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@@ -171,6 +171,7 @@ uint64 walkaddr(pagetable_t, uint64);
int copyout(pagetable_t, uint64, char *, uint64);
int copyin(pagetable_t, char *, uint64, uint64);
int copyinstr(pagetable_t, char *, uint64, uint64);
+uint64 lazyalloc(struct proc * p, uint64 va);
// plic.c
void plicinit(void);
@@ -43,12 +43,15 @@ sys_sbrk(void)
{
int addr;
int n;
+ struct proc *p = myproc();
if(argint(0, &n) < 0)
return -1;
- addr = myproc()->sz;
- if(growproc(n) < 0)
- return -1;
+ addr = p->sz; // old sz
+ p->sz += n;
+ if (n < 0) {
+ uvmdealloc(p->pagetable, addr, p->sz);
+ }
return addr;
}
@@ -67,6 +67,11 @@ usertrap(void)
syscall();
} else if((which_dev = devintr()) != 0){
// ok
+ } else if((r_scause() == 13) || (r_scause() == 15)){ // page fault
+ // lazy allocation
+ if (lazyalloc(myproc(), r_stval()) <= 0) {
+ p->killed = 1;
+ }
} else {
printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
printf(" sepc=%p stval=%p\n", r_sepc(), r_stval());
@@ -5,6 +5,8 @@
#include "riscv.h"
#include "defs.h"
#include "fs.h"
+#include "spinlock.h"
+#include "proc.h"
/*
* the kernel's page table.
@@ -102,12 +104,19 @@ walkaddr(pagetable_t pagetable, uint64 va)
pte = walk(pagetable, va, 0);
if(pte == 0)
- return 0;
+ goto lzac;
if((*pte & PTE_V) == 0)
- return 0;
+ goto lzac;
if((*pte & PTE_U) == 0)
- return 0;
+ goto lzac;
pa = PTE2PA(*pte);
+
+ if (0) {
+lzac:
+ if ((pa = lazyalloc(myproc(), va)) <= 0)
+ pa = 0;
+ }
+
return pa;
}
@@ -157,7 +166,8 @@ mappages(pagetable_t pagetable, uint64 va, uint64 size, uint64 pa, int perm)
if((pte = walk(pagetable, a, 1)) == 0)
return -1;
if(*pte & PTE_V)
- panic("remap");
+ // panic("remap");
+ ;
*pte = PA2PTE(pa) | perm | PTE_V;
if(a == last)
break;
@@ -180,10 +190,14 @@ uvmunmap(pagetable_t pagetable, uint64 va, uint64 npages, int do_free)
panic("uvmunmap: not aligned");
for(a = va; a < va + npages*PGSIZE; a += PGSIZE){
- if((pte = walk(pagetable, a, 0)) == 0)
- panic("uvmunmap: walk");
- if((*pte & PTE_V) == 0)
- panic("uvmunmap: not mapped");
+ if((pte = walk(pagetable, a, 0)) == 0) {
+ // panic("uvmunmap: walk");
+ continue;
+ }
+ if((*pte & PTE_V) == 0) {
+ // panic("uvmunmap: not mapped");
+ continue;
+ }
if(PTE_FLAGS(*pte) == PTE_V)
panic("uvmunmap: not a leaf");
if(do_free){
@@ -314,10 +328,14 @@ uvmcopy(pagetable_t old, pagetable_t new, uint64 sz)
char *mem;
for(i = 0; i < sz; i += PGSIZE){
- if((pte = walk(old, i, 0)) == 0)
- panic("uvmcopy: pte should exist");
- if((*pte & PTE_V) == 0)
- panic("uvmcopy: page not present");
+ if((pte = walk(old, i, 0)) == 0){
+ // panic("uvmcopy: pte should exist");
+ continue;
+ }
+ if((*pte & PTE_V) == 0){
+ // panic("uvmcopy: page not present");
+ continue;
+ }
pa = PTE2PA(*pte);
flags = PTE_FLAGS(*pte);
if((mem = kalloc()) == 0)
@@ -440,3 +458,40 @@ copyinstr(pagetable_t pagetable, char *dst, uint64 srcva, uint64 max)
return -1;
}
}
+
+
+// lazy allocation memory va for proc p: handle page-fault.
+// return allocated memory (pa), 0 for failed
+uint64 lazyalloc(struct proc * p, uint64 va){
+#define lazyalloc_debug 0
+#define lazyalloc_warn(info) { \
+ printf("lazyalloc(): %s", info); \
+ printf(" scause %p pid=%d\n", r_scause(), p->pid); \
+ printf(" sepc=%p stval=%p\n", r_sepc(), r_stval()); \
+}
+ if(va >= p->sz || va < PGROUNDUP(p->trapframe->sp)){
+ #if lazyalloc_debug
+ lazyalloc_warn("vm addr higher then any allocated with sbrk\n");
+ #endif
+ return 0;
+ }
+ char * mem;
+ uint64 a = PGROUNDDOWN(va);
+ mem = kalloc();
+ if(mem == 0){
+ #if lazyalloc_debug
+ lazyalloc_warn("kalloc() == 0\n");
+ #endif
+ return 0;
+ }
+ memset(mem, 0, PGSIZE);
+ if(mappages(p->pagetable, a, PGSIZE, (uint64)mem, PTE_W|PTE_X|PTE_R|PTE_U) != 0){
+ #if lazyalloc_debug
+ lazyalloc_warn("mappages() != 0\n");
+ #endif
+ kfree(mem);
+ return 0;
+ }
+
+ return (uint64)mem;
+}
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