msic.c

一个简单的操作系统minix的核心代码

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				src/kernel/misc.c	 	 
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08800	/* This file contains a collection of miscellaneous procedures:
08801	 *      mem_init:       initialize memory tables.  Some memory is reported
08802	 *                      by the BIOS, some is guesstimated and checked later
08803	 *      env_parse       parse environment variable.
08804	 *      bad_assertion   for debugging
08805	 *      bad_compare     for debugging
08806	 */
08807	
08808	#include "kernel.h"
08809	#include "assert.h"
08810	#include <stdlib.h>
08811	#include <minix/com.h>
08812	
08813	#define EM_BASE     0x100000L   /* base of extended memory on AT's */
08814	#define SHADOW_BASE 0xFA0000L   /* base of RAM shadowing ROM on some AT's */
08815	#define SHADOW_MAX  0x060000L   /* maximum usable shadow memory (16M limit) */
08816	
08817	/*=========================================================================*
08818	 *                              mem_init                                   *
08819	 *=========================================================================*/
08820	PUBLIC void mem_init()
08821	{
08822	/* Initialize the memory size tables.  This is complicated by fragmentation
08823	 * and different access strategies for protected mode.  There must be a
08824	 * chunk at 0 big enough to hold Minix proper.  For 286 and 386 processors,
08825	 * there can be extended memory (memory above 1MB).  This usually starts at
08826	 * 1MB, but there may be another chunk just below 16MB, reserved under DOS
08827	 * for shadowing ROM, but available to Minix if the hardware can be re-mapped.
08828	 * In protected mode, extended memory is accessible assuming CLICK_SIZE is
08829	 * large enough, and is treated as ordinary memory.
08830	 */
08831	
08832	  u32_t ext_clicks;
08833	  phys_clicks max_clicks;
08834	
08835	  /* Get the size of ordinary memory from the BIOS. */
08836	  mem[0].size = k_to_click(low_memsize);        /* base = 0 */
08837	
08838	  if (pc_at && protected_mode) {
08839	        /* Get the size of extended memory from the BIOS.  This is special
08840	         * except in protected mode, but protected mode is now normal.
08841	         * Note that no more than 16M can be addressed in 286 mode, so make
08842	         * sure that the highest memory address fits in a short when counted
08843	         * in clicks.
08844	         */
08845	        ext_clicks = k_to_click((u32_t) ext_memsize);
08846	        max_clicks = USHRT_MAX - (EM_BASE >> CLICK_SHIFT);
08847	        mem[1].size = MIN(ext_clicks, max_clicks);
08848	        mem[1].base = EM_BASE >> CLICK_SHIFT;
08849	
08850	        if (ext_memsize <= (unsigned) ((SHADOW_BASE - EM_BASE) / 1024)
08851	                        && check_mem(SHADOW_BASE, SHADOW_MAX) == SHADOW_MAX) {
08852	                /* Shadow ROM memory. */
08853	                mem[2].size = SHADOW_MAX >> CLICK_SHIFT;
08854	                mem[2].base = SHADOW_BASE >> CLICK_SHIFT;
08855	        }
08856	  }
08857	
08858	  /* Total system memory. */
08859	  tot_mem_size = mem[0].size + mem[1].size + mem[2].size;
08860	}
	
08862	/*=========================================================================*
08863	 *                              env_parse                                  *
08864	 *=========================================================================*/
08865	PUBLIC int env_parse(env, fmt, field, param, min, max)
08866	char *env;              /* environment variable to inspect */
08867	char *fmt;              /* template to parse it with */
08868	int field;              /* field number of value to return */
08869	long *param;            /* address of parameter to get */
08870	long min, max;          /* minimum and maximum values for the parameter */
08871	{
08872	/* Parse an environment variable setting, something like "DPETH0=300:3".
08873	 * Panic if the parsing fails.  Return EP_UNSET if the environment variable
08874	 * is not set, EP_OFF if it is set to "off", EP_ON if set to "on" or a
08875	 * field is left blank, or EP_SET if a field is given (return value through
08876	 * *param).  Commas and colons may be used in the environment and format
08877	 * string, fields in the environment string may be empty, and punctuation
08878	 * may be missing to skip fields.  The format string contains characters
08879	 * 'd', 'o', 'x' and 'c' to indicate that 10, 8, 16, or 0 is used as the
08880	 * last argument to strtol.
08881	 */
08882	
08883	  char *val, *end;
08884	  long newpar;
08885	  int i = 0, radix, r;
08886	
08887	  if ((val = k_getenv(env)) == NIL_PTR) return(EP_UNSET);
08888	  if (strcmp(val, "off") == 0) return(EP_OFF);
08889	  if (strcmp(val, "on") == 0) return(EP_ON);
08890	
08891	  r = EP_ON;
08892	  for (;;) {
08893	        while (*val == ' ') val++;
08894	
08895	        if (*val == 0) return(r);       /* the proper exit point */
08896	
08897	        if (*fmt == 0) break;           /* too many values */
08898	
08899	        if (*val == ',' || *val == ':') {
08900	                /* Time to go to the next field. */
08901	                if (*fmt == ',' || *fmt == ':') i++;
08902	                if (*fmt++ == *val) val++;
08903	        } else {
08904	                /* Environment contains a value, get it. */
08905	                switch (*fmt) {
08906	                case 'd':       radix =   10;   break;
08907	                case 'o':       radix =  010;   break;
08908	                case 'x':       radix = 0x10;   break;
08909	                case 'c':       radix =    0;   break;
08910	                default:        goto badenv;
08911	                }
08912	                newpar = strtol(val, &end, radix);
08913	
08914	                if (end == val) break;  /* not a number */
08915	                val = end;
08916	
08917	                if (i == field) {
08918	                        /* The field requested. */
08919	                        if (newpar < min || newpar > max) break;
08920	                        *param = newpar;
08921	                        r = EP_SET;
08922	                }
08923	        }
08924	  }
08925	badenv:
08926	  printf("Bad environment setting: '%s = %s'\n", env, k_getenv(env));
08927	  panic("", NO_NUM);
08928	  /*NOTREACHED*/
08929	}
	
08931	#if DEBUG
08932	/*=========================================================================*
08933	 *                              bad_assertion                              *
08934	 *=========================================================================*/
08935	PUBLIC void bad_assertion(file, line, what)
08936	char *file;
08937	int line;
08938	char *what;
08939	{
08940	  printf("panic at %s(%d): assertion \"%s\" failed\n", file, line, what);
08941	  panic(NULL, NO_NUM);
08942	}
	
08944	/*=========================================================================*
08945	 *                              bad_compare                                *
08946	 *=========================================================================*/
08947	PUBLIC void bad_compare(file, line, lhs, what, rhs)
08948	char *file;
08949	int line;
08950	int lhs;
08951	char *what;
08952	int rhs;
08953	{
08954	  printf("panic at %s(%d): compare (%d) %s (%d) failed\n",
08955	        file, line, lhs, what, rhs);
08956	  panic(NULL, NO_NUM);
08957	}
08958	#endif /* DEBUG */