Imbus/xv6-riscv-kernel
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Merge branch 'riscv' of g.csail.mit.edu:xv6-dev into riscv

Browse source
This commit is contained in:
Frans Kaashoek 2019-07-17 05:53:47 -04:00
commit b924e44f06
13 changed files with 190 additions and 124 deletions
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12
README
View file

@ -31,7 +31,7 @@ Toomey, Stephen Tu, Pablo Ventura, Xi Wang, Keiichi Watanabe, Nicolas
Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng, and Zou Chang Wei.
The code in the files that constitute xv6 is
Copyright 2006-2018 Frans Kaashoek, Robert Morris, and Russ Cox.
Copyright 2006-2019 Frans Kaashoek, Robert Morris, and Russ Cox.
ERROR REPORTS
@ -42,9 +42,7 @@ simplifications and clarifications than new features.
BUILDING AND RUNNING XV6
To build xv6 on an x86 ELF machine (like Linux or FreeBSD), run
"make". On non-x86 or non-ELF machines (like OS X, even on x86), you
will need to install a cross-compiler gcc suite capable of producing
x86 ELF binaries (see https://pdos.csail.mit.edu/6.828/).
Then run "make TOOLPREFIX=i386-jos-elf-". Now install the QEMU PC
simulator and run "make qemu".
You will need a RISC-V "newlib" tool chain from
https://github.com/riscv/riscv-gnu-toolchain, and qemu compiled for
riscv64-softmmu. Once they are installed, and in your shell
search path, you can run "make qemu".

4
kernel/kalloc.c
View file

@ -55,8 +55,9 @@ kfree(void *pa)
// Fill with junk to catch dangling refs.
memset(pa, 1, PGSIZE);
acquire(&kmem.lock);
r = (struct run*)pa;
acquire(&kmem.lock);
r->next = kmem.freelist;
kmem.freelist = r;
release(&kmem.lock);
@ -75,6 +76,7 @@ kalloc(void)
if(r)
kmem.freelist = r->next;
release(&kmem.lock);
if(r)
memset((char*)r, 5, PGSIZE); // fill with junk
return (void*)r;

103
kernel/proc.c
View file

@ -6,20 +6,16 @@
#include "proc.h"
#include "defs.h"
struct proc proc[NPROC];
struct cpu cpus[NCPU];
struct proc proc[NPROC];
struct proc *initproc;
struct spinlock pid_lock;
int nextpid = 1;
struct spinlock pid_lock;
extern void forkret(void);
// for returning out of the kernel
extern void sysexit(void);
static void wakeup1(struct proc *chan);
extern char trampout[]; // trampoline.S
@ -68,8 +64,10 @@ allocpid() {
int pid;
acquire(&pid_lock);
pid = nextpid++;
pid = nextpid;
nextpid = nextpid + 1;
release(&pid_lock);
return pid;
}
@ -77,7 +75,7 @@ allocpid() {
// Look in the process table for an UNUSED proc.
// If found, initialize state required to run in the kernel,
// and return with p->lock held.
// Otherwise return 0.
// If there are no free procs, return 0.
static struct proc*
allocproc(void)
{
@ -98,6 +96,7 @@ found:
// Allocate a page for the kernel stack.
if((p->kstack = kalloc()) == 0){
release(&p->lock);
return 0;
}
@ -105,6 +104,7 @@ found:
if((p->tf = (struct trapframe *)kalloc()) == 0){
kfree(p->kstack);
p->kstack = 0;
release(&p->lock);
return 0;
}
@ -145,16 +145,13 @@ freeproc(struct proc *p)
}
// Create a page table for a given process,
// with no users pages, but with trampoline pages.
// Called both when creating a process, and
// by exec() when building tentative new memory image,
// which might fail.
// with no user pages, but with trampoline pages.
pagetable_t
proc_pagetable(struct proc *p)
{
pagetable_t pagetable;
// An empty user page table.
// An empty page table.
pagetable = uvmcreate();
// map the trampoline code (for system call return)
@ -172,9 +169,7 @@ proc_pagetable(struct proc *p)
}
// Free a process's page table, and free the
// physical memory the page table refers to.
// Called both when a process exits and from
// exec() if it fails.
// physical memory it refers to.
void
proc_freepagetable(pagetable_t pagetable, uint64 sz)
{
@ -187,9 +182,12 @@ proc_freepagetable(pagetable_t pagetable, uint64 sz)
// a user program that calls exec("/init")
// od -t xC initcode
uchar initcode[] = {
0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x05, 0x02, 0x97, 0x05, 0x00, 0x00, 0x93, 0x85, 0x05, 0x02,
0x9d, 0x48, 0x73, 0x00, 0x00, 0x00, 0x89, 0x48, 0x73, 0x00, 0x00, 0x00, 0xef, 0xf0, 0xbf, 0xff,
0x2f, 0x69, 0x6e, 0x69, 0x74, 0x00, 0x00, 0x01, 0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x17, 0x05, 0x00, 0x00, 0x13, 0x05, 0x05, 0x02,
0x97, 0x05, 0x00, 0x00, 0x93, 0x85, 0x05, 0x02,
0x9d, 0x48, 0x73, 0x00, 0x00, 0x00, 0x89, 0x48,
0x73, 0x00, 0x00, 0x00, 0xef, 0xf0, 0xbf, 0xff,
0x2f, 0x69, 0x6e, 0x69, 0x74, 0x00, 0x00, 0x01,
0x20, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00
};
@ -203,12 +201,14 @@ userinit(void)
p = allocproc();
initproc = p;
// allocate one user page and copy init's instructions
// and data into it.
uvminit(p->pagetable, initcode, sizeof(initcode));
p->sz = PGSIZE;
// prepare for the very first "return" from kernel to user.
p->tf->epc = 0;
p->tf->sp = PGSIZE;
p->tf->epc = 0; // user program counter
p->tf->sp = PGSIZE; // user stack pointer
safestrcpy(p->name, "initcode", sizeof(p->name));
p->cwd = namei("/");
@ -218,7 +218,7 @@ userinit(void)
release(&p->lock);
}
// Grow current process's memory by n bytes.
// Grow or shrink user memory by n bytes.
// Return 0 on success, -1 on failure.
int
growproc(int n)
@ -240,8 +240,8 @@ growproc(int n)
return 0;
}
// Create a new process, copying p as the parent.
// Sets up child kernel stack to return as if from system call.
// Create a new process, copying the parent.
// Sets up child kernel stack to return as if from fork() system call.
int
fork(void)
{
@ -287,8 +287,8 @@ fork(void)
return pid;
}
// Pass p's abandoned children to init. p and p's parent
// are locked.
// Pass p's abandoned children to init.
// Caller must hold p->lock and parent->lock.
void
reparent(struct proc *p, struct proc *parent) {
struct proc *pp;
@ -312,7 +312,6 @@ reparent(struct proc *p, struct proc *parent) {
}
}
// Exit the current process. Does not return.
// An exited process remains in the zombie state
// until its parent calls wait().
@ -343,6 +342,7 @@ exit(void)
acquire(&p->lock);
// Give our children to init.
reparent(p, p->parent);
p->state = ZOMBIE;
@ -366,13 +366,20 @@ wait(void)
int havekids, pid;
struct proc *p = myproc();
// hold p->lock for the whole time to avoid lost
// wakeups from a child's exit().
acquire(&p->lock);
for(;;){
// Scan through table looking for exited children.
havekids = 0;
for(np = proc; np < &proc[NPROC]; np++){
if(np->parent != p)
continue;
// this code uses np->parent without holding np->lock.
// acquiring the lock first would cause a deadlock,
// since np might be an ancestor, and we already hold p->lock.
if(np->parent == p){
// np->parent can't change between the check and the acquire()
// because only the parent changes it, and we're the parent.
acquire(&np->lock);
havekids = 1;
if(np->state == ZOMBIE){
@ -385,6 +392,7 @@ wait(void)
}
release(&np->lock);
}
}
// No point waiting if we don't have any children.
if(!havekids || p->killed){
@ -392,7 +400,7 @@ wait(void)
return -1;
}
// Wait for children to exit. (See wakeup1 call in reparent.)
// Wait for a child to exit.
sleep(p, &p->lock); //DOC: wait-sleep
}
}
@ -401,8 +409,8 @@ wait(void)
// Per-CPU process scheduler.
// Each CPU calls scheduler() after setting itself up.
// Scheduler never returns. It loops, doing:
// - choose a process to run
// - swtch to start running that process
// - choose a process to run.
// - swtch to start running that process.
// - eventually that process transfers control
// via swtch back to the scheduler.
void
@ -413,7 +421,7 @@ scheduler(void)
c->proc = 0;
for(;;){
// Enable interrupts on this processor.
// Give devices a brief chance to interrupt.
intr_on();
for(p = proc; p < &proc[NPROC]; p++) {
@ -435,7 +443,7 @@ scheduler(void)
}
}
// Enter scheduler. Must hold only p->lock
// Switch to scheduler. Must hold only p->lock
// and have changed proc->state. Saves and restores
// intena because intena is a property of this
// kernel thread, not this CPU. It should
@ -512,12 +520,13 @@ sleep(void *chan, struct spinlock *lk)
// change p->state and then call sched.
// Once we hold p->lock, we can be
// guaranteed that we won't miss any wakeup
// (wakeup runs with p->lock locked),
// (wakeup locks p->lock),
// so it's okay to release lk.
if(lk != &p->lock){ //DOC: sleeplock0
acquire(&p->lock); //DOC: sleeplock1
release(lk);
}
// Go to sleep.
p->chan = chan;
p->state = SLEEPING;
@ -535,8 +544,8 @@ sleep(void *chan, struct spinlock *lk)
}
//PAGEBREAK!
// Wake up p, used by exit()
// Caller should lock p.
// Wake up p if it is sleeping in wait(); used by exit().
// Caller must hold p->lock.
static void
wakeup1(struct proc *p)
{
@ -545,8 +554,8 @@ wakeup1(struct proc *p)
}
}
// Wake up all processes sleeping on chan. Never
// called when holding a p->lock
// Wake up all processes sleeping on chan.
// Must be called without any p->lock.
void
wakeup(void *chan)
{
@ -562,25 +571,25 @@ wakeup(void *chan)
}
// Kill the process with the given pid.
// Process won't exit until it returns
// to user space (see trap in trap.c).
// The victim won't exit until it tries to return
// to user space (see usertrap() in trap.c).
int
kill(int pid)
{
struct proc *p;
for(p = proc; p < &proc[NPROC]; p++){
if(p->pid == pid){
acquire(&p->lock);
if(p->pid != pid)
panic("kill");
if(p->pid == pid){
p->killed = 1;
// Wake process from sleep if necessary.
if(p->state == SLEEPING)
if(p->state == SLEEPING){
// Wake process from sleep().
p->state = RUNNABLE;
}
release(&p->lock);
return 0;
}
release(&p->lock);
}
return -1;
}

38
kernel/proc.h
View file

@ -18,10 +18,10 @@ struct context {
uint64 s11;
};
// Per-CPU state
// Per-CPU state.
struct cpu {
struct proc *proc; // The process running on this cpu or null
struct context scheduler; // swtch() here to enter scheduler
struct proc *proc; // The process running on this cpu, or null.
struct context scheduler; // swtch() here to enter scheduler().
int noff; // Depth of push_off() nesting.
int intena; // Were interrupts enabled before push_off()?
};
@ -30,21 +30,25 @@ extern struct cpu cpus[NCPU];
//PAGEBREAK: 17
// per-process data for the early trap handling code in trampoline.S.
// per-process data for the trap handling code in trampoline.S.
// sits in a page by itself just under the trampoline page in the
// user page table. not specially mapped in the kernel page table.
// the sscratch register points here.
// trampoline.S saves user registers, then restores kernel_sp and
// kernel_satp.
// includes callee-saved registers like s0-s11 because the
// trampin in trampoline.S saves user registers in the trapframe,
// then initializes registers from the trapframe's
// kernel_sp, kernel_hartid, kernel_satp, and jumps to kernel_trap.
// usertrapret() and trampout in trampoline.S set up
// the trapframe's kernel_*, restore user registers from the
// trapframe, switch to the user page table, and enter user space.
// the trapframe includes callee-saved user registers like s0-s11 because the
// return-to-user path via usertrapret() doesn't return through
// the entire kernel call stack.
struct trapframe {
/* 0 */ uint64 kernel_satp;
/* 8 */ uint64 kernel_sp;
/* 0 */ uint64 kernel_satp; // kernel page table
/* 8 */ uint64 kernel_sp; // top of process's kernel stack
/* 16 */ uint64 kernel_trap; // usertrap()
/* 24 */ uint64 epc; // saved user program counter
/* 32 */ uint64 hartid;
/* 32 */ uint64 kernel_hartid; // saved kernel tp
/* 40 */ uint64 ra;
/* 48 */ uint64 sp;
/* 56 */ uint64 gp;
@ -83,16 +87,20 @@ enum procstate { UNUSED, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };
// Per-process state
struct proc {
struct spinlock lock;
// p->lock must be held when using these:
enum procstate state; // Process state
struct proc *parent; // Parent process
void *chan; // If non-zero, sleeping on chan
int killed; // If non-zero, have been killed
int pid; // Process ID
// these are private to the process, so p->lock need not be held.
char *kstack; // Bottom of kernel stack for this process
uint64 sz; // Size of process memory (bytes)
pagetable_t pagetable; // Page table
enum procstate state; // Process state
int pid; // Process ID
struct proc *parent; // Parent process
struct trapframe *tf; // data page for trampoline.S
struct context context; // swtch() here to run process
void *chan; // If non-zero, sleeping on chan
int killed; // If non-zero, have been killed
struct file *ofile[NOFILE]; // Open files
struct inode *cwd; // Current directory
char name[16]; // Process name (debugging)

11
kernel/riscv.h
View file

@ -312,6 +312,17 @@ r_ra()
return x;
}
// tell the machine to finish any previous writes to
// PTEs, so that a subsequent use of a virtual
// address or load of the SATP will see those writes.
// perhaps this also flushes the TLB.
static inline void
sfence_vma()
{
// the zero, zero means flush all TLB entries.
asm volatile("sfence.vma zero, zero");
}
#define PGSIZE 4096 // bytes per page
#define PGSHIFT 12 // bits of offset within a page

13
kernel/spinlock.c
View file

@ -18,8 +18,6 @@ initlock(struct spinlock *lk, char *name)
// Acquire the lock.
// Loops (spins) until the lock is acquired.
// Holding a lock for a long time may cause
// other CPUs to waste time spinning to acquire it.
void
acquire(struct spinlock *lk)
{
@ -27,7 +25,7 @@ acquire(struct spinlock *lk)
if(holding(lk))
panic("acquire");
// On RISC-V, this turns into an atomic swap:
// On RISC-V, sync_lock_test_and_set turns into an atomic swap:
// a5 = 1
// s1 = &lk->locked
// amoswap.w.aq a5, a5, (s1)
@ -59,9 +57,10 @@ release(struct spinlock *lk)
__sync_synchronize();
// Release the lock, equivalent to lk->locked = 0.
// This code can't use a C assignment, since it might
// not be atomic.
// On RISC-V, this turns into an atomic swap:
// This code doesn't use a C assignment, since the C standard
// implies that an assignment might be implemented with
// multiple store instructions.
// On RISC-V, sync_lock_release turns into an atomic swap:
// s1 = &lk->locked
// amoswap.w zero, zero, (s1)
__sync_lock_release(&lk->locked);
@ -81,7 +80,7 @@ holding(struct spinlock *lk)
}
// push_off/pop_off are like intr_off()/intr_on() except that they are matched:
// it takes two pop_off to undo two push_off. Also, if interrupts
// it takes two pop_off()s to undo two push_off()s. Also, if interrupts
// are initially off, then push_off, pop_off leaves them off.
void

2
kernel/spinlock.h
View file

@ -5,7 +5,5 @@ struct spinlock {
// For debugging:
char *name; // Name of lock.
struct cpu *cpu; // The cpu holding the lock.
struct cpu *last_release;
uint64 last_pc;
};

16
kernel/syscall.c
View file

@ -157,8 +157,8 @@ static uint64 (*syscalls[])(void) = {
[SYS_close] sys_close,
};
static void
dosyscall(void)
void
syscall(void)
{
int num;
struct proc *p = myproc();
@ -174,15 +174,3 @@ dosyscall(void)
p->tf->a0 = -1;
}
}
void
syscall()
{
if(myproc()->killed)
exit();
dosyscall();
if(myproc()->killed)
exit();
return;
}

6
kernel/trampoline.S
View file

@ -17,7 +17,8 @@ trampout:
# a0: p->tf in user page table
# a1: new value for satp, for user page table
# switch to user page table
# switch to user page table.
sfence.vma zero, zero
csrw satp, a1
# put the saved user a0 in sscratch, so we
@ -120,7 +121,7 @@ trampin:
# restore kernel stack pointer from p->tf->kernel_sp
ld sp, 8(a0)
# make tp hold the current hartid, from p->tf->hartid
# make tp hold the current hartid, from p->tf->kernel_hartid
ld tp, 32(a0)
# remember the address of usertrap(), p->tf->kernel_trap
@ -128,6 +129,7 @@ trampin:
# restore kernel page table from p->tf->kernel_satp
ld t1, 0(a0)
sfence.vma zero, zero
csrw satp, t1
# a0 is no longer valid, since the kernel page

25
kernel/trap.c
View file

@ -53,6 +53,9 @@ usertrap(void)
if(r_scause() == 8){
// system call
if(p->killed)
exit();
// sepc points to the ecall instruction,
// but we want to return to the next instruction.
p->tf->epc += 4;
@ -100,7 +103,7 @@ usertrapret(void)
p->tf->kernel_satp = r_satp();
p->tf->kernel_sp = (uint64)p->kstack + PGSIZE;
p->tf->kernel_trap = (uint64)usertrap;
p->tf->hartid = r_tp();
p->tf->kernel_hartid = r_tp();
// set up the registers that trampoline.S's sret will use
// to get to user space.
@ -155,6 +158,15 @@ kerneltrap()
w_sstatus(sstatus);
}
void
clockintr()
{
acquire(&tickslock);
ticks++;
wakeup(&ticks);
release(&tickslock);
}
// check if it's an external interrupt or software interrupt,
// and handle it.
// returns 2 if timer interrupt,
@ -179,16 +191,15 @@ devintr()
plic_complete(irq);
return 1;
} else if(scause == 0x8000000000000001){
// software interrupt from a machine-mode timer interrupt.
// software interrupt from a machine-mode timer interrupt,
// forwarded by machinevec in kernelvec.S.
if(cpuid() == 0){
acquire(&tickslock);
ticks++;
wakeup(&ticks);
release(&tickslock);
clockintr();
}
// acknowledge.
// acknowledge the software interrupt by clearing
// the SSIP bit in sip.
w_sip(r_sip() & ~2);
return 2;

16
kernel/virtio_disk.c
View file

@ -20,7 +20,7 @@
// the address of virtio mmio register r.
#define R(r) ((volatile uint32 *)(VIRTIO0 + (r)))
struct spinlock virtio_disk_lock;
struct spinlock vdisk_lock;
// memory for virtio descriptors &c for queue 0.
// this is a global instead of allocated because it has
@ -49,7 +49,7 @@ virtio_disk_init(void)
{
uint32 status = 0;
initlock(&virtio_disk_lock, "virtio_disk");
initlock(&vdisk_lock, "virtio_disk");
if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 ||
*R(VIRTIO_MMIO_VERSION) != 1 ||
@ -168,7 +168,7 @@ virtio_disk_rw(struct buf *b)
{
uint64 sector = b->blockno * (BSIZE / 512);
acquire(&virtio_disk_lock);
acquire(&vdisk_lock);
// the spec says that legacy block operations use three
// descriptors: one for type/reserved/sector, one for
@ -180,7 +180,7 @@ virtio_disk_rw(struct buf *b)
if(alloc3_desc(idx) == 0) {
break;
}
sleep(&free[0], &virtio_disk_lock);
sleep(&free[0], &vdisk_lock);
}
// format the three descriptors.
@ -234,16 +234,16 @@ virtio_disk_rw(struct buf *b)
// Wait for virtio_disk_intr() to say request has finished.
while((b->flags & (B_VALID|B_DIRTY)) != B_VALID){
sleep(b, &virtio_disk_lock);
sleep(b, &vdisk_lock);
}
release(&virtio_disk_lock);
release(&vdisk_lock);
}
void
virtio_disk_intr()
{
acquire(&virtio_disk_lock);
acquire(&vdisk_lock);
while((used_idx % NUM) != (used->id % NUM)){
int id = used->elems[used_idx].id;
@ -262,5 +262,5 @@ virtio_disk_intr()
used_idx = (used_idx + 1) % NUM;
}
release(&virtio_disk_lock);
release(&vdisk_lock);
}

1
kernel/vm.c
View file

@ -61,6 +61,7 @@ kvminit()
void
kvminithart()
{
sfence_vma();
w_satp(MAKE_SATP(kernel_pagetable));
}

39
user/usertests.c
View file

@ -506,6 +506,44 @@ twochildren(void)
printf(1, "twochildren ok\n");
}
// concurrent forks to try to expose locking bugs.
void
forkfork(void)
{
int ppid = getpid();
printf(1, "forkfork test\n");
for(int i = 0; i < 2; i++){
int pid = fork();
if(pid < 0){
printf(1, "fork failed");
exit();
}
if(pid == 0){
for(int j = 0; j < 200; j++){
int pid1 = fork();
if(pid1 < 0){
printf(1, "fork failed\n");
kill(ppid);
exit();
}
if(pid1 == 0){
exit();
}
wait();
}
exit();
}
}
for(int i = 0; i < 2; i++){
wait();
}
printf(1, "forkfork ok\n");
}
void
forkforkfork(void)
{
@ -1858,6 +1896,7 @@ main(int argc, char *argv[])
reparent();
twochildren();
forkfork();
forkforkfork();
argptest();