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Simplify allocuvm/deallocuvm to operate in a contiguous memory model. This makes their interface match up better with proc->sz and also simplifies the callers (it even gets the main body of exec on one page).

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This commit is contained in:
Austin Clements 2010-09-02 18:28:36 -04:00
parent d49d31381d
commit 79cd8b3eed
4 changed files with 44 additions and 51 deletions
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4
defs.h
View file

@ -157,8 +157,8 @@ void kvmalloc(void);
void vmenable(void);
pde_t* setupkvm(void);
char* uva2ka(pde_t*, char*);
int allocuvm(pde_t*, char*, uint);
int deallocuvm(pde_t *pgdir, char *addr, uint sz);
int allocuvm(pde_t*, uint, uint);
int deallocuvm(pde_t*, uint, uint);
void freevm(pde_t*);
void inituvm(pde_t*, char*, uint);
int loaduvm(pde_t*, char*, struct inode *ip, uint, uint);

26
exec.c
View file

@ -11,7 +11,7 @@ exec(char *path, char **argv)
{
char *mem, *s, *last;
int i, argc, arglen, len, off;
uint sz, sp, spoffset, argp;
uint sz, sp, spbottom, argp;
struct elfhdr elf;
struct inode *ip;
struct proghdr ph;
@ -41,22 +41,18 @@ exec(char *path, char **argv)
continue;
if(ph.memsz < ph.filesz)
goto bad;
if(!allocuvm(pgdir, (char *)ph.va, ph.memsz))
if(!(sz = allocuvm(pgdir, sz, ph.va + ph.memsz)))
goto bad;
if(ph.va + ph.memsz > sz)
sz = ph.va + ph.memsz;
if(!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
goto bad;
}
iunlockput(ip);
// Allocate and initialize stack at sz
sz = PGROUNDUP(sz);
if(!allocuvm(pgdir, (char *)sz, PGSIZE))
sz = spbottom = PGROUNDUP(sz);
if(!(sz = allocuvm(pgdir, sz, sz + PGSIZE)))
goto bad;
mem = uva2ka(pgdir, (char *)sz);
spoffset = sz;
sz += PGSIZE;
mem = uva2ka(pgdir, (char *)spbottom);
arglen = 0;
for(argc=0; argv[argc]; argc++)
@ -67,22 +63,22 @@ exec(char *path, char **argv)
argp = sz - arglen - 4*(argc+1);
// Copy argv strings and pointers to stack.
*(uint*)(mem+argp-spoffset + 4*argc) = 0; // argv[argc]
*(uint*)(mem+argp-spbottom + 4*argc) = 0; // argv[argc]
for(i=argc-1; i>=0; i--){
len = strlen(argv[i]) + 1;
sp -= len;
memmove(mem+sp-spoffset, argv[i], len);
*(uint*)(mem+argp-spoffset + 4*i) = sp; // argv[i]
memmove(mem+sp-spbottom, argv[i], len);
*(uint*)(mem+argp-spbottom + 4*i) = sp; // argv[i]
}
// Stack frame for main(argc, argv), below arguments.
sp = argp;
sp -= 4;
*(uint*)(mem+sp-spoffset) = argp;
*(uint*)(mem+sp-spbottom) = argp;
sp -= 4;
*(uint*)(mem+sp-spoffset) = argc;
*(uint*)(mem+sp-spbottom) = argc;
sp -= 4;
*(uint*)(mem+sp-spoffset) = 0xffffffff; // fake return pc
*(uint*)(mem+sp-spbottom) = 0xffffffff; // fake return pc
// Save program name for debugging.
for(last=s=path; *s; s++)

7
proc.c
View file

@ -142,14 +142,15 @@ userinit(void)
int
growproc(int n)
{
uint sz = proc->sz;
if(n > 0){
if(!allocuvm(proc->pgdir, (char *)proc->sz, n))
if(!(sz = allocuvm(proc->pgdir, sz, sz + n)))
return -1;
} else if(n < 0){
if(!deallocuvm(proc->pgdir, (char *)(proc->sz + n), 0 - n))
if(!(sz = deallocuvm(proc->pgdir, sz, sz + n)))
return -1;
}
proc->sz += n;
proc->sz = sz;
switchuvm(proc);
return 0;
}

58
vm.c
View file

@ -228,54 +228,50 @@ loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
return 1;
}
// Allocate sz bytes more memory for a process starting at the
// given user address; allocates physical memory and page
// table entries. addr and sz need not be page-aligned.
// It is a no-op for any parts of the requested memory
// that are already allocated.
// Allocate memory to the process to bring its size from oldsz to
// newsz. Allocates physical memory and page table entries. oldsz and
// newsz need not be page-aligned, nor does newsz have to be larger
// than oldsz. Returns the new process size or 0 on error.
int
allocuvm(pde_t *pgdir, char *addr, uint sz)
allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
{
if(addr + sz > (char*)USERTOP)
if(newsz > USERTOP)
return 0;
char *a = PGROUNDDOWN(addr);
char *last = PGROUNDDOWN(addr + sz - 1);
for(; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte == 0 || (*pte & PTE_P) == 0){
char *mem = kalloc();
if(mem == 0){
cprintf("allocuvm out of memory\n");
deallocuvm(pgdir, addr, sz);
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
char *a = (char *)PGROUNDUP(oldsz);
char *last = PGROUNDDOWN(newsz - 1);
for (; a <= last; a += PGSIZE){
char *mem = kalloc();
if(mem == 0){
cprintf("allocuvm out of memory\n");
deallocuvm(pgdir, newsz, oldsz);
return 0;
}
memset(mem, 0, PGSIZE);
mappages(pgdir, a, PGSIZE, PADDR(mem), PTE_W|PTE_U);
}
return 1;
return newsz > oldsz ? newsz : oldsz;
}
// Deallocate some of the user pages. If addr is not page-aligned,
// then only deallocates starting at the next page boundary.
// Deallocate user pages to bring the process size from oldsz to
// newsz. oldsz and newsz need not be page-aligned, nor does newsz
// need to be less than oldsz. oldsz can be larger than the actual
// process size. Returns the new process size.
int
deallocuvm(pde_t *pgdir, char *addr, uint sz)
deallocuvm(pde_t *pgdir, uint oldsz, uint newsz)
{
if(addr + sz > (char*)USERTOP)
return 0;
char *a = (char *)PGROUNDUP((uint)addr);
char *last = PGROUNDDOWN(addr + sz - 1);
char *a = (char *)PGROUNDUP(newsz);
char *last = PGROUNDDOWN(oldsz - 1);
for(; a <= last; a += PGSIZE){
pte_t *pte = walkpgdir(pgdir, a, 0);
if(pte && (*pte & PTE_P) != 0){
uint pa = PTE_ADDR(*pte);
if(pa == 0)
panic("deallocuvm");
panic("kfree");
kfree((void *) pa);
*pte = 0;
}
}
return 1;
return newsz < oldsz ? newsz : oldsz;
}
// Free a page table and all the physical memory pages
@ -287,7 +283,7 @@ freevm(pde_t *pgdir)
if(!pgdir)
panic("freevm: no pgdir");
deallocuvm(pgdir, 0, USERTOP);
deallocuvm(pgdir, USERTOP, 0);
for(i = 0; i < NPDENTRIES; i++){
if(pgdir[i] & PTE_P)
kfree((void *) PTE_ADDR(pgdir[i]));