From 04ef7ff2756fdc4e3bf79213b10b82aa2bf6dec3 Mon Sep 17 00:00:00 2001
From: bunnie <bunnie@kosagi.com>
Date: Thu, 7 Mar 2024 20:09:47 +0800
Subject: [PATCH] create the swapper crate

---
 services/xous-swapper/Cargo.toml  | 33 +++++++++++
 services/xous-swapper/src/main.rs | 91 +++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 services/xous-swapper/Cargo.toml
 create mode 100644 services/xous-swapper/src/main.rs

diff --git a/services/xous-swapper/Cargo.toml b/services/xous-swapper/Cargo.toml
new file mode 100644
index 000000000..f394aee80
--- /dev/null
+++ b/services/xous-swapper/Cargo.toml
@@ -0,0 +1,33 @@
+[package]
+authors = ["bunnie <bunnie@kosagi.com>"]
+description = "Xous microkernel OS inter-process name resolution server"
+edition = "2018"
+name = "xous-swapper"
+version = "0.1.0"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/betrusted-io/xous-core/"
+homepage = "https://betrusted.io/"
+
+# Dependency versions enforced by Cargo.lock.
+[dependencies]
+xous-api-names = "0.9.56"
+log-server = { package = "xous-api-log", version = "0.1.54" }
+xous = "0.9.58"
+xous-ipc = "0.9.58"
+num-derive = { version = "0.3.3", default-features = false }
+num-traits = { version = "0.2.14", default-features = false }
+log = "0.4.14"
+
+utralib = { version = "0.1.24", optional = true, default-features = false }
+
+[target.'cfg(any(windows,unix))'.dependencies]
+
+[features]
+cramium-soc = ["utralib/cramium-soc"]
+cramium-fpga = ["utralib/cramium-fpga"]
+precursor = ["utralib/precursor"]
+hosted = ["utralib/hosted"]
+renode = ["utralib/renode"]
+# for now, debug-print only works on Precursor targets
+debug-print = ["precursor", "utralib/precursor"]
+default = ["debug-print"]
diff --git a/services/xous-swapper/src/main.rs b/services/xous-swapper/src/main.rs
new file mode 100644
index 000000000..3a1bd4570
--- /dev/null
+++ b/services/xous-swapper/src/main.rs
@@ -0,0 +1,91 @@
+use core::fmt::{Error, Write};
+
+use utralib::*;
+
+#[derive(Debug, num_derive::FromPrimitive, num_derive::ToPrimitive)]
+#[repr(usize)]
+pub enum Opcode {
+    /// Take the page lent to us, encrypt it and write it to swap
+    WriteToSwap = 0,
+    /// Find the requested page, decrypt it, and return it
+    ReadFromSwap = 1,
+    /// Kernel message advising us that a page of RAM was allocated
+    AllocateAdvisory = 2,
+    /// Kernel message requesting N pages to be swapped out.
+    Trim = 3,
+    /// Kernel message informing us that we have pages to free.
+    Free = 4,
+}
+
+pub struct DebugUart {
+    #[cfg(feature = "debug-print")]
+    csr: CSR<u32>,
+}
+impl DebugUart {
+    #[cfg(feature = "debug-print")]
+    pub fn new() -> Self {
+        let debug_uart_mem = xous::syscall::map_memory(
+            xous::MemoryAddress::new(utra::app_uart::HW_APP_UART_BASE),
+            None,
+            4096,
+            xous::MemoryFlags::R | xous::MemoryFlags::W,
+        )
+        .expect("couldn't claim the debug UART");
+        let debug_uart = CSR::new(debug_uart_mem.as_mut_ptr() as *mut u32);
+
+        Self { csr: debug_uart }
+    }
+
+    #[cfg(feature = "debug-print")]
+    pub fn putc(&mut self, c: u8) {
+        // Wait until TXFULL is `0`
+        while self.csr.r(utra::app_uart::TXFULL) != 0 {}
+        self.csr.wfo(utra::app_uart::RXTX_RXTX, c as u32);
+    }
+
+    #[cfg(not(feature = "debug-print"))]
+    pub fn new() -> Self { Self {} }
+
+    #[cfg(not(feature = "debug-print"))]
+    pub fn putc(&self, _c: u8) {}
+}
+
+impl Write for DebugUart {
+    fn write_str(&mut self, s: &str) -> Result<(), Error> {
+        for c in s.bytes() {
+            self.putc(c);
+        }
+        Ok(())
+    }
+}
+
+fn main() {
+    // init the log, but this is mostly unused.
+    log_server::init_wait().unwrap();
+    log::set_max_level(log::LevelFilter::Info);
+    log::info!("my PID is {}", xous::process::id());
+
+    // swapper is not allowed to use `log` for debugging under most circumstances, because
+    // the swapper can't send messages when handling a swap call. Instead, we use a local
+    // debug UART to handle this. This needs to be enabled with the "debug-print" feature
+    // and is mutually exclusive with the "gdb-stub" feature in the kernel since it uses
+    // the same physical hardware.
+    let mut duart = DebugUart::new();
+    write!(duart, "Swapper started.\n\r");
+
+    let sid = xous::create_server().unwrap();
+    loop {
+        let msg = xous::receive_message(shch_sid).unwrap();
+        let op: Option<Opcode> = FromPrimitive::from_usize(msg.body.id());
+        write!(duart, "Swapper got {:?}", msg);
+        match op {
+            Some(Opcode::WriteToSwap) => {
+                unimplemented!();
+            }
+            // ... todo, other opcodes.
+            _ => {
+                write!(duart, "Unknown opcode {:?}", op);
+            }
+        }
+    }
+}