From 4087a6e7fc773ba4eb217dfc196dfe1eee84b25d Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Wed, 10 Aug 2022 20:35:42 -0400
Subject: [PATCH 01/14] Read and write p->killed using atomics
---
kernel/console.c | 2 +-
kernel/pipe.c | 4 ++--
kernel/proc.c | 4 ++--
kernel/sysproc.c | 2 +-
kernel/trap.c | 6 +++---
5 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/kernel/console.c b/kernel/console.c
index 23a2d35..b8fa1de 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -89,7 +89,7 @@ consoleread(int user_dst, uint64 dst, int n)
// wait until interrupt handler has put some
// input into cons.buffer.
while(cons.r == cons.w){
- if(myproc()->killed){
+ if(__sync_add_and_fetch(&(myproc()->killed), 0)){
release(&cons.lock);
return -1;
}
diff --git a/kernel/pipe.c b/kernel/pipe.c
index b6eefb9..e438d7e 100644
--- a/kernel/pipe.c
+++ b/kernel/pipe.c
@@ -81,7 +81,7 @@ pipewrite(struct pipe *pi, uint64 addr, int n)
acquire(&pi->lock);
while(i < n){
- if(pi->readopen == 0 || pr->killed){
+ if(pi->readopen == 0 || __sync_add_and_fetch(&pr->killed,0)){
release(&pi->lock);
return -1;
}
@@ -111,7 +111,7 @@ piperead(struct pipe *pi, uint64 addr, int n)
acquire(&pi->lock);
while(pi->nread == pi->nwrite && pi->writeopen){ //DOC: pipe-empty
- if(pr->killed){
+ if(__sync_add_and_fetch(&pr->killed,0)){
release(&pi->lock);
return -1;
}
diff --git a/kernel/proc.c b/kernel/proc.c
index 2d0ffa1..221f0f8 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -422,7 +422,7 @@ wait(uint64 addr)
}
// No point waiting if we don't have any children.
- if(!havekids || p->killed){
+ if(!havekids || __sync_add_and_fetch(&p->killed, 0)){
release(&wait_lock);
return -1;
}
@@ -588,7 +588,7 @@ kill(int pid)
for(p = proc; p < &proc[NPROC]; p++){
acquire(&p->lock);
if(p->pid == pid){
- p->killed = 1;
+ __sync_bool_compare_and_swap(&p->killed, 0, 1);
if(p->state == SLEEPING){
// Wake process from sleep().
p->state = RUNNABLE;
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index e8bcda9..61b715b 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -63,7 +63,7 @@ sys_sleep(void)
acquire(&tickslock);
ticks0 = ticks;
while(ticks - ticks0 < n){
- if(myproc()->killed){
+ if(__sync_add_and_fetch(&(myproc()->killed), 0)){
release(&tickslock);
return -1;
}
diff --git a/kernel/trap.c b/kernel/trap.c
index 75fb3ec..b879f01 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -53,7 +53,7 @@ usertrap(void)
if(r_scause() == 8){
// system call
- if(p->killed)
+ if(__sync_add_and_fetch(&p->killed, 0))
exit(-1);
// sepc points to the ecall instruction,
@@ -70,10 +70,10 @@ usertrap(void)
} else {
printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
printf(" sepc=%p stval=%p\n", r_sepc(), r_stval());
- p->killed = 1;
+ __sync_bool_compare_and_swap(&p->killed, 0, 1);
}
- if(p->killed)
+ if(__sync_add_and_fetch(&p->killed, 0))
exit(-1);
// give up the CPU if this is a timer interrupt.
From 975f3b31d3fac2c271df3107263df6ae454a98be Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Thu, 11 Aug 2022 07:23:17 -0400
Subject: [PATCH 02/14] Clean up using killed()
---
kernel/console.c | 2 +-
kernel/defs.h | 1 +
kernel/pipe.c | 4 ++--
kernel/proc.c | 8 +++++++-
kernel/sysproc.c | 2 +-
kernel/trap.c | 4 ++--
6 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/kernel/console.c b/kernel/console.c
index b8fa1de..d6eb209 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -89,7 +89,7 @@ consoleread(int user_dst, uint64 dst, int n)
// wait until interrupt handler has put some
// input into cons.buffer.
while(cons.r == cons.w){
- if(__sync_add_and_fetch(&(myproc()->killed), 0)){
+ if(killed(myproc())){
release(&cons.lock);
return -1;
}
diff --git a/kernel/defs.h b/kernel/defs.h
index 62b9292..7181d4d 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -90,6 +90,7 @@ void proc_mapstacks(pagetable_t);
pagetable_t proc_pagetable(struct proc *);
void proc_freepagetable(pagetable_t, uint64);
int kill(int);
+int killed(struct proc*);
struct cpu* mycpu(void);
struct cpu* getmycpu(void);
struct proc* myproc();
diff --git a/kernel/pipe.c b/kernel/pipe.c
index e438d7e..f6b501a 100644
--- a/kernel/pipe.c
+++ b/kernel/pipe.c
@@ -81,7 +81,7 @@ pipewrite(struct pipe *pi, uint64 addr, int n)
acquire(&pi->lock);
while(i < n){
- if(pi->readopen == 0 || __sync_add_and_fetch(&pr->killed,0)){
+ if(pi->readopen == 0 || killed(pr)){
release(&pi->lock);
return -1;
}
@@ -111,7 +111,7 @@ piperead(struct pipe *pi, uint64 addr, int n)
acquire(&pi->lock);
while(pi->nread == pi->nwrite && pi->writeopen){ //DOC: pipe-empty
- if(__sync_add_and_fetch(&pr->killed,0)){
+ if(killed(pr)){
release(&pi->lock);
return -1;
}
diff --git a/kernel/proc.c b/kernel/proc.c
index 221f0f8..24680b6 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -422,7 +422,7 @@ wait(uint64 addr)
}
// No point waiting if we don't have any children.
- if(!havekids || __sync_add_and_fetch(&p->killed, 0)){
+ if(!havekids || killed(p)){
release(&wait_lock);
return -1;
}
@@ -601,6 +601,12 @@ kill(int pid)
return -1;
}
+int
+killed(struct proc *p)
+{
+ return __sync_add_and_fetch(&p->killed, 0);
+}
+
// Copy to either a user address, or kernel address,
// depending on usr_dst.
// Returns 0 on success, -1 on error.
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index 61b715b..99a36a7 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -63,7 +63,7 @@ sys_sleep(void)
acquire(&tickslock);
ticks0 = ticks;
while(ticks - ticks0 < n){
- if(__sync_add_and_fetch(&(myproc()->killed), 0)){
+ if(killed(myproc())){
release(&tickslock);
return -1;
}
diff --git a/kernel/trap.c b/kernel/trap.c
index b879f01..f895aea 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -53,7 +53,7 @@ usertrap(void)
if(r_scause() == 8){
// system call
- if(__sync_add_and_fetch(&p->killed, 0))
+ if(killed(p))
exit(-1);
// sepc points to the ecall instruction,
@@ -73,7 +73,7 @@ usertrap(void)
__sync_bool_compare_and_swap(&p->killed, 0, 1);
}
- if(__sync_add_and_fetch(&p->killed, 0))
+ if(killed(p))
exit(-1);
// give up the CPU if this is a timer interrupt.
From 429c7b717edd4c23d3666327986052b9b6eb29eb Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Thu, 11 Aug 2022 08:42:52 -0400
Subject: [PATCH 03/14] Use atomic store_n and load_n
---
kernel/proc.c | 4 ++--
kernel/trap.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/proc.c b/kernel/proc.c
index 24680b6..b4f8a80 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -588,7 +588,7 @@ kill(int pid)
for(p = proc; p < &proc[NPROC]; p++){
acquire(&p->lock);
if(p->pid == pid){
- __sync_bool_compare_and_swap(&p->killed, 0, 1);
+ __atomic_store_n(&p->killed, 1, __ATOMIC_SEQ_CST);
if(p->state == SLEEPING){
// Wake process from sleep().
p->state = RUNNABLE;
@@ -604,7 +604,7 @@ kill(int pid)
int
killed(struct proc *p)
{
- return __sync_add_and_fetch(&p->killed, 0);
+ return __atomic_load_n(&p->killed, __ATOMIC_SEQ_CST);
}
// Copy to either a user address, or kernel address,
diff --git a/kernel/trap.c b/kernel/trap.c
index f895aea..1039911 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -70,7 +70,7 @@ usertrap(void)
} else {
printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
printf(" sepc=%p stval=%p\n", r_sepc(), r_stval());
- __sync_bool_compare_and_swap(&p->killed, 0, 1);
+ __atomic_store_n(&p->killed, 1, __ATOMIC_SEQ_CST);
}
if(killed(p))
From 4f716c8550b406c3e4b3e0c21b986ef99bc06c40 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Thu, 11 Aug 2022 14:22:00 -0400
Subject: [PATCH 04/14] Use p->lock to read p->killed
---
kernel/defs.h | 1 +
kernel/proc.c | 17 +++++++++++++++--
kernel/trap.c | 2 +-
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/kernel/defs.h b/kernel/defs.h
index 7181d4d..e38ec00 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -91,6 +91,7 @@ pagetable_t proc_pagetable(struct proc *);
void proc_freepagetable(pagetable_t, uint64);
int kill(int);
int killed(struct proc*);
+void setkilled(struct proc*);
struct cpu* mycpu(void);
struct cpu* getmycpu(void);
struct proc* myproc();
diff --git a/kernel/proc.c b/kernel/proc.c
index b4f8a80..5e37cb7 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -588,7 +588,7 @@ kill(int pid)
for(p = proc; p < &proc[NPROC]; p++){
acquire(&p->lock);
if(p->pid == pid){
- __atomic_store_n(&p->killed, 1, __ATOMIC_SEQ_CST);
+ p->killed = 1;
if(p->state == SLEEPING){
// Wake process from sleep().
p->state = RUNNABLE;
@@ -601,10 +601,23 @@ kill(int pid)
return -1;
}
+void
+setkilled(struct proc *p)
+{
+ acquire(&p->lock);
+ p->killed = 1;
+ release(&p->lock);
+}
+
int
killed(struct proc *p)
{
- return __atomic_load_n(&p->killed, __ATOMIC_SEQ_CST);
+ int k;
+
+ acquire(&p->lock);
+ k = p->killed;
+ release(&p->lock);
+ return k;
}
// Copy to either a user address, or kernel address,
diff --git a/kernel/trap.c b/kernel/trap.c
index 1039911..44c9cdc 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -70,7 +70,7 @@ usertrap(void)
} else {
printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
printf(" sepc=%p stval=%p\n", r_sepc(), r_stval());
- __atomic_store_n(&p->killed, 1, __ATOMIC_SEQ_CST);
+ setkilled(p);
}
if(killed(p))
From 7a6d57235c41df877b3fb2322cf770e65e864058 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Fri, 12 Aug 2022 14:59:30 -0400
Subject: [PATCH 05/14] Costmestic change (thanks Harry Porter)
---
kernel/syscall.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/syscall.c b/kernel/syscall.c
index 95b9f70..dd7a33e 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -12,7 +12,7 @@ int
fetchaddr(uint64 addr, uint64 *ip)
{
struct proc *p = myproc();
- if(addr >= p->sz || addr+sizeof(uint64) > p->sz)
+ if(addr >= p->sz || addr+sizeof(uint64) > p->sz) // both tests needed, in case of overflow
return -1;
if(copyin(p->pagetable, (char *)ip, addr, sizeof(*ip)) != 0)
return -1;
@@ -25,9 +25,8 @@ int
fetchstr(uint64 addr, char *buf, int max)
{
struct proc *p = myproc();
- int err = copyinstr(p->pagetable, buf, addr, max);
- if(err < 0)
- return err;
+ if(copyinstr(p->pagetable, buf, addr, max) < 0)
+ return -1;
return strlen(buf);
}
From 1d4c437ea17e3254fe6138fd8dd181de413a43bf Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Wed, 17 Aug 2022 20:37:22 -0400
Subject: [PATCH 06/14] Use uint64 (thanks carlclone and Harry Porter)
---
kernel/proc.c | 2 +-
kernel/sysproc.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/proc.c b/kernel/proc.c
index 580b3b6..3bb2618 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -259,7 +259,7 @@ userinit(void)
int
growproc(int n)
{
- uint sz;
+ uint64 sz;
struct proc *p = myproc();
sz = p->sz;
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index 8ca45ba..c74def2 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -40,7 +40,7 @@ sys_wait(void)
uint64
sys_sbrk(void)
{
- int addr;
+ uint64 addr;
int n;
if(argint(0, &n) < 0)
From f2ee8690addf0aa52b5de2061fe6d659574406f9 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Wed, 17 Aug 2022 20:38:11 -0400
Subject: [PATCH 07/14] x
---
user/user.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/user/user.h b/user/user.h
index 8ac6395..4d398d5 100644
--- a/user/user.h
+++ b/user/user.h
@@ -9,7 +9,7 @@ int write(int, const void*, int);
int read(int, void*, int);
int close(int);
int kill(int);
-int exec(char*, char**);
+int exec(const char*, char**);
int open(const char*, int);
int mknod(const char*, short, short);
int unlink(const char*);
From 63ef3b8c9fd15d5ea5775813cda94a3c64cff0d3 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Mon, 22 Aug 2022 13:49:15 -0400
Subject: [PATCH 08/14] slightly better comments
---
kernel/trampoline.S | 31 +++++++++++++++----------------
kernel/trap.c | 6 +++---
2 files changed, 18 insertions(+), 19 deletions(-)
diff --git a/kernel/trampoline.S b/kernel/trampoline.S
index 2ce4886..0aaa413 100644
--- a/kernel/trampoline.S
+++ b/kernel/trampoline.S
@@ -1,18 +1,19 @@
- #
- # code to switch between user and kernel space.
#
- # this code is mapped at the same virtual address
- # (TRAMPOLINE) in user and kernel space so that
- # it continues to work when it switches page tables.
- #
- # kernel.ld causes this to be aligned
- # to a page boundary.
+ # low-level code to handle traps from user space into
+ # the kernel, and returns from kernel to user.
+ #
+ # the kernel maps the page holding this code
+ # at the same virtual address (TRAMPOLINE)
+ # in user and kernel space so that it continues
+ # to work when it switches page tables.
+ # kernel.ld causes this code to start at
+ # a page boundary.
#
#include "riscv.h"
#include "memlayout.h"
- .section trampsec
+.section trampsec
.globl trampoline
trampoline:
.align 4
@@ -31,7 +32,7 @@ uservec:
# each process has a separate p->trapframe memory area,
# but it's mapped to the same virtual address
- # (TRAPFRAME) in every process.
+ # (TRAPFRAME) in every process's user page table.
li a0, TRAPFRAME
# save the user registers in TRAPFRAME
@@ -70,29 +71,27 @@ uservec:
csrr t0, sscratch
sd t0, 112(a0)
- # restore kernel stack pointer from p->trapframe->kernel_sp
+ # initialize kernel stack pointer, from p->trapframe->kernel_sp
ld sp, 8(a0)
# make tp hold the current hartid, from p->trapframe->kernel_hartid
ld tp, 32(a0)
- # load the address of usertrap(), p->trapframe->kernel_trap
+ # load the address of usertrap(), from p->trapframe->kernel_trap
ld t0, 16(a0)
- # restore kernel page table from p->trapframe->kernel_satp
+ # load the kernel page table, from p->trapframe->kernel_satp
ld t1, 0(a0)
csrw satp, t1
sfence.vma zero, zero
- # a0 is no longer valid, since the kernel page
- # table does not specially map p->tf.
-
# jump to usertrap(), which does not return
jr t0
.globl userret
userret:
# userret(pagetable)
+ # called by usertrapret() in trap.c to
# switch from kernel to user.
# a0: user page table, for satp.
diff --git a/kernel/trap.c b/kernel/trap.c
index 75fb3ec..524da44 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -60,8 +60,8 @@ usertrap(void)
// but we want to return to the next instruction.
p->trapframe->epc += 4;
- // an interrupt will change sstatus &c registers,
- // so don't enable until done with those registers.
+ // an interrupt will change sepc, scause, and sstatus,
+ // so enable only now that we're done with those registers.
intr_on();
syscall();
@@ -101,7 +101,7 @@ usertrapret(void)
w_stvec(trampoline_uservec);
// set up trapframe values that uservec will need when
- // the process next re-enters the kernel.
+ // the process next traps into the kernel.
p->trapframe->kernel_satp = r_satp(); // kernel page table
p->trapframe->kernel_sp = p->kstack + PGSIZE; // process's kernel stack
p->trapframe->kernel_trap = (uint64)usertrap;
From 7086197c27f7c00544ca006561336d8d5791a482 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Mon, 22 Aug 2022 19:36:11 -0400
Subject: [PATCH 09/14] Simplify uartputc slightly (thanks Harry Porter)
---
kernel/uart.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/kernel/uart.c b/kernel/uart.c
index af571b1..e3b3b8a 100644
--- a/kernel/uart.c
+++ b/kernel/uart.c
@@ -92,22 +92,18 @@ uartputc(int c)
for(;;)
;
}
-
- while(1){
- if(uart_tx_w == uart_tx_r + UART_TX_BUF_SIZE){
- // buffer is full.
- // wait for uartstart() to open up space in the buffer.
- sleep(&uart_tx_r, &uart_tx_lock);
- } else {
- uart_tx_buf[uart_tx_w % UART_TX_BUF_SIZE] = c;
- uart_tx_w += 1;
- uartstart();
- release(&uart_tx_lock);
- return;
- }
+ while(uart_tx_w == uart_tx_r + UART_TX_BUF_SIZE){
+ // buffer is full.
+ // wait for uartstart() to open up space in the buffer.
+ sleep(&uart_tx_r, &uart_tx_lock);
}
+ uart_tx_buf[uart_tx_w % UART_TX_BUF_SIZE] = c;
+ uart_tx_w += 1;
+ uartstart();
+ release(&uart_tx_lock);
}
+
// alternate version of uartputc() that doesn't
// use interrupts, for use by kernel printf() and
// to echo characters. it spins waiting for the uart's
From 2a391ebc8ba1fd0e6f0899277218d531fd5c7396 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Mon, 22 Aug 2022 19:53:09 -0400
Subject: [PATCH 10/14] Make argint() and argaddr() of type void (thanks Harry
Porter)
---
kernel/defs.h | 4 ++--
kernel/syscall.c | 9 +++------
kernel/sysfile.c | 29 +++++++++++++++++------------
kernel/sysproc.c | 15 +++++----------
4 files changed, 27 insertions(+), 30 deletions(-)
diff --git a/kernel/defs.h b/kernel/defs.h
index 62b9292..48641f5 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -132,9 +132,9 @@ int strncmp(const char*, const char*, uint);
char* strncpy(char*, const char*, int);
// syscall.c
-int argint(int, int*);
+void argint(int, int*);
int argstr(int, char*, int);
-int argaddr(int, uint64 *);
+void argaddr(int, uint64 *);
int fetchstr(uint64, char*, int);
int fetchaddr(uint64, uint64*);
void syscall();
diff --git a/kernel/syscall.c b/kernel/syscall.c
index dd7a33e..ee94696 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -53,21 +53,19 @@ argraw(int n)
}
// Fetch the nth 32-bit system call argument.
-int
+void
argint(int n, int *ip)
{
*ip = argraw(n);
- return 0;
}
// Retrieve an argument as a pointer.
// Doesn't check for legality, since
// copyin/copyout will do that.
-int
+void
argaddr(int n, uint64 *ip)
{
*ip = argraw(n);
- return 0;
}
// Fetch the nth word-sized system call argument as a null-terminated string.
@@ -77,8 +75,7 @@ int
argstr(int n, char *buf, int max)
{
uint64 addr;
- if(argaddr(n, &addr) < 0)
- return -1;
+ argaddr(n, &addr);
return fetchstr(addr, buf, max);
}
diff --git a/kernel/sysfile.c b/kernel/sysfile.c
index 5dc453b..970a72a 100644
--- a/kernel/sysfile.c
+++ b/kernel/sysfile.c
@@ -24,8 +24,7 @@ argfd(int n, int *pfd, struct file **pf)
int fd;
struct file *f;
- if(argint(n, &fd) < 0)
- return -1;
+ argint(n, &fd);
if(fd < 0 || fd >= NOFILE || (f=myproc()->ofile[fd]) == 0)
return -1;
if(pfd)
@@ -73,7 +72,9 @@ sys_read(void)
int n;
uint64 p;
- if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argaddr(1, &p) < 0)
+ argaddr(1, &p);
+ argint(2, &n);
+ if(argfd(0, 0, &f) < 0)
return -1;
return fileread(f, p, n);
}
@@ -84,8 +85,10 @@ sys_write(void)
struct file *f;
int n;
uint64 p;
-
- if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argaddr(1, &p) < 0)
+
+ argaddr(1, &p);
+ argint(2, &n);
+ if(argfd(0, 0, &f) < 0)
return -1;
return filewrite(f, p, n);
@@ -110,7 +113,8 @@ sys_fstat(void)
struct file *f;
uint64 st; // user pointer to struct stat
- if(argfd(0, 0, &f) < 0 || argaddr(1, &st) < 0)
+ argaddr(1, &st);
+ if(argfd(0, 0, &f) < 0)
return -1;
return filestat(f, st);
}
@@ -292,7 +296,8 @@ sys_open(void)
struct inode *ip;
int n;
- if((n = argstr(0, path, MAXPATH)) < 0 || argint(1, &omode) < 0)
+ argint(1, &omode);
+ if((n = argstr(0, path, MAXPATH)) < 0)
return -1;
begin_op();
@@ -375,9 +380,9 @@ sys_mknod(void)
int major, minor;
begin_op();
+ argint(1, &major);
+ argint(2, &minor);
if((argstr(0, path, MAXPATH)) < 0 ||
- argint(1, &major) < 0 ||
- argint(2, &minor) < 0 ||
(ip = create(path, T_DEVICE, major, minor)) == 0){
end_op();
return -1;
@@ -419,7 +424,8 @@ sys_exec(void)
int i;
uint64 uargv, uarg;
- if(argstr(0, path, MAXPATH) < 0 || argaddr(1, &uargv) < 0){
+ argaddr(1, &uargv);
+ if(argstr(0, path, MAXPATH) < 0) {
return -1;
}
memset(argv, 0, sizeof(argv));
@@ -462,8 +468,7 @@ sys_pipe(void)
int fd0, fd1;
struct proc *p = myproc();
- if(argaddr(0, &fdarray) < 0)
- return -1;
+ argaddr(0, &fdarray);
if(pipealloc(&rf, &wf) < 0)
return -1;
fd0 = -1;
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index c74def2..ecaa8cc 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -10,8 +10,7 @@ uint64
sys_exit(void)
{
int n;
- if(argint(0, &n) < 0)
- return -1;
+ argint(0, &n);
exit(n);
return 0; // not reached
}
@@ -32,8 +31,7 @@ uint64
sys_wait(void)
{
uint64 p;
- if(argaddr(0, &p) < 0)
- return -1;
+ argaddr(0, &p);
return wait(p);
}
@@ -43,8 +41,7 @@ sys_sbrk(void)
uint64 addr;
int n;
- if(argint(0, &n) < 0)
- return -1;
+ argint(0, &n);
addr = myproc()->sz;
if(growproc(n) < 0)
return -1;
@@ -57,8 +54,7 @@ sys_sleep(void)
int n;
uint ticks0;
- if(argint(0, &n) < 0)
- return -1;
+ argint(0, &n);
acquire(&tickslock);
ticks0 = ticks;
while(ticks - ticks0 < n){
@@ -77,8 +73,7 @@ sys_kill(void)
{
int pid;
- if(argint(0, &pid) < 0)
- return -1;
+ argint(0, &pid);
return kill(pid);
}
From 2f0b4d698bc48f4efb4b9fdca20f415ec765bf41 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Mon, 22 Aug 2022 19:58:33 -0400
Subject: [PATCH 11/14] Use pp instead of np to be more consistent
---
kernel/proc.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/kernel/proc.c b/kernel/proc.c
index 3bb2618..1ed3ee5 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -390,7 +390,7 @@ exit(int status)
int
wait(uint64 addr)
{
- struct proc *np;
+ struct proc *pp;
int havekids, pid;
struct proc *p = myproc();
@@ -399,27 +399,27 @@ wait(uint64 addr)
for(;;){
// Scan through table looking for exited children.
havekids = 0;
- for(np = proc; np < &proc[NPROC]; np++){
- if(np->parent == p){
+ for(pp = proc; pp < &proc[NPROC]; pp++){
+ if(pp->parent == p){
// make sure the child isn't still in exit() or swtch().
- acquire(&np->lock);
+ acquire(&pp->lock);
havekids = 1;
- if(np->state == ZOMBIE){
+ if(pp->state == ZOMBIE){
// Found one.
- pid = np->pid;
- if(addr != 0 && copyout(p->pagetable, addr, (char *)&np->xstate,
- sizeof(np->xstate)) < 0) {
- release(&np->lock);
+ pid = pp->pid;
+ if(addr != 0 && copyout(p->pagetable, addr, (char *)&pp->xstate,
+ sizeof(pp->xstate)) < 0) {
+ release(&pp->lock);
release(&wait_lock);
return -1;
}
- freeproc(np);
- release(&np->lock);
+ freeproc(pp);
+ release(&pp->lock);
release(&wait_lock);
return pid;
}
- release(&np->lock);
+ release(&pp->lock);
}
}
From bc48c2be47ed4994d23327980737fef441fbbcc8 Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Mon, 22 Aug 2022 20:44:02 -0400
Subject: [PATCH 12/14] Add ref to this nice page about Chapter 9's regexp
matcher
---
user/grep.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/user/grep.c b/user/grep.c
index 19882b9..2315a0c 100644
--- a/user/grep.c
+++ b/user/grep.c
@@ -62,7 +62,8 @@ main(int argc, char *argv[])
}
// Regexp matcher from Kernighan & Pike,
-// The Practice of Programming, Chapter 9.
+// The Practice of Programming, Chapter 9, or
+// https://www.cs.princeton.edu/courses/archive/spr09/cos333/beautiful.html
int matchhere(char*, char*);
int matchstar(int, char*, char*);
From dc405cdb7b4e4d4bb3fc50b3e7f44e8795c0218e Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Tue, 23 Aug 2022 08:23:12 -0400
Subject: [PATCH 13/14] don't panic if out of disk space when extending a
directory.
---
kernel/fs.c | 3 ++-
kernel/sysfile.c | 9 +++++++--
user/usertests.c | 30 ++++++++++++++++++++++++++++++
3 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/kernel/fs.c b/kernel/fs.c
index 247a86f..b220491 100644
--- a/kernel/fs.c
+++ b/kernel/fs.c
@@ -573,6 +573,7 @@ dirlookup(struct inode *dp, char *name, uint *poff)
}
// Write a new directory entry (name, inum) into the directory dp.
+// Returns 0 on success, -1 on failure (e.g. out of disk blocks).
int
dirlink(struct inode *dp, char *name, uint inum)
{
@@ -597,7 +598,7 @@ dirlink(struct inode *dp, char *name, uint inum)
strncpy(de.name, name, DIRSIZ);
de.inum = inum;
if(writei(dp, 0, (uint64)&de, off, sizeof(de)) != sizeof(de))
- panic("dirlink");
+ return -1;
return 0;
}
diff --git a/kernel/sysfile.c b/kernel/sysfile.c
index 970a72a..4c0470e 100644
--- a/kernel/sysfile.c
+++ b/kernel/sysfile.c
@@ -279,8 +279,13 @@ create(char *path, short type, short major, short minor)
panic("create dots");
}
- if(dirlink(dp, name, ip->inum) < 0)
- panic("create: dirlink");
+ if(dirlink(dp, name, ip->inum) < 0){
+ // oops. we don't need ip after all.
+ ip->nlink = 0;
+ iupdate(ip);
+ iunlockput(ip);
+ ip = 0;
+ }
iunlockput(dp);
diff --git a/user/usertests.c b/user/usertests.c
index 4ab34da..968034a 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -2738,6 +2738,36 @@ diskfull(char *s)
close(fd);
}
+ // now that there are no free blocks, test that dirlink()
+ // merely fails (doesn't panic) if it can't extend
+ // directory content.
+ int nzz = 128;
+ for(int i = 0; i < nzz; i++){
+ char name[32];
+ name[0] = 'z';
+ name[1] = 'z';
+ name[2] = '0' + (i / 32);
+ name[3] = '0' + (i % 32);
+ name[4] = '\0';
+ unlink(name);
+ int fd = open(name, O_CREATE|O_RDWR|O_TRUNC);
+ if(fd < 0){
+ printf("%s: could not create file %s\n", s, name);
+ break;
+ }
+ close(fd);
+ }
+
+ for(int i = 0; i < nzz; i++){
+ char name[32];
+ name[0] = 'z';
+ name[1] = 'z';
+ name[2] = '0' + (i / 32);
+ name[3] = '0' + (i % 32);
+ name[4] = '\0';
+ unlink(name);
+ }
+
for(int i = 0; i < fi; i++){
char name[32];
name[0] = 'b';
From 8621be8f3d105cd73ffbc681f9810d04b083b0ae Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Tue, 23 Aug 2022 08:52:15 -0400
Subject: [PATCH 14/14] tolerate out of disk when creating . and .. in mkdir()
---
kernel/sysfile.c | 25 ++++++++++++++++---------
user/usertests.c | 5 +++++
2 files changed, 21 insertions(+), 9 deletions(-)
diff --git a/kernel/sysfile.c b/kernel/sysfile.c
index 4c0470e..d8a6fca 100644
--- a/kernel/sysfile.c
+++ b/kernel/sysfile.c
@@ -272,24 +272,31 @@ create(char *path, short type, short major, short minor)
iupdate(ip);
if(type == T_DIR){ // Create . and .. entries.
- dp->nlink++; // for ".."
- iupdate(dp);
// No ip->nlink++ for ".": avoid cyclic ref count.
if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0)
- panic("create dots");
+ goto fail;
}
- if(dirlink(dp, name, ip->inum) < 0){
- // oops. we don't need ip after all.
- ip->nlink = 0;
- iupdate(ip);
- iunlockput(ip);
- ip = 0;
+ if(dirlink(dp, name, ip->inum) < 0)
+ goto fail;
+
+ if(type == T_DIR){
+ // now that success is guaranteed:
+ dp->nlink++; // for ".."
+ iupdate(dp);
}
iunlockput(dp);
return ip;
+
+ fail:
+ // something went wrong. de-allocate ip.
+ ip->nlink = 0;
+ iupdate(ip);
+ iunlockput(ip);
+ iunlockput(dp);
+ return 0;
}
uint64
diff --git a/user/usertests.c b/user/usertests.c
index 968034a..60d1762 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -2712,6 +2712,8 @@ diskfull(char *s)
{
int fi;
int done = 0;
+
+ unlink("diskfulldir");
for(fi = 0; done == 0; fi++){
char name[32];
@@ -2758,6 +2760,9 @@ diskfull(char *s)
close(fd);
}
+ mkdir("diskfulldir");
+ unlink("diskfulldir");
+
for(int i = 0; i < nzz; i++){
char name[32];
name[0] = 'z';