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Updated to allow for system calls that change process state

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This commit is contained in:
Stephen Marz 2020-04-24 14:39:33 -04:00
parent e39f6b71c5
commit 599627b74a
6 changed files with 309 additions and 128 deletions
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30
risc_v/src/asm/trap.S
View File

@ -38,9 +38,6 @@ m_trap_vector:
# in cpu.rs we have a structure of:
# 32 gp regs 0
# 32 fp regs 256
# SATP register 512
# Trap stack 520
# CPU HARTID 528
# We use t6 as the temporary register because it is the very
# bottom register (x31)
.set i, 0
@ -99,15 +96,22 @@ switch_to_user:
# a2 - SATP Register
csrw mscratch, a0
// Load program counter
ld a1, 520(a0)
// Load satp
ld a2, 512(a0)
# Load program counter
ld a1, 520(a0)
# Load satp
ld a2, 512(a0)
# Load processor mode
ld a3, 552(a0)
# Pid
# ld a4, 544(a0)
# 1 << 7 is MPIE
# Since user mode is 00, we don't need to set anything
# in MPP (bits 12:11)
li t0, 1 << 7 | 1 << 5
# Combine enable bits with mode bits.
slli a3, a3, 11
or t0, t0, a3
csrw mstatus, t0
csrw mepc, a1
csrw satp, a2
@ -128,11 +132,21 @@ switch_to_user:
load_gp %i, t6
.set i, i+1
.endr
# j .
mret
.global make_syscall
make_syscall:
# We're setting this up to work with libgloss
# They want a7 to be the system call number and all parameters
# in a0 - a5
mv a7, a0
mv a0, a1
mv a1, a2
mv a2, a3
mv a3, a4
mv a4, a5
mv a5, a6
ecall
ret

12
risc_v/src/cpu.rs
View File

@ -20,10 +20,18 @@ pub enum SatpMode {
Sv48 = 9,
}
#[repr(usize)]
pub enum CpuMode {
User = 0,
Supervisor = 1,
Machine = 3,
}
/// The trap frame is set into a structure
/// and packed into each hart's mscratch register.
/// This allows for quick reference and full
/// context switch handling.
/// To make offsets easier, everything will be a usize (8 bytes)
#[repr(C)]
#[derive(Clone, Copy)]
pub struct TrapFrame {
@ -33,6 +41,8 @@ pub struct TrapFrame {
pub pc: usize, // 520
pub hartid: usize, // 528
pub qm: usize, // 536
pub pid: usize, // 544
pub mode: usize, // 552
}
/// Rust requires that we initialize our structures
@ -51,6 +61,8 @@ impl TrapFrame {
pc: 0,
hartid: 0,
qm: 1,
pid: 0,
mode: 0,
}
}
}

200
risc_v/src/process.rs
View File

@ -3,15 +3,8 @@
// Stephen Marz
// 27 Nov 2019
use crate::{cpu::{TrapFrame, satp_fence_asid, build_satp, SatpMode},
page::{alloc,
dealloc,
map,
unmap,
zalloc,
EntryBits,
Table,
PAGE_SIZE}};
use crate::{cpu::{build_satp, satp_fence_asid, CpuMode, SatpMode, TrapFrame},
page::{alloc, dealloc, map, unmap, zalloc, EntryBits, Table, PAGE_SIZE}};
use alloc::collections::vec_deque::VecDeque;
// How many pages are we going to give a process for their
@ -42,6 +35,56 @@ extern "C" {
fn make_syscall(a: usize) -> usize;
}
/// Set a process' state to running. This doesn't do any checks.
/// If this PID is not found, this returns false. Otherwise, it
/// returns true.
pub fn set_running(pid: u16) -> bool {
// Yes, this is O(n). A better idea here would be a static list
// of process pointers.
let mut retval = false;
unsafe {
if let Some(mut pl) = PROCESS_LIST.take() {
for proc in pl.iter_mut() {
if proc.pid == pid {
proc.set_state(ProcessState::Running);
retval = true;
break;
}
}
// Now, we no longer need the owned Deque, so we hand it
// back by replacing the PROCESS_LIST's None with the
// Some(pl).
PROCESS_LIST.replace(pl);
}
}
retval
}
/// Set a process' state to waiting. This doesn't do any checks.
/// If this PID is not found, this returns false. Otherwise, it
/// returns true.
pub fn set_waiting(pid: u16) -> bool {
// Yes, this is O(n). A better idea here would be a static list
// of process pointers.
let mut retval = false;
unsafe {
if let Some(mut pl) = PROCESS_LIST.take() {
for proc in pl.iter_mut() {
if proc.pid == pid {
proc.set_state(ProcessState::Waiting);
retval = true;
break;
}
}
// Now, we no longer need the owned Deque, so we hand it
// back by replacing the PROCESS_LIST's None with the
// Some(pl).
PROCESS_LIST.replace(pl);
}
}
retval
}
/// We will eventually move this function out of here, but its
/// job is just to take a slot in the process list.
fn init_process() {
@ -50,6 +93,7 @@ fn init_process() {
let mut i: usize = 0;
loop {
i += 1;
// Eventually, this will be a sleep system call.
if i > 100_000_000 {
unsafe {
make_syscall(1);
@ -89,6 +133,61 @@ pub fn add_process_default(pr: fn()) {
}
}
/// Add a kernel process.
pub fn add_kernel_process(func: fn()) {
// This is the Rust-ism that really trips up C++ programmers.
// PROCESS_LIST is wrapped in an Option<> enumeration, which
// means that the Option owns the Deque. We can only borrow from
// it or move ownership to us. In this case, we choose the
// latter, where we move ownership to us, add a process, and
// then move ownership back to the PROCESS_LIST.
// This allows mutual exclusion as anyone else trying to grab
// the process list will get None rather than the Deque.
if let Some(mut pl) = unsafe { PROCESS_LIST.take() } {
// .take() will replace PROCESS_LIST with None and give
// us the only copy of the Deque.
let func_addr = func as usize;
let func_vaddr = func_addr; //- 0x6000_0000;
// println!("func_addr = {:x} -> {:x}", func_addr, func_vaddr);
// We will convert NEXT_PID below into an atomic increment when
// we start getting into multi-hart processing. For now, we want
// a process. Get it to work, then improve it!
let mut ret_proc = Process { frame: zalloc(1) as *mut TrapFrame,
stack: alloc(STACK_PAGES),
pid: unsafe { NEXT_PID },
root: zalloc(1) as *mut Table,
state: ProcessState::Running,
data: ProcessData::zero(),
sleep_until: 0, };
unsafe {
NEXT_PID += 1;
}
// Now we move the stack pointer to the bottom of the
// allocation. The spec shows that register x2 (2) is the stack
// pointer.
// We could use ret_proc.stack.add, but that's an unsafe
// function which would require an unsafe block. So, convert it
// to usize first and then add PAGE_SIZE is better.
// We also need to set the stack adjustment so that it is at the
// bottom of the memory and far away from heap allocations.
unsafe {
(*ret_proc.frame).pc = func_vaddr;
(*ret_proc.frame).regs[2] = ret_proc.stack as usize + STACK_PAGES * 4096;
(*ret_proc.frame).mode = CpuMode::Machine as usize;
(*ret_proc.frame).pid = ret_proc.pid as usize;
}
pl.push_back(ret_proc);
// Now, we no longer need the owned Deque, so we hand it
// back by replacing the PROCESS_LIST's None with the
// Some(pl).
unsafe { PROCESS_LIST.replace(pl); }
}
// TODO: When we get to multi-hart processing, we need to keep
// trying to grab the process list. We can do this with an
// atomic instruction. but right now, we're a single-processor
// computer.
}
/// This should only be called once, and its job is to create
/// the init process. Right now, this process is in the kernel,
/// but later, it should call the shell.
@ -134,50 +233,58 @@ pub enum ProcessState {
// C-style ABI.
#[repr(C)]
pub struct Process {
frame: *mut TrapFrame,
stack: *mut u8,
pid: u16,
root: *mut Table,
state: ProcessState,
data: ProcessData,
sleep_until: usize,
frame: *mut TrapFrame,
stack: *mut u8,
pid: u16,
root: *mut Table,
state: ProcessState,
data: ProcessData,
sleep_until: usize,
}
impl Process {
pub fn get_frame_address(&self) -> usize {
self.frame as usize
}
pub fn get_program_counter(&self) -> usize {
unsafe { (*self.frame).pc }
}
pub fn get_table_address(&self) -> usize {
self.root as usize
}
pub fn get_state(&self) -> &ProcessState {
&self.state
}
pub fn set_state(&mut self, ps: ProcessState) {
self.state = ps;
}
pub fn get_pid(&self) -> u16 {
self.pid
}
pub fn get_sleep_until(&self) -> usize {
self.sleep_until
}
pub fn new_default(func: fn()) -> Self {
let func_addr = func as usize;
let func_vaddr = func_addr; //- 0x6000_0000;
// println!("func_addr = {:x} -> {:x}", func_addr, func_vaddr);
// We will convert NEXT_PID below into an atomic increment when
// we start getting into multi-hart processing. For now, we want
// a process. Get it to work, then improve it!
let mut ret_proc =
Process { frame: zalloc(1) as *mut TrapFrame,
stack: alloc(STACK_PAGES),
pid: unsafe { NEXT_PID },
root: zalloc(1) as *mut Table,
state: ProcessState::Running,
data: ProcessData::zero(),
sleep_until: 0
};
// println!("func_addr = {:x} -> {:x}", func_addr, func_vaddr);
// We will convert NEXT_PID below into an atomic increment when
// we start getting into multi-hart processing. For now, we want
// a process. Get it to work, then improve it!
let mut ret_proc = Process { frame: zalloc(1) as *mut TrapFrame,
stack: alloc(STACK_PAGES),
pid: unsafe { NEXT_PID },
root: zalloc(1) as *mut Table,
state: ProcessState::Running,
data: ProcessData::zero(),
sleep_until: 0, };
unsafe {
satp_fence_asid(NEXT_PID as usize);
NEXT_PID += 1;
@ -194,50 +301,37 @@ impl Process {
unsafe {
(*ret_proc.frame).pc = func_vaddr;
(*ret_proc.frame).regs[2] = STACK_ADDR + PAGE_SIZE * STACK_PAGES;
(*ret_proc.frame).mode = CpuMode::User as usize;
(*ret_proc.frame).pid = ret_proc.pid as usize;
}
// Map the stack on the MMU
let pt;
unsafe {
pt = &mut *ret_proc.root;
(*ret_proc.frame).satp = build_satp(SatpMode::Sv39, ret_proc.pid as usize, ret_proc.root as usize);
(*ret_proc.frame).satp =
build_satp(SatpMode::Sv39, ret_proc.pid as usize, ret_proc.root as usize);
}
// We need to map the stack onto the user process' virtual
// memory This gets a little hairy because we need to also map
// the function code too.
for i in 0..STACK_PAGES {
let addr = i * PAGE_SIZE;
map(
pt,
STACK_ADDR + addr,
saddr + addr,
EntryBits::UserReadWrite.val(),
0,
);
map(pt, STACK_ADDR + addr, saddr + addr, EntryBits::UserReadWrite.val(), 0);
// println!("Set stack from 0x{:016x} -> 0x{:016x}", STACK_ADDR + addr, saddr + addr);
}
// Map the program counter on the MMU and other bits
for i in 0..=100 {
let modifier = i * 0x1000;
map(
pt,
func_vaddr + modifier,
func_addr + modifier,
EntryBits::UserReadWriteExecute.val(),
0,
);
map(pt, func_vaddr + modifier, func_addr + modifier, EntryBits::UserReadWriteExecute.val(), 0);
}
// This is the make_syscall function
// The reason we need this is because we're running a process
// that is inside of the kernel. When we start loading from a block
// devices, we can load the instructions anywhere in memory.
map(pt, 0x8000_0000, 0x8000_0000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_1000, 0x8000_1000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_2000, 0x8000_2000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_3000, 0x8000_3000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_4000, 0x8000_4000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_5000, 0x8000_5000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_6000, 0x8000_6000, EntryBits::UserReadExecute.val(), 0);
map(pt, 0x8000_7000, 0x8000_7000, EntryBits::UserReadExecute.val(), 0);
// devices, we can load the instructions anywhere in memory.
for i in 0..=7 {
let addr = 0x8000_0000 | i << 12;
map(pt, addr, addr, EntryBits::UserReadExecute.val(), 0);
}
ret_proc
}
}

49
risc_v/src/sched.rs
View File

@ -6,36 +6,35 @@
use crate::process::{ProcessState, PROCESS_LIST};
pub fn schedule() -> usize {
let mut frame_addr: usize = 0x1111;
unsafe {
if let Some(mut pl) = PROCESS_LIST.take() {
pl.rotate_left(1);
let mut frame_addr: usize = 0;
// let mut mepc: usize = 0;
// let mut satp: usize = 0;
// let mut pid: usize = 0;
if let Some(prc) = pl.front() {
match prc.get_state() {
ProcessState::Running => {
frame_addr =
prc.get_frame_address();
// satp = prc.get_table_address();
// pid = prc.get_pid() as usize;
},
ProcessState::Sleeping => {},
_ => {},
let mut done = false;
while !done {
pl.rotate_left(1);
// let mut mepc: usize = 0;
// let mut satp: usize = 0;
// let mut pid: usize = 0;
if let Some(prc) = pl.front() {
match prc.get_state() {
ProcessState::Running => {
frame_addr =
prc.get_frame_address();
done = true;
// println!("Process is running on frame 0x{:x}", frame_addr);
// satp = prc.get_table_address();
// pid = prc.get_pid() as usize;
},
ProcessState::Sleeping => {},
_ => {},
}
}
}
// println!("Scheduling {}", pid);
PROCESS_LIST.replace(pl);
if frame_addr != 0 {
// MODE 8 is 39-bit virtual address MMU
// I'm using the PID as the address space
// identifier to hopefully help with (not?)
// flushing the TLB whenever we switch
// processes.
return frame_addr;
}
}
else {
println!("could not take process list");
}
}
0
frame_addr
}

118
risc_v/src/syscall.rs
View File

@ -3,35 +3,93 @@
// Stephen Marz
// 3 Jan 2020
use crate::cpu::TrapFrame;
use crate::{block::process_read, cpu::TrapFrame};
pub fn do_syscall(mepc: usize, frame: *mut TrapFrame) -> usize {
let syscall_number;
unsafe {
// A0 is X10, so it's register number 10.
syscall_number = (*frame).regs[10];
// for i in 0..32 {
// print!("regs[{:02}] = 0x{:08x} ", i, (*frame).regs[i]);
// if (i+1) % 4 == 0 {
// println!();
// }
// }
}
match syscall_number {
0 => {
// Exit
// Currently, we cannot kill a process, it runs forever. We will delete
// the process later and free the resources, but for now, we want to get
// used to how processes will be scheduled on the CPU.
mepc + 4
},
1 => {
println!("Test syscall");
mepc + 4
},
_ => {
println!("Unknown syscall number {}", syscall_number);
mepc + 4
}
}
}
let syscall_number;
unsafe {
// A7 is X17, so it's register number 17.
syscall_number = (*frame).regs[17];
// for i in 0..32 {
// print!("regs[{:02}] = 0x{:08x} ", i, (*frame).regs[i]);
// if (i+1) % 4 == 0 {
// println!();
// }
// }
}
// These system call numbers come from libgloss so that we can use newlib
// for our system calls.
// Libgloss wants the system call number in A7 and arguments in A0..A6
// #define SYS_getcwd 17
// #define SYS_dup 23
// #define SYS_fcntl 25
// #define SYS_faccessat 48
// #define SYS_chdir 49
// #define SYS_openat 56
// #define SYS_close 57
// #define SYS_getdents 61
// #define SYS_lseek 62
// #define SYS_read 63
// #define SYS_write 64
// #define SYS_writev 66
// #define SYS_pread 67
// #define SYS_pwrite 68
// #define SYS_fstatat 79
// #define SYS_fstat 80
// #define SYS_exit 93
// #define SYS_exit_group 94
// #define SYS_kill 129
// #define SYS_rt_sigaction 134
// #define SYS_times 153
// #define SYS_uname 160
// #define SYS_gettimeofday 169
// #define SYS_getpid 172
// #define SYS_getuid 174
// #define SYS_geteuid 175
// #define SYS_getgid 176
// #define SYS_getegid 177
// #define SYS_brk 214
// #define SYS_munmap 215
// #define SYS_mremap 216
// #define SYS_mmap 222
// #define SYS_open 1024
// #define SYS_link 1025
// #define SYS_unlink 1026
// #define SYS_mkdir 1030
// #define SYS_access 1033
// #define SYS_stat 1038
// #define SYS_lstat 1039
// #define SYS_time 1062
// #define SYS_getmainvars 2011
match syscall_number {
0 | 93 => {
// Exit
// Currently, we cannot kill a process, it runs forever. We will delete
// the process later and free the resources, but for now, we want to get
// used to how processes will be scheduled on the CPU.
mepc + 4
},
1 => {
println!("Test syscall");
mepc + 4
},
63 => unsafe {
// Read system call
// This is an asynchronous call. This will get the process going. We won't hear the answer until
// we an interrupt back.
let _ = process_read(
(*frame).pid as u16,
(*frame).regs[10],
(*frame).regs[11] as *mut u8,
(*frame).regs[12] as u32,
(*frame).regs[13] as u64,
);
// If we return 0, the trap handler will schedule another process.
0
},
_ => {
println!("Unknown syscall number {}", syscall_number);
mepc + 4
},
}
}

28
risc_v/src/trap.rs
View File

@ -37,11 +37,15 @@ extern "C" fn m_trap(epc: usize,
// number. So, here we narrow down just the cause number.
let cause_num = cause & 0xfff;
let mut return_pc = epc;
unsafe {
(*frame).pc = return_pc;
}
if is_async {
// Asynchronous trap
match cause_num {
3 => {
// Machine software
// We will use this to awaken our other CPUs so they can process
// processes.
println!("Machine software interrupt CPU #{}", hart);
},
7 => {
@ -80,19 +84,19 @@ extern "C" fn m_trap(epc: usize,
// them later.
loop {}
},
8 => {
// Environment (system) call from User mode
8 | 9 | 11 => unsafe {
// Environment (system) call from User, Supervisor, and Machine modes
// println!("E-call from User mode! CPU#{} -> 0x{:08x}", hart, epc);
return_pc = do_syscall(return_pc, frame);
},
9 => {
// Environment (system) call from Supervisor mode
println!("E-call from Supervisor mode! CPU#{} -> 0x{:08x}", hart, epc);
return_pc = do_syscall(return_pc, frame);
},
11 => {
// Environment (system) call from Machine mode
panic!("E-call from Machine mode! CPU#{} -> 0x{:08x}\n", hart, epc);
if return_pc == 0 {
// We are about to schedule something else here, so we need to store PAST
// the system call so that when we resume this process, we're after the ecall.
(*frame).pc += 4;
let frame = schedule();
// let p = frame as *const crate::process::Process;
schedule_next_context_switch(1);
rust_switch_to_user(frame);
}
},
// Page faults
12 => {