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 "../out/asm-offsets.h" // BREGS_*
14 /****************************************************************
15 * Include of 16bit C code
16 ****************************************************************/
19 .include "out/blob.16.s"
22 /****************************************************************
24 ****************************************************************/
26 // Call a C function - this does the minimal work necessary to
27 // call into C. It sets up %ds, backs up %es, and backs up
28 // those registers that are call clobbered by the C compiler.
31 pushl %eax // Save registers clobbered by C code
36 movw %ss, %ax // Move %ss to %ds
38 pushl %esp // Backup %esp, then clear high bits
41 popl %esp // Restore %esp (including high bits)
42 popw %ds // Restore registers saved above
49 // Call a C function with current register list as an
50 // argument. This backs up the registers and sets %eax
51 // to point to the backup. On return, the registers are
52 // restored from the structure.
53 .macro ENTRY_ARG cfunc
55 pushl %eax // Save registers (matches struct bregs)
63 movw %ss, %ax // Move %ss to %ds
65 movl %esp, %ebx // Backup %esp, then zero high bits
67 movl %esp, %eax // First arg is pointer to struct bregs
69 movl %ebx, %esp // Restore %esp (including high bits)
70 popw %ds // Restore registers (from struct bregs)
80 // As above, but don't mangle %esp
81 .macro ENTRY_ARG_ESP cfunc
83 pushl %eax // Save registers (matches struct bregs)
91 movw %ss, %ax // Move %ss to %ds
93 movl %esp, %eax // First arg is pointer to struct bregs
95 popw %ds // Restore registers (from struct bregs)
105 // Macro to reset the 16bit stack
110 movl $ BUILD_STACK_ADDR , %esp
114 // Specify a location in the fixed part of bios area.
116 .section .text.fixed.addr
117 .org \addr - BUILD_START_FIXED
121 /****************************************************************
123 ****************************************************************/
129 andl $~(CR0_CD|CR0_NW), %eax
132 // init the stack pointer
135 pushl $_code32__start
137 // Fall through to transition32 function below
140 /****************************************************************
142 ****************************************************************/
144 // Place CPU into 32bit mode from 16bit mode.
145 // Clobbers: %eax, flags, stack registers, cr0, idt/gdt
152 orb $A20_ENABLE_BIT, %al
155 // Set segment descriptors
156 lidt %cs:pmode_IDT_info
157 lgdt %cs:rombios32_gdt_48
159 // Enable protected mode
164 // start protected mode code
165 ljmpl $SEG32_MODE32_CS, $(BUILD_BIOS_ADDR + 1f)
169 // init data segments
170 movl $SEG32_MODE32_DS, %eax
180 // Call a 16bit function from 32bit mode.
181 // %eax = address of struct bregs
182 // Clobbers: all gp registers, flags, stack registers, cr0, idt/gdt
183 .global __call16_from32
187 // restore data segment limits to 0xffff
188 movw $SEG32_MODE16_DS, %ax
197 andb $~A20_ENABLE_BIT, %al
200 // Jump to 16bit mode
201 ljmpw $SEG32_MODE16_CS, $1f
205 // Disable protected mode
210 // far jump to flush CPU queue after transition to real mode
214 // restore IDT to normal real-mode defaults
215 lidt %cs:rmode_IDT_info
217 // Clear segment registers
223 movw %ax, %ss // Assume stack is in segment 0
227 // Set __call16 return address to be transition32
230 // Fall through to __call16
233 // Call a 16bit function from 16bit mode with a specified cpu register state
234 // %eax = address of struct bregs
235 // Clobbers: all gp registers, es
241 // Setup for iretw call
243 pushw $1f // return point
244 pushw BREGS_flags(%eax) // flags
245 pushl BREGS_ip(%eax) // CS:IP
247 // Load calling registers.
248 movl BREGS_edi(%eax), %edi
249 movl BREGS_esi(%eax), %esi
250 movl BREGS_ebx(%eax), %ebx
251 movl BREGS_edx(%eax), %edx
252 movl BREGS_ecx(%eax), %ecx
253 movw BREGS_es(%eax), %es
254 movw BREGS_ds(%eax), %ds
255 movl %ss:BREGS_eax(%eax), %eax
258 iretw // XXX - just do a lcalll
260 // Store flags, eax, ecx
263 movl 0x06(%esp), %eax
264 movl %ecx, %ss:BREGS_ecx(%eax)
265 movw %ds, %ss:BREGS_ds(%eax)
267 movw %cx, %ds // Restore %ds == %ss
269 movl %ecx, BREGS_eax(%eax)
271 movw %cx, BREGS_flags(%eax)
273 // Store remaining registers
274 movw %es, BREGS_es(%eax)
275 movl %edi, BREGS_edi(%eax)
276 movl %esi, BREGS_esi(%eax)
277 movl %ebx, BREGS_ebx(%eax)
278 movl %edx, BREGS_edx(%eax)
289 .global apm16protected_entry
290 apm16protected_entry:
293 ENTRY_ARG handle_1553
294 addw $4, %sp // pop dummy
295 popfw // restore flags
299 .global apm32protected_entry
300 apm32protected_entry:
302 pushw %cs // Setup for long jump to 16bit mode
308 ENTRY_ARG_ESP handle_1553
310 movw $2f,(%esp) // Setup for long jump back to 32bit mode
315 addl $4, %esp // pop call address
319 // 32bit elf entry point
324 lidtl (BUILD_BIOS_ADDR + pmode_IDT_info)
325 lgdtl (BUILD_BIOS_ADDR + rombios32_gdt_48)
326 movl $BUILD_STACK_ADDR, %esp
327 ljmpl $SEG32_MODE32_CS, $_code32__start
331 // Shutdown a CPU. We want this in the 0xf000 section to ensure that
332 // the code wont be overwritten with something else. (Should
333 // something spurious wake up the CPU, we want to be sure that the hlt
334 // insn will still be present and will shutdown the CPU.)
335 .global permanent_halt
342 /****************************************************************
344 ****************************************************************/
346 // Protected mode IDT descriptor
348 // I just make the limit 0, so the machine will shutdown
349 // if an exception occurs during protected mode memory
352 // Set base to f0000 to correspond to beginning of BIOS,
353 // in case I actually define an IDT later
356 .word 0x0000 // limit 15:00
357 .long 0xf0000 // base 16:47
359 // Real mode IDT descriptor
361 // Set to typical real-mode values.
365 .word 0x03ff // limit 15:00
366 .long 0 // base 16:47
377 // 32 bit flat code segment (SEG32_MODE32_CS)
378 .word 0xffff, 0, 0x9b00, 0x00cf
379 // 32 bit flat data segment (SEG32_MODE32_DS)
380 .word 0xffff, 0, 0x9300, 0x00cf
381 // 16 bit code segment base=0xf0000 limit=0xffff (SEG32_MODE16_CS)
382 .word 0xffff, 0, 0x9b0f, 0x0000
383 // 16 bit data segment base=0x0 limit=0xffff (SEG32_MODE16_DS)
384 .word 0xffff, 0, 0x9300, 0x0000
386 // We need a copy of this string in the 0xf000 segment, but we are not
387 // actually a PnP BIOS, so make sure it is *not* aligned, so OSes will
388 // not see it if they scan.
396 /****************************************************************
397 * Interrupt entry points
398 ****************************************************************/
400 // Define an entry point for an interrupt (no args passed).
404 cli // In case something far-calls instead of using "int"
409 // Define an entry point for an interrupt (can read/modify args).
410 .macro IRQ_ENTRY_ARG num
413 cli // In case something far-calls instead of using "int"
414 ENTRY_ARG handle_\num
432 // XXX - Fixed Disk Parameter Table
438 .include "out/cbt.proc.16.s"
442 // XXX - Baud Rate Generator Table
450 // int 18/19 are special - they reset the stack and do not return.
454 pushl $_code32_handle_19
460 pushl $_code32_handle_18
464 .macro IRQ_TRAMPOLINE num
465 .global irq_trampoline_0x\num
466 irq_trampoline_0x\num :
497 .include "out/floppy_dbt.proc.16.s"
514 .global freespace2_start, freespace2_end
528 .include "out/font.proc.16.s"
538 // XXX - Initial Interrupt Vector Offsets Loaded by POST
541 // XXX - BIOS_COPYRIGHT_STRING
542 .ascii "(c) 2002 MandrakeSoft S.A. Written by Kevin Lawton & the Bochs team."
545 .global dummy_iret_handler
552 ORG 0xfff0 // Power-up Entry Point
553 ljmpw $SEG_BIOS, $post16
560 .byte CONFIG_MODEL_ID
562 .global bios_checksum