Initial revision

kernel/start.c

@@ -0,0 +1,95 @@
+/* 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);
+}