fork/wait/exit work

1 files changed, 149 insertions, 136 deletions

diff --git a/proc.c b/proc.c
index 3c0acbd..e574db0 100644
--- a/proc.c
+++ b/proc.c
@@ -1,18 +1,20 @@
 #include "types.h"
-#include "defs.h"
 #include "param.h"
 #include "memlayout.h"
-#include "mmu.h"
-#include "x86.h"
+#include "riscv.h"
 #include "proc.h"
 #include "spinlock.h"
+#include "defs.h"
 
 struct {
   struct spinlock lock;
   struct proc proc[NPROC];
 } ptable;
 
-static struct proc *initproc;
+// XXX riscv move somewhere else
+struct cpu cpus[NCPU];
+
+struct proc *initproc;
 
 int nextpid = 1;
 extern void forkret(void);
@@ -22,57 +24,36 @@ extern void sysexit(void);
 
 static void wakeup1(void *chan);
 
+extern char trampstart[]; // trampoline.S
+
 void
-pinit(void)
+procinit(void)
 {
   initlock(&ptable.lock, "ptable");
 }
 
-// Must be called with interrupts disabled
+// Must be called with interrupts disabled.
+// XXX riscv
 int
 cpuid() {
-  return mycpu()-cpus;
-}
-
-// Must be called with interrupts disabled to avoid the caller being
-// rescheduled between reading lapicid and running through the loop.
-struct cpu*
-getmycpu(void)
-{
-  int apicid, i;
-  
-  if(readeflags()&FL_IF)
-    panic("getmycpu called with interrupts enabled\n");
-  
-  apicid = lapicid();
-  // APIC IDs are not guaranteed to be contiguous.
-  for (i = 0; i < ncpu; ++i) {
-    if (cpus[i].apicid == apicid)
-      return &cpus[i];
-  }
-  panic("unknown apicid\n");
+  return 0;
 }
 
-// Return this core's cpu struct using %gs. %gs points this core's struct
-// cpu. Offet 24 in struct cpu is cpu.
+// Return this core's cpu struct.
+// XXX riscv
 struct cpu*
 mycpu(void) {
   struct cpu *c;
-  asm volatile("mov %%gs:24, %0" : "=r" (c));
+  c = &cpus[0];
   return c;
 }
 
 // Disable interrupts so that we are not rescheduled
 // while reading proc from the cpu structure
+// XXX riscv
 struct proc*
 myproc(void) {
-  struct cpu *c;
-  struct proc *p;
-  pushcli();
-  c = mycpu();
-  p = c->proc;
-  popcli();
-  return p;
+  return cpus[0].proc;
 }
 
 //PAGEBREAK: 32
@@ -84,7 +65,6 @@ static struct proc*
 allocproc(void)
 {
   struct proc *p;
-  char *sp;
 
   acquire(&ptable.lock);
 
@@ -101,56 +81,73 @@ found:
 
   release(&ptable.lock);
 
-  // Allocate kernel stack.
+  // Allocate a page for the kernel stack.
   if((p->kstack = kalloc()) == 0){
     p->state = UNUSED;
     return 0;
   }
-  sp = p->kstack + KSTACKSIZE;
 
-  // Leave room for syscall frame.
-  sp -= sizeof *p->sf;
+  // Allocate a trapframe page.
+  if((p->tf = (struct trapframe *)kalloc()) == 0){
+    p->state = UNUSED;
+    return 0;
+  }
 
-  if ((uint64) sp % 16)
-    panic("misaligned sp");
+  // An empty user page table.
+  p->pagetable = uvmcreate();
 
-  p->sf = (struct sysframe*)sp;
+  // map the trampoline code (for system call return)
+  // at the highest user virtual address.
+  // only the supervisor uses it, on the way
+  // to/from user space, so not PTE_U.
+  mappages(p->pagetable, TRAMPOLINE, PGSIZE,
+           (uint64)trampstart, PTE_R | PTE_X);
 
-  // Set up new context to start executing at forkret,
-  // which returns to sysexit.
-  sp -= sizeof(uint64);
-  *(uint64*)sp = (uint64)sysexit;
+  // map the trapframe, for trampoline.S.
+  mappages(p->pagetable, (TRAMPOLINE - PGSIZE), PGSIZE,
+           (uint64)(p->tf), PTE_R | PTE_W);
 
-  sp -= sizeof *p->context;
-  p->context = (struct context*)sp;
-  memset(p->context, 0, sizeof *p->context);
-  p->context->rip = (uint64)forkret;
+  // Set up new context to start executing at forkret,
+  // which returns to user space.
+  memset(&p->context, 0, sizeof p->context);
+  p->context.ra = (uint64)forkret;
+  p->context.sp = (uint64)p->kstack + PGSIZE;
 
   return p;
 }
 
+// XXX hack because I don't know how to incorporate initcode
+// into the kernel binary. just the exec system call, no arguments.
+// manually copied from initcode.asm.
+unsigned char initcode[] = {
+  0x85, 0x48,             // li a7, 1 -- SYS_fork
+  0x73, 0x00, 0x00, 0x00, // ecall
+  0x8d, 0x48,             // li a7, 3 -- SYS_wait
+  0x73, 0x00, 0x00, 0x00, // ecall
+  0x89, 0x48,             // li a7, 2 -- SYS_exit
+  0x73, 0x00, 0x00, 0x00, // ecall
+};
+
 //PAGEBREAK: 32
 // Set up first user process.
 void
 userinit(void)
 {
   struct proc *p;
-  extern char _binary_initcode_start[], _binary_initcode_size[];
 
   p = allocproc();
-  
   initproc = p;
-  if((p->pgdir = setupkvm()) == 0)
-    panic("userinit: out of memory?");
-  inituvm(p->pgdir, _binary_initcode_start, (uint64)_binary_initcode_size);
+  
+  uvminit(p->pagetable, initcode, sizeof(initcode));
   p->sz = PGSIZE;
-  memset(p->sf, 0, sizeof(*p->sf));
-  p->sf->r11 = FL_IF;
-  p->sf->rsp = PGSIZE;
-  p->sf->rcx = 0;  // beginning of initcode.S
+
+  // prepare for the very first kernel->user.
+  p->tf->epc = 0;
+  p->tf->sp = PGSIZE;
 
   safestrcpy(p->name, "initcode", sizeof(p->name));
-  p->cwd = namei("/");
+  // XXX riscv
+  //p->cwd = namei("/");
 
   // this assignment to p->state lets other cores
   // run this process. the acquire forces the above
@@ -163,62 +160,65 @@ userinit(void)
   release(&ptable.lock);
 }
 
+#if 0
+
 // Grow current process's memory by n bytes.
 // Return 0 on success, -1 on failure.
 int
 growproc(int n)
 {
   uint sz;
-  struct proc *curproc = myproc();
+  struct proc *p = myproc();
 
-  sz = curproc->sz;
+  sz = p->sz;
   if(n > 0){
-    if((sz = allocuvm(curproc->pgdir, sz, sz + n)) == 0)
+    if((sz = allocuvm(p->pagetable, sz, sz + n)) == 0)
       return -1;
   } else if(n < 0){
-    if((sz = deallocuvm(curproc->pgdir, sz, sz + n)) == 0)
+    if((sz = uvmdealloc(p->pagetable, sz, sz + n)) == 0)
       return -1;
   }
-  curproc->sz = sz;
-  switchuvm(curproc);
+  p->sz = sz;
+  switchuvm(p);
   return 0;
 }
+#endif
 
-// Create a new process copying p as the parent.
-// Sets up stack to return as if from system call.
-// Caller must set state of returned proc to RUNNABLE.
+// Create a new process, copying p as the parent.
+// Sets up child kernel stack to return as if from system call.
 int
 fork(void)
 {
   int i, pid;
   struct proc *np;
-  struct proc *curproc = myproc();
+  struct proc *p = myproc();
 
   // Allocate process.
   if((np = allocproc()) == 0){
     return -1;
   }
 
-  // Copy process state from proc.
-  if((np->pgdir = copyuvm(curproc->pgdir, curproc->sz)) == 0){
-    kfree(np->kstack);
-    np->kstack = 0;
-    np->state = UNUSED;
-    return -1;
-  }
-  np->sz = curproc->sz;
-  np->parent = curproc;
-  *np->sf = *curproc->sf;
+  // Copy user memory from parent to child.
+  uvmcopy(p->pagetable, np->pagetable, p->sz);
+  np->sz = p->sz;
 
-  // Clear %eax so that fork returns 0 in the child.
-  np->sf->rax = 0;
+  np->parent = p;
 
+  // copy saved user registers.
+  *(np->tf) = *(p->tf);
+
+  // Cause fork to return 0 in the child.
+  np->tf->a0 = 0;
+
+#if 0 // XXX riscv
+  // increment reference counts on open file descriptors.
   for(i = 0; i < NOFILE; i++)
-    if(curproc->ofile[i])
-      np->ofile[i] = filedup(curproc->ofile[i]);
-  np->cwd = idup(curproc->cwd);
+    if(p->ofile[i])
+      np->ofile[i] = filedup(p->ofile[i]);
+  np->cwd = idup(p->cwd);
+#endif
 
-  safestrcpy(np->name, curproc->name, sizeof(curproc->name));
+  safestrcpy(np->name, p->name, sizeof(p->name));
 
   pid = np->pid;
 
@@ -233,46 +233,48 @@ fork(void)
 
 // Exit the current process.  Does not return.
 // An exited process remains in the zombie state
-// until its parent calls wait() to find out it exited.
+// until its parent calls wait().
 void
 exit(void)
 {
-  struct proc *curproc = myproc();
-  struct proc *p;
+  struct proc *p = myproc();
+  struct proc *pp;
   int fd;
 
-  if(curproc == initproc)
+  if(p == initproc)
     panic("init exiting");
 
+#if 0 // XXX riscv
   // Close all open files.
   for(fd = 0; fd < NOFILE; fd++){
-    if(curproc->ofile[fd]){
-      fileclose(curproc->ofile[fd]);
-      curproc->ofile[fd] = 0;
+    if(p->ofile[fd]){
+      fileclose(p->ofile[fd]);
+      p->ofile[fd] = 0;
     }
   }
 
   begin_op();
-  iput(curproc->cwd);
+  iput(p->cwd);
   end_op();
-  curproc->cwd = 0;
+#endif
+  p->cwd = 0;
 
   acquire(&ptable.lock);
 
   // Parent might be sleeping in wait().
-  wakeup1(curproc->parent);
+  wakeup1(p->parent);
 
   // Pass abandoned children to init.
-  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
-    if(p->parent == curproc){
-      p->parent = initproc;
-      if(p->state == ZOMBIE)
+  for(pp = ptable.proc; pp < &ptable.proc[NPROC]; pp++){
+    if(pp->parent == p){
+      pp->parent = initproc;
+      if(pp->state == ZOMBIE)
         wakeup1(initproc);
     }
   }
 
   // Jump into the scheduler, never to return.
-  curproc->state = ZOMBIE;
+  p->state = ZOMBIE;
   sched();
   panic("zombie exit");
 }
@@ -282,42 +284,47 @@ exit(void)
 int
 wait(void)
 {
-  struct proc *p;
+  struct proc *np;
   int havekids, pid;
-  struct proc *curproc = myproc();
+  struct proc *p = myproc();
   
   acquire(&ptable.lock);
   for(;;){
     // Scan through table looking for exited children.
     havekids = 0;
-    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
-      if(p->parent != curproc)
+    for(np = ptable.proc; np < &ptable.proc[NPROC]; np++){
+      if(np->parent != p)
         continue;
       havekids = 1;
-      if(p->state == ZOMBIE){
+      if(np->state == ZOMBIE){
         // Found one.
-        pid = p->pid;
-        kfree(p->kstack);
-        p->kstack = 0;
-        freevm(p->pgdir, p->sz);
-         p->pid = 0;
-        p->parent = 0;
-        p->name[0] = 0;
-        p->killed = 0;
-        p->state = UNUSED;
+        pid = np->pid;
+        kfree(np->kstack);
+        np->kstack = 0;
+        kfree((void*)np->tf);
+        np->tf = 0;
+        unmappages(np->pagetable, TRAMPOLINE, PGSIZE, 0);
+        unmappages(np->pagetable, TRAMPOLINE-PGSIZE, PGSIZE, 0);
+        uvmfree(np->pagetable, np->sz);
+        np->pagetable = 0;
+        np->pid = 0;
+        np->parent = 0;
+        np->name[0] = 0;
+        np->killed = 0;
+        np->state = UNUSED;
         release(&ptable.lock);
         return pid;
       }
     }
 
     // No point waiting if we don't have any children.
-    if(!havekids || curproc->killed){
+    if(!havekids || p->killed){
       release(&ptable.lock);
       return -1;
     }
 
     // Wait for children to exit.  (See wakeup1 call in proc_exit.)
-    sleep(curproc, &ptable.lock);  //DOC: wait-sleep
+    sleep(p, &ptable.lock);  //DOC: wait-sleep
   }
 }
 
@@ -338,7 +345,8 @@ scheduler(void)
   c->proc = 0;
   for(;;){
     // Enable interrupts on this processor.
-    sti();
+    // XXX riscv
+    //sti();
     
     // Loop over process table looking for process to run.
     acquire(&ptable.lock);
@@ -350,11 +358,11 @@ scheduler(void)
       // to release ptable.lock and then reacquire it
       // before jumping back to us.
       c->proc = p;
-      switchuvm(p);
       p->state = RUNNING;
 
-      swtch(&(c->scheduler), p->context);
-      switchkvm();
+      printf("switch...\n");
+      swtch(&c->scheduler, &p->context);
+      printf("switch returned\n");
 
       // Process is done running for now.
       // It should have changed its p->state before coming back.
@@ -380,14 +388,10 @@ sched(void)
 
   if(!holding(&ptable.lock))
     panic("sched ptable.lock");
-  if(mycpu()->ncli != 1)
-    panic("sched locks");
   if(p->state == RUNNING)
     panic("sched running");
-  if(readeflags()&FL_IF)
-    panic("sched interruptible");
   intena = mycpu()->intena;
-  swtch(&p->context, mycpu()->scheduler);
+  swtch(&p->context, &mycpu()->scheduler);
   mycpu()->intena = intena;
 }
 
@@ -402,24 +406,29 @@ yield(void)
 }
 
 // A fork child's very first scheduling by scheduler()
-// will swtch here.  "Return" to user space.
+// will swtch to forkret.
 void
 forkret(void)
 {
+  struct proc *p = myproc();
+
   static int first = 1;
   // Still holding ptable.lock from scheduler.
   release(&ptable.lock);
 
+  printf("entering forkret\n");
+
   if (first) {
     // Some initialization functions must be run in the context
     // of a regular process (e.g., they call sleep), and thus cannot
     // be run from main().
     first = 0;
-    iinit(ROOTDEV);
-    initlog(ROOTDEV);
+    // XXX riscv
+    //iinit(ROOTDEV);
+    //initlog(ROOTDEV);
   }
-  
-  // Return to "caller", actually trapret (see allocproc).
+
+  usertrapret();
 }
 
 // Atomically release lock and sleep on chan.
@@ -483,6 +492,8 @@ wakeup(void *chan)
   release(&ptable.lock);
 }
 
+#if 0
+
 // Kill the process with the given pid.
 // Process won't exit until it returns
 // to user space (see trap in trap.c).
@@ -533,12 +544,14 @@ procdump(void)
       state = states[p->state];
     else
       state = "???";
-    cprintf("%d %s %s", p->pid, state, p->name);
+    printf("%d %s %s", p->pid, state, p->name);
     if(p->state == SLEEPING){
       getcallerpcs((uint64*)p->context->rbp+2, pc);
       for(i=0; i<10 && pc[i] != 0; i++)
-        cprintf(" %p", pc[i]);
+        printf(" %p", pc[i]);
     }
-    cprintf("\n");
+    printf("\n");
   }
 }
+
+#endif