processes: start defining what a process is

Signed-off-by: Sean Cross <sean@xobs.io>

src/definitions.rs

@@ -0,0 +1,70 @@
+use core::num::NonZeroUsize;
+
+#[allow(dead_code)] pub type MemoryAddress = NonZeroUsize;
+#[allow(dead_code)] pub type MemorySize = NonZeroUsize;
+#[allow(dead_code)] pub type StackPointer = usize;
+#[allow(dead_code)] pub type MessageId = usize;
+
+#[allow(dead_code)] pub type XousPid = u8;
+#[allow(dead_code)] pub type XousMessageSender = usize;
+#[allow(dead_code)] pub type XousConnection = usize;
+
+/// Server ID
+#[allow(dead_code)] pub type XousSid = usize;
+
+/// Equivalent to a RISC-V Hart ID
+#[allow(dead_code)] pub type XousCpuId = usize;
+
+#[allow(dead_code)]
+#[derive(Debug)]
+pub enum XousError {
+    BadAlignment,
+    BadAddress,
+    OutOfMemory,
+    MemoryInUse,
+    InterruptNotFound,
+    InterruptInUse,
+    InvalidString,
+    ServerExists,
+    ServerNotFound,
+    ProcessNotFound,
+    ProcessNotChild,
+    ProcessTerminated,
+    Timeout,
+}
+
+#[allow(dead_code)]
+pub struct XousContext {
+    stack: StackPointer,
+    pid: XousPid,
+}
+
+#[allow(dead_code)]
+pub struct XousMemoryMessage {
+    id: MessageId,
+    in_buf: Option<MemoryAddress>,
+    in_buf_size: Option<MemorySize>,
+    out_buf: Option<MemoryAddress>,
+    out_buf_size: Option<MemorySize>,
+}
+
+#[allow(dead_code)]
+pub struct XousScalarMessage {
+    id: MessageId,
+    arg1: usize,
+    arg2: usize,
+    arg3: usize,
+    arg4: usize,
+}
+
+#[allow(dead_code)]
+pub enum XousMessage {
+    Memory(XousMemoryMessage),
+    Scalar(XousScalarMessage),
+}
+
+#[allow(dead_code)]
+pub struct XousMessageReceived {
+    sender: XousMessageSender,
+    message: XousMessage,
+}

src/irq.rs

@@ -1,4 +1,4 @@
-use crate::syscalls;
+use crate::definitions::XousError;
 use crate::filled_array;
 use xous_riscv::register::{mstatus, vmim};
 
@@ -28,15 +28,15 @@ pub fn handle(irqs_pending: usize) {
     }
 }
 
-pub fn sys_interrupt_claim(irq: usize, f: fn(usize)) -> Result<(), syscalls::XousError> {
+pub fn sys_interrupt_claim(irq: usize, f: fn(usize)) -> Result<(), XousError> {
     // Unsafe is required since we're accessing a static mut array.
     // However, we disable interrupts to prevent contention on this array.
     unsafe {
         mstatus::clear_mie();
         let result = if irq > IRQ_HANDLERS.len() {
-            Err(syscalls::XousError::InterruptNotFound)
+            Err(XousError::InterruptNotFound)
         } else if IRQ_HANDLERS[irq].is_some() {
-            Err(syscalls::XousError::InterruptInUse)
+            Err(XousError::InterruptInUse)
         } else {
             IRQ_HANDLERS[irq] = Some(f);
             // Note that the vexriscv "IRQ Mask" register is inverse-logic --

src/lib.rs

@@ -9,4 +9,4 @@ extern crate xous_riscv;
 // }
 
 // Allow consumers of this library to make syscalls
-pub mod syscalls;
+// pub mod syscalls;

src/main.rs

@@ -2,10 +2,12 @@
 #![no_main]
 
 extern crate xous_riscv;
-mod syscalls;
+mod definitions;
 mod irq;
 mod macros;
 mod mem;
+mod processtable;
+mod syscalls;
 
 pub use irq::sys_interrupt_claim;
 
@@ -13,7 +15,7 @@ use core::panic::PanicInfo;
 use xous_kernel_riscv_rt::xous_kernel_entry;
 use xous_riscv::register::{mcause, mstatus, mie, vmim, vmip};
 use mem::MemoryManager;
-
+use processtable::ProcessTable;
 
 #[panic_handler]
 fn handle_panic(_arg: &PanicInfo) -> ! {
@@ -35,7 +37,8 @@ fn xous_main() -> ! {
         mie::set_mext();
         mstatus::set_mie(); // Enable CPU interrupts
     }
-    let mm = MemoryManager::new();
+    let mut mm = MemoryManager::new();
+    let mut pt = ProcessTable::new(&mut mm);
     sys_interrupt_claim(2, |_| {
         let uart_ptr = 0xE000_1800 as *mut usize;
         print_str(uart_ptr, "hello, world!\r\n");

src/mem.rs

@@ -1,4 +1,5 @@
-use crate::syscalls::{XousError, XousPid};
+use crate::definitions::{XousError, XousPid, MemoryAddress};
+use core::num::NonZeroUsize;
 use xous_riscv::register::mstatus;
 
 const FLASH_START: usize = 0x20000000;
@@ -21,10 +22,10 @@ const RAM_PAGE_COUNT: usize = RAM_SIZE / PAGE_SIZE;
 const IO_PAGE_COUNT: usize = IO_SIZE;
 const LCD_PAGE_COUNT: usize = LCD_SIZE / PAGE_SIZE;
 pub struct MemoryManager {
-    flash: [u8; FLASH_PAGE_COUNT],
-    ram: [u8; RAM_PAGE_COUNT],
-    io: [u8; IO_PAGE_COUNT],
-    lcd: [u8; LCD_PAGE_COUNT],
+    flash: [XousPid; FLASH_PAGE_COUNT],
+    ram: [XousPid; RAM_PAGE_COUNT],
+    io: [XousPid; IO_PAGE_COUNT],
+    lcd: [XousPid; LCD_PAGE_COUNT],
 }
 
 extern "C" {
@@ -40,6 +41,10 @@ extern "C" {
     static mut _estack: usize;
     static mut _sstack: usize;
 
+    // Boundaries of the .text section
+    static mut _stext: usize;
+    static mut _etext: usize;
+
     // Boundaries of the heap
     static _sheap: usize;
     static _eheap: usize;
@@ -52,9 +57,9 @@ use core::mem::transmute;
 
 /// Initialzie the memory map.
 /// This will go through memory and map anything that the kernel is
-/// using to process 0xff, then allocate a pagetable for this process
-/// and place it at the usual offset.
-/// Finally, it will enable the MMU.
+/// using to process 1, then allocate a pagetable for this process
+/// and place it at the usual offset.  The MMU will not be enabled yet,
+/// as the process entry has not yet been created.
 impl MemoryManager {
     pub fn new() -> MemoryManager {
         let mut mm = MemoryManager {
@@ -80,6 +85,10 @@ impl MemoryManager {
         let end_stack = unsafe { transmute::<&usize, usize>(&_sstack) };
         let stack_range = (start_stack..end_stack).step_by(PAGE_SIZE);
 
+        let start_text = unsafe { transmute::<&usize, usize>(&_stext) };
+        let end_text = unsafe { transmute::<&usize, usize>(&_etext) };
+        let text_range = (start_text..end_text).step_by(PAGE_SIZE);
+
         for region in bss_range {
             mm.claim_page(region & !0xfff, 1).unwrap();
         }
@@ -92,10 +101,40 @@ impl MemoryManager {
             mm.claim_page(region & !0xfff, 1).unwrap();
         }
 
+        for region in text_range {
+            mm.claim_page(region & !0xfff, 1).unwrap();
+        }
+
         unsafe { mstatus::set_mie() };
         mm
     }
 
+    pub fn alloc_page(&mut self, pid: XousPid) -> Result<MemoryAddress, XousError> {
+        // Go through all RAM pages looking for a free page.
+        // Optimization: start from the previous address.
+        for index in 0..RAM_PAGE_COUNT {
+            if self.ram[index] == 0 {
+                self.ram[index] = pid;
+                let page_addr = (index * PAGE_SIZE + RAM_START) as *mut u32;
+                // Zero-out the page
+                unsafe {
+                    for i in 0..PAGE_SIZE/4 {
+                        *page_addr.add(i) = 0;
+                    }
+                }
+                let new_page = unsafe { transmute::<*mut u32, usize>(page_addr) };
+                return Ok(NonZeroUsize::new(new_page).unwrap());
+            }
+        }
+        Err(XousError::OutOfMemory)
+    }
+
+    // Create an identity mapping, copying the kernel to itself.
+    pub fn create_identity(&mut self, satp: MemoryAddress, pid: XousPid) -> Result<(), XousError> {
+
+        Err(XousError::OutOfMemory)
+    }
+
     fn claim_page(&mut self, addr: usize, pid: XousPid) -> Result<(), XousError> {
         // Ensure the address lies on a page boundary
         if addr & 0xfff != 0 {
@@ -119,7 +158,7 @@ impl MemoryManager {
             return Err(XousError::BadAddress);
         }
         if tbl[page] != 0 && tbl[page] != pid {
-            return Err(XousError::OutOfMemory);
+            return Err(XousError::MemoryInUse);
         }
         tbl[page] = pid;
         Ok(())

src/processtable.rs

@@ -0,0 +1,26 @@
+use crate::definitions::{XousError, XousPid, MemoryAddress};
+use crate::mem::MemoryManager;
+use crate::filled_array;
+
+const MAX_PROCESS_COUNT: usize = 256;
+
+struct Process {
+    satp: Option<MemoryAddress>,
+}
+
+pub struct ProcessTable {
+    processes: [Process; MAX_PROCESS_COUNT],
+}
+
+impl ProcessTable {
+    pub fn new(mm: &mut MemoryManager) -> Self {
+        let mut pt = ProcessTable {
+            processes: filled_array![Process { satp: None }; 256],
+        };
+
+        // Allocate a root page table for PID 1
+        pt.processes[1].satp = Some(mm.alloc_page(1).unwrap());
+        mm.create_identity(pt.processes[1].satp.unwrap(), 1);
+        pt
+    }
+}

src/syscalls.rs

@@ -1,72 +1,4 @@
-use core::num::NonZeroUsize;
-
-#[allow(dead_code)] pub type MemoryAddress = NonZeroUsize;
-#[allow(dead_code)] pub type MemorySize = NonZeroUsize;
-#[allow(dead_code)] pub type StackPointer = usize;
-#[allow(dead_code)] pub type MessageId = usize;
-
-#[allow(dead_code)] pub type XousPid = u8;
-#[allow(dead_code)] pub type XousMessageSender = usize;
-#[allow(dead_code)] pub type XousConnection = usize;
-
-/// Server ID
-#[allow(dead_code)] pub type XousSid = usize;
-
-/// Equivalent to a RISC-V Hart ID
-#[allow(dead_code)] pub type XousCpuId = usize;
-
-#[allow(dead_code)]
-#[derive(Debug)]
-pub enum XousError {
-    BadAlignment,
-    BadAddress,
-    OutOfMemory,
-    InterruptNotFound,
-    InterruptInUse,
-    InvalidString,
-    ServerExists,
-    ServerNotFound,
-    ProcessNotFound,
-    ProcessNotChild,
-    ProcessTerminated,
-    Timeout,
-}
-
-#[allow(dead_code)]
-pub struct XousContext {
-    stack: StackPointer,
-    pid: XousPid,
-}
-
-#[allow(dead_code)]
-pub struct XousMemoryMessage {
-    id: MessageId,
-    in_buf: Option<MemoryAddress>,
-    in_buf_size: Option<MemorySize>,
-    out_buf: Option<MemoryAddress>,
-    out_buf_size: Option<MemorySize>,
-}
-
-#[allow(dead_code)]
-pub struct XousScalarMessage {
-    id: MessageId,
-    arg1: usize,
-    arg2: usize,
-    arg3: usize,
-    arg4: usize,
-}
-
-#[allow(dead_code)]
-pub enum XousMessage {
-    Memory(XousMemoryMessage),
-    Scalar(XousScalarMessage),
-}
-
-#[allow(dead_code)]
-pub struct XousMessageReceived {
-    sender: XousMessageSender,
-    message: XousMessage,
-}
+use super::definitions::*;
 
 extern "Rust" {
     /// Allocates kernel structures for a new process, and returns the new PID.

xous-kernel-riscv-rt/link.x

@@ -52,6 +52,7 @@ SECTIONS
        This is required by LLD to ensure the LMA of the following .data
        section will have the correct alignment. */
     . = ALIGN(4);
+    _etext = .;
   } > REGION_RODATA
 
   .data : ALIGN(4)