Initial checkin.

Makefile

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+# Legacy Bios build system
+#
+# Copyright (C) 2008  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+# Output directory
+OUT=out/
+
+# Source files
+SRC16=floppy.c disk.c system.c clock.c serial.c kbd.c output.c boot.c
+SRC32=post.c output.c
+
+# Default compiler flags (note -march=armv4 is needed for 16 bit insns)
+CFLAGS = -Wall -Os -MD -m32 -march=i386 -mregparm=2 -ffreestanding
+CFLAGS16 = -Wall -Os -MD -m32 -DMODE16 -march=i386 -mregparm=2 -ffreestanding -fno-jump-tables
+
+all: $(OUT) $(OUT)rom.bin
+
+# Run with "make V=1" to see the actual compile commands
+ifdef V
+Q=
+else
+Q=@
+endif
+
+.PHONY : all FORCE
+
+vpath %.c src
+vpath %.S src
+
+################ Build rules
+$(OUT)%.proc.16.s: $(OUT)%.16.s
+	@echo "  Moving data sections to text in $<"
+	$(Q)sed 's/\t.section\t.rodata.*// ; s/\t.data//' < $< > $@
+
+$(OUT)%.16.s: %.c
+	@echo "  Generating assembler for $<"
+	$(Q)$(CC) $(CFLAGS16) -fwhole-program -S -combine -c $< -o $@
+
+$(OUT)%.lds: %.lds.S
+	@echo "  Precompiling $<"
+	$(Q)$(CPP) -P $< -o $@
+
+$(OUT)%.bin: $(OUT)%.o
+	@echo "  Extracting binary $@"
+	$(Q)objcopy -O binary $< $@
+
+$(OUT)%.offset.auto.h: $(OUT)%.o
+	@echo "  Generating symbol offset header $@"
+	$(Q)nm $< | ./tools/defsyms.py > $@
+
+$(OUT)blob.16.s:
+	@echo "  Generating whole program assembler $@"
+	$(Q)$(CC) $(CFLAGS16) -fwhole-program -S -combine -c $(addprefix src/, $(SRC16)) -o $@
+
+$(OUT)romlayout16.o: romlayout.S $(OUT)blob.proc.16.s $(OUT)font.proc.16.s $(OUT)cbt.proc.16.s
+	@echo "  Generating 16bit layout of $@"
+	$(Q)$(CC) $(CFLAGS16) -c $< -o $@
+
+$(OUT)rom16.o: $(OUT)romlayout16.o
+	@echo "  Linking $@"
+	$(Q)ld -melf_i386 -Ttext 0 $< -o $@
+
+$(OUT)rom16.bin: $(OUT)rom16.o
+	@echo "  Extracting binary $@"
+	$(Q)objcopy -O binary $< $@
+
+$(OUT)romlayout32.o: $(OUT)rom16.offset.auto.h
+	@echo "  Compiling whole program $@"
+	$(Q)$(CC) $(CFLAGS) -fwhole-program -combine -c $(addprefix src/, $(SRC32)) -o $@
+
+$(OUT)rom32.o: $(OUT)romlayout32.o $(OUT)rombios32.lds
+	@echo "  Linking $@"
+	$(Q)ld -T $(OUT)rombios32.lds $< -o $@
+
+$(OUT)rom.bin: $(OUT)rom16.bin $(OUT)rom32.bin $(OUT)rom16.offset.auto.h $(OUT)rom32.offset.auto.h
+	@echo "  Building $@"
+	$(Q)./tools/buildrom.py
+
+####### Generic rules
+clean:
+	rm -rf $(OUT)
+
+$(OUT):
+	mkdir $@
+
+-include $(OUT)*.d

README

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+This code implements an X86 legacy bios.  It is intended to be
+compiled using standard gnu tools (eg, gas and gcc).
+
+To build, one should be able to run "make" in the main directory.  The
+resulting file "out/rom.bin" contains the processed bios image.
+
+The code has been successfully compiled with gcc 4.1.2 and gas
+2.17.50.0.18.
+
+
+Overview of files:
+
+The src/ directory contains the bios source code.  The post.c code is
+compiled in 32bit mode.  The output.c code is compiled twice - once in
+16bit mode and once in 32bit mode.  The remaining c files are compiled
+in 16bit mode.
+
+The tools/ directory contains helper utilities for manipulating and
+building the final rom.
+
+The out/ directory is created by the build process - it contains all
+temporary and final files.
+
+
+Build overview:
+
+The 16bit code is compiled via gcc to assembler (file out/blob.16.s).
+The gcc "-fwhole-program" option is used to optimize the process so
+that gcc can efficiently compile and discard unneeded code.
+
+This resulting assembler code is pulled into romlayout.S.  The gas
+option ".code16gcc" is used prior to including the gcc generated
+assembler - this option enables gcc to be used to generate valid 16
+bit code.  The romlayout.S also defines all the mandatory bios visible
+memory locations.
+
+The post code (post.c) is written in 32bits.  The 16bit post vector
+(in romlayout.S) transitions the cpu into 32 bit mode before calling
+the initialization code in post.c.
+
+In the last step, the compiled 32 bit code is merged into the 16 bit
+code so that one binary file contains both.  Currently, both 16bit and
+32bit code will be located in the 64K block at segment 0xf000.
+
+
+GCC 16 bit limitations:
+
+Although the 16bit code is compiled with gcc, developers need to be
+aware of the environment.  In particular, global variables _must_ be
+treated specially.
+
+The code has full access to stack variables and general purpose
+registers.  The entry code in romlayout.S will push the original
+registers on the stack before calling the C code and then pop them off
+(including any required changes) before returning from the interrupt.
+Changes to CS, DS, and ES segment registers in C code is also safe.
+Changes to other segment registers (SS, FS, GS) need to be restored
+manually.
+
+Stack variables (and pointers to stack variables) work as they
+normally do in standard C code.
+
+However, variables stored outside the stack need to be accessed via
+the GET_VAR and SET_VAR macros.  This is due to the 16bit segment
+nature of the X86 cpu when it is in "real mode".  The C entry code
+will set DS and SS to point to the stack segment.  Variables not on
+the stack need to be accessed via an explicit segment register.
+Global constant definitions (those in 0xf000) can be accessed via the
+CS segment register.  Any other access requires altering one of the
+other segment registers (usually ES) and then accessing the variable
+via that segment register.

TODO

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+Make header files work with either 32bit or 16bit code.
+
+Fix makefiles so that they rebuild the required files automatically.
+
+Make sure gdt/idt tables are properly aligned
+
+Cleanup setting of ES on GET/SET_BDA
+
+Make sure inline assembly isn't preventing inlining of calling
+functions.
+
+Convert remaining parts of rombios.c to new code.
+
+Convert rombios32 and apm bios stuff to new code.
+
+Allow one to select adding 32 bit code to 0xf000 or in a separate
+location.
+
+Try generating bios tables at compile time.
+
+Move e820 map generation to post time (just have e820 code copy pre
+made tables back to user).

src/biosvar.h

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+// Variable layouts of bios.
+//
+// Copyright (C) 2008  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "types.h" // u8
+#include "farptr.h" // SET_SEG
+
+
+/****************************************************************
+ * Bios Data Area (BDA)
+ ****************************************************************/
+
+struct ivec {
+    u16 offset;
+    u16 seg;
+};
+
+struct bios_data_area_s {
+    // 00:00
+    struct ivec ivecs[256];
+    // 30:00
+//    u8 stack[256];
+    // 40:00
+    u16 port_com1, port_com2, port_com3, port_com4;
+    u16 port_lpt1, port_lpt2, port_lpt3;
+    u16 ebda_seg;
+    // 40:10
+    u16 equipment_list_flags;
+    u8 pad1;
+    u16 mem_size_kb;
+    u8 pad2;
+    u8 ps2_ctrl_flag;
+    u16 kbd_flag;
+    u8 alt_keypad;
+    u16 kbd_buf_head;
+    u16 kbd_buf_tail;
+    // 40:1e
+    u8 kbd_buf[32];
+    u8 floppy_recalibration_status;
+    u8 floppy_motor_status;
+    // 40:40
+    u8 floppy_motor_counter;
+    u8 floppy_last_status;
+    u8 floppy_return_status[7];
+    u8 other1[0x7];
+    // 40:50
+    u8 other2[0x1c];
+    // 40:6c
+    u32 timer_counter;
+    // 40:70
+    u8 timer_rollover;
+    u8 other4[0x0f];
+    // 40:80
+    u16 kbd_buf_start_offset;
+    u16 kbd_buf_end_offset;
+    u8 other5[7];
+    u8 floppy_last_data_rate;
+    u8 other6[3];
+    u8 floppy_harddisk_info;
+    // 40:90
+    u8 floppy_media_state[4];
+    u8 floppy_track0;
+    u8 floppy_track1;
+    u8 kbd_mode;
+    u8 kbd_led;
+    u32 ptr_user_wait_complete_flag;
+    u32 user_wait_timeout;
+    // 40:A0
+    u8 rtc_wait_flag;
+} __attribute__((packed));
+
+// BDA floppy_recalibration_status bitdefs
+#define FRS_TIMEOUT (1<<7)
+
+// BDA rtc_wait_flag bitdefs
+#define RWS_WAIT_PENDING (1<<0)
+#define RWS_WAIT_ELAPSED (1<<7)
+
+// BDA floppy_media_state bitdefs
+#define FMS_DRIVE_STATE_MASK        (0x07)
+#define FMS_MEDIA_DRIVE_ESTABLISHED (1<<4)
+#define FMS_DOUBLE_STEPPING         (1<<5)
+#define FMS_DATA_RATE_MASK          (0xc0)
+
+// Accessor functions
+#define GET_BDA(var) ({                                         \
+    SET_SEG(ES, 0x0000);                                        \
+    GET_VAR(ES, ((struct bios_data_area_s *)0)->var); })
+#define SET_BDA(var, val) do {                                  \
+        SET_SEG(ES, 0x0000);                                    \
+        SET_VAR(ES, ((struct bios_data_area_s *)0)->var, val);  \
+    } while (0)
+#define CLEARBITS_BDA(var, val) do {                                    \
+        typeof(((struct bios_data_area_s *)0)->var) __val = GET_BDA(var); \
+        SET_BDA(var, (__val & ~(val)));                                 \
+    } while (0)
+#define SETBITS_BDA(var, val) do {                                      \
+        typeof(((struct bios_data_area_s *)0)->var) __val = GET_BDA(var); \
+        SET_BDA(var, (__val | (val)));                                  \
+    } while (0)
+
+
+/****************************************************************
+ * Extended Bios Data Area (EBDA)
+ ****************************************************************/
+
+struct extended_bios_data_area_s {
+    u8 size;
+    u8 other1[0x3c];
+
+    // FDPT - Can be splitted in data members if needed
+    u8 fdpt0[0x10];
+    u8 fdpt1[0x10];
+
+    u8 other2[0xC4];
+
+    // ATA Driver data
+    //ata_t   ata;
+
+#if BX_ELTORITO_BOOT
+    // El Torito Emulation data
+    cdemu_t cdemu;
+#endif // BX_ELTORITO_BOOT
+};
+
+
+/****************************************************************
+ * Extended Bios Data Area (EBDA)
+ ****************************************************************/
+
+#define UREG(ER, R, RH, RL) union { u32 ER; struct { u16 R; u16 R ## _hi; }; struct { u8 RL; u8 RH; u8 R ## _hilo; u8 R ## _hihi; }; }
+
+struct bregs {
+    u16 ds;
+    u16 es;
+    UREG(edi, di, di_hi, di_lo);
+    UREG(esi, si, si_hi, si_lo);
+    UREG(ebp, bp, bp_hi, bp_lo);
+    UREG(esp, sp, sp_hi, sp_lo);
+    UREG(ebx, bx, bh, bl);
+    UREG(edx, dx, dh, dl);
+    UREG(ecx, cx, ch, cl);
+    UREG(eax, ax, ah, al);
+    u16 ip;
+    u16 cs;
+    u16 flags;
+} __attribute__((packed));
+
+// bregs flags bitdefs
+#define F_CF (1<<9)
+
+static inline void
+set_cf(struct bregs *regs, int cond)
+{
+    if (cond)
+        regs->flags |= F_CF;
+    else
+        regs->flags &= ~F_CF;
+}
+
+
+/****************************************************************
+ * Bios Config Table
+ ****************************************************************/
+
+struct bios_config_table_s {
+    // XXX
+    u8 x;
+};
+
+extern struct bios_config_table_s BIOS_CONFIG_TABLE;
+
+
+/****************************************************************
+ * Memory layout info
+ ****************************************************************/
+
+#define SEG_BIOS     0xf000
+
+#define EBDA_SEG           0x9FC0
+#define EBDA_SIZE          1              // In KiB
+#define BASE_MEM_IN_K   (640 - EBDA_SIZE)