1 // Rom layout and bios assembler to C interface.
3 // Copyright (C) 2008 Kevin O'Connor <kevin@koconnor.net>
4 // Copyright (C) 2002 MandrakeSoft S.A.
6 // This file may be distributed under the terms of the GNU GPLv3 license.
8 #include "config.h" // CONFIG_*
9 #include "ioport.h" // PORT_A20
10 #include "bregs.h" // CR0_*
11 #include "cmos.h" // CMOS_RESET_CODE
12 #include "../out/asm-offsets.h" // BREGS_*
15 /****************************************************************
16 * Include of 16bit C code
17 ****************************************************************/
20 .include "out/ccode.16.s"
23 /****************************************************************
25 ****************************************************************/
27 // Call a C function - this does the minimal work necessary to
28 // call into C. It sets up %ds, backs up %es, and backs up
29 // those registers that are call clobbered by the C compiler.
32 pushl %eax // Save registers clobbered by C code
37 movw %ss, %ax // Move %ss to %ds
39 pushl %esp // Backup %esp, then clear high bits
42 popl %esp // Restore %esp (including high bits)
43 popw %ds // Restore registers saved above
50 // Call a C function with current register list as an
51 // argument. This backs up the registers and sets %eax
52 // to point to the backup. On return, the registers are
53 // restored from the structure.
54 .macro ENTRY_ARG cfunc
56 pushl %eax // Save registers (matches struct bregs)
64 movw %ss, %ax // Move %ss to %ds
66 movl %esp, %ebx // Backup %esp, then zero high bits
68 movl %esp, %eax // First arg is pointer to struct bregs
70 movl %ebx, %esp // Restore %esp (including high bits)
71 popw %ds // Restore registers (from struct bregs)
81 // As above, but don't mangle %esp
82 .macro ENTRY_ARG_ESP cfunc
84 pushl %eax // Save registers (matches struct bregs)
92 movw %ss, %ax // Move %ss to %ds
94 movl %esp, %eax // First arg is pointer to struct bregs
96 popw %ds // Restore registers (from struct bregs)
106 // Macro to reset the 16bit stack
111 movl $ BUILD_STACK_ADDR , %esp
115 // Specify a location in the fixed part of bios area.
117 .section .text.fixed.addr
118 .org \addr - BUILD_START_FIXED
122 /****************************************************************
124 ****************************************************************/
130 andl $~(CR0_CD|CR0_NW), %eax
133 // Check for restart indicator.
134 movl $CMOS_RESET_CODE, %eax
135 outb %al, $PORT_CMOS_INDEX
136 inb $PORT_CMOS_DATA, %al
140 // Normal entry point
143 pushl $_code32__start
145 // Fall through to transition32 function below
148 /****************************************************************
150 ****************************************************************/
152 // Place CPU into 32bit mode from 16bit mode.
153 // Clobbers: %eax, flags, stack registers, cr0, idt/gdt
160 orb $A20_ENABLE_BIT, %al
163 // Set segment descriptors
164 lidtw %cs:pmode_IDT_info
165 lgdtw %cs:rombios32_gdt_48
167 // Enable protected mode
172 // start 32bit protected mode code
173 ljmpl $SEG32_MODE32_CS, $(BUILD_BIOS_ADDR + 1f)
177 // init data segments
178 movl $SEG32_MODE32_DS, %eax
187 // Call a 16bit function from 32bit mode.
188 // %eax = address of struct bregs
189 // Clobbers: all gp registers, flags, stack registers, cr0, idt/gdt
190 .global __call16_from32, __call16big_from32
194 // restore data segment limits to 0xffff
195 movl $SEG32_MODE16_DS, %eax
204 andb $~A20_ENABLE_BIT, %al
207 // Jump to 16bit mode
208 ljmpw $SEG32_MODE16_CS, $1f
213 movl $SEG32_MODE16BIG_DS, %eax
220 ljmpl $SEG32_MODE16BIG_CS, $(BUILD_BIOS_ADDR + 1f)
224 // Disable protected mode
229 // far jump to flush CPU queue after transition to real mode
233 // restore IDT to normal real-mode defaults
234 lidtw %cs:rmode_IDT_info
236 // Clear segment registers
242 movw %ax, %ss // Assume stack is in segment 0
246 // Set __call16 return address to be transition32
249 // Fall through to __call16
252 // Call a 16bit function from 16bit mode with a specified cpu register state
253 // %eax = address of struct bregs
254 // Clobbers: all gp registers, es
260 // Setup for iretw call
262 pushw $1f // return point
263 pushw BREGS_flags(%eax) // flags
264 pushl BREGS_ip(%eax) // CS:IP
266 // Load calling registers.
267 movl BREGS_edi(%eax), %edi
268 movl BREGS_esi(%eax), %esi
269 movl BREGS_ebx(%eax), %ebx
270 movl BREGS_edx(%eax), %edx
271 movl BREGS_ecx(%eax), %ecx
272 movw BREGS_es(%eax), %es
273 movw BREGS_ds(%eax), %ds
274 movl %ss:BREGS_eax(%eax), %eax
277 iretw // XXX - just do a lcalll
279 // Store flags, eax, ecx
282 movl 0x06(%esp), %eax
283 movl %ecx, %ss:BREGS_ecx(%eax)
284 movw %ds, %ss:BREGS_ds(%eax)
286 movw %cx, %ds // Restore %ds == %ss
288 movl %ecx, BREGS_eax(%eax)
290 movw %cx, BREGS_flags(%eax)
292 // Store remaining registers
293 movw %es, BREGS_es(%eax)
294 movl %edi, BREGS_edi(%eax)
295 movl %esi, BREGS_esi(%eax)
296 movl %ebx, BREGS_ebx(%eax)
297 movl %edx, BREGS_edx(%eax)
306 // Entry point when a post call looks like a resume.
308 // Save old shutdown status.
311 // Clear shutdown status register.
312 movl $CMOS_RESET_CODE, %eax
313 outb %al, $PORT_CMOS_INDEX
315 outb %al, $PORT_CMOS_DATA
317 // Use a stack in EBDA
320 movw BDA_ebda_seg, %ss
321 movl $EBDA_resume_stack_top, %esp
330 .global apm16protected_entry
331 apm16protected_entry:
334 ENTRY_ARG handle_1553
335 addw $4, %sp // pop dummy
336 popfw // restore flags
340 .global apm32protected_entry
341 apm32protected_entry:
343 pushw %cs // Setup for long jump to 16bit mode
349 ENTRY_ARG_ESP handle_1553
351 movw $2f,(%esp) // Setup for long jump back to 32bit mode
356 addl $4, %esp // pop call address
360 // 32bit elf entry point
365 lidtl (BUILD_BIOS_ADDR + pmode_IDT_info)
366 lgdtl (BUILD_BIOS_ADDR + rombios32_gdt_48)
367 movl $BUILD_STACK_ADDR, %esp
368 ljmpl $SEG32_MODE32_CS, $_code32__start
372 // Shutdown a CPU. We want this in the 0xf000 section to ensure that
373 // the code wont be overwritten with something else. (Should
374 // something spurious wake up the CPU, we want to be sure that the hlt
375 // insn will still be present and will shutdown the CPU.)
376 .global permanent_halt
383 /****************************************************************
385 ****************************************************************/
387 // Protected mode IDT descriptor
389 // I just make the limit 0, so the machine will shutdown
390 // if an exception occurs during protected mode memory
393 // Set base to f0000 to correspond to beginning of BIOS,
394 // in case I actually define an IDT later
397 .word 0x0000 // limit 15:00
398 .long 0xf0000 // base 16:47
400 // Real mode IDT descriptor
402 // Set to typical real-mode values.
406 .word 0x03ff // limit 15:00
407 .long 0 // base 16:47
410 .word (rombios32_gdt_end - rombios32_gdt)
411 .long (BUILD_BIOS_ADDR + rombios32_gdt)
417 // 32 bit flat code segment (SEG32_MODE32_CS)
418 .word 0xffff, 0, 0x9b00, 0x00cf
419 // 32 bit flat data segment (SEG32_MODE32_DS)
420 .word 0xffff, 0, 0x9300, 0x00cf
421 // 16 bit code segment base=0xf0000 limit=0xffff (SEG32_MODE16_CS)
422 .word 0xffff, 0, 0x9b0f, 0x0000
423 // 16 bit data segment base=0x0 limit=0xffff (SEG32_MODE16_DS)
424 .word 0xffff, 0, 0x9300, 0x0000
425 // 16 bit code segment base=0 limit=0xffffffff (SEG32_MODE16BIG_CS)
426 .word 0xffff, 0, 0x9b00, 0x008f
427 // 16 bit data segment base=0 limit=0xffffffff (SEG32_MODE16BIG_DS)
428 .word 0xffff, 0, 0x9300, 0x008f
431 // We need a copy of this string in the 0xf000 segment, but we are not
432 // actually a PnP BIOS, so make sure it is *not* aligned, so OSes will
433 // not see it if they scan.
441 /****************************************************************
442 * Interrupt entry points
443 ****************************************************************/
445 // Define an entry point for an interrupt (no args passed).
449 cli // In case something far-calls instead of using "int"
454 // Define an entry point for an interrupt (can read/modify args).
455 .macro IRQ_ENTRY_ARG num
458 cli // In case something far-calls instead of using "int"
459 ENTRY_ARG handle_\num
477 // XXX - Fixed Disk Parameter Table
483 .include "out/cbt.proc.16.s"
487 // XXX - Baud Rate Generator Table
495 // int 18/19 are special - they reset the stack and do not return.
499 pushl $_code32_handle_19
505 pushl $_code32_handle_18
509 .macro IRQ_TRAMPOLINE num
510 .global irq_trampoline_0x\num
511 irq_trampoline_0x\num :
543 .include "out/floppy_dbt.proc.16.s"
560 .global freespace2_start, freespace2_end
574 .include "out/font.proc.16.s"
584 // XXX - Initial Interrupt Vector Offsets Loaded by POST
587 // XXX - BIOS_COPYRIGHT_STRING
588 .ascii "(c) 2002 MandrakeSoft S.A. Written by Kevin Lawton & the Bochs team."
591 .global dummy_iret_handler
598 ORG 0xfff0 // Power-up Entry Point
601 ljmpw $SEG_BIOS, $post16
608 .byte CONFIG_MODEL_ID
610 .global bios_checksum