Rearrange vm.c so it's in logical order and prints nicely. Shorten a few functions in uninteresting ways to make them fit.

1 files changed, 129 insertions, 135 deletions

diff --git a/vm.c b/vm.c
index 9c0783d..f3436b7 100644
--- a/vm.c
+++ b/vm.c
@@ -6,33 +6,38 @@
 #include "proc.h"
 #include "elf.h"
 
-// The mappings from logical to linear 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.
-// 
-// setupkvm() and exec() set up every page table like this:
-//   0..640K          : user memory (text, data, stack, heap)
-//   640K..1M         : mapped direct (for IO space)
-//   1M..end          : mapped direct (for the kernel's text and data)
-//   end..PHYSTOP     : mapped direct (kernel heap and user pages)
-//   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 addresses
-// range from 0 till 640KB (USERTOP), which where the I/O hole starts
-// (both in physical memory and in the kernel's virtual address
-// space).
-
 #define USERTOP  0xA0000
 
 static pde_t *kpgdir;  // for use in scheduler()
 
+// Set up CPU's kernel segment descriptors.
+// Run once at boot time on each CPU.
+void
+ksegment(void)
+{
+  struct cpu *c;
+
+  // Map virtual addresses to linear addresses using identity map.
+  // Cannot share a CODE descriptor for both kernel and user
+  // because it would have to have DPL_USR, but the CPU forbids
+  // an interrupt from CPL=0 to DPL=3.
+  c = &cpus[cpunum()];
+  c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
+  c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
+  c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, DPL_USER);
+  c->gdt[SEG_UDATA] = SEG(STA_W, 0, 0xffffffff, DPL_USER);
+
+  // map cpu, and curproc
+  c->gdt[SEG_KCPU] = SEG(STA_W, &c->cpu, 8, 0);
+
+  lgdt(c->gdt, sizeof(c->gdt));
+  loadgs(SEG_KCPU << 3);
+  
+  // Initialize cpu-local storage.
+  cpu = c;
+  proc = 0;
+}
+
 // return the address of the PTE in page table pgdir
 // that corresponds to linear address va.  if create!=0,
 // create any required page table pages.
@@ -50,10 +55,8 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
     return 0;
   else {
     pgtab = (pte_t*) r;
-
     // Make sure all those PTE_P bits are zero.
     memset(pgtab, 0, PGSIZE);
-
     // The permissions here are overly generous, but they can
     // be further restricted by the permissions in the page table 
     // entries, if necessary.
@@ -68,9 +71,9 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
 static int
 mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
 {
-  char *first = PGROUNDDOWN(la);
+  char *a = PGROUNDDOWN(la);
   char *last = PGROUNDDOWN(la + size - 1);
-  char *a = first;
+
   while(1){
     pte_t *pte = walkpgdir(pgdir, a, 1);
     if(pte == 0)
@@ -86,32 +89,75 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
   return 1;
 }
 
-// Set up CPU's kernel segment descriptors.
-// Run once at boot time on each CPU.
+// The mappings from logical to linear 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.
+// 
+// setupkvm() and exec() set up every page table like this:
+//   0..640K          : user memory (text, data, stack, heap)
+//   640K..1M         : mapped direct (for IO space)
+//   1M..end          : mapped direct (for the kernel's text and data)
+//   end..PHYSTOP     : mapped direct (kernel heap and user pages)
+//   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 addresses
+// range from 0 till 640KB (USERTOP), which where the I/O hole starts
+// (both in physical memory and in the kernel's virtual address
+// space).
+
+// Allocate one page table for the machine for the kernel address
+// space for scheduler processes.
 void
-ksegment(void)
+kvmalloc(void)
 {
-  struct cpu *c;
+  kpgdir = setupkvm();
+}
 
-  // Map virtual addresses to linear addresses using identity map.
-  // Cannot share a CODE descriptor for both kernel and user
-  // because it would have to have DPL_USR, but the CPU forbids
-  // an interrupt from CPL=0 to DPL=3.
-  c = &cpus[cpunum()];
-  c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
-  c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
-  c->gdt[SEG_UCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, DPL_USER);
-  c->gdt[SEG_UDATA] = SEG(STA_W, 0, 0xffffffff, DPL_USER);
+// Set up kernel part of a page table.
+pde_t*
+setupkvm(void)
+{
+  pde_t *pgdir;
 
-  // map cpu, and curproc
-  c->gdt[SEG_KCPU] = SEG(STA_W, &c->cpu, 8, 0);
+  // Allocate page directory
+  if(!(pgdir = (pde_t *) kalloc()))
+    return 0;
+  memset(pgdir, 0, PGSIZE);
+  if(// Map IO space from 640K to 1Mbyte
+     !mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W) ||
+     // Map kernel and free memory pool
+     !mappages(pgdir, (void *)0x100000, PHYSTOP-0x100000, 0x100000, PTE_W) ||
+     // Map devices such as ioapic, lapic, ...
+     !mappages(pgdir, (void *)0xFE000000, 0x2000000, 0xFE000000, PTE_W))
+    return 0;
+  return pgdir;
+}
 
-  lgdt(c->gdt, sizeof(c->gdt));
-  loadgs(SEG_KCPU << 3);
-  
-  // Initialize cpu-local storage.
-  cpu = c;
-  proc = 0;
+// Turn on paging.
+void
+vmenable(void)
+{
+  uint cr0;
+
+  switchkvm(); // load kpgdir into cr3
+  cr0 = rcr0();
+  cr0 |= CR0_PG;
+  lcr0(cr0);
+}
+
+// Switch h/w page table register to the kernel-only page table, for when
+// no process is running.
+void
+switchkvm()
+{
+  lcr3(PADDR(kpgdir));   // Switch to the kernel page table
 }
 
 // Switch h/w page table and TSS registers to point to process p.
@@ -134,36 +180,6 @@ switchuvm(struct proc *p)
   popcli();
 }
 
-// Switch h/w page table register to the kernel-only page table, for when
-// no process is running.
-void
-switchkvm()
-{
-  lcr3(PADDR(kpgdir));   // Switch to the kernel page table
-}
-
-// Set up kernel part of a page table.
-pde_t*
-setupkvm(void)
-{
-  pde_t *pgdir;
-
-  // Allocate page directory
-  if(!(pgdir = (pde_t *) kalloc()))
-    return 0;
-  memset(pgdir, 0, PGSIZE);
-  // Map IO space from 640K to 1Mbyte
-  if(!mappages(pgdir, (void *)USERTOP, 0x60000, USERTOP, PTE_W))
-    return 0;
-  // Map kernel and free memory pool
-  if(!mappages(pgdir, (void *)0x100000, PHYSTOP-0x100000, 0x100000, PTE_W))
-    return 0;
-  // Map devices such as ioapic, lapic, ...
-  if(!mappages(pgdir, (void *)0xFE000000, 0x2000000, 0xFE000000, PTE_W))
-    return 0;
-  return pgdir;
-}
-
 // return the physical address that a given user address
 // maps to. the result is also a kernel logical address,
 // since the kernel maps the physical memory allocated to user
@@ -177,6 +193,37 @@ uva2ka(pde_t *pgdir, char *uva)
   return (char *)pa;
 }
 
+void
+inituvm(pde_t *pgdir, char *init, uint sz)
+{
+  char *mem = kalloc();
+  if (sz >= PGSIZE)
+    panic("inituvm: more than a page");
+  memset(mem, 0, PGSIZE);
+  mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
+  memmove(mem, init, sz);
+}
+
+int
+loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
+{
+  uint i, pa, n;
+  pte_t *pte;
+
+  if((uint)addr % PGSIZE != 0)
+    panic("loaduvm: addr must be page aligned\n");
+  for(i = 0; i < sz; i += PGSIZE){
+    if(!(pte = walkpgdir(pgdir, addr+i, 0)))
+      panic("loaduvm: address should exist\n");
+    pa = PTE_ADDR(*pte);
+    if(sz - i < PGSIZE) n = sz - i;
+    else n = PGSIZE;
+    if(readi(ip, (char *)pa, offset+i, n) != n)
+      return 0;
+  }
+  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.
@@ -187,10 +234,9 @@ allocuvm(pde_t *pgdir, char *addr, uint sz)
 {
   if(addr + sz > (char*)USERTOP)
     return 0;
-  char *first = PGROUNDDOWN(addr);
+  char *a = PGROUNDDOWN(addr);
   char *last = PGROUNDDOWN(addr + sz - 1);
-  char *a;
-  for(a = first; a <= last; a += PGSIZE){
+  for(; a <= last; a += PGSIZE){
     pte_t *pte = walkpgdir(pgdir, a, 0);
     if(pte == 0 || (*pte & PTE_P) == 0){
       char *mem = kalloc();
@@ -213,10 +259,9 @@ deallocuvm(pde_t *pgdir, char *addr, uint sz)
 {
   if(addr + sz > (char*)USERTOP)
     return 0;
-  char *first = (char*) PGROUNDUP((uint)addr);
+  char *a = (char *)PGROUNDUP((uint)addr);
   char *last = PGROUNDDOWN(addr + sz - 1);
-  char *a;
-  for(a = first; a <= last; a += PGSIZE){
+  for(; a <= last; a += PGSIZE){
     pte_t *pte = walkpgdir(pgdir, a, 0);
     if(pte && (*pte & PTE_P) != 0){
       uint pa = PTE_ADDR(*pte);
@@ -246,37 +291,6 @@ freevm(pde_t *pgdir)
   kfree((void *) pgdir);
 }
 
-int
-loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
-{
-  uint i, pa, n;
-  pte_t *pte;
-
-  if((uint)addr % PGSIZE != 0)
-    panic("loaduvm: addr must be page aligned\n");
-  for(i = 0; i < sz; i += PGSIZE){
-    if(!(pte = walkpgdir(pgdir, addr+i, 0)))
-      panic("loaduvm: address should exist\n");
-    pa = PTE_ADDR(*pte);
-    if(sz - i < PGSIZE) n = sz - i;
-    else n = PGSIZE;
-    if(readi(ip, (char *)pa, offset+i, n) != n)
-      return 0;
-  }
-  return 1;
-}
-
-void
-inituvm(pde_t *pgdir, char *init, uint sz)
-{
-  char *mem = kalloc();
-  if (sz >= PGSIZE)
-    panic("inituvm: more than a page");
-  memset(mem, 0, PGSIZE);
-  mappages(pgdir, 0, PGSIZE, PADDR(mem), PTE_W|PTE_U);
-  memmove(mem, init, sz);
-}
-
 // given a parent process's page table, create a copy
 // of it for a child.
 pde_t*
@@ -307,23 +321,3 @@ bad:
   return 0;
 }
 
-// Allocate one page table for the machine for the kernel address
-// space for scheduler processes.
-void
-kvmalloc(void)
-{
-  kpgdir = setupkvm();
-}
-
-// Turn on paging.
-void
-vmenable(void)
-{
-  uint cr0;
-
-  switchkvm(); // load kpgdir into cr3
-  cr0 = rcr0();
-  cr0 |= CR0_PG;
-  lcr0(cr0);
-}
-