diff --git a/console.c b/console.c
index 86c080e1d2b5183f6e6ee8838d532c6b5cc2550b..5dad05aed670ca9cba6f619a993ad8297377add3 100644
--- a/console.c
+++ b/console.c
@@ -58,7 +58,7 @@ real_cons_putc(int c)
if((ind / 80) >= 24){
// scroll up
- memcpy(crt, crt + 80, sizeof(crt[0]) * (23 * 80));
+ memmove(crt, crt + 80, sizeof(crt[0]) * (23 * 80));
ind -= 80;
memset(crt + ind, 0, sizeof(crt[0]) * ((24 * 80) - ind));
}
diff --git a/defs.h b/defs.h
index 824b986358e411420d3c51ba5ba81d2356bd53d6..a11cc5757f84cf519d91dcfde909952a3a0abf1f 100644
--- a/defs.h
+++ b/defs.h
@@ -12,7 +12,7 @@ void cons_putc(int);
struct proc;
struct jmpbuf;
void setupsegs(struct proc *);
-struct proc * newproc(void);
+struct proc * copyproc(struct proc*);
struct spinlock;
void sleep(void *, struct spinlock *);
void wakeup(void *);
@@ -32,7 +32,6 @@ void tvinit(void);
void idtinit(void);
// string.c
-void * memcpy(void *dst, void *src, unsigned n);
void * memset(void *dst, int c, unsigned n);
int memcmp(const void *v1, const void *v2, unsigned n);
void *memmove(void *dst, const void *src, unsigned n);
@@ -92,3 +91,4 @@ void ide_init(void);
void ide_intr(void);
void* ide_start_read(uint32_t secno, void *dst, unsigned nsecs);
int ide_finish_read(void *);
+
diff --git a/main.c b/main.c
index 70e93cf47a9eff5bb465540139a5b09553bb851d..5f2d698a740911927878f34714486a886c7e6981 100644
--- a/main.c
+++ b/main.c
@@ -81,7 +81,7 @@ main()
// become interruptable
sti();
- p = newproc();
+ p = copyproc(&proc[0]);
load_icode(p, _binary_usertests_start, (unsigned) _binary_usertests_size);
//load_icode(p, _binary_userfs_start, (unsigned) _binary_userfs_size);
@@ -122,7 +122,7 @@ load_icode(struct proc *p, uint8_t *binary, unsigned size)
panic("load_icode: icode wants to be above UTOP");
// Load/clear the segment
- memcpy(p->mem + ph->p_va, binary + ph->p_offset, ph->p_filesz);
+ memmove(p->mem + ph->p_va, binary + ph->p_offset, ph->p_filesz);
memset(p->mem + ph->p_va + ph->p_filesz, 0, ph->p_memsz - ph->p_filesz);
}
}
diff --git a/proc.c b/proc.c
index 01d8f2f59598f8f9e6f980e68168cdbca3eab9c9..c854576d2512bc1352a5a826f66ec18a962ca6f9 100644
--- a/proc.c
+++ b/proc.c
@@ -13,6 +13,7 @@ struct proc proc[NPROC];
struct proc *curproc[NCPU];
int next_pid = 1;
extern void forkret(void);
+extern void forkret1(struct Trapframe*);
/*
* set up a process's task state and segment descriptors
@@ -42,84 +43,87 @@ setupsegs(struct proc *p)
p->gdt_pd.pd_base = (unsigned) p->gdt;
}
-extern void trapret();
+// Look in the process table for an UNUSED proc.
+// If found, change state to EMBRYO and return it.
+// Otherwise return 0.
+struct proc*
+allocproc(void)
+{
+ int i;
+ struct proc *p;
+
+ for(i = 0; i < NPROC; i++){
+ p = &proc[i];
+ if(p->state == UNUSED){
+ p->state = EMBRYO;
+ return p;
+ }
+ }
+ return 0;
+}
-/*
- * internal fork(). does not copy kernel stack; instead,
- * sets up the stack to return as if from system call.
- * caller must set state to RUNNABLE.
- */
+// Create a new process copying p as the parent.
+// Does not copy the kernel stack.
+// Instead, sets up stack to return as if from system call.
+// Caller must arrange for process to run (set state to RUNNABLE).
struct proc *
-newproc()
+copyproc(struct proc* p)
{
+ int i;
struct proc *np;
- struct proc *op;
- int fd;
+ // Allocate process.
acquire(&proc_table_lock);
-
- for(np = &proc[1]; np < &proc[NPROC]; np++){
- if(np->state == UNUSED){
- np->state = EMBRYO;
- break;
- }
- }
- if(np >= &proc[NPROC]){
+ if((np = allocproc()) == 0){
release(&proc_table_lock);
return 0;
}
-
- // copy from proc[0] if we're bootstrapping
- op = curproc[cpu()];
- if(op == 0)
- op = &proc[0];
-
np->pid = next_pid++;
- np->ppid = op->pid;
-
+ np->ppid = p->pid;
release(&proc_table_lock);
- np->sz = op->sz;
- np->mem = kalloc(op->sz);
- if(np->mem == 0)
+ // Copy process image memory.
+ np->sz = p->sz;
+ np->mem = kalloc(np->sz);
+ if(np->mem == 0){
+ np->state = UNUSED;
return 0;
- memcpy(np->mem, op->mem, np->sz);
+ }
+ memmove(np->mem, p->mem, np->sz);
+
+ // Allocate kernel stack.
np->kstack = kalloc(KSTACKSIZE);
if(np->kstack == 0){
- kfree(np->mem, op->sz);
+ kfree(np->mem, np->sz);
np->state = UNUSED;
return 0;
}
+
+ // Initialize segment table.
setupsegs(np);
+
+ // Copy trapframe registers from parent.
+ np->tf = (struct Trapframe*)(np->kstack + KSTACKSIZE) - 1;
+ *np->tf = *p->tf;
- // set up kernel stack to return to user space
- np->tf = (struct Trapframe *) (np->kstack + KSTACKSIZE - sizeof(struct Trapframe));
- *(np->tf) = *(op->tf);
- np->tf->tf_regs.reg_eax = 0; // so fork() returns 0 in child
-
- // Set up new jmpbuf to start executing forkret (see trapasm.S)
- // with esp pointing at tf. Forkret will call forkret1 (below) to release
- // the proc_table_lock and then jump into the usual trap return code.
+ // Clear %eax so that fork system call returns 0 in child.
+ np->tf->tf_regs.reg_eax = 0;
+
+ // Set up new jmpbuf to start executing at forkret (see below).
memset(&np->jmpbuf, 0, sizeof np->jmpbuf);
- np->jmpbuf.jb_eip = (unsigned) forkret;
- np->jmpbuf.jb_esp = (unsigned) np->tf - 4; // -4 for the %eip that isn't actually there
+ np->jmpbuf.jb_eip = (unsigned)forkret;
+ np->jmpbuf.jb_esp = (unsigned)np->tf;
// Copy file descriptors
- for(fd = 0; fd < NOFILE; fd++){
- np->fds[fd] = op->fds[fd];
- if(np->fds[fd])
- fd_reference(np->fds[fd]);
+ for(i = 0; i < NOFILE; i++){
+ np->fds[i] = p->fds[i];
+ if(np->fds[i])
+ fd_reference(np->fds[i]);
}
return np;
}
-void
-forkret1(void)
-{
- release(&proc_table_lock);
-}
-
// Per-CPU process scheduler.
// Each CPU calls scheduler() after setting itself up.
// Scheduler never returns. It loops, doing:
@@ -199,7 +203,7 @@ sched(void)
// Give up the CPU for one scheduling round.
void
-yield()
+yield(void)
{
struct proc *p;
@@ -211,6 +215,18 @@ yield()
release(&proc_table_lock);
}
+// A process's very first scheduling by scheduler()
+// will longjmp here to do the first jump into user space.
+void
+forkret(void)
+{
+ // Still holding proc_table_lock from scheduler.
+ release(&proc_table_lock);
+
+ // Jump into assembly, never to return.
+ forkret1(curproc[cpu()]->tf);
+}
+
// Atomically release lock and sleep on chan.
// Reacquires lock when reawakened.
void
diff --git a/string.c b/string.c
index c88e7de252010edfe441b02d9f3e8b1894cccc12..07082e5abad77c4d71328e4b757c7a41295e32bf 100644
--- a/string.c
+++ b/string.c
@@ -1,18 +1,6 @@
#include "types.h"
#include "defs.h"
-void *
-memcpy(void *dst, void *src, unsigned n)
-{
- char *d = (char *) dst;
- char *s = (char *) src;
-
- while(n-- > 0)
- *d++ = *s++;
-
- return dst;
-}
-
void *
memset(void *dst, int c, unsigned n)
{
@@ -69,3 +57,21 @@ strncmp(const char *p, const char *q, unsigned n)
else
return (int) ((unsigned char) *p - (unsigned char) *q);
}
+
+// Memcpy is deprecated and should NOT be called.
+// Use memmove instead, which has defined semantics
+// when the two memory ranges overlap.
+// Memcpy is here only because gcc compiles some
+// structure assignments into calls to memcpy.
+void *
+memcpy(void *dst, void *src, unsigned n)
+{
+ char *d = (char *) dst;
+ char *s = (char *) src;
+
+ while(n-- > 0)
+ *d++ = *s++;
+
+ return dst;
+}
+
diff --git a/syscall.c b/syscall.c
index 420a578141ab143b3e415c374dc4f01b755cc173..6ac739f88bef6f18725076c58ea467e853f173d3 100644
--- a/syscall.c
+++ b/syscall.c
@@ -30,7 +30,7 @@ fetchint(struct proc *p, unsigned addr, int *ip)
if(addr > p->sz - 4)
return -1;
- memcpy(ip, p->mem + addr, 4);
+ memmove(ip, p->mem + addr, 4);
return 0;
}
@@ -49,7 +49,7 @@ putint(struct proc *p, unsigned addr, int ip)
{
if(addr > p->sz - 4)
return -1;
- memcpy(p->mem + addr, &ip, 4);
+ memmove(p->mem + addr, &ip, 4);
return 0;
}
@@ -150,13 +150,10 @@ sys_fork(void)
{
struct proc *np;
- np = newproc();
- if(np){
- np->state = RUNNABLE;
- return np->pid;
- } else {
+ if((np = copyproc(curproc[cpu()])) == 0)
return -1;
- }
+ np->state = RUNNABLE;
+ return np->pid;
}
int
diff --git a/trapasm.S b/trapasm.S
index e0e27be23ca908f2fc30279793b14f6689284843..3e0f37562a269a7bb382e17192a4307d07bed7f8 100644
--- a/trapasm.S
+++ b/trapasm.S
@@ -30,9 +30,9 @@ trapret:
addl $0x8, %esp /* trapno and errcode */
iret
-.globl forkret
-forkret:
- call forkret1
+.globl forkret1
+forkret1:
+ movl 4(%esp), %esp
jmp trapret
.globl acpu