mem.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * Memory and machine-specific definitions.  Used in C and assembler.
 */

/*
 * Sizes
 */
#define	BI2BY		8			/* bits per byte */
#define	BI2WD		32			/* bits per word */
#define	BY2WD		4			/* bytes per word */
#define	BY2V		8			/* bytes per double word */
#define	BY2PG		4096			/* bytes per page */
#define	WD2PG		(BY2PG/BY2WD)		/* words per page */
#define	BY2XPG		(4096*1024)	/* bytes per big page */
#define	PGSHIFT		12			/* log(BY2PG) */
#define	ROUND(s, sz)	(((s)+((sz)-1))&~((sz)-1))
#define	PGROUND(s)	ROUND(s, BY2PG)
#define	BLOCKALIGN	8

#define	MAXMACH		8			/* max # cpus system can run */
#define	KSTACK		4096			/* Size of kernel stack */

/*
 * Time
 */
#define	HZ		(100)			/* clock frequency */
#define	MS2HZ		(1000/HZ)		/* millisec per clock tick */
#define	TK2SEC(t)	((t)/HZ)		/* ticks to seconds */

/*
 *  Address spaces
 */
#define	KZERO		0xF0000000		/* base of kernel address space */
#define	KTZERO		(KZERO+0x100000)		/* first address in kernel text - 9load sits below */
#define	VPT			(KZERO-VPTSIZE)
#define	VPTSIZE		BY2XPG
#define	NVPT		(VPTSIZE/BY2WD)
#define	KMAP		(VPT-KMAPSIZE)
#define	KMAPSIZE	BY2XPG
#define	VMAP		(KMAP-VMAPSIZE)
#define	VMAPSIZE	(0x10000000-VPTSIZE-KMAPSIZE)
#define	UZERO		0			/* base of user address space */
#define	UTZERO		(UZERO+BY2PG)		/* first address in user text */
#define	USTKTOP		(VMAP-BY2PG)		/* byte just beyond user stack */
#define	USTKSIZE	(16*1024*1024)		/* size of user stack */
#define	TSTKTOP		(USTKTOP-USTKSIZE)	/* end of new stack in sysexec */
#define	TSTKSIZ 	100

/*
 * Fundamental addresses - bottom 64kB saved for return to real mode
 */
#define	CONFADDR	(KZERO+0x1200)		/* info passed from boot loader */
#define	TMPADDR		(KZERO+0x2000)		/* used for temporary mappings */
#define	APBOOTSTRAP	(KZERO+0x3000)		/* AP bootstrap code */
#define	RMUADDR		(KZERO+0x7C00)		/* real mode Ureg */
#define	RMCODE		(KZERO+0x8000)		/* copy of first page of KTEXT */
#define	RMBUF		(KZERO+0x9000)		/* buffer for user space - known to vga */
#define	IDTADDR		(KZERO+0x10800)		/* idt */
#define	REBOOTADDR	(0x11000)		/* reboot code - physical address */
#define	CPU0PDB		(KZERO+0x12000)		/* bootstrap processor PDB */
#define	CPU0PTE		(KZERO+0x13000)		/* bootstrap processor PTE's for 0-4MB */
#define	CPU0GDT		(KZERO+0x14000)		/* bootstrap processor GDT */
#define	MACHADDR	(KZERO+0x15000)		/* as seen by current processor */
#define	CPU0MACH	(KZERO+0x16000)		/* Mach for bootstrap processor */
#define	MACHSIZE	BY2PG
/*
 * N.B.  ramscan knows that CPU0MACH+BY2PG is the end of reserved data
 * N.B.  _startPADDR knows that CPU0PDB is the first reserved page
 * and that there are 5 of them.
 */

/*
 *  known x86 segments (in GDT) and their selectors
 */
#define	NULLSEG	0	/* null segment */
#define	KDSEG	1	/* kernel data/stack */
#define	KESEG	2	/* kernel executable */	
#define	UDSEG	3	/* user data/stack */
#define	UESEG	4	/* user executable */
#define	TSSSEG	5	/* task segment */
#define	APMCSEG		6	/* APM code segment */
#define	APMCSEG16	7	/* APM 16-bit code segment */
#define	APMDSEG		8	/* APM data segment */
#define	KESEG16		9	/* kernel executable 16-bit */
#define	NGDT		10	/* number of GDT entries required */
/* #define	APM40SEG	8	/* APM segment 0x40 */

#define	SELGDT	(0<<2)	/* selector is in gdt */
#define	SELLDT	(1<<2)	/* selector is in ldt */

#define	SELECTOR(i, t, p)	(((i)<<3) | (t) | (p))

#define	NULLSEL	SELECTOR(NULLSEG, SELGDT, 0)
#define	KDSEL	SELECTOR(KDSEG, SELGDT, 0)
#define	KESEL	SELECTOR(KESEG, SELGDT, 0)
#define	UESEL	SELECTOR(UESEG, SELGDT, 3)
#define	UDSEL	SELECTOR(UDSEG, SELGDT, 3)
#define	TSSSEL	SELECTOR(TSSSEG, SELGDT, 0)
#define	APMCSEL 	SELECTOR(APMCSEG, SELGDT, 0)
#define	APMCSEL16	SELECTOR(APMCSEG16, SELGDT, 0)
#define	APMDSEL		SELECTOR(APMDSEG, SELGDT, 0)
/* #define	APM40SEL	SELECTOR(APM40SEG, SELGDT, 0) */

/*
 *  fields in segment descriptors
 */
#define	SEGDATA	(0x10<<8)	/* data/stack segment */
#define	SEGEXEC	(0x18<<8)	/* executable segment */
#define	SEGTSS	(0x9<<8)	/* TSS segment */
#define	SEGCG	(0x0C<<8)	/* call gate */
#define	SEGIG	(0x0E<<8)	/* interrupt gate */
#define	SEGTG	(0x0F<<8)	/* trap gate */
#define	SEGTYPE	(0x1F<<8)

#define	SEGP	(1<<15)		/* segment present */
#define	SEGPL(x) ((x)<<13)	/* priority level */
#define	SEGB	(1<<22)		/* granularity 1==4k (for expand-down) */
#define	SEGG	(1<<23)		/* granularity 1==4k (for other) */
#define	SEGE	(1<<10)		/* expand down */
#define	SEGW	(1<<9)		/* writable (for data/stack) */
#define	SEGR	(1<<9)		/* readable (for code) */
#define	SEGD	(1<<22)		/* default 1==32bit (for code) */

/*
 *  virtual MMU
 */
#define	PTEMAPMEM	(1024*1024)	
#define	PTEPERTAB	(PTEMAPMEM/BY2PG)
#define	SEGMAPSIZE	1984
#define	SSEGMAPSIZE	16
#define	PPN(x)		((x)&~(BY2PG-1))

/*
 *  physical MMU
 */
#define	PTEVALID	(1<<0)
#define	PTEWT		(1<<3)
#define	PTEUNCACHED	(1<<4)
#define	PTEWRITE	(1<<1)
#define	PTERONLY	(0<<1)
#define	PTEKERNEL	(0<<2)
#define	PTEUSER		(1<<2)
#define	PTESIZE		(1<<7)
#define	PTEGLOBAL	(1<<8)

/*
 * Macros for calculating offsets within the page directory base
 * and page tables. 
 */
#define	PDX(va)		((((ulong)(va))>>22) & 0x03FF)
#define	PTX(va)		((((ulong)(va))>>12) & 0x03FF)

#define	getpgcolor(a)	0