96 lines
2.9 KiB
C
96 lines
2.9 KiB
C
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/* 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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/* Environment strings passed by loader. */
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PRIVATE char k_environ[128*sizeof(char *)];
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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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/* Record where the kernel and the monitor are. */
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code_base = seg2phys(cs);
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data_base = seg2phys(ds);
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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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mon_params = seg2phys(mds) + parmoff;
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mon_parmsize = MAX(parmsize,sizeof(k_environ));
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if (parmsize > sizeof k_environ - 2) parmsize = sizeof k_environ - 2;
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phys_copy(mon_params, vir2phys(k_environ), (phys_bytes) parmsize);
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/* Type of VDU: */
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envp = getkenv("video");
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if (kstrcmp(envp, "ega") == 0) ega = TRUE;
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if (kstrcmp(envp, "vga") == 0) vga = ega = TRUE;
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/* Processor? */
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processor = katoi(getkenv("processor")); /* 86, 186, 286, 386, ... */
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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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pc_at = TRUE;
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} else
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if (kstrcmp(envp, "mca") == 0) {
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pc_at = ps_mca = TRUE;
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}
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/* Decide if mode is protected. */
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#if _WORD_SIZE == 2
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protected_mode = processor >= 286;
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if (!protected_mode) mon_return = 0;
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#endif
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/* Return to assembler code to switch to protected mode (if 286), reload
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* selectors and call main().
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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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