util/ipc: add IPC abstraction

target/ast10x0/tests/util_ipc/async_transaction/BUILD.bazel

@@ -0,0 +1,124 @@
+# Licensed under the Apache-2.0 license
+# SPDX-License-Identifier: Apache-2.0
+
+load("@pigweed//pw_kernel/tooling:rust_app.bzl", "rust_app")
+load("@pigweed//pw_kernel/tooling:system_image.bzl", "system_image", "system_image_test")
+load("@pigweed//pw_kernel/tooling:target_codegen.bzl", "target_codegen")
+load("@pigweed//pw_kernel/tooling:target_linker_script.bzl", "target_linker_script")
+load("@pigweed//pw_kernel/tooling/panic_detector:rust_binary_no_panics_test.bzl", "rust_binary_no_panics_test")
+load("@rules_rust//rust:defs.bzl", "rust_binary")
+load("//target/ast10x0:defs.bzl", "TARGET_COMPATIBLE_WITH")
+
+# ── System configuration ───────────────────────────────────────────────────────
+
+filegroup(
+    name = "system_config",
+    srcs = ["system.json5"],
+)
+
+# ── Kernel image ───────────────────────────────────────────────────────────────
+
+target_codegen(
+    name = "codegen",
+    arch = "@pigweed//pw_kernel/arch/arm_cortex_m:arch_arm_cortex_m",
+    system_config = ":system_config",
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+)
+
+target_linker_script(
+    name = "linker_script",
+    system_config = ":system_config",
+    tags = ["kernel"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+    template = "//target/ast10x0:linker_script_template",
+)
+
+rust_binary(
+    name = "target",
+    srcs = ["target.rs"],
+    edition = "2024",
+    tags = ["kernel"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+    deps = [
+        ":codegen",
+        ":linker_script",
+        "//target/ast10x0:entry",
+        "@pigweed//pw_kernel/arch/arm_cortex_m:arch_arm_cortex_m",
+        "@pigweed//pw_kernel/kernel",
+        "@pigweed//pw_kernel/subsys/console:console_backend",
+        "@pigweed//pw_kernel/target:target_common",
+        "@pigweed//pw_kernel/userspace",
+        "@pigweed//pw_log/rust:pw_log",
+    ],
+)
+
+# ── Handler app ─────────────────────────────────────────────────────────────────
+# Exercises util_ipc::IpcHandler; increments the byte it's sent.
+
+rust_app(
+    name = "handler",
+    srcs = ["handler_main.rs"],
+    codegen_crate_name = "app_handler",
+    edition = "2024",
+    system_config = ":system_config",
+    tags = ["kernel"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+    deps = [
+        "//util/ipc",
+        "@pigweed//pw_kernel/userspace",
+        "@pigweed//pw_status/rust:pw_status",
+    ],
+)
+
+# ── Initiator app ───────────────────────────────────────────────────────────────
+# Exercises util_ipc::IpcInitiator and util_ipc::AsyncTransaction; calls
+# debug_shutdown(Ok|Err) to report the result.
+
+rust_app(
+    name = "initiator",
+    srcs = ["initiator_main.rs"],
+    codegen_crate_name = "app_initiator",
+    edition = "2024",
+    system_config = ":system_config",
+    tags = ["kernel"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+    deps = [
+        "//util/ipc",
+        "@pigweed//pw_kernel/userspace",
+        "@pigweed//pw_log/rust:pw_log",
+        "@pigweed//pw_status/rust:pw_status",
+    ],
+)
+
+# ── System image ───────────────────────────────────────────────────────────────
+
+system_image(
+    name = "async_transaction_image",
+    apps = [
+        ":handler",
+        ":initiator",
+    ],
+    kernel = ":target",
+    platform = "//target/ast10x0",
+    system_config = ":system_config",
+    tags = ["kernel"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+    visibility = ["//visibility:public"],
+)
+
+# ── Test target ────────────────────────────────────────────────────────────────
+# Run with:
+#   bazel test --config=virt_ast10x0 //target/ast10x0/tests/util_ipc/async_transaction:async_transaction_qemu_test
+
+system_image_test(
+    name = "async_transaction_qemu_test",
+    image = ":async_transaction_image",
+    tags = ["qemu_only"],
+    target_compatible_with = TARGET_COMPATIBLE_WITH,
+)
+
+rust_binary_no_panics_test(
+    name = "no_panics_test",
+    binary = ":async_transaction_image",
+    tags = ["kernel"],
+)

target/ast10x0/tests/util_ipc/async_transaction/handler_main.rs

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+// Licensed under the Apache-2.0 license
+// SPDX-License-Identifier: Apache-2.0
+
+//! Handler side of the util/ipc AsyncTransaction QEMU test.
+//!
+//! Exercises `util_ipc::IpcHandler`: waits for a request, reads it, and
+//! responds with the request byte incremented by one. A request of
+//! `GATED_REQUEST` is held until the initiator raises Signals::USER.
+
+#![no_main]
+#![no_std]
+
+use app_handler::handle;
+use pw_status::Error;
+use userspace::entry;
+use userspace::syscall::{self, Signals};
+use userspace::time::Instant;
+use util_ipc::{IpcHandle, IpcHandler};
+
+/// Request byte that parks the handler instead of responding: it raises
+/// Signals::USER on the initiator to say it is parked, then waits for the
+/// initiator to raise USER back before responding. The parked signal is
+/// what makes the initiator's "pending" observation deterministic.
+const GATED_REQUEST: u8 = 0x40;
+
+#[entry]
+fn entry() {
+    let ipc = IpcHandle::new(handle::IPC);
+
+    loop {
+        if syscall::object_wait(handle::IPC, Signals::READABLE, Instant::MAX).is_err() {
+            continue;
+        }
+
+        let mut buf = [0u8; 1];
+        match ipc.read(0, &mut buf) {
+            Ok(1) => {
+                if buf[0] == GATED_REQUEST {
+                    // Tell the initiator we are parked, wait for its
+                    // release, then lower the parked signal again.
+                    if ipc.set_peer_user_signal(true).is_err()
+                        || syscall::object_wait(handle::IPC, Signals::USER, Instant::MAX).is_err()
+                    {
+                        continue;
+                    }
+                    let _ = ipc.set_peer_user_signal(false);
+                }
+                buf[0] = buf[0].wrapping_add(1);
+                let _ = ipc.respond(&buf);
+            }
+            // Transaction was cancelled by the initiator while we were
+            // waking up; go back to waiting for the next one.
+            Ok(_) | Err(Error::Unavailable) => continue,
+            Err(_) => continue,
+        }
+    }
+}
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}