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
12 /****************************************************************
13 * Include of 16bit C code
14 ****************************************************************/
17 .include "out/blob.16.s"
20 /****************************************************************
22 ****************************************************************/
24 // Call a C function - this does the minimal work necessary to
25 // call into C. It sets up %ds, backs up %es, and backs up
26 // those registers that are call clobbered by the C compiler.
29 pushl %eax // Save registers clobbered by C code
34 movw %ss, %ax // Move %ss to %ds
36 pushl %esp // Backup %esp, then clear high bits
39 popl %esp // Restore %esp (including high bits)
40 popw %ds // Restore registers saved above
47 // Call a C function with current register list as an
48 // argument. This backs up the registers and sets %eax
49 // to point to the backup. On return, the registers are
50 // restored from the structure.
51 .macro ENTRY_ARG cfunc
53 pushl %eax // Save registers (matches struct bregs)
61 movw %ss, %ax // Move %ss to %ds
63 movl %esp, %ebx // Backup %esp, then zero high bits
65 movl %esp, %eax // First arg is pointer to struct bregs
67 movl %ebx, %esp // Restore %esp (including high bits)
68 popw %ds // Restore registers (from struct bregs)
78 // As above, but don't mangle %esp
79 .macro ENTRY_ARG_ESP cfunc
81 pushl %eax // Save registers (matches struct bregs)
89 movw %ss, %ax // Move %ss to %ds
91 movl %esp, %eax // First arg is pointer to struct bregs
93 popw %ds // Restore registers (from struct bregs)
103 // Macro to reset the 16bit stack
108 movl $ BUILD_STACK_ADDR , %esp
112 // Specify a location in the fixed part of bios area.
114 .section .text.fixed.addr
115 .org \addr - BUILD_START_FIXED
119 /****************************************************************
121 ****************************************************************/
127 andl $0x9fffffff, %eax
130 // init the stack pointer
133 pushl $_code32__start
135 // Fall through to transition32 function below
138 /****************************************************************
140 ****************************************************************/
142 // Place CPU into 32bit mode from 16bit mode.
143 // Clobbers: %eax, flags, stack registers, cr0, idt/gdt
150 orb $A20_ENABLE_BIT, %al
153 // Set segment descriptors
154 lidt %cs:pmode_IDT_info
155 lgdt %cs:rombios32_gdt_48
162 // start protected mode code
163 ljmpl $SEG32_MODE32_CS, $(BUILD_BIOS_ADDR + 1f)
167 // init data segments
168 movl $SEG32_MODE32_DS, %eax
178 // Call a 16bit function from 32bit mode.
179 // %eax = address of struct bregs
180 // Clobbers: all gp registers, flags, stack registers, cr0, idt/gdt
181 .global __call16_from32
185 // restore data segment limits to 0xffff
186 movw $SEG32_MODE16_DS, %ax
195 andb $~A20_ENABLE_BIT, %al
198 // Jump to 16bit mode
199 ljmpw $SEG32_MODE16_CS, $1f
203 // reset PE bit in CR0
208 // far jump to flush CPU queue after transition to real mode
212 // restore IDT to normal real-mode defaults
213 lidt %cs:rmode_IDT_info
215 // Clear segment registers
221 movw %ax, %ss // Assume stack is in segment 0
225 // Set __call16 return address to be transition32
228 // Fall through to __call16
231 // Call a 16bit function from 16bit mode with a specified cpu register state
232 // %eax = address of struct bregs
233 // Clobbers: all gp registers, es
239 // Setup for iretw call
241 pushw $1f // return point
242 pushw 0x20(%eax) // flags
243 pushl 0x1c(%eax) // CS:IP
245 // Load calling registers.
246 movl 0x04(%eax), %edi
247 movl 0x08(%eax), %esi
248 movl 0x0c(%eax), %ebx
249 movl 0x10(%eax), %edx
250 movl 0x14(%eax), %ecx
251 movw 0x02(%eax), %es // XXX - should load %ds too
252 movl 0x18(%eax), %eax
255 iretw // XXX - just do a lcalll
257 // Store flags, eax, ecx
260 movl 0x06(%esp), %eax
261 movl %ecx, %ss:0x14(%eax) // Save %ecx
263 movw %cx, %ds // Restore %ds == %ss
265 movl %ecx, 0x18(%eax) // Save %eax
267 movw %cx, 0x20(%eax) // Save flags
269 // Store remaining registers
271 movl %edi, 0x04(%eax)
272 movl %esi, 0x08(%eax)
273 movl %ebx, 0x0c(%eax)
274 movl %edx, 0x10(%eax)
285 .global apm16protected_entry
286 apm16protected_entry:
289 ENTRY_ARG handle_1553
290 addw $4, %sp // pop dummy
291 popfw // restore flags
295 .global apm32protected_entry
296 apm32protected_entry:
298 pushw %cs // Setup for long jump to 16bit mode
304 ENTRY_ARG_ESP handle_1553
306 movw $2f,(%esp) // Setup for long jump back to 32bit mode
311 addl $4, %esp // pop call address
315 // 32bit elf entry point
320 lidtl (BUILD_BIOS_ADDR + pmode_IDT_info)
321 lgdtl (BUILD_BIOS_ADDR + rombios32_gdt_48)
322 movl $BUILD_STACK_ADDR, %esp
323 ljmpl $SEG32_MODE32_CS, $_code32__start
327 // Shutdown a CPU. We want this in the 0xf000 section to ensure that
328 // the code wont be overwritten with something else. (Should
329 // something spurious wake up the CPU, we want to be sure that the hlt
330 // insn will still be present and will shutdown the CPU.)
331 .global permanent_halt
338 /****************************************************************
340 ****************************************************************/
342 // Protected mode IDT descriptor
344 // I just make the limit 0, so the machine will shutdown
345 // if an exception occurs during protected mode memory
348 // Set base to f0000 to correspond to beginning of BIOS,
349 // in case I actually define an IDT later
352 .word 0x0000 // limit 15:00
353 .long 0xf0000 // base 16:47
355 // Real mode IDT descriptor
357 // Set to typical real-mode values.
361 .word 0x03ff // limit 15:00
362 .long 0 // base 16:47
373 // 32 bit flat code segment (SEG32_MODE32_CS)
374 .word 0xffff, 0, 0x9b00, 0x00cf
375 // 32 bit flat data segment (SEG32_MODE32_DS)
376 .word 0xffff, 0, 0x9300, 0x00cf
377 // 16 bit code segment base=0xf0000 limit=0xffff (SEG32_MODE16_CS)
378 .word 0xffff, 0, 0x9b0f, 0x0000
379 // 16 bit data segment base=0x0 limit=0xffff (SEG32_MODE16_DS)
380 .word 0xffff, 0, 0x9300, 0x0000
382 // We need a copy of this string in the 0xf000 segment, but we are not
383 // actually a PnP BIOS, so make sure it is *not* aligned, so OSes will
384 // not see it if they scan.
392 /****************************************************************
393 * Interrupt entry points
394 ****************************************************************/
396 // Define an entry point for an interrupt (no args passed).
400 cli // In case something far-calls instead of using "int"
405 // Define an entry point for an interrupt (can read/modify args).
406 .macro IRQ_ENTRY_ARG num
409 cli // In case something far-calls instead of using "int"
410 ENTRY_ARG handle_\num
428 // XXX - Fixed Disk Parameter Table
434 .include "out/cbt.proc.16.s"
438 // XXX - Baud Rate Generator Table
446 // int 18/19 are special - they reset the stack and do not return.
450 pushl $_code32_handle_19
456 pushl $_code32_handle_18
460 .macro IRQ_TRAMPOLINE num
461 .global irq_trampoline_0x\num
462 irq_trampoline_0x\num :
493 .include "out/floppy_dbt.proc.16.s"
510 .global freespace2_start, freespace2_end
524 .include "out/font.proc.16.s"
534 // XXX - Initial Interrupt Vector Offsets Loaded by POST
537 // XXX - BIOS_COPYRIGHT_STRING
538 .ascii "(c) 2002 MandrakeSoft S.A. Written by Kevin Lawton & the Bochs team."
541 .global dummy_iret_handler
548 ORG 0xfff0 // Power-up Entry Point
549 ljmpw $SEG_BIOS, $post16
556 .byte CONFIG_MODEL_ID
558 .global bios_checksum