272226230
Change-Id: Ie6e03e92acca8f0947febefa80587c0db0010c49

libs/smccc/Android.bp

@@ -0,0 +1,18 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+rust_library_rlib {
+    name: "libsmccc",
+    crate_name: "smccc",
+    srcs: ["src/lib.rs"],
+    prefer_rlib: true,
+    rustlibs: [
+        "libpsci",
+    ],
+    no_stdlibs: true,
+    stdlibs: [
+        "libcore.rust_sysroot",
+    ],
+    apex_available: ["com.android.virt"],
+}

libs/smccc/src/lib.rs

@@ -0,0 +1,22 @@
+// Copyright 2023, 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.
+
+//! Structs and functions for making SMCCC calls following the SMC Calling
+//! Convention version 1.4.
+
+#![no_std]
+
+mod smccc;
+
+pub use smccc::{checked_hvc64, checked_hvc64_expect_zero, hvc64, Error, Result};

libs/smccc/src/smccc.rs

@@ -12,8 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//! Structs and functions for making SMCCC calls.
+
 use core::{fmt, result};
-use psci::smccc::hvc64;
+// Ideally, smccc shouldn't depend on psci. Smccc isn't split as a separate
+// upstream crate currently mostly for maintenance consideration.
+// See b/245889995 for more context.
+pub use psci::smccc::hvc64;
 
 /// Standard SMCCC error values as described in DEN 0028E.
 #[derive(Debug, Clone)]
@@ -42,8 +47,11 @@ impl fmt::Display for Error {
     }
 }
 
+/// Result type with smccc::Error.
 pub type Result<T> = result::Result<T, Error>;
 
+/// Makes a checked HVC64 call to the hypervisor, following the SMC Calling Convention version 1.4.
+/// Returns Ok only when the return code is 0.
 pub fn checked_hvc64_expect_zero(function: u32, args: [u64; 17]) -> Result<()> {
     match checked_hvc64(function, args)? {
         0 => Ok(()),
@@ -51,6 +59,8 @@ pub fn checked_hvc64_expect_zero(function: u32, args: [u64; 17]) -> Result<()> {
     }
 }
 
+/// Makes a checked HVC64 call to the hypervisor, following the SMC Calling Convention version 1.4.
+/// Returns Ok with the return code only when the return code >= 0.
 pub fn checked_hvc64(function: u32, args: [u64; 17]) -> Result<u64> {
     match hvc64(function, args)[0] as i64 {
         ret if ret >= 0 => Ok(ret as u64),

pvmfw/Android.bp

@@ -20,10 +20,10 @@ rust_ffi_static {
         "liblibfdt",
         "liblog_rust_nostd",
         "libonce_cell_nostd",
-        "libpsci",
         "libpvmfw_avb_nostd",
         "libpvmfw_embedded_key",
         "libpvmfw_fdt_template",
+        "libsmccc",
         "libstatic_assertions",
         "libtinyvec_nostd",
         "libuuid_nostd",

pvmfw/src/hvc.rs

@@ -16,8 +16,8 @@
 
 pub mod trng;
 
-use crate::smccc::{self, checked_hvc64, checked_hvc64_expect_zero};
 use log::info;
+use smccc::{self, checked_hvc64, checked_hvc64_expect_zero};
 
 const ARM_SMCCC_TRNG_VERSION: u32 = 0x8400_0050;
 #[allow(dead_code)]

pvmfw/src/hvc/trng.rs

@@ -14,7 +14,6 @@
 
 use core::fmt;
 use core::result;
-use psci::smccc;
 
 /// Standard SMCCC TRNG error values as described in DEN 0098 1.0 REL0.
 #[derive(Debug, Clone)]

pvmfw/src/hypervisor.rs

@@ -15,7 +15,6 @@
 //! Wrappers around hypervisor back-ends.
 
 use crate::hvc;
-use crate::smccc;
 
 pub fn hyp_meminfo() -> smccc::Result<u64> {
     hvc::kvm_hyp_meminfo()

pvmfw/src/main.rs

@@ -35,7 +35,6 @@ mod memory;
 mod mmio_guard;
 mod mmu;
 mod rand;
-mod smccc;
 mod virtio;
 
 use alloc::boxed::Box;

pvmfw/src/memory.rs

@@ -20,7 +20,6 @@ use crate::helpers::{self, align_down, align_up, page_4kb_of, SIZE_4KB};
 use crate::hypervisor::{hyp_meminfo, mem_share, mem_unshare};
 use crate::mmio_guard;
 use crate::mmu;
-use crate::smccc;
 use alloc::alloc::alloc_zeroed;
 use alloc::alloc::dealloc;
 use alloc::alloc::handle_alloc_error;

pvmfw/src/mmio_guard.rs

@@ -16,7 +16,6 @@
 
 use crate::helpers;
 use crate::hypervisor::{mmio_guard_enroll, mmio_guard_info, mmio_guard_map, mmio_guard_unmap};
-use crate::smccc;
 use core::{fmt, result};
 
 #[derive(Debug, Clone)]