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xv6-cs450
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Various cleanup: 

- Got rid of dummy proc[0].  Now proc[0] is init.
 - Added initcode.S to exec /init, so that /init is
   just a regular binary.
 - Moved exec out of sysfile to exec.c
 - Moved code dealing with fs guts (like struct inode)
   from sysfile.c to fs.c.  Code dealing with system call
   arguments stays in sysfile.c
 - Refactored directory routines in fs.c; should be simpler.
 - Changed iget to return *unlocked* inode structure.
   This solves the lookup-then-use race in namei
   without introducing deadlocks.
   It also enabled getting rid of the dummy proc[0].
This commit is contained in:
rsc 2007-08-21 19:22:08 +00:00
parent 2d61a40b20
commit f32f3638f4
12 changed files with 456 additions and 415 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
BUGS
View File

@ -11,14 +11,15 @@ proc.c:
factor out switching and scheduling code from process code
kalloc.c
more cleanups
shuffle for formatting
ide.c: synchronous disk write -> polling disk write. search for
(a)synchronous; xv6 doesn't have asynchronous writes.
syscall.c:
cannot convince runoff1 to split the extern lists to fill previous page completely.
fs.c: split all name operations off in name.c? (starting with namei but move
fs.c: split all name operations off in name.c? (starting with namei but
wdir keep in fs.c)
locking?
shuffle for formatting
pipe.c:
more comments?
@ -31,6 +32,19 @@ sysfile.c:
general:
sizeof parens?
bio.c:
decide odd or even
bwrite doesn't need a second argument
file.c:
move fileincref onto page 1?
L=$HOME/mit/l
(for i in *.c; do xoc -x xgnu -x ./nodecleq.zeta --typesonly $i; done) 2>&1 | grep warning
saw random sharedfd failure.
why does fdalloc consume reference?
why mkdir and create?

13
Makefile
View File

@ -21,6 +21,7 @@ OBJS = \
vectors.o\
bio.o\
fs.o\
exec.o\
8253pit.o\
# Cross-compiling (e.g., on Mac OS X)
@ -34,7 +35,7 @@ LD = $(TOOLPREFIX)ld
OBJCOPY = $(TOOLPREFIX)objcopy
OBJDUMP = $(TOOLPREFIX)objdump
# On newer gcc you may need to add -fno-stack-protector to $(CFLAGS)
CFLAGS = -fno-builtin -O2 -Wall -MD
CFLAGS = -fno-builtin -O2 -Wall -MD -ggdb -fno-stack-protector
AS = $(TOOLPREFIX)gas
xv6.img : bootblock kernel fs.img
@ -50,12 +51,16 @@ bootblock : bootasm.S bootmain.c
$(OBJCOPY) -S -O binary bootblock.o bootblock
./sign.pl bootblock
kernel : $(OBJS) bootother.S _init
kernel : $(OBJS) bootother.S initcode.S
$(CC) -nostdinc -I. -c bootother.S
$(LD) -N -e start -Ttext 0x7000 -o bootother.out bootother.o
$(OBJCOPY) -S -O binary bootother.out bootother
$(OBJDUMP) -S bootother.o > bootother.asm
$(LD) -Ttext 0x100000 -e main0 -o kernel $(OBJS) -b binary bootother _init
$(CC) -nostdinc -I. -c initcode.S
$(LD) -N -e start -Ttext 0 -o initcode.out initcode.o
$(OBJCOPY) -S -O binary initcode.out initcode
$(OBJDUMP) -S initcode.o > initcode.asm
$(LD) -Ttext 0x100000 -e main0 -o kernel $(OBJS) -b binary initcode bootother
$(OBJDUMP) -S kernel > kernel.asm
$(OBJDUMP) -t kernel | awk '/SYMBOL TABLE/ { go=1; next } go {print $$1, $$NF}' >kernel.sym
@ -132,7 +137,7 @@ PRINT = \
proc.h proc.c setjmp.S kalloc.c\
syscall.h trapasm.S traps.h trap.c vectors.pl syscall.c sysproc.c\
buf.h dev.h fcntl.h stat.h file.h fs.h fsvar.h file.c fs.c bio.c ide.c sysfile.c\
pipe.c\
pipe.c exec.c\
mp.h ioapic.h mp.c lapic.c ioapic.c picirq.c\
console.c\
string.c\

8
defs.h
View File

@ -40,6 +40,7 @@ int memcmp(const void*, const void*, uint);
void* memmove(void*, const void*, uint);
int strncmp(const char*, const char*, uint);
char* safestrcpy(char*, const char*, int);
int strlen(const char*);
// syscall.c
void syscall(void);
@ -135,11 +136,16 @@ int readi(struct inode*, char*, uint, uint);
int writei(struct inode*, char*, uint, uint);
struct inode* mknod(char*, short, short, short);
struct inode* dircreat(struct inode*, char*, int, short, short, short);
int dirlookup(struct inode*, char*, int, uint*, uint*);
struct inode* dirlookup(struct inode*, char*, int, uint*);
int unlink(char*);
void iupdate(struct inode*);
int link(char*, char*);
struct inode* igetroot(void);
int mkdir(char *path);
struct inode* create(char *path);
// exec.c
int exec(char*, char**);
// number of elements in fixed-size array
#define NELEM(x) (sizeof(x)/sizeof((x)[0]))

136
exec.c Normal file
View File

@ -0,0 +1,136 @@
#include "types.h"
#include "stat.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "x86.h"
#include "traps.h"
#include "syscall.h"
#include "spinlock.h"
#include "buf.h"
#include "fs.h"
#include "fsvar.h"
#include "elf.h"
#include "file.h"
#include "fcntl.h"
int
exec(char *path, char **argv)
{
uint sz, sp, p1, p2;
int i, nargs, argbytes, len;
struct inode *ip;
struct elfhdr elf;
struct proghdr ph;
char *mem;
char *s, *last;
sz = 0;
mem = 0;
if((ip = namei(path)) == 0)
return -1;
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
sz += ph.memsz;
}
sz += 4096 - (sz % 4096);
sz += 4096;
mem = kalloc(sz);
if(mem == 0)
goto bad;
memset(mem, 0, sz);
argbytes = 0;
for(i = 0; argv[i]; i++){
len = strlen(argv[i]);
argbytes += len + 1;
}
nargs = i;
// argn\0
// ...
// arg0\0
// 0
// ptr to argn
// ...
// 12: ptr to arg0
// 8: argv (points to ptr to arg0)
// 4: argc
// 0: fake return pc
sp = sz - argbytes - (nargs+1)*4 - 4 - 4 - 4;
*(uint*)(mem + sp) = 0xffffffff;
*(uint*)(mem + sp + 4) = nargs;
*(uint*)(mem + sp + 8) = (uint)(sp + 12);
p1 = sp + 12;
p2 = sp + 12 + (nargs + 1) * 4;
for(i = 0; i < nargs; i++){
len = strlen(argv[i]);
memmove(mem + p2, argv[i], len + 1);
*(uint*)(mem + p1) = p2;
p1 += 4;
p2 += len + 1;
}
*(uint*)(mem + p1) = 0;
// Save name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(cp->name, last, sizeof cp->name);
// commit to the new image.
kfree(cp->mem, cp->sz);
cp->sz = sz;
cp->mem = mem;
mem = 0;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad2;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.va + ph.memsz > sz)
goto bad2;
if(readi(ip, cp->mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
goto bad2;
memset(cp->mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
}
iput(ip);
cp->tf->eip = elf.entry;
cp->tf->esp = sp;
setupsegs(cp);
return 0;
bad:
if(mem)
kfree(mem, sz);
iput(ip);
return -1;
bad2:
iput(ip);
proc_exit();
return 0;
}

253
fs.c
View File

@ -25,8 +25,6 @@
#define min(a, b) ((a) < (b) ? (a) : (b))
static void ifree(struct inode*);
// Blocks.
// Allocate a disk block.
@ -116,30 +114,25 @@ iinit(void)
}
// Find the inode with number inum on device dev
// and return an in-memory copy. Loads the inode
// from disk into the in-core table if necessary.
// The returned inode is locked and has its ref count incremented.
// Caller must iput the return value when done with it.
// and return the in-memory copy. The returned inode
// has its reference count incremented (and thus must be
// idecref'ed), but is *unlocked*, meaning that none of the fields
// except dev and inum are guaranteed to be initialized.
// This convention gives the caller maximum control over blocking;
// it also guarantees that iget will not sleep, which is useful in
// the early igetroot and when holding other locked inodes.
struct inode*
iget(uint dev, uint inum)
{
struct inode *ip, *empty;
struct dinode *dip;
struct buf *bp;
acquire(&icache.lock);
loop:
// Try for cached inode.
empty = 0;
for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){
if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){
if(ip->busy){
sleep(ip, &icache.lock);
goto loop;
}
ip->ref++;
ip->busy = 1;
release(&icache.lock);
return ip;
}
@ -155,52 +148,61 @@ iget(uint dev, uint inum)
ip->dev = dev;
ip->inum = inum;
ip->ref = 1;
ip->busy = 1;
ip->flags = 0;
release(&icache.lock);
bp = bread(dev, IBLOCK(inum));
dip = &((struct dinode*)(bp->data))[inum % IPB];
ip->type = dip->type;
ip->major = dip->major;
ip->minor = dip->minor;
ip->nlink = dip->nlink;
ip->size = dip->size;
memmove(ip->addrs, dip->addrs, sizeof(ip->addrs));
brelse(bp);
return ip;
}
// Iget the inode for the file system root (/).
// This gets called before there is a current process: it cannot sleep!
struct inode*
igetroot(void)
{
return iget(ROOTDEV, 1);
struct inode *ip;
ip = iget(ROOTDEV, 1);
return ip;
}
// Lock the given inode.
void
ilock(struct inode *ip)
{
struct buf *bp;
struct dinode *dip;
if(ip->ref < 1)
panic("ilock");
acquire(&icache.lock);
while(ip->busy)
while(ip->flags & I_BUSY)
sleep(ip, &icache.lock);
ip->busy = 1;
ip->flags |= I_BUSY;
release(&icache.lock);
if(!(ip->flags & I_VALID)){
bp = bread(ip->dev, IBLOCK(ip->inum));
dip = &((struct dinode*)(bp->data))[ip->inum % IPB];
ip->type = dip->type;
ip->major = dip->major;
ip->minor = dip->minor;
ip->nlink = dip->nlink;
ip->size = dip->size;
memmove(ip->addrs, dip->addrs, sizeof(ip->addrs));
brelse(bp);
ip->flags |= I_VALID;
}
}
// Unlock the given inode.
void
iunlock(struct inode *ip)
{
if(ip->busy != 1 || ip->ref < 1)
if(!(ip->flags & I_BUSY) || ip->ref < 1)
panic("iunlock");
acquire(&icache.lock);
ip->busy = 0;
ip->flags &= ~I_BUSY;
wakeup(ip);
release(&icache.lock);
}
@ -209,19 +211,8 @@ iunlock(struct inode *ip)
void
iput(struct inode *ip)
{
if(ip->ref < 1 || ip->busy != 1)
panic("iput");
if((ip->ref == 1) && (ip->nlink == 0)) {
itrunc(ip);
ifree(ip);
}
acquire(&icache.lock);
ip->ref -= 1;
ip->busy = 0;
wakeup(ip);
release(&icache.lock);
iunlock(ip);
idecref(ip);
}
// Increment reference count for ip.
@ -229,31 +220,42 @@ iput(struct inode *ip)
struct inode*
iincref(struct inode *ip)
{
ilock(ip);
acquire(&icache.lock);
ip->ref++;
iunlock(ip);
release(&icache.lock);
return ip;
}
// Caller holds reference to unlocked ip.
// Drop reference.
// Caller holds reference to unlocked ip. Drop reference.
void
idecref(struct inode *ip)
{
ilock(ip);
iput(ip);
acquire(&icache.lock);
if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0) {
// inode is no longer used: truncate and free inode.
if(ip->flags & I_BUSY)
panic("idecref busy");
ip->flags |= I_BUSY;
release(&icache.lock);
// XXX convince rsc that no one will come find this inode.
itrunc(ip);
ip->type = 0;
iupdate(ip);
acquire(&icache.lock);
ip->flags &= ~I_BUSY;
}
ip->ref--;
release(&icache.lock);
}
// Allocate a new inode with the given type on device dev.
struct inode*
ialloc(uint dev, short type)
{
struct inode *ip;
int inum, ninodes;
struct buf *bp;
struct dinode *dip;
struct superblock *sb;
int ninodes;
int inum;
struct buf *bp;
bp = bread(dev, 1);
sb = (struct superblock*)bp->data;
@ -268,8 +270,7 @@ ialloc(uint dev, short type)
dip->type = type;
bwrite(bp, IBLOCK(inum)); // mark it allocated on the disk
brelse(bp);
ip = iget(dev, inum);
return ip;
return iget(dev, inum);
}
brelse(bp);
}
@ -295,15 +296,6 @@ iupdate(struct inode *ip)
brelse(bp);
}
// Free (delete) the given inode.
// Caller must have ip locked.
static void
ifree(struct inode *ip)
{
ip->type = 0;
iupdate(ip);
}
// Inode contents
//
// The contents (data) associated with each inode is stored
@ -465,15 +457,15 @@ writei(struct inode *ip, char *src, uint off, uint n)
// set *poff to the byte offset of the directory entry
// set *pinum to the inode number
// return 0.
int
dirlookup(struct inode *dp, char *name, int namelen, uint *poff, uint *pinum)
struct inode*
dirlookup(struct inode *dp, char *name, int namelen, uint *poff)
{
uint off;
uint off, inum;
struct buf *bp;
struct dirent *de;
if(dp->type != T_DIR)
return -1;
return 0;
for(off = 0; off < dp->size; off += BSIZE){
bp = bread(dp->dev, bmap(dp, off / BSIZE, 0));
@ -487,24 +479,30 @@ dirlookup(struct inode *dp, char *name, int namelen, uint *poff, uint *pinum)
// entry matches path element
if(poff)
*poff = off + (uchar*)de - bp->data;
if(pinum)
*pinum = de->inum;
inum = de->inum;
brelse(bp);
return 0;
return iget(dp->dev, inum);
}
}
brelse(bp);
}
return -1;
return 0;
}
// Write a new directory entry (name, ino) into the directory dp.
// Caller must have locked dp.
void
dirwrite(struct inode *dp, char *name, int namelen, uint ino)
int
dirlink(struct inode *dp, char *name, int namelen, uint ino)
{
int off;
struct dirent de;
struct inode *ip;
// Double-check that name is not present.
if((ip = dirlookup(dp, name, namelen, 0)) != 0){
idecref(ip);
return -1;
}
// Look for an empty dirent.
for(off = 0; off < dp->size; off += sizeof(de)){
@ -519,9 +517,10 @@ dirwrite(struct inode *dp, char *name, int namelen, uint ino)
namelen = DIRSIZ;
memmove(de.name, name, namelen);
memset(de.name+namelen, 0, DIRSIZ-namelen);
if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
panic("dirwrite");
return 0;
}
// Create a new inode named name inside dp
@ -535,13 +534,19 @@ dircreat(struct inode *dp, char *name, int namelen, short type, short major, sho
ip = ialloc(dp->dev, type);
if(ip == 0)
return 0;
ilock(ip);
ip->major = major;
ip->minor = minor;
ip->size = 0;
ip->nlink = 1;
iupdate(ip);
dirwrite(dp, name, namelen, ip->inum);
if(dirlink(dp, name, namelen, ip->inum) < 0){
ip->nlink = 0;
iupdate(ip);
iput(ip);
return 0;
}
return ip;
}
@ -590,17 +595,16 @@ skipelem(char *path, char **name, int *len)
struct inode*
_namei(char *path, int parent, char **pname, int *pnamelen)
{
struct inode *dp;
struct inode *dp, *ip;
char *name;
int namelen;
uint off, dev, inum;
uint off;
if(*path == '/')
dp = igetroot();
else {
else
dp = iincref(cp->cwd);
ilock(dp);
}
ilock(dp);
while((path = skipelem(path, &name, &namelen)) != 0){
// Truncate names in path to DIRSIZ chars.
@ -617,12 +621,12 @@ _namei(char *path, int parent, char **pname, int *pnamelen)
return dp;
}
if(dirlookup(dp, name, namelen, &off, &inum) < 0)
if((ip = dirlookup(dp, name, namelen, &off)) == 0)
goto fail;
dev = dp->dev;
iput(dp);
dp = iget(dev, inum);
ilock(ip);
dp = ip;
if(dp->type == 0 || dp->nlink < 1)
panic("namei");
}
@ -660,10 +664,6 @@ mknod(char *path, short type, short major, short minor)
if((dp = nameiparent(path, &name, &namelen)) == 0)
return 0;
if(dirlookup(dp, name, namelen, 0, 0) >= 0){
iput(dp);
return 0;
}
ip = dircreat(dp, name, namelen, type, major, minor);
iput(dp);
return ip;
@ -675,13 +675,13 @@ unlink(char *path)
{
struct inode *ip, *dp;
struct dirent de;
uint off, inum, dev;
uint off;
char *name;
int namelen;
if((dp = nameiparent(path, &name, &namelen)) == 0)
return -1;
if(dirlookup(dp, name, namelen, &off, 0) < 0){
if((ip = dirlookup(dp, name, namelen, &off)) == 0){
iput(dp);
return -1;
}
@ -691,20 +691,17 @@ unlink(char *path)
// Cannot remove "." or ".." - the 2 and 3 count the trailing NUL.
if(memcmp(de.name, ".", 2) == 0 || memcmp(de.name, "..", 3) == 0){
idecref(ip);
iput(dp);
return -1;
}
inum = de.inum;
memset(&de, 0, sizeof(de));
if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
panic("unlink dir write");
dev = dp->dev;
iput(dp);
ip = iget(dev, inum);
ilock(ip);
if(ip->nlink < 1)
panic("unlink nlink < 1");
ip->nlink--;
@ -729,30 +726,76 @@ link(char *old, char *new)
return -1;
}
iunlock(ip);
if((dp = nameiparent(new, &name, &namelen)) == 0){
idecref(ip);
return -1;
}
if(dirlookup(dp, name, namelen, 0, 0) >= 0){
iput(dp);
idecref(ip);
return -1;
}
if(dp->dev != ip->dev){
if(dp->dev != ip->dev || dirlink(dp, name, namelen, ip->inum) < 0){
idecref(ip);
iput(dp);
return -1;
}
iput(dp);
// LOCKING ERROR HERE! TWO LOCKS HELD AT ONCE.
// XXX write ordering wrong here too.
ilock(ip);
ip->nlink++;
iupdate(ip);
iput(ip);
return 0;
}
dirwrite(dp, name, namelen, ip->inum);
int
mkdir(char *path)
{
struct inode *dp, *ip;
char *name;
int namelen;
// XXX write ordering is screwy here- do we care?
if((dp = nameiparent(path, &name, &namelen)) == 0)
return -1;
if((ip = dircreat(dp, name, namelen, T_DIR, 0, 0)) == 0){
iput(dp);
return -1;
}
dp->nlink++;
iupdate(dp);
if(dirlink(ip, ".", 1, ip->inum) < 0 || dirlink(ip, "..", 2, dp->inum) < 0)
panic("mkdir");
iput(dp);
iput(ip);
return 0;
}
struct inode*
create(char *path)
{
struct inode *dp, *ip;
char *name;
int namelen;
if((dp = nameiparent(path, &name, &namelen)) == 0)
return 0;
if((ip = dirlookup(dp, name, namelen, 0)) != 0){
iput(dp);
ilock(ip);
if(ip->type == T_DIR){
iput(ip);
return 0;
}
return ip;
}
if((ip = dircreat(dp, name, namelen, T_FILE, 0, 0)) == 0){
iput(dp);
return 0;
}
iput(dp);
return ip;
}

7
fsvar.h
View File

@ -4,7 +4,7 @@ struct inode {
uint dev; // Device number
uint inum; // Inode number
int ref; // Reference count
int busy; // Is the inode "locked"?
int flags; // I_BUSY, I_VALID
short type; // copy of disk inode
short major;
@ -16,6 +16,5 @@ struct inode {
#define ROOTDEV 1 // Device number of root file system
#define NAMEI_LOOKUP 1
#define NAMEI_CREATE 2
#define NAMEI_DELETE 3
#define I_BUSY 0x1
#define I_VALID 0x2

28
initcode.S Normal file
View File

@ -0,0 +1,28 @@
# Initial process execs /init.
#include "syscall.h"
#include "traps.h"
# exec(init, argv)
start:
pushl $argv
pushl $init
pushl $0
movl $SYS_exec, %eax
int $T_SYSCALL
# for(;;) exit();
exit:
movl $SYS_exit, %eax
int $T_SYSCALL
jmp exit
# "/init\0"
init:
.string "/init\0"
.p2align 2
argv:
.long init
.long 0

120
main.c
View File

@ -11,9 +11,8 @@
#include "spinlock.h"
extern char edata[], end[];
extern uchar _binary__init_start[], _binary__init_size[];
void process0();
void proc0init();
// Bootstrap processor starts running C code here.
// This is called main0 not main so that it can have
@ -24,7 +23,6 @@ main0(void)
{
int i;
static int bcpu; // cannot be on stack
struct proc *p;
// clear BSS
memset(edata, 0, end - edata);
@ -54,15 +52,6 @@ main0(void)
fileinit();
iinit(); // i-node table
// initialize process 0
p = &proc[0];
p->state = RUNNABLE;
p->kstack = kalloc(KSTACKSIZE);
// cause proc[0] to start in kernel at process0
p->jmpbuf.eip = (uint) process0;
p->jmpbuf.esp = (uint) (p->kstack + KSTACKSIZE - 4);
// make sure there's a TSS
setupsegs(0);
@ -86,6 +75,9 @@ main0(void)
cpus[cpu()].nlock--;
sti();
// initialize process 0
proc0init();
scheduler();
}
@ -114,77 +106,45 @@ mpmain(void)
scheduler();
}
// proc[0] starts here, called by scheduler() in the ordinary way.
void
process0(void)
{
extern struct spinlock proc_table_lock;
struct proc *p0, *p1;
struct trapframe tf;
release(&proc_table_lock);
p0 = &proc[0];
p0->cwd = igetroot();
iunlock(p0->cwd);
// Dummy user memory to make copyproc() happy.
// Must be big enough to hold the init binary and stack.
p0->sz = 2*PAGE;
p0->mem = kalloc(p0->sz);
// Fake a trap frame as if a user process had made a system
// call, so that copyproc will have a place for the new
// process to return to.
p0->tf = &tf;
memset(p0->tf, 0, sizeof(struct trapframe));
p0->tf->es = p0->tf->ds = p0->tf->ss = (SEG_UDATA << 3) | DPL_USER;
p0->tf->cs = (SEG_UCODE << 3) | DPL_USER;
p0->tf->eflags = FL_IF;
p0->tf->esp = p0->sz;
char initcode[] = {
/* push ptr to argv */ 0x6a, 0x1c,
/* push ptr to "/init" */ 0x6a, 0x16,
/* push fake ret addr */ 0x6a, 0x00,
/* mov $SYS_exec, %eax */ 0xb8, 0x09, 0x00, 0x00, 0x00,
/* int $0x30 */ 0xcd, 0x30,
/* Lx: */
/* mov $SYS_exit, %eax */ 0xb8, 0x02, 0x00, 0x00, 0x00,
/* int $0x30 */ 0xcd, 0x30,
/* jmp Lx */ 0xeb, 0xf7,
// Push bogus return address, both to cause problems
// if main returns and also because gcc can generate
// function prologs that expect to be able to read the
// return address off the stack without causing a fault.
p0->tf->esp -= 4;
*(uint*)(p0->mem + p0->tf->esp) = 0xefefefef;
p1 = copyproc(p0);
load_icode(p1, _binary__init_start, (uint) _binary__init_size);
p1->state = RUNNABLE;
safestrcpy(p1->name, "init", sizeof p1->name);
proc_wait();
panic("init exited");
}
/* "/init\0" */ 0x2f, 0x69, 0x6e, 0x69, 0x74, 0x00,
/* ptr to "/init" */ 0x16, 0x00, 0x00, 0x00,
/* 0 */ 0x00, 0x00, 0x00, 0x00
};
void
load_icode(struct proc *p, uchar *binary, uint size)
proc0init(void)
{
int i;
struct elfhdr *elf;
struct proghdr *ph;
struct proc *p;
extern uchar _binary_initcode_start[], _binary_initcode_size[];
p = copyproc(0);
p->sz = PAGE;
p->mem = kalloc(p->sz);
p->cwd = igetroot();
memset(&p->tf, 0, sizeof p->tf);
p->tf->es = p->tf->ds = p->tf->ss = (SEG_UDATA << 3) | DPL_USER;
p->tf->cs = (SEG_UCODE << 3) | DPL_USER;
p->tf->eflags = FL_IF;
p->tf->esp = p->sz;
// Push dummy return address to placate gcc.
p->tf->esp -= 4;
*(uint*)(p->mem + p->tf->esp) = 0xefefefef;
elf = (struct elfhdr*) binary;
if(elf->magic != ELF_MAGIC)
panic("load_icode: not an ELF binary");
p->tf->eip = elf->entry;
// Map and load segments as directed.
ph = (struct proghdr*) (binary + elf->phoff);
for(i = 0; i < elf->phnum; i++, ph++) {
if(ph->type != ELF_PROG_LOAD)
continue;
if(ph->va + ph->memsz < ph->va)
panic("load_icode: overflow in proghdr");
if(ph->va + ph->memsz >= p->sz)
panic("load_icode: icode too large");
// Load/clear the segment
memmove(p->mem + ph->va, binary + ph->offset, ph->filesz);
memset(p->mem + ph->va + ph->filesz, 0, ph->memsz - ph->filesz);
}
p->tf->eip = 0;
memmove(p->mem, _binary_initcode_start, (int)_binary_initcode_size);
safestrcpy(p->name, "initcode", sizeof p->name);
p->state = RUNNABLE;
}

50
proc.c
View File

@ -109,47 +109,43 @@ copyproc(struct proc *p)
return 0;
}
np->pid = next_pid++;
np->ppid = p->pid;
release(&proc_table_lock);
// Copy user memory.
np->sz = p->sz;
np->mem = kalloc(np->sz);
if(np->mem == 0){
np->state = UNUSED;
return 0;
}
memmove(np->mem, p->mem, np->sz);
// Allocate kernel stack.
np->kstack = kalloc(KSTACKSIZE);
if(np->kstack == 0){
kfree(np->mem, np->sz);
np->mem = 0;
if((np->kstack = kalloc(KSTACKSIZE)) == 0){
np->state = UNUSED;
return 0;
}
// Copy trapframe registers from parent.
np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;
memmove(np->tf, p->tf, sizeof(*np->tf));
// Clear %eax so that fork system call returns 0 in child.
np->tf->eax = 0;
if(p){ // Copy process state from p.
np->ppid = p->pid;
memmove(np->tf, p->tf, sizeof *np->tf);
np->sz = p->sz;
if((np->mem = kalloc(np->sz)) == 0){
kfree(np->kstack, KSTACKSIZE);
np->kstack = 0;
np->state = UNUSED;
return 0;
}
memmove(np->mem, p->mem, np->sz);
for(i = 0; i < NOFILE; i++){
np->ofile[i] = p->ofile[i];
if(np->ofile[i])
fileincref(np->ofile[i]);
}
np->cwd = iincref(p->cwd);
}
// Set up new jmpbuf to start executing at forkret (see below).
memset(&np->jmpbuf, 0, sizeof np->jmpbuf);
np->jmpbuf.eip = (uint)forkret;
np->jmpbuf.esp = (uint)np->tf - 4;
// Copy file descriptors
for(i = 0; i < NOFILE; i++){
np->ofile[i] = p->ofile[i];
if(np->ofile[i])
fileincref(np->ofile[i]);
}
np->cwd = iincref(p->cwd);
// Clear %eax so that fork system call returns 0 in child.
np->tf->eax = 0;
return np;
}

10
string.c
View File

@ -75,3 +75,13 @@ safestrcpy(char *s, const char *t, int n)
return os;
}
int
strlen(const char *s)
{
int n;
for(n = 0; s[n]; n++)
;
return n;
}

1
syscall.c
View File

@ -53,7 +53,6 @@ fetchstr(struct proc *p, uint addr, char **pp)
int
argint(int argno, int *ip)
{
return fetchint(cp, cp->tf->esp + 4 + 4*argno, ip);
}

221
sysfile.c
View File

@ -114,42 +114,22 @@ sys_close(void)
int
sys_open(void)
{
struct inode *ip, *dp;
char *path, *name;
int namelen;
int omode;
int fd, dev;
uint inum;
char *path;
int fd, omode;
struct file *f;
struct inode *ip;
if(argstr(0, &path) < 0 || argint(1, &omode) < 0)
return -1;
switch(omode & O_CREATE){
default:
case 0: // regular open
if((ip = namei(path)) == 0)
return -1;
break;
case O_CREATE:
if((dp = nameiparent(path, &name, &namelen)) == 0)
return -1;
if(dirlookup(dp, name, namelen, 0, &inum) >= 0){
dev = dp->dev;
iput(dp);
ip = iget(dev, inum);
}else{
if((ip = dircreat(dp, name, namelen, T_FILE, 0, 0)) == 0){
iput(dp);
return -1;
}
iput(dp);
}
break;
}
if(omode & O_CREATE)
ip = create(path);
else
ip = namei(path);
if(ip == 0)
return -1;
if(ip->type == T_DIR && (omode & (O_RDWR|O_WRONLY|O_CREATE))){
if(ip->type == T_DIR && (omode & (O_RDWR|O_WRONLY))){
iput(ip);
return -1;
}
@ -194,6 +174,7 @@ sys_mknod(void)
argint(2, &major) < 0 || argint(3, &minor) < 0)
return -1;
// XXX why this check?
if(len >= DIRSIZ)
return -1;
@ -206,45 +187,11 @@ sys_mknod(void)
int
sys_mkdir(void)
{
struct inode *nip;
struct inode *dp;
char *name, *path;
struct dirent de;
int namelen;
char *path;
if(argstr(0, &path) < 0)
return -1;
dp = nameiparent(path, &name, &namelen);
if(dp == 0)
return -1;
if(dirlookup(dp, name, namelen, 0, 0) >= 0){
iput(dp);
return -1;
}
nip = dircreat(dp, name, namelen, T_DIR, 0, 0);
if(nip == 0){
iput(dp);
return -1;
}
dp->nlink++;
iupdate(dp);
memset(de.name, '\0', DIRSIZ);
de.name[0] = '.';
de.inum = nip->inum;
writei(nip, (char*) &de, 0, sizeof(de));
de.inum = dp->inum;
de.name[1] = '.';
writei(nip, (char*) &de, sizeof(de), sizeof(de));
iput(dp);
iput(nip);
return 0;
return mkdir(path);
}
int
@ -315,132 +262,30 @@ sys_link(void)
return link(old, new);
}
#define ARGMAX 10
int
sys_exec(void)
{
uint sz=0, ap, sp, p1, p2;
int i, nargs, argbytes, len;
struct inode *ip;
struct elfhdr elf;
struct proghdr ph;
char *mem = 0;
char *path, *s, *last;
uint argv;
if(argstr(0, &path) < 0 || argint(1, (int*)&argv) < 0)
char *path, *argv[ARGMAX];
int i;
uint uargv, uarg;
if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0)
return -1;
if((ip = namei(path)) == 0)
return -1;
if(readi(ip, (char*)&elf, 0, sizeof(elf)) < sizeof(elf))
goto bad;
if(elf.magic != ELF_MAGIC)
goto bad;
sz = 0;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.memsz < ph.filesz)
goto bad;
sz += ph.memsz;
}
sz += 4096 - (sz % 4096);
sz += 4096;
mem = kalloc(sz);
if(mem == 0)
goto bad;
memset(mem, 0, sz);
nargs = 0;
argbytes = 0;
for(i = 0;; i++){
if(fetchint(cp, argv + 4*i, (int*)&ap) < 0)
goto bad;
if(ap == 0)
memset(argv, 0, sizeof argv);
for(i=0;; i++){
if(i >= ARGMAX)
return -1;
if(fetchint(cp, uargv+4*i, (int*)&uarg) < 0)
return -1;
if(uarg == 0){
argv[i] = 0;
break;
len = fetchstr(cp, ap, &s);
if(len < 0)
goto bad;
nargs++;
argbytes += len + 1;
}
if(fetchstr(cp, uarg, &argv[i]) < 0)
return -1;
}
// argn\0
// ...
// arg0\0
// 0
// ptr to argn
// ...
// 12: ptr to arg0
// 8: argv (points to ptr to arg0)
// 4: argc
// 0: fake return pc
sp = sz - argbytes - (nargs+1)*4 - 4 - 4 - 4;
*(uint*)(mem + sp) = 0xffffffff;
*(uint*)(mem + sp + 4) = nargs;
*(uint*)(mem + sp + 8) = (uint)(sp + 12);
p1 = sp + 12;
p2 = sp + 12 + (nargs + 1) * 4;
for(i = 0; i < nargs; i++){
fetchint(cp, argv + 4*i, (int*)&ap);
len = fetchstr(cp, ap, &s);
memmove(mem + p2, s, len + 1);
*(uint*)(mem + p1) = p2;
p1 += 4;
p2 += len + 1;
}
*(uint*)(mem + p1) = 0;
// Save name for debugging.
for(last=s=path; *s; s++)
if(*s == '/')
last = s+1;
safestrcpy(cp->name, last, sizeof cp->name);
// commit to the new image.
kfree(cp->mem, cp->sz);
cp->sz = sz;
cp->mem = mem;
mem = 0;
for(i = 0; i < elf.phnum; i++){
if(readi(ip, (char*)&ph, elf.phoff + i * sizeof(ph),
sizeof(ph)) != sizeof(ph))
goto bad2;
if(ph.type != ELF_PROG_LOAD)
continue;
if(ph.va + ph.memsz > sz)
goto bad2;
if(readi(ip, cp->mem + ph.va, ph.offset, ph.filesz) != ph.filesz)
goto bad2;
memset(cp->mem + ph.va + ph.filesz, 0, ph.memsz - ph.filesz);
}
iput(ip);
cp->tf->eip = elf.entry;
cp->tf->esp = sp;
setupsegs(cp);
return 0;
bad:
if(mem)
kfree(mem, sz);
iput(ip);
return -1;
bad2:
iput(ip);
proc_exit();
return 0;
return exec(path, argv);
}