minix/kernel/start.c
2005-04-21 14:53:53 +00:00

95 lines
2.9 KiB
C
Executable file

/* 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"
/* Environment strings passed by loader. */
PRIVATE char k_environ[128*sizeof(char *)];
/*==========================================================================*
* 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.
*/
register char *envp;
unsigned mon_start;
/* Record where the kernel and the monitor are. */
code_base = seg2phys(cs);
data_base = seg2phys(ds);
/* Initialize protected mode descriptors. */
prot_init();
/* Copy the boot parameters to kernel memory. */
mon_params = seg2phys(mds) + parmoff;
mon_parmsize = MAX(parmsize,sizeof(k_environ));
if (parmsize > sizeof k_environ - 2) parmsize = sizeof k_environ - 2;
phys_copy(mon_params, vir2phys(k_environ), (phys_bytes) parmsize);
/* Type of VDU: */
envp = getkenv("video");
if (kstrcmp(envp, "ega") == 0) ega = TRUE;
if (kstrcmp(envp, "vga") == 0) vga = ega = TRUE;
/* Processor? */
processor = katoi(getkenv("processor")); /* 86, 186, 286, 386, ... */
/* XT, AT or MCA bus? */
envp = getkenv("bus");
if (envp == NIL_PTR || kstrcmp(envp, "at") == 0) {
pc_at = TRUE;
} else
if (kstrcmp(envp, "mca") == 0) {
pc_at = ps_mca = TRUE;
}
/* Decide if mode is protected. */
#if _WORD_SIZE == 2
protected_mode = processor >= 286;
if (!protected_mode) mon_return = 0;
#endif
/* Return to assembler code to switch to protected mode (if 286), reload
* selectors and call main().
*/
}
/*==========================================================================*
* getkenv *
*==========================================================================*/
PUBLIC char *getkenv(name)
_CONST char *name;
{
/* Get environment value - kernel version of getenv to avoid setting up the
* usual environment array.
*/
register _CONST char *namep;
register char *envp;
for (envp = k_environ; *envp != 0;) {
for (namep = name; *namep != 0 && *namep == *envp; namep++, envp++)
;
if (*namep == '\0' && *envp == '=') return(envp + 1);
while (*envp++ != 0)
;
}
return(NIL_PTR);
}