179 lines
6.3 KiB
C
Executable File
179 lines
6.3 KiB
C
Executable File
/* This file contains the C startup code for Minix on Intel processors.
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* It cooperates with mpx.s to set up a good environment for main().
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*
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* This code runs in real mode for a 16 bit kernel and may have to switch
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* to protected mode for a 286.
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*
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* For a 32 bit kernel this already runs in protected mode, but the selectors
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* are still those given by the BIOS with interrupts disabled, so the
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* descriptors need to be reloaded and interrupt descriptors made.
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*/
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#include "kernel.h"
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#include "protect.h"
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#include "proc.h"
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/* Environment strings passed by loader. */
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PRIVATE char k_environ[128*sizeof(char *)];
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FORWARD _PROTOTYPE( void mem_init, (void) );
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/*==========================================================================*
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* cstart *
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*==========================================================================*/
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PUBLIC void cstart(cs, ds, mds, parmoff, parmsize)
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U16_t cs, ds; /* kernel code and data segment */
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U16_t mds; /* monitor data segment */
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U16_t parmoff, parmsize; /* boot parameters offset and length */
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{
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/* Perform system initializations prior to calling main(). Most settings are
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* determined with help of the environment strings passed by MINIX' loader.
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*/
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register char *envp;
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unsigned mon_start;
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extern int etext, end;
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/* Decide if mode is protected; 386 or higher implies protected mode.
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* This must be done first, because it is needed for, e.g., seg2phys().
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* For 286 machines we cannot decide on protected mode, yet. This is
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* done below.
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*/
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#if _WORD_SIZE != 2
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machine.protected = 1;
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#endif
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/* Record where the kernel and the monitor are. */
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kinfo.code_base = seg2phys(cs);
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kinfo.code_size = (phys_bytes) &etext; /* size of code segment */
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kinfo.data_base = seg2phys(ds);
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kinfo.data_size = (phys_bytes) &end; /* size of data segment */
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/* Initialize protected mode descriptors. */
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prot_init();
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/* Copy the boot parameters to kernel memory. */
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kinfo.params_base = seg2phys(mds) + parmoff;
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kinfo.params_size = MAX(parmsize,sizeof(k_environ)-2);
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phys_copy(kinfo.params_base, vir2phys(k_environ), kinfo.params_size);
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/* Record miscellaneous information for user-space servers. */
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kstrncpy(kinfo.version, OS_RELEASE "." OS_VERSION, 6);
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kinfo.proc_addr = (vir_bytes) proc;
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kinfo.kmem_base = vir2phys(0);
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kinfo.kmem_size = (phys_bytes) &end;
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/* Processor? */
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machine.processor=katoi(getkenv("processor")); /* 86, 186, 286, 386, ... */
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/* Decide if mode is protected for older machines. */
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#if _WORD_SIZE == 2
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machine.protected = machine.processor >= 286;
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#endif
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if (! machine.protected) mon_return = 0;
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/* XT, AT or MCA bus? */
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envp = getkenv("bus");
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if (envp == NIL_PTR || kstrcmp(envp, "at") == 0) {
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machine.pc_at = TRUE; /* PC-AT compatible hardware */
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} else if (kstrcmp(envp, "mca") == 0) {
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machine.pc_at = machine.ps_mca = TRUE; /* PS/2 with micro channel */
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}
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/* Type of VDU: */
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envp = getkenv("video"); /* EGA or VGA video unit */
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if (kstrcmp(envp, "ega") == 0) machine.vdu_ega = TRUE;
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if (kstrcmp(envp, "vga") == 0) machine.vdu_vga = machine.vdu_ega = TRUE;
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/* Initialize free memory list from size passed by boot monitor. */
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mem_init();
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/* Return to assembler code to switch to protected mode (if 286),
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* reload selectors and call main().
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*/
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}
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/* In real mode only 1M can be addressed, and in 16-bit protected we can go
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* no further than we can count in clicks. (The 286 is further limited by
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* its 24 bit address bus, but we can assume in that case that no more than
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* 16M memory is reported by the BIOS.)
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*/
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#define MAX_REAL 0x00100000L
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#define MAX_16BIT (0xFFF0L << CLICK_SHIFT)
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/*=========================================================================*
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* mem_init *
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*=========================================================================*/
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PRIVATE void mem_init()
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{
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/* Initialize the free memory list from the 'memory' boot variable. Translate
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* the byte offsets and sizes in this list to clicks, properly truncated. Also
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* make sure that we don't exceed the maximum address space of the 286 or the
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* 8086, i.e. when running in 16-bit protected mode or real mode.
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*/
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long base, size, limit;
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char *s, *end; /* use to parse boot variable */
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int i;
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struct memory *memp;
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#if _WORD_SIZE == 2
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unsigned long max_address;
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#endif
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/* The available memory is determined by MINIX' boot loader as a list of
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* (base:size)-pairs in boothead.s. The 'memory' boot variable is set in
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* in boot.s. The format is "b0:s0,b1:s1,b2:s2", where b0:s0 is low mem,
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* b1:s1 is mem between 1M and 16M, b2:s2 is mem above 16M. Pairs b1:s1
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* and b2:s2 are combined if the memory is adjacent.
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*/
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s = getkenv("memory"); /* get memory boot variable */
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for (i = 0; i < NR_MEMS; i++) {
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memp = &mem[i]; /* result is stored here */
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base = size = 0;
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if (*s != 0) { /* end of boot variable */
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/* Expect base to be read (end != s) and ':' as next char. */
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base = kstrtoul(s, &end, 0x10); /* get number */
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if (end != s && *end == ':') s = ++end; /* skip ':' */
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else *s=0; /* fake end for next; should not happen */
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/* Expect size to be read and skip ',', unless at end. */
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size = kstrtoul(s, &end, 0x10); /* get number */
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if (end != s && *end == ',') s = ++end; /* skip ',' */
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else if (end != s && *end == 0) s = end; /* end found */
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else *s=0; /* fake end for next; should not happen */
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}
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limit = base + size;
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#if _WORD_SIZE == 2
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max_address = kinfo.protected ? MAX_16BIT : MAX_REAL;
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if (limit > max_address) limit = max_address;
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#endif
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base = (base + CLICK_SIZE-1) & ~(long)(CLICK_SIZE-1);
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limit &= ~(long)(CLICK_SIZE-1);
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if (limit <= base) continue;
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memp->base = base >> CLICK_SHIFT;
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memp->size = (limit - base) >> CLICK_SHIFT;
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}
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}
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/*==========================================================================*
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* getkenv *
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*==========================================================================*/
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PUBLIC char *getkenv(name)
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_CONST char *name;
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{
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/* Get environment value - kernel version of getenv to avoid setting up the
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* usual environment array.
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*/
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register _CONST char *namep;
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register char *envp;
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for (envp = k_environ; *envp != 0;) {
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for (namep = name; *namep != 0 && *namep == *envp; namep++, envp++)
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;
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if (*namep == '\0' && *envp == '=') return(envp + 1);
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while (*envp++ != 0)
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;
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}
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return(NIL_PTR);
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}
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