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more regular kmap[] and description

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This commit is contained in:
Robert Morris 2011-09-13 12:28:45 -04:00
parent 90a81b3228
commit 7e7cb106d0
3 changed files with 27 additions and 24 deletions
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2
entry.S
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@ -36,7 +36,7 @@ multiboot_header:
.globl _start
_start = V2P_WO(entry)
# Entering xv6 on boot processor. Machine is mostly set up.
# Entering xv6 on boot processor, with paging off.
.globl entry
entry:
# Turn on page size extension for 4Mbyte pages

8
memlayout.h
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@ -10,13 +10,13 @@
#ifndef __ASSEMBLER__
static inline uint v2p(void *a) { return (uint) a - KERNBASE; }
static inline void *p2v(uint a) { return (void *) a + KERNBASE; }
static inline uint v2p(void *a) { return ((uint) (a)) - KERNBASE; }
static inline void *p2v(uint a) { return (void *) ((a) + KERNBASE); }
#endif
#define V2P(a) ((uint) a - KERNBASE)
#define P2V(a) ((void *) a + KERNBASE)
#define V2P(a) (((uint) (a)) - KERNBASE)
#define P2V(a) (((void *) (a)) + KERNBASE)
#define V2P_WO(x) ((x) - KERNBASE) // same as V2P, but without casts
#define P2V_WO(x) ((x) + KERNBASE) // same as V2P, but without casts

41
vm.c
View file

@ -90,36 +90,39 @@ mappages(pde_t *pgdir, void *va, uint size, uint pa,
return 0;
}
// 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 accessing kernel memory.
// There is one page table per process, plus one that's used when
// a CPU is not running any process (kpgdir). The kernel uses the
// current process's page table during system calls and interrupts;
// page protection bits prevent user code from using the kernel's
// mappings.
//
// setupkvm() and exec() set up every page table like this:
// 0..KERNBASE: user memory (text+data+stack+heap), mapped to some free
// phys memory
//
// 0..KERNBASE: user memory (text+data+stack+heap), mapped to
// phys memory allocated by the kernel
// KERNBASE..KERNBASE+EXTMEM: mapped to 0..EXTMEM (for I/O space)
// KERNBASE+EXTMEM..KERNBASE+end: mapped to EXTMEM..end kernel,
// w. no write permission
// KERNBASE+end..KERBASE+PHYSTOP: mapped to end..PHYSTOP,
// rw data + free memory
// KERNBASE+EXTMEM..data: mapped to EXTMEM..V2P(data)
// for the kernel's instructions and r/o data
// data..KERNBASE+PHYSTOP: mapped to V2P(data)..PHYSTOP,
// rw data + free physical memory
// 0xfe000000..0: mapped direct (devices such as ioapic)
//
// The kernel allocates memory for its heap and for user memory
// 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.
// The kernel allocates physical memory for its heap and for user memory
// between V2P(end) and the end of physical memory (PHYSTOP)
// (directly addressable from end..P2V(PHYSTOP)).
// This table defines the kernel's mappings, which are present in
// every process's page table.
static struct kmap {
void *virt;
uint phys_start;
uint phys_end;
int perm;
} kmap[] = {
{ P2V(0), 0, 1024*1024, PTE_W}, // I/O space
{ (void*)KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text+rodata
{ data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory
{ (void*)DEVSPACE, DEVSPACE, 0, PTE_W}, // more devices
{ (void*) KERNBASE, 0, EXTMEM, PTE_W}, // I/O space
{ (void*) KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text+rodata
{ (void*) data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory
{ (void*) DEVSPACE, DEVSPACE, 0, PTE_W}, // more devices
};
// Set up kernel part of a page table.