minix/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"

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 */
  unsigned mon_start;
  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 kernel memory. */
  kinfo.params_base = seg2phys(mds) + parmoff;
  kinfo.params_size = MAX(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;
  kstrncpy(kinfo.release, OS_RELEASE, 4);
  kstrncpy(kinfo.version, OS_VERSION, 4);
  kinfo.proc_addr = (vir_bytes) proc;
  kinfo.kmem_base = vir2phys(0);
  kinfo.kmem_size = (phys_bytes) &end;	

  /* Processor?  86, 186, 286, 386, ... */
  machine.processor=katoi(get_value(params, "processor")); 

  /* Decide if mode is protected for older machines. */
#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 || kstrcmp(value, "at") == 0) {
      machine.pc_at = TRUE;			/* PC-AT compatible hardware */
  } else if (kstrcmp(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 (kstrcmp(value, "ega") == 0) machine.vdu_ega = TRUE;
  if (kstrcmp(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);
}