Use static page table for boot, mapping first 4Mbyte; no more segment trick
Allocate proper kernel page table immediately in main using boot allocator Remove pginit Simplify address space layout a tiny bit More to come (e.g., superpages to simplify static table)
This commit is contained in:
Frans Kaashoek
parent
3a03810643
commit
66ba8079c7
9 changed files with 1101 additions and 103 deletions
5
Makefile
5
Makefile
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@ -72,7 +72,8 @@ AS = $(TOOLPREFIX)gas
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LD = $(TOOLPREFIX)ld
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OBJCOPY = $(TOOLPREFIX)objcopy
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OBJDUMP = $(TOOLPREFIX)objdump
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CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
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#CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
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CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
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CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
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ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
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# FreeBSD ld wants ``elf_i386_fbsd''
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@ -198,7 +199,7 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
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then echo "-gdb tcp::$(GDBPORT)"; \
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else echo "-s -p $(GDBPORT)"; fi)
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ifndef CPUS
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CPUS := 2
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CPUS := 1
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endif
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QEMUOPTS = -hdb fs.img xv6.img -smp $(CPUS) -m 512
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5
defs.h
5
defs.h
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@ -62,7 +62,7 @@ extern uchar ioapicid;
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void ioapicinit(void);
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// kalloc.c
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char* pgalloc(void);
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char* boot_alloc(void);
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char* kalloc(void);
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void kfree(char*);
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void kinit(void);
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@ -161,11 +161,10 @@ void uartintr(void);
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void uartputc(int);
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// vm.c
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void pginit(char* (*alloc)());
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void seginit(void);
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void kvmalloc(void);
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void vmenable(void);
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pde_t* setupkvm(void);
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pde_t* setupkvm(char* (*alloc)());
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char* uva2ka(pde_t*, char*);
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int allocuvm(pde_t*, uint, uint);
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int deallocuvm(pde_t*, uint, uint);
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2
exec.c
2
exec.c
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@ -29,7 +29,7 @@ exec(char *path, char **argv)
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if(elf.magic != ELF_MAGIC)
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goto bad;
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if((pgdir = setupkvm()) == 0)
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if((pgdir = setupkvm(kalloc)) == 0)
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goto bad;
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// Load program into memory.
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4
kalloc.c
4
kalloc.c
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@ -23,11 +23,13 @@ char *newend;
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// simple page allocator to get off the ground during boot
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char *
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pgalloc(void)
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boot_alloc(void)
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{
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if (newend == 0)
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newend = end;
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if ((uint) newend >= KERNBASE + 0x400000)
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panic("only first 4Mbyte are mapped during boot");
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void *p = (void*)PGROUNDUP((uint)newend);
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memset(p, 0, PGSIZE);
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newend = newend + PGSIZE;
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@ -5,8 +5,7 @@
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#define KSTKSIZE (8*PGSIZE) // size of a kernel stack
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#define IOSPACEB 0x0A0000 // begin IO space
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#define IOSPACEE 0x100000 // end IO space
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#define DEVSPACE 0xFE000000 // other devices are in the top of the phys address space
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#define PHYSTOP 0xE000000 // use phys mem up to here as free pool
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// Key addresses for address space layout (see kmap in vm.c for the layout)
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27
multiboot.S
27
multiboot.S
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@ -41,8 +41,8 @@ multiboot_header:
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# boot loader - bootasm.S - sets up.
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.globl multiboot_entry
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multiboot_entry:
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lgdt V2P_WO(gdtdesc)
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ljmp $(SEG_KCODE<<3), $mbstart32
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# lgdt V2P_WO(gdtdesc)
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# ljmp $(SEG_KCODE<<3), $mbstart32
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mbstart32:
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# Set up the protected-mode data segment registers
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@ -54,21 +54,22 @@ mbstart32:
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movw %ax, %fs # -> FS
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movw %ax, %gs # -> GS
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movl $(V2P_WO(bootpgdir)), %eax
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movl %eax, %cr3
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# Turn on paging.
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movl %cr0, %eax
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orl $(CR0_PE|CR0_PG|CR0_WP), %eax
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movl %eax, %cr0
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# now switch to using addresses above KERNBASE
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# call addresses are pc-relative so we jump though this hoop:
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mov $relocated, %eax
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jmp *%eax
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relocated:
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# Set up the stack pointer and call into C.
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movl $(stack + STACK), %esp
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call main
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spin:
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jmp spin
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# Bootstrap GDT
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.p2align 2 # force 4 byte alignment
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gdt:
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SEG_NULLASM # null seg
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SEG_ASM(STA_X|STA_R, -KERNBASE, 0xffffffff) # code seg
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SEG_ASM(STA_W, -KERNBASE, 0xffffffff) # data seg
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gdtdesc:
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.word (gdtdesc - gdt - 1) # sizeof(gdt) - 1
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.long V2P_WO(gdt) # address gdt
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.comm stack, STACK
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2
proc.c
2
proc.c
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@ -83,7 +83,7 @@ userinit(void)
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p = allocproc();
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initproc = p;
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if((p->pgdir = setupkvm()) == 0)
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if((p->pgdir = setupkvm(kalloc)) == 0)
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panic("userinit: out of memory?");
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inituvm(p->pgdir, _binary_initcode_start, (int)_binary_initcode_size);
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p->sz = PGSIZE;
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94
vm.c
94
vm.c
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@ -11,64 +11,6 @@ extern char data[]; // defined in data.S
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static pde_t *kpgdir; // for use in scheduler()
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struct segdesc gdt[NSEGS];
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// page map for during boot
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// XXX build a static page table in assembly
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static void
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pgmap(void *va, void *last, uint pa)
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{
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pde_t *pde;
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pte_t *pgtab;
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pte_t *pte;
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for(;;){
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pde = &kpgdir[PDX(va)];
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pde_t pdev = *pde;
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if (pdev == 0) {
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pgtab = (pte_t *) pgalloc();
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*pde = v2p(pgtab) | PTE_P | PTE_W;
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} else {
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pgtab = (pte_t*)p2v(PTE_ADDR(pdev));
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}
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pte = &pgtab[PTX(va)];
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*pte = pa | PTE_W | PTE_P;
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if(va == last)
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break;
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va += PGSIZE;
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pa += PGSIZE;
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}
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}
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// set up a page table to get off the ground
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void
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pginit(char* (*alloc)(void))
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{
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uint cr0;
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kpgdir = (pde_t *) alloc();
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pgmap((void *) 0, (void *) PHYSTOP, 0); // map pa 0 at va 0
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pgmap((void *) KERNBASE, (void *) (KERNBASE+PHYSTOP), 0); // map pa 0 at va KERNBASE
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pgmap((void*)0xFE000000, 0, 0xFE000000);
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switchkvm(); // load kpgdir into cr3
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cr0 = rcr0();
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cr0 |= CR0_PG;
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lcr0(cr0); // paging on
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// new gdt
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gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0xffffffff, 0);
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gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
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lgdt((void *)v2p(gdt), sizeof(gdt));
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loadgs(SEG_KDATA << 3);
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loadfs(SEG_KDATA << 3);
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loades(SEG_KDATA << 3);
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loadds(SEG_KDATA << 3);
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loadss(SEG_KDATA << 3);
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__asm volatile("ljmp %0,$1f\n 1:\n" :: "i" (SEG_KCODE << 3)); // reload cs
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}
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// Set up CPU's kernel segment descriptors.
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// Run once at boot time on each CPU.
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void
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@ -101,7 +43,7 @@ seginit(void)
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// that corresponds to linear address va. If create!=0,
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// create any required page table pages.
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static pte_t *
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walkpgdir(pde_t *pgdir, const void *va, int create)
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walkpgdir(pde_t *pgdir, const void *va, int create, char* (*alloc)(void))
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{
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pde_t *pde;
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pte_t *pgtab;
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@ -110,7 +52,7 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
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if(*pde & PTE_P){
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pgtab = (pte_t*)p2v(PTE_ADDR(*pde));
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} else {
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if(!create || (pgtab = (pte_t*)kalloc()) == 0)
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if(!create || (pgtab = (pte_t*)alloc()) == 0)
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return 0;
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// Make sure all those PTE_P bits are zero.
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memset(pgtab, 0, PGSIZE);
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@ -126,7 +68,7 @@ walkpgdir(pde_t *pgdir, const void *va, int create)
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// physical addresses starting at pa. la and size might not
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// be page-aligned.
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static int
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mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
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mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm, char* (*alloc)(void))
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{
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char *a, *last;
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pte_t *pte;
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@ -134,7 +76,7 @@ mappages(pde_t *pgdir, void *la, uint size, uint pa, int perm)
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a = PGROUNDDOWN(la);
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last = PGROUNDDOWN(la + size - 1);
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for(;;){
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pte = walkpgdir(pgdir, a, 1);
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pte = walkpgdir(pgdir, a, 1, alloc);
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if(pte == 0)
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return -1;
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if(*pte & PTE_P)
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@ -175,25 +117,25 @@ static struct kmap {
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uint e;
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int perm;
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} kmap[] = {
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{ P2V(IOSPACEB), IOSPACEB, IOSPACEE, PTE_W}, // I/O space
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{ P2V(0), 0, 1024*1024, PTE_W}, // First 1Mbyte contains BIOS and IO section
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{ (void *)KERNLINK, V2P(KERNLINK), V2P(data), 0}, // kernel text, rodata
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{ data, V2P(data), PHYSTOP, PTE_W}, // kernel data, memory
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{ (void*)0xFE000000, 0xFE000000, 0, PTE_W}, // device mappings
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{ (void*)DEVSPACE, DEVSPACE, 0, PTE_W}, // device mappings
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};
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// Set up kernel part of a page table.
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pde_t*
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setupkvm(void)
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setupkvm(char* (*alloc)(void))
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{
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pde_t *pgdir;
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struct kmap *k;
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if((pgdir = (pde_t*)kalloc()) == 0)
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if((pgdir = (pde_t*)alloc()) == 0)
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return 0;
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memset(pgdir, 0, PGSIZE);
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k = kmap;
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for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
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if(mappages(pgdir, k->l, k->e - k->p, (uint)k->p, k->perm) < 0)
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if(mappages(pgdir, k->l, k->e - k->p, (uint)k->p, k->perm, alloc) < 0)
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return 0;
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return pgdir;
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@ -204,7 +146,7 @@ setupkvm(void)
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void
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kvmalloc(void)
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{
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kpgdir = setupkvm();
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kpgdir = setupkvm(boot_alloc);
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switchkvm();
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}
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@ -265,7 +207,7 @@ inituvm(pde_t *pgdir, char *init, uint sz)
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panic("inituvm: more than a page");
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mem = kalloc();
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memset(mem, 0, PGSIZE);
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mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U);
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mappages(pgdir, 0, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc);
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memmove(mem, init, sz);
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}
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@ -280,7 +222,7 @@ loaduvm(pde_t *pgdir, char *addr, struct inode *ip, uint offset, uint sz)
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if((uint)addr % PGSIZE != 0)
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panic("loaduvm: addr must be page aligned");
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for(i = 0; i < sz; i += PGSIZE){
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if((pte = walkpgdir(pgdir, addr+i, 0)) == 0)
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if((pte = walkpgdir(pgdir, addr+i, 0, kalloc)) == 0)
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panic("loaduvm: address should exist");
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pa = PTE_ADDR(*pte);
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if(sz - i < PGSIZE)
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@ -315,7 +257,7 @@ allocuvm(pde_t *pgdir, uint oldsz, uint newsz)
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return 0;
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}
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memset(mem, 0, PGSIZE);
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mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U);
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mappages(pgdir, (char*)a, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc);
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}
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return newsz;
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}
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@ -335,7 +277,7 @@ deallocuvm(pde_t *pgdir, uint oldsz, uint newsz)
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a = PGROUNDUP(newsz);
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for(; a < oldsz; a += PGSIZE){
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pte = walkpgdir(pgdir, (char*)a, 0);
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pte = walkpgdir(pgdir, (char*)a, 0, kalloc);
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if(pte && (*pte & PTE_P) != 0){
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pa = PTE_ADDR(*pte);
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if(pa == 0)
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@ -377,10 +319,10 @@ copyuvm(pde_t *pgdir, uint sz)
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uint pa, i;
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char *mem;
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if((d = setupkvm()) == 0)
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if((d = setupkvm(kalloc)) == 0)
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return 0;
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for(i = 0; i < sz; i += PGSIZE){
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if((pte = walkpgdir(pgdir, (void*)i, 0)) == 0)
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if((pte = walkpgdir(pgdir, (void*)i, 0, kalloc)) == 0)
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panic("copyuvm: pte should exist");
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if(!(*pte & PTE_P))
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panic("copyuvm: page not present");
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@ -388,7 +330,7 @@ copyuvm(pde_t *pgdir, uint sz)
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if((mem = kalloc()) == 0)
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goto bad;
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memmove(mem, (char*)p2v(pa), PGSIZE);
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if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U) < 0)
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if(mappages(d, (void*)i, PGSIZE, v2p(mem), PTE_W|PTE_U, kalloc) < 0)
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goto bad;
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}
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return d;
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@ -405,7 +347,7 @@ uva2ka(pde_t *pgdir, char *uva)
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{
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pte_t *pte;
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pte = walkpgdir(pgdir, uva, 0);
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pte = walkpgdir(pgdir, uva, 0, kalloc);
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if((*pte & PTE_P) == 0)
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return 0;
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if((*pte & PTE_U) == 0)
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