Initial source

1 files changed, 265 insertions, 0 deletions

diff --git a/i386/pc/i16/i16_raw.c b/i386/pc/i16/i16_raw.c
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+++ b/i386/pc/i16/i16_raw.c
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+/* 
+ * Copyright (c) 1995-1994 The University of Utah and
+ * the Computer Systems Laboratory at the University of Utah (CSL).
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify and distribute this software is hereby
+ * granted provided that (1) source code retains these copyright, permission,
+ * and disclaimer notices, and (2) redistributions including binaries
+ * reproduce the notices in supporting documentation, and (3) all advertising
+ * materials mentioning features or use of this software display the following
+ * acknowledgement: ``This product includes software developed by the
+ * Computer Systems Laboratory at the University of Utah.''
+ *
+ * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
+ * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
+ * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
+ *
+ * CSL requests users of this software to return to csl-dist@cs.utah.edu any
+ * improvements that they make and grant CSL redistribution rights.
+ *
+ *      Author: Bryan Ford, University of Utah CSL
+ */
+/*
+	This file rovides a default implementation
+	of real/pmode switching code.
+	Assumes that, as far as it's concerned,
+	low linear address always map to physical addresses.
+	(The low linear mappings can be changed,
+	but must be changed back before switching back to real mode.)
+
+	Provides:
+		i16_raw_switch_to_pmode()
+		i16_raw_switch_to_real_mode()
+
+		i16_raw_start()
+			Called in real mode.
+			Initializes the pmode switching system,
+			switches to pmode for the first time,
+			and calls the 32-bit function raw_start().
+
+	Depends on:
+
+		paging.h:
+			raw_paging_enable()
+			raw_paging_disable()
+			raw_paging_init()
+
+		a20.h:
+			i16_enable_a20()
+			i16_disable_a20()
+
+		real.h:
+			real_cs
+*/
+
+#include <mach/boolean.h>
+#include <mach/machine/code16.h>
+#include <mach/machine/vm_param.h>
+#include <mach/machine/proc_reg.h>
+#include <mach/machine/pio.h>
+#include <mach/machine/seg.h>
+#include <mach/machine/eflags.h>
+#include <mach/machine/pmode.h>
+
+#include "config.h"
+#include "cpu.h"
+#include "i16.h"
+#include "vm_param.h"
+#include "pic.h"
+#include "debug.h"
+#include "i16_a20.h"
+#include "i16_switch.h"
+
+int irq_master_base, irq_slave_base;
+
+/* Set to true when everything is initialized properly.  */
+static boolean_t inited;
+
+/* Saved value of eflags register for real mode.  */
+static unsigned real_eflags;
+
+
+
+#ifdef ENABLE_PAGING
+#define RAW_PAGING_ENABLE() raw_paging_enable()
+#define RAW_PAGING_DISABLE() raw_paging_disable()
+#define RAW_PAGING_INIT() raw_paging_init()
+#else
+#define RAW_PAGING_ENABLE() ((void)0)
+#define RAW_PAGING_DISABLE() ((void)0)
+#define RAW_PAGING_INIT() ((void)0)
+#endif
+
+
+CODE16
+
+void i16_raw_switch_to_pmode()
+{
+	/* No interrupts from now on please.  */
+	i16_cli();
+
+	/* Save the eflags register for switching back later.  */
+	real_eflags = get_eflags();
+
+	/* Enable the A20 address line.  */
+	i16_enable_a20();
+
+	/* Load the GDT.
+	   Note that we have to do this each time we enter pmode,
+	   not just the first,
+	   because other real-mode programs may have switched to pmode
+	   and back again in the meantime, trashing the GDT pointer.  */
+	{
+		struct pseudo_descriptor pdesc;
+
+		pdesc.limit = sizeof(cpu[0].tables.gdt)-1;
+		pdesc.linear_base = boot_image_pa
+				    + (vm_offset_t)&cpu[0].tables.gdt;
+		i16_set_gdt(&pdesc);
+	}
+
+	/* Switch into protected mode.  */
+	i16_enter_pmode(KERNEL_16_CS);
+
+	/* Reload all the segment registers from the new GDT.  */
+	set_ds(KERNEL_DS);
+	set_es(KERNEL_DS);
+	set_fs(0);
+	set_gs(0);
+	set_ss(KERNEL_DS);
+
+	i16_do_32bit(
+
+		if (inited)
+		{
+			/* Turn paging on if necessary.  */
+			RAW_PAGING_ENABLE();
+
+			/* Load the CPU tables into the processor.  */
+			cpu_tables_load(&cpu[0]);
+
+			/* Program the PIC so the interrupt vectors won't
+			   conflict with the processor exception vectors.  */
+			pic_init(PICM_VECTBASE, PICS_VECTBASE);
+		}
+
+		/* Make sure our flags register is appropriate.  */
+		set_eflags((get_eflags()
+			   & ~(EFL_IF | EFL_DF | EFL_NT))
+			   | EFL_IOPL_USER);
+	);
+}
+
+void i16_raw_switch_to_real_mode()
+{
+	/* Make sure interrupts are disabled.  */
+	cli();
+
+	/* Avoid sending DOS bogus coprocessor exceptions.
+	   XXX should we save/restore all of CR0?  */
+	i16_clts();
+
+	i16_do_32bit(
+		/* Turn paging off if necessary.  */
+		RAW_PAGING_DISABLE();
+
+		/* Reprogram the PIC back to the settings DOS expects.  */
+		pic_init(0x08, 0x70);
+	);
+
+	/* Make sure all the segment registers are 16-bit.
+	   The code segment definitely is already,
+	   because we're running 16-bit code.  */
+	set_ds(KERNEL_16_DS);
+	set_es(KERNEL_16_DS);
+	set_fs(KERNEL_16_DS);
+	set_gs(KERNEL_16_DS);
+	set_ss(KERNEL_16_DS);
+
+	/* Switch back to real mode.  */
+	i16_leave_pmode(real_cs);
+
+	/* Load the real-mode segment registers.  */
+	set_ds(real_cs);
+	set_es(real_cs);
+	set_fs(real_cs);
+	set_gs(real_cs);
+	set_ss(real_cs);
+
+	/* Load the real-mode IDT.  */
+	{
+		struct pseudo_descriptor pdesc;
+
+		pdesc.limit = 0xffff;
+		pdesc.linear_base = 0;
+		i16_set_idt(&pdesc);
+	}
+
+	/* Disable the A20 address line.  */
+	i16_disable_a20();
+
+	/* Restore the eflags register to its original real-mode state.
+	   Note that this will leave interrupts disabled
+	   since it was saved after the cli() above.  */
+	set_eflags(real_eflags);
+}
+
+void i16_raw_start()
+{
+	/* Make sure we're not already in protected mode.  */
+	if (i16_get_msw() & CR0_PE)
+		i16_die("The processor is in an unknown "
+			"protected mode environment.");
+
+	do_debug(i16_puts("Real mode detected"));
+
+	/* Minimally initialize the GDT.  */
+	i16_gdt_init_temp();
+
+	/* Switch to protected mode for the first time.
+	   This won't load all the processor tables and everything yet,
+	   since they're not fully initialized.  */
+	i16_raw_switch_to_pmode();
+
+	/* We can now hop in and out of 32-bit mode at will.  */
+	i16_do_32bit(
+
+		/* Now that we can access all physical memory,
+		   collect the memory regions we discovered while in 16-bit mode
+		   and add them to our free memory list.
+		   We can't do this before now because the free list nodes
+		   are stored in the free memory itself,
+		   which is probably out of reach of our 16-bit segments.  */
+		phys_mem_collect();
+
+		/* Initialize paging if necessary.
+		   Do it before initializing the other processor tables
+		   because they might have to be located
+		   somewhere in high linear memory.  */
+		RAW_PAGING_INIT();
+
+		/* Initialize the processor tables.  */
+		cpu_init(&cpu[0]);
+
+		/* Initialize the hardware interrupt vectors in the IDT.  */
+		irq_master_base = PICM_VECTBASE;
+		irq_slave_base = PICS_VECTBASE;
+		idt_irq_init();
+
+		inited = TRUE;
+
+		/* Switch to real mode and back again once more,
+		   to make sure everything's loaded properly.  */
+		do_16bit(
+			i16_raw_switch_to_real_mode();
+			i16_raw_switch_to_pmode();
+		);
+
+		raw_start();
+	);
+}
+
+void (*i16_switch_to_real_mode)() = i16_raw_switch_to_real_mode;
+void (*i16_switch_to_pmode)() = i16_raw_switch_to_pmode;
+