FreeBSD/Linux Kernel Cross Reference
sys/kernel/start.c

     /* This file contains the C startup code for Minix on Intel processors.
      * It cooperates with mpx.s to set up a good environment for main().
      *
      * This code runs in real mode for a 16 bit kernel and may have to switch
      * to protected mode for a 286.
      * For a 32 bit kernel this already runs in protected mode, but the selectors
      * are still those given by the BIOS with interrupts disabled, so the
      * descriptors need to be reloaded and interrupt descriptors made.
      */
    
    #include "kernel.h"
    #include "protect.h"
    #include "proc.h"
    #include <stdlib.h>
    #include <string.h>
    
    FORWARD _PROTOTYPE( char *get_value, (_CONST char *params, _CONST char *key));
    /*===========================================================================*
     *                              cstart                                       *
     *===========================================================================*/
    PUBLIC void cstart(cs, ds, mds, parmoff, parmsize)
    U16_t cs, ds;                   /* kernel code and data segment */
    U16_t mds;                      /* monitor data segment */
    U16_t parmoff, parmsize;        /* boot parameters offset and length */
    {
    /* Perform system initializations prior to calling main(). Most settings are
     * determined with help of the environment strings passed by MINIX' loader.
     */
      char params[128*sizeof(char *)];              /* boot monitor parameters */
      register char *value;                         /* value in key=value pair */
      extern int etext, end;
    
      /* Decide if mode is protected; 386 or higher implies protected mode.
       * This must be done first, because it is needed for, e.g., seg2phys().
       * For 286 machines we cannot decide on protected mode, yet. This is 
       * done below. 
       */
    #if _WORD_SIZE != 2
      machine.protected = 1;        
    #endif
    
      /* Record where the kernel and the monitor are. */
      kinfo.code_base = seg2phys(cs);
      kinfo.code_size = (phys_bytes) &etext;        /* size of code segment */
      kinfo.data_base = seg2phys(ds);
      kinfo.data_size = (phys_bytes) &end;          /* size of data segment */
    
      /* Initialize protected mode descriptors. */
      prot_init();
    
      /* Copy the boot parameters to the local buffer. */
      kinfo.params_base = seg2phys(mds) + parmoff;
      kinfo.params_size = MIN(parmsize,sizeof(params)-2);
      phys_copy(kinfo.params_base, vir2phys(params), kinfo.params_size);
    
      /* Record miscellaneous information for user-space servers. */
      kinfo.nr_procs = NR_PROCS;
      kinfo.nr_tasks = NR_TASKS;
      strncpy(kinfo.release, OS_RELEASE, sizeof(kinfo.release));
      kinfo.release[sizeof(kinfo.release)-1] = '\0';
      strncpy(kinfo.version, OS_VERSION, sizeof(kinfo.version));
      kinfo.version[sizeof(kinfo.version)-1] = '\0';
      kinfo.proc_addr = (vir_bytes) proc;
      kinfo.kmem_base = vir2phys(0);
      kinfo.kmem_size = (phys_bytes) &end;  
    
      /* Processor?  86, 186, 286, 386, ... 
       * Decide if mode is protected for older machines. 
       */
      machine.processor=atoi(get_value(params, "processor")); 
    #if _WORD_SIZE == 2
      machine.protected = machine.processor >= 286;         
    #endif
      if (! machine.protected) mon_return = 0;
    
      /* XT, AT or MCA bus? */
      value = get_value(params, "bus");
      if (value == NIL_PTR || strcmp(value, "at") == 0) {
          machine.pc_at = TRUE;                     /* PC-AT compatible hardware */
      } else if (strcmp(value, "mca") == 0) {
          machine.pc_at = machine.ps_mca = TRUE;    /* PS/2 with micro channel */
      }
    
      /* Type of VDU: */
      value = get_value(params, "video");           /* EGA or VGA video unit */
      if (strcmp(value, "ega") == 0) machine.vdu_ega = TRUE;
      if (strcmp(value, "vga") == 0) machine.vdu_vga = machine.vdu_ega = TRUE;
    
      /* Return to assembler code to switch to protected mode (if 286), 
       * reload selectors and call main().
       */
    }
    
    /*===========================================================================*
     *                              get_value                                    *
     *===========================================================================*/
    
    PRIVATE char *get_value(params, name)
    _CONST char *params;                            /* boot monitor parameters */
   _CONST char *name;                              /* key to look up */
   {
   /* Get environment value - kernel version of getenv to avoid setting up the
    * usual environment array.
    */
     register _CONST char *namep;
     register char *envp;
   
     for (envp = (char *) params; *envp != 0;) {
           for (namep = name; *namep != 0 && *namep == *envp; namep++, envp++)
                   ;
           if (*namep == '\0' && *envp == '=') return(envp + 1);
           while (*envp++ != 0)
                   ;
     }
     return(NIL_PTR);
   }

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