kata-os-logger: support no logging interface connection out of a component

When a CAmkES component lacks an outbound connection to send log msgs
there will be no logger_log symbol. Use a weak ref here to handle that
without resorting to a feature or similar.

Mark logger connections as "maybe" so they are optional.

Change-Id: I6ecd939014d26a612d115741fd2ac673afa40857
GitOrigin-RevId: 0b1bf2611cbb628500cae37889c6547a996d50e9

apps/system/components/MailboxDriver/MailboxDriver.camkes

@@ -25,5 +25,5 @@ component MailboxDriver {
   consumes Interrupt rtirq;
   consumes Interrupt eirq;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
 }

apps/system/components/MemoryManager/MemoryManager.camkes

@@ -20,7 +20,7 @@ import <MemoryInterface.camkes>;
 component MemoryManager {
   provides MemoryInterface memory;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
 
   // Enable KataOS CAmkES support.
   attribute int kataos = true;

apps/system/components/MlCoordinator/MlCoordinator.camkes

@@ -16,6 +16,7 @@ import <LoggerInterface.camkes>;
 import <MemoryInterface.camkes>;
 import <MlCoordinatorInterface.camkes>;
 import <SecurityCoordinatorInterface.camkes>;
+import <TimerServiceInterface.camkes>;
 
 component MlCoordinator {
   control;
@@ -32,7 +33,7 @@ component MlCoordinator {
   dataport Buf CSR;
   dataport Buf(0x1000000) TCM;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
   uses MemoryInterface memory;
   uses SecurityCoordinatorInterface security;
 

apps/system/components/ProcessManager/ProcessManager.camkes

@@ -24,7 +24,7 @@ component ProcessManager {
   provides PackageManagementInterface pkg_mgmt;
   provides ProcessControlInterface proc_ctrl;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
   uses MemoryInterface memory;
   uses SecurityCoordinatorInterface security;
 

apps/system/components/SDKRuntime/SDKRuntime.camkes

@@ -20,7 +20,7 @@ import <SDKRuntimeInterface.camkes>;
 component SDKRuntime {
   provides SDKRuntimeInterface sdk_runtime;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
 
   // Enable KataOS CAmkES support.
   attribute int kataos = true;

apps/system/components/SecurityCoordinator/SecurityCoordinator.camkes

@@ -22,7 +22,7 @@ import <MailboxInterface.camkes>;
 component SecurityCoordinator {
   provides SecurityCoordinatorInterface security;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
   uses MemoryInterface memory;
   uses MailboxAPI mailbox_api;
 

apps/system/components/StorageManager/StorageManager.camkes

@@ -21,7 +21,7 @@ import <StorageInterface.camkes>;
 component StorageManager {
   provides StorageInterface storage;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
   uses SecurityCoordinatorInterface security;
 
   // Enable KataOS CAmkES support.

apps/system/components/TimerService/TimerService.camkes

@@ -20,7 +20,7 @@ component TimerService {
   dataport Buf csr;
   consumes Interrupt timer_interrupt;
 
-  uses LoggerInterface logger;
+  maybe uses LoggerInterface logger;
 
   // Enable KataOS CAmkES support.
   attribute int kataos = true;

apps/system/components/kata-os-common/src/logger/Cargo.toml

@@ -8,4 +8,4 @@ arrayvec = { version = "0.7", default-features = false }
 core2 = { version = "0.3", default-features = false }
 # Disable default so we don't pull in CString which requires an allocator
 cstr_core = { version = "0.2.3", default-features = false }
-log = "0.4"
+log = { version = "0.4" }

apps/system/components/kata-os-common/src/logger/src/lib.rs

@@ -13,6 +13,14 @@
 // limitations under the License.
 
 #![cfg_attr(not(test), no_std)]
+#![feature(linkage)]
+
+extern "C" {
+    // NB: components may not have a logging connection in which case
+    //   logger_log will be undefined/null.
+    #[linkage = "extern_weak"]
+    static logger_log: *const ();
+}
 
 use core2::io::{Cursor, Write};
 use cstr_core::CStr;
@@ -28,10 +36,12 @@ impl log::Log for KataLogger {
     fn enabled(&self, _metadata: &Metadata) -> bool { true }
 
     fn log(&self, record: &Record) {
-        if self.enabled(record.metadata()) {
+        let typed_logger_log: Option<extern "C" fn(level: u8, msg: *const u8)> =
-            extern "C" {
+            unsafe { core::mem::transmute(logger_log) };
-                fn logger_log(level: u8, msg: *const cstr_core::c_char);
+        if typed_logger_log.is_none() {
+            return;
         }
+        if self.enabled(record.metadata()) {
             let mut buf = [0 as u8; MAX_MSG_LEN];
             let mut cur = Cursor::new(&mut buf[..]);
             // Log msgs are of the form: '<target>::<fmt'd-msg>
@@ -41,7 +51,6 @@ impl log::Log for KataLogger {
                 cur.write(b"...\0").expect("write!");
                 ()
             });
-            unsafe {
             // If an embedded nul is identified, replace the message; there
             // are likely better solutions but this should not happen.
             fn embedded_nul_cstr<'a>(
@@ -55,7 +64,7 @@ impl log::Log for KataLogger {
             }
             // NB: this releases the ref on buf held by the Cursor
             let pos = cur.position() as usize;
-                logger_log(
+            (typed_logger_log.unwrap())(
                 record.level() as u8,
                 match CStr::from_bytes_with_nul(&buf[..pos]) {
                     Ok(cstr) => cstr,
@@ -65,7 +74,6 @@ impl log::Log for KataLogger {
             );
         }
     }
-    }
 
     fn flush(&self) {}
 }