vmm.c
#include <vmm.h>
#include <sync.h>
#include <string.h>
#include <assert.h>
#include <stdio.h>
#include <error.h>
#include <pmm.h>
#include <x86.h>
#include <swap.h>
#include <kmalloc.h>
/*
vmm design include two parts: mm_struct (mm) & vma_struct (vma)
mm is the memory manager for the set of continuous virtual memory
area which have the same PDT. vma is a continuous virtual memory area.
There a linear link list for vma & a redblack link list for vma in mm.
---------------
mm related functions:
golbal functions
struct mm_struct * mm_create(void)
void mm_destroy(struct mm_struct *mm)
int do_pgfault(struct mm_struct *mm, uint32_t error_code, uintptr_t addr)
--------------
vma related functions:
global functions
struct vma_struct * vma_create (uintptr_t vm_start, uintptr_t vm_end,...)
void insert_vma_struct(struct mm_struct *mm, struct vma_struct *vma)
struct vma_struct * find_vma(struct mm_struct *mm, uintptr_t addr)
local functions
inline void check_vma_overlap(struct vma_struct *prev, struct vma_struct *next)
---------------
check correctness functions
void check_vmm(void);
void check_vma_struct(void);
void check_pgfault(void);
*/
static void check_vmm(void);
static void check_vma_struct(void);
static void check_pgfault(void);
// mm_create - alloc a mm_struct & initialize it.
struct mm_struct *
mm_create(void) {
struct mm_struct *mm = kmalloc(sizeof(struct mm_struct));
if (mm != NULL) {
list_init(&(mm->mmap_list));
mm->mmap_cache = NULL;
mm->pgdir = NULL;
mm->map_count = 0;
if (swap_init_ok) swap_init_mm(mm);
else mm->sm_priv = NULL;
set_mm_count(mm, 0);
sem_init(&(mm->mm_sem), 1);
}
return mm;
}
// vma_create - alloc a vma_struct & initialize it. (addr range: vm_start~vm_end)
struct vma_struct *
vma_create(uintptr_t vm_start, uintptr_t vm_end, uint32_t vm_flags) {
struct vma_struct *vma = kmalloc(sizeof(struct vma_struct));
if (vma != NULL) {
vma->vm_start = vm_start;
vma->vm_end = vm_end;
vma->vm_flags = vm_flags;
}
return vma;
}
// find_vma - find a vma (vma->vm_start <= addr <= vma_vm_end)
struct vma_struct *
find_vma(struct mm_struct *mm, uintptr_t addr) {
struct vma_struct *vma = NULL;
if (mm != NULL) {
vma = mm->mmap_cache;
if (!(vma != NULL && vma->vm_start <= addr && vma->vm_end > addr)) {
bool found = 0;
list_entry_t *list = &(mm->mmap_list), *le = list;
while ((le = list_next(le)) != list) {
vma = le2vma(le, list_link);
if (vma->vm_start<=addr && addr < vma->vm_end) {
found = 1;
break;
}
}
if (!found) {
vma = NULL;
}
}
if (vma != NULL) {
mm->mmap_cache = vma;
}
}
return vma;
}
// check_vma_overlap - check if vma1 overlaps vma2 ?
static inline void
check_vma_overlap(struct vma_struct *prev, struct vma_struct *next) {
assert(prev->vm_start < prev->vm_end);
assert(prev->vm_end <= next->vm_start);
assert(next->vm_start < next->vm_end);
}
// insert_vma_struct -insert vma in mm's list link
void
insert_vma_struct(struct mm_struct *mm, struct vma_struct *vma) {
assert(vma->vm_start < vma->vm_end);
list_entry_t *list = &(mm->mmap_list);
list_entry_t *le_prev = list, *le_next;
list_entry_t *le = list;
while ((le = list_next(le)) != list) {
struct vma_struct *mmap_prev = le2vma(le, list_link);
if (mmap_prev->vm_start > vma->vm_start) {
break;
}
le_prev = le;
}
le_next = list_next(le_prev);
/* check overlap */
if (le_prev != list) {
check_vma_overlap(le2vma(le_prev, list_link), vma);
}
if (le_next != list) {
check_vma_overlap(vma, le2vma(le_next, list_link));
}
vma->vm_mm = mm;
list_add_after(le_prev, &(vma->list_link));
mm->map_count ++;
}
// mm_destroy - free mm and mm internal fields
void
mm_destroy(struct mm_struct *mm) {
assert(mm_count(mm) == 0);
list_entry_t *list = &(mm->mmap_list), *le;
while ((le = list_next(list)) != list) {
list_del(le);
kfree(le2vma(le, list_link)); //kfree vma
}
kfree(mm); //kfree mm
mm=NULL;
}
int
mm_map(struct mm_struct *mm, uintptr_t addr, size_t len, uint32_t vm_flags,
struct vma_struct **vma_store) {
uintptr_t start = ROUNDDOWN(addr, PGSIZE), end = ROUNDUP(addr + len, PGSIZE);
if (!USER_ACCESS(start, end)) {
return -E_INVAL;
}
assert(mm != NULL);
int ret = -E_INVAL;
struct vma_struct *vma;
if ((vma = find_vma(mm, start)) != NULL && end > vma->vm_start) {
goto out;
}
ret = -E_NO_MEM;
if ((vma = vma_create(start, end, vm_flags)) == NULL) {
goto out;
}
insert_vma_struct(mm, vma);
if (vma_store != NULL) {
*vma_store = vma;
}
ret = 0;
out:
return ret;
}
int
dup_mmap(struct mm_struct *to, struct mm_struct *from) {
assert(to != NULL && from != NULL);
list_entry_t *list = &(from->mmap_list), *le = list;
while ((le = list_prev(le)) != list) {
struct vma_struct *vma, *nvma;
vma = le2vma(le, list_link);
nvma = vma_create(vma->vm_start, vma->vm_end, vma->vm_flags);
if (nvma == NULL) {
return -E_NO_MEM;
}
insert_vma_struct(to, nvma);
bool share = 0;
if (copy_range(to->pgdir, from->pgdir, vma->vm_start, vma->vm_end, share) != 0) {
return -E_NO_MEM;
}
}
return 0;
}
void
exit_mmap(struct mm_struct *mm) {
assert(mm != NULL && mm_count(mm) == 0);
pde_t *pgdir = mm->pgdir;
list_entry_t *list = &(mm->mmap_list), *le = list;
while ((le = list_next(le)) != list) {
struct vma_struct *vma = le2vma(le, list_link);
unmap_range(pgdir, vma->vm_start, vma->vm_end);
}
while ((le = list_next(le)) != list) {
struct vma_struct *vma = le2vma(le, list_link);
exit_range(pgdir, vma->vm_start, vma->vm_end);
}
}
bool
copy_from_user(struct mm_struct *mm, void *dst, const void *src, size_t len, bool writable) {
if (!user_mem_check(mm, (uintptr_t)src, len, writable)) {
return 0;
}
memcpy(dst, src, len);
return 1;
}
bool
copy_to_user(struct mm_struct *mm, void *dst, const void *src, size_t len) {
if (!user_mem_check(mm, (uintptr_t)dst, len, 1)) {
return 0;
}
memcpy(dst, src, len);
return 1;
}
// vmm_init - initialize virtual memory management
// - now just call check_vmm to check correctness of vmm
void
vmm_init(void) {
check_vmm();
}
// check_vmm - check correctness of vmm
static void
check_vmm(void) {
size_t nr_free_pages_store = nr_free_pages();
check_vma_struct();
check_pgfault();
//assert(nr_free_pages_store == nr_free_pages());
cprintf("check_vmm() succeeded.\n");
}
static void
check_vma_struct(void) {
size_t nr_free_pages_store = nr_free_pages();
struct mm_struct *mm = mm_create();
assert(mm != NULL);
int step1 = 10, step2 = step1 * 10;
int i;
for (i = step1; i >= 1; i --) {
struct vma_struct *vma = vma_create(i * 5, i * 5 + 2, 0);
assert(vma != NULL);
insert_vma_struct(mm, vma);
}
for (i = step1 + 1; i <= step2; i ++) {
struct vma_struct *vma = vma_create(i * 5, i * 5 + 2, 0);
assert(vma != NULL);
insert_vma_struct(mm, vma);
}
list_entry_t *le = list_next(&(mm->mmap_list));
for (i = 1; i <= step2; i ++) {
assert(le != &(mm->mmap_list));
struct vma_struct *mmap = le2vma(le, list_link);
assert(mmap->vm_start == i * 5 && mmap->vm_end == i * 5 + 2);
le = list_next(le);
}
for (i = 5; i <= 5 * step2; i +=5) {
struct vma_struct *vma1 = find_vma(mm, i);
assert(vma1 != NULL);
struct vma_struct *vma2 = find_vma(mm, i+1);
assert(vma2 != NULL);
struct vma_struct *vma3 = find_vma(mm, i+2);
assert(vma3 == NULL);
struct vma_struct *vma4 = find_vma(mm, i+3);
assert(vma4 == NULL);
struct vma_struct *vma5 = find_vma(mm, i+4);
assert(vma5 == NULL);
assert(vma1->vm_start == i && vma1->vm_end == i + 2);
assert(vma2->vm_start == i && vma2->vm_end == i + 2);
}
for (i =4; i>=0; i--) {
struct vma_struct *vma_below_5= find_vma(mm,i);
if (vma_below_5 != NULL ) {
cprintf("vma_below_5: i %x, start %x, end %x\n",i, vma_below_5->vm_start, vma_below_5->vm_end);
}
assert(vma_below_5 == NULL);
}
mm_destroy(mm);
// assert(nr_free_pages_store == nr_free_pages());
cprintf("check_vma_struct() succeeded!\n");
}
struct mm_struct *check_mm_struct;
// check_pgfault - check correctness of pgfault handler
static void
check_pgfault(void) {
size_t nr_free_pages_store = nr_free_pages();
check_mm_struct = mm_create();
assert(check_mm_struct != NULL);
struct mm_struct *mm = check_mm_struct;
pde_t *pgdir = mm->pgdir = boot_pgdir;
assert(pgdir[0] == 0);
struct vma_struct *vma = vma_create(0, PTSIZE, VM_WRITE);
assert(vma != NULL);
insert_vma_struct(mm, vma);
uintptr_t addr = 0x100;
assert(find_vma(mm, addr) == vma);
int i, sum = 0;
for (i = 0; i < 100; i ++) {
*(char *)(addr + i) = i;
sum += i;
}
for (i = 0; i < 100; i ++) {
sum -= *(char *)(addr + i);
}
assert(sum == 0);
page_remove(pgdir, ROUNDDOWN(addr, PGSIZE));
free_page(pde2page(pgdir[0]));
pgdir[0] = 0;
mm->pgdir = NULL;
mm_destroy(mm);
check_mm_struct = NULL;
assert(nr_free_pages_store == nr_free_pages());
cprintf("check_pgfault() succeeded!\n");
}
//page fault number
volatile unsigned int pgfault_num=0;
/* do_pgfault - interrupt handler to process the page fault execption
* @mm : the control struct for a set of vma using the same PDT
* @error_code : the error code recorded in trapframe->tf_err which is setted by x86 hardware
* @addr : the addr which causes a memory access exception, (the contents of the CR2 register)
*
* CALL GRAPH: trap--> trap_dispatch-->pgfault_handler-->do_pgfault
* The processor provides ucore's do_pgfault function with two items of information to aid in diagnosing
* the exception and recovering from it.
* (1) The contents of the CR2 register. The processor loads the CR2 register with the
* 32-bit linear address that generated the exception. The do_pgfault fun can
* use this address to locate the corresponding page directory and page-table
* entries.
* (2) An error code on the kernel stack. The error code for a page fault has a format different from
* that for other exceptions. The error code tells the exception handler three things:
* -- The P flag (bit 0) indicates whether the exception was due to a not-present page (0)
* or to either an access rights violation or the use of a reserved bit (1).
* -- The W/R flag (bit 1) indicates whether the memory access that caused the exception
* was a read (0) or write (1).
* -- The U/S flag (bit 2) indicates whether the processor was executing at user mode (1)
* or supervisor mode (0) at the time of the exception.
*/
int
do_pgfault(struct mm_struct *mm, uint32_t error_code, uintptr_t addr) {
int ret = -E_INVAL;
//try to find a vma which include addr
struct vma_struct *vma = find_vma(mm, addr);
pgfault_num++;
//If the addr is in the range of a mm's vma?
if (vma == NULL || vma->vm_start > addr) {
cprintf("not valid addr %x, and can not find it in vma\n", addr);
goto failed;
}
//check the error_code
switch (error_code & 3) {
default:
/* error code flag : default is 3 ( W/R=1, P=1): write, present */
case 2: /* error code flag : (W/R=1, P=0): write, not present */
if (!(vma->vm_flags & VM_WRITE)) {
cprintf("do_pgfault failed: error code flag = write AND not present, but the addr's vma cannot write\n");
goto failed;
}
break;
case 1: /* error code flag : (W/R=0, P=1): read, present */
cprintf("do_pgfault failed: error code flag = read AND present\n");
goto failed;
case 0: /* error code flag : (W/R=0, P=0): read, not present */
if (!(vma->vm_flags & (VM_READ | VM_EXEC))) {
cprintf("do_pgfault failed: error code flag = read AND not present, but the addr's vma cannot read or exec\n");
goto failed;
}
}
/* IF (write an existed addr ) OR
* (write an non_existed addr && addr is writable) OR
* (read an non_existed addr && addr is readable)
* THEN
* continue process
*/
uint32_t perm = PTE_U;
if (vma->vm_flags & VM_WRITE) {
perm |= PTE_W;
}
addr = ROUNDDOWN(addr, PGSIZE);
ret = -E_NO_MEM;
pte_t *ptep=NULL;
/*LAB3 EXERCISE 1: YOUR CODE
* Maybe you want help comment, BELOW comments can help you finish the code
*
* Some Useful MACROs and DEFINEs, you can use them in below implementation.
* MACROs or Functions:
* get_pte : get an pte and return the kernel virtual address of this pte for la
* if the PT contians this pte didn't exist, alloc a page for PT (notice the 3th parameter '1')
* pgdir_alloc_page : call alloc_page & page_insert functions to allocate a page size memory & setup
* an addr map pa<--->la with linear address la and the PDT pgdir
* DEFINES:
* VM_WRITE : If vma->vm_flags & VM_WRITE == 1/0, then the vma is writable/non writable
* PTE_W 0x002 // page table/directory entry flags bit : Writeable
* PTE_U 0x004 // page table/directory entry flags bit : User can access
* VARIABLES:
* mm->pgdir : the PDT of these vma
*
*/
#if 0
/*LAB3 EXERCISE 1: YOUR CODE*/
ptep = ??? //(1) try to find a pte, if pte's PT(Page Table) isn't existed, then create a PT.
if (*ptep == 0) {
//(2) if the phy addr isn't exist, then alloc a page & map the phy addr with logical addr
}
else {
/*LAB3 EXERCISE 2: YOUR CODE
* Now we think this pte is a swap entry, we should load data from disk to a page with phy addr,
* and map the phy addr with logical addr, trigger swap manager to record the access situation of this page.
*
* Some Useful MACROs and DEFINEs, you can use them in below implementation.
* MACROs or Functions:
* swap_in(mm, addr, &page) : alloc a memory page, then according to the swap entry in PTE for addr,
* find the addr of disk page, read the content of disk page into this memroy page
* page_insert ： build the map of phy addr of an Page with the linear addr la
* swap_map_swappable ： set the page swappable
*/
/*
* LAB5 CHALLENGE ( the implmentation Copy on Write)
There are 2 situlations when code comes here.
1) *ptep & PTE_P == 1, it means one process try to write a readonly page.
If the vma includes this addr is writable, then we can set the page writable by rewrite the *ptep.
This method could be used to implement the Copy on Write (COW) thchnology(a fast fork process method).
2) *ptep & PTE_P == 0 & but *ptep!=0, it means this pte is a swap entry.
We should add the LAB3's results here.
*/
if(swap_init_ok) {
struct Page *page=NULL;
//(1）According to the mm AND addr, try to load the content of right disk page
// into the memory which page managed.
//(2) According to the mm, addr AND page, setup the map of phy addr <---> logical addr
//(3) make the page swappable.
//(4) [NOTICE]: you myabe need to update your lab3's implementation for LAB5's normal execution.
}
else {
cprintf("no swap_init_ok but ptep is %x, failed\n",*ptep);
goto failed;
}
}
#endif
// try to find a pte, if pte's PT(Page Table) isn't existed, then create a PT.
// (notice the 3th parameter '1')
if ((ptep = get_pte(mm->pgdir, addr, 1)) == NULL) {
cprintf("get_pte in do_pgfault failed\n");
goto failed;
}
if (*ptep == 0) { // if the phy addr isn't exist, then alloc a page & map the phy addr with logical addr
if (pgdir_alloc_page(mm->pgdir, addr, perm) == NULL) {
cprintf("pgdir_alloc_page in do_pgfault failed\n");
goto failed;
}
}
else {
struct Page *page=NULL;
cprintf("do pgfault: ptep %x, pte %x\n",ptep, *ptep);
if (*ptep & PTE_P) {
//if process write to this existed readonly page (PTE_P means existed), then should be here now.
//we can implement the delayed memory space copy for fork child process (AKA copy on write, COW).
//we didn't implement now, we will do it in future.
panic("error write a non-writable pte");
//page = pte2page(*ptep);
} else{
// if this pte is a swap entry, then load data from disk to a page with phy addr
// and call page_insert to map the phy addr with logical addr
if(swap_init_ok) {
if ((ret = swap_in(mm, addr, &page)) != 0) {
cprintf("swap_in in do_pgfault failed\n");
goto failed;
}
}
else {
cprintf("no swap_init_ok but ptep is %x, failed\n",*ptep);
goto failed;
}
}
page_insert(mm->pgdir, page, addr, perm);
swap_map_swappable(mm, addr, page, 1);
page->pra_vaddr = addr;
}
ret = 0;
failed:
return ret;
}
bool
user_mem_check(struct mm_struct *mm, uintptr_t addr, size_t len, bool write) {
if (mm != NULL) {
if (!USER_ACCESS(addr, addr + len)) {
return 0;
}
struct vma_struct *vma;
uintptr_t start = addr, end = addr + len;
while (start < end) {
if ((vma = find_vma(mm, start)) == NULL || start < vma->vm_start) {
return 0;
}
if (!(vma->vm_flags & ((write) ? VM_WRITE : VM_READ))) {
return 0;
}
if (write && (vma->vm_flags & VM_STACK)) {
if (start < vma->vm_start + PGSIZE) { //check stack start & size
return 0;
}
}
start = vma->vm_end;
}
return 1;
}
return KERN_ACCESS(addr, addr + len);
}
bool
copy_string(struct mm_struct *mm, char *dst, const char *src, size_t maxn) {
size_t alen, part = ROUNDDOWN((uintptr_t)src + PGSIZE, PGSIZE) - (uintptr_t)src;
while (1) {
if (part > maxn) {
part = maxn;
}
if (!user_mem_check(mm, (uintptr_t)src, part, 0)) {
return 0;
}
if ((alen = strnlen(src, part)) < part) {
memcpy(dst, src, alen + 1);
return 1;
}
if (part == maxn) {
return 0;
}
memcpy(dst, src, part);
dst += part, src += part, maxn -= part;
part = PGSIZE;
}
}Last updated