sanchayanmaity/xv6-cs450
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity

Cleanup comments and fit setupkvm on same page as kmap, which aligns lots of other things

Browse source
This commit is contained in:
Austin Clements 2011-09-02 14:34:29 -04:00
parent 14835ec987
commit 9e4272c14e
1 changed files with 6 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
vm.c
View file

@ -92,10 +92,9 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa,
// The mappings from logical to virtual are one to one (i.e.,
// segmentation doesn't do anything). There is one page table per
// process, plus one that's used when a CPU is not running any
// process (kpgdir). A user process uses the same page table as
// the kernel; the page protection bits prevent it from using
// anything other than its memory.
// process, plus one that's used when a CPU is not running any process
// (kpgdir). A user process uses the same page table as the kernel; the
// page protection bits prevent it from accessing kernel memory.
//
// setupkvm() and exec() set up every page table like this:
// 0..KERNBASE: user memory (text+data+stack+heap), mapped to some free
@ -108,10 +107,9 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa,
// 0xfe000000..0: mapped direct (devices such as ioapic)
//
// The kernel allocates memory for its heap and for user memory
// between kernend and the end of physical memory (PHYSTOP).
// The virtual address space of each user program includes the kernel
// (which is inaccessible in user mode). The user program sits in
// the bottom of the address space, and the kernel at the top at KERNBASE.
// between KERNBASE+end and the end of physical memory (PHYSTOP).
// The user program sits in the bottom of the address space, and the
// kernel at the top at KERNBASE.
static struct kmap {
void *virt;
uint phys_start;
@ -134,14 +132,12 @@ setupkvm(char* (*alloc)(void))
if((pgdir = (pde_t*)alloc()) == 0)
return 0;
memset(pgdir, 0, PGSIZE);
k = kmap;
if (p2v(PHYSTOP) > (void*)DEVSPACE)
panic("PHYSTOP too high");
for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
if(mappages(pgdir, k->virt, k->phys_end - k->phys_start,
(uint)k->phys_start, k->perm, alloc) < 0)
return 0;
return pgdir;
}