biostramp.S revision 1.9
1 /* $NetBSD: biostramp.S,v 1.9 2001/05/02 13:12:45 jdolecek Exp $ */ 2 3 /*- 4 * Copyright (c) 1996 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by John Kohl. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 /* 40 * biostramp.S: provide a means for NetBSD to call BIOS interrupts 41 * by switching to real mode, calling it, and switching 42 * back to protected & paging mode. 43 */ 44 45 /* 46 * Micro$haft's book on i386/i486 programming says you should do the following 47 * to return to real mode from protected mode: 48 * 49 * 1) disable paging, by jumping to code with identical virtual and physical 50 * addresses, clearing PG in CR0, and zeroing CR3 (PDBR). 51 * 52 * 2) segment descriptors must be byte-granular with limit 64k-1, def32 = 0, 53 * (i.e. 16-bit data accesses and/or 80286 instructions) 54 * CS must be executable; DS,ES,FS,GS should be writable 55 * 56 * 3) disable interrupts, load IDTR with original value (base 0, limit 1023) 57 * 58 * 4) clear PE in CR0, execute FAR jump to load CS. 59 * 60 * 5) load SP, and off you go 61 * 62 */ 63 64 #include "assym.h" 65 66 #include <i386/include/param.h> 67 #include <i386/include/specialreg.h> 68 #include <i386/include/segments.h> 69 #include <i386/include/apmvar.h> 70 #include <i386/include/psl.h> 71 #include <i386/include/asm.h> 72 73 #define addr32 .byte 0x67 74 #define data32 .byte 0x66 75 76 .set MYBASE,NBPG 77 .set MYSCRATCH,NBPG+NBPG 78 .set CR3_ADDR,(MYSCRATCH-4) 79 .set IDTR_SAVE_ADDR,CR3_ADDR-6 80 .set GDTR_SAVE_ADDR,IDTR_SAVE_ADDR-6 81 .set GDTR_LOCAL_ADDR,GDTR_SAVE_ADDR-6 82 .set STACK_PTR_ADDR,GDTR_LOCAL_ADDR-4 83 .set BASE_PTR_ADDR,STACK_PTR_ADDR-4 84 .set FUNCTION_ADDR,(BASE_PTR_ADDR-2) 85 .set GDT_COPY_ADDR,(FUNCTION_ADDR-NGDT*8) 86 .set EAX_REGADDR,(GDT_COPY_ADDR-4) 87 .set EBX_REGADDR,(EAX_REGADDR-4) 88 .set ECX_REGADDR,(EBX_REGADDR-4) 89 .set EDX_REGADDR,(ECX_REGADDR-4) 90 .set ESI_REGADDR,(EDX_REGADDR-4) 91 .set EDI_REGADDR,(ESI_REGADDR-4) 92 .set EFLAGS_REGADDR,(EDI_REGADDR-4) 93 .set ES_REGADDR, (EFLAGS_REGADDR-4) 94 .set ENDREGADDR,(ES_REGADDR-4) 95 96 .set REALSTACK,ENDREGADDR-20 # leave a red zone? 97 98 #define COPY_FLAGS (PSL_C|PSL_PF|PSL_AF|PSL_Z|PSL_N|PSL_D|PSL_V) 99 100 /* 101 * do_bios_call(int function, struct bioscall *regs) 102 */ 103 104 ENTRY(do_bios_call) 105 pushl %ebp 106 movl %esp,%ebp /* set up frame ptr */ 107 pushl %esi 108 pushl %edi 109 pushl %ebx 110 pushl %ds 111 pushl %es 112 pushl %fs 113 pushl %gs 114 115 # copy data to where the real-mode hook can handle it 116 movl 8(%ebp),%eax 117 movw %ax,FUNCTION_ADDR 118 movl 12(%ebp),%ebx 119 movl BIOSCALLREG_EAX(%ebx),%eax 120 movl %eax,EAX_REGADDR 121 movl BIOSCALLREG_EBX(%ebx),%eax 122 movl %eax,EBX_REGADDR 123 movl BIOSCALLREG_ECX(%ebx),%eax 124 movl %eax,ECX_REGADDR 125 movl BIOSCALLREG_EDX(%ebx),%eax 126 movl %eax,EDX_REGADDR 127 movl BIOSCALLREG_ESI(%ebx),%eax 128 movl %eax,ESI_REGADDR 129 movl BIOSCALLREG_EDI(%ebx),%eax 130 movl %eax,EDI_REGADDR 131 # merge current flags with certain provided flags 132 movl BIOSCALLREG_EFLAGS(%ebx),%ecx 133 pushfl 134 popl %eax 135 andl $~(COPY_FLAGS|PSL_I),%eax 136 andl $COPY_FLAGS,%ecx 137 orl %ecx,%eax 138 movl %eax,EFLAGS_REGADDR 139 movl $0, ES_REGADDR 140 141 # save flags, disable interrupts, do real mode stuff 142 pushfl 143 144 # save GDT 145 sgdt GDTR_SAVE_ADDR 146 147 # copy the GDT to local area 148 movl GDTR_SAVE_ADDR+2,%esi 149 movl $GDT_COPY_ADDR,%edi 150 movl $(NGDT*8),%ecx 151 cld 152 rep 153 movsb 154 movw $(NGDT*8)-1,GDTR_LOCAL_ADDR 155 movl $GDT_COPY_ADDR,GDTR_LOCAL_ADDR+2 156 157 # install GDT copy 158 lgdt GDTR_LOCAL_ADDR 159 160 cli 161 162 # save IDT 163 sidt IDTR_SAVE_ADDR 164 165 # set up new stack: save old ones, create new segs 166 movl %esp,STACK_PTR_ADDR 167 movl %ebp,BASE_PTR_ADDR 168 movl $REALSTACK,%esp 169 movl $0,%ebp # leave no trace, there is none. 170 171 # save CR3 172 movl %cr3,%eax 173 movl %eax,CR3_ADDR 174 175 # turn off paging 176 movl %cr0,%eax 177 andl $~(CR0_PG),%eax 178 movl %eax,%cr0 179 180 # flush TLB, drop PDBR 181 xorl %eax,%eax 182 movl %eax,%cr3 183 184 ## load 16-bit segment descriptors 185 movw $GSEL(GBIOSDATA_SEL,SEL_KPL),%bx 186 movw %bx,%ds 187 movw %bx,%es 188 movw %bx,%fs 189 movw %bx,%gs 190 191 ljmp $GSEL(GBIOSCODE_SEL,SEL_KPL),$x16+MYBASE 192 193 x16: 194 # turn off protected mode--yikes! 195 mov %cr0,%eax 196 data32 197 and $~CR0_PE,%eax 198 mov %eax,%cr0 199 200 # need inter-segment jump to reload real-mode CS 201 data32 202 ljmp $(MYBASE>>4),$xreal 203 204 xreal: # really in real mode now 205 # set up segment selectors. Note: everything is now relative 206 # to zero-base in this file, except %ss. 207 # data items in our scratch area need to reflect MYADDR 208 xorl %ax,%ax 209 movw %ax,%ss 210 211 movw %cs,%ax 212 movw %ax,%es 213 movw %ax,%fs 214 movw %ax,%gs 215 movw %ax,%ds 216 217 ## load IDT, now that we are here. 218 addr32 219 lidt IDT_bios 220 221 # Don't forget that we're in real mode, with 16-bit default data. 222 # all these movl's are really movw's, and movw's are movl's! 223 addr32 224 movw EDI_REGADDR-MYBASE,%edi 225 addr32 226 movw ESI_REGADDR-MYBASE,%esi 227 addr32 228 movw EDX_REGADDR-MYBASE,%edx 229 addr32 230 movw ECX_REGADDR-MYBASE,%ecx 231 addr32 232 movw EBX_REGADDR-MYBASE,%ebx 233 addr32 234 movb FUNCTION_ADDR-MYBASE,%al 235 addr32 236 movb %al,intaddr+1 # self modifying code, yuck. no indirect interrupt instruction! 237 # long jump to flush processor cache to reflect code modification 238 data32 239 ljmp $(MYBASE>>4),$flushit 240 flushit: 241 addr32 242 movw EFLAGS_REGADDR-MYBASE,%eax 243 pushl %eax 244 popfl 245 addr32 246 movw EAX_REGADDR-MYBASE,%eax 247 248 intaddr: 249 int $0xff 250 251 # save results 252 pushf 253 addr32 254 movw %eax,EAX_REGADDR-MYBASE 255 addr32 256 movw %ebx,EBX_REGADDR-MYBASE 257 addr32 258 movw %ecx,ECX_REGADDR-MYBASE 259 addr32 260 movw %edx,EDX_REGADDR-MYBASE 261 addr32 262 movw %esi,ESI_REGADDR-MYBASE 263 addr32 264 movw %edi,EDI_REGADDR-MYBASE 265 pop %eax 266 addr32 267 movw %eax,EFLAGS_REGADDR-MYBASE 268 addr32 269 movw %es,ES_REGADDR-MYBASE 270 271 # and return to protected mode 272 cli # just to be sure 273 274 mov %cr0,%eax 275 data32 276 or $CR0_PE,%eax 277 mov %eax,%cr0 278 279 # long jump to 32-bit code segment 280 data32 281 ljmp $GSEL(GCODE_SEL,SEL_KPL),$x32+MYBASE 282 x32: 283 #back in 32-bit mode/protected mode (but not paging yet). 284 # Reload the segment registers & IDT 285 286 movw $GSEL(GDATA_SEL,SEL_KPL),%bx 287 movw %bx,%ds 288 movw %bx,%ss 289 movw %bx,%es 290 291 # reload PDBR 292 movl CR3_ADDR,%eax 293 movl %eax,%cr3 294 movl %cr0,%eax 295 orl $CR0_PG,%eax 296 movl %eax,%cr0 297 298 # reload system copy of GDT 299 lgdt GDTR_SAVE_ADDR 300 301 # restore protected-mode stack 302 movl STACK_PTR_ADDR,%esp 303 movl BASE_PTR_ADDR,%ebp 304 305 #restore protected-mode IDT 306 lidt IDTR_SAVE_ADDR 307 308 # copy back arguments from holding pen 309 310 movl 12(%ebp),%ebx 311 movl EAX_REGADDR,%eax 312 movl %eax,BIOSCALLREG_EAX(%ebx) 313 movl EBX_REGADDR,%eax 314 movl %eax,BIOSCALLREG_EBX(%ebx) 315 movl ECX_REGADDR,%eax 316 movl %eax,BIOSCALLREG_ECX(%ebx) 317 movl EDX_REGADDR,%eax 318 movl %eax,BIOSCALLREG_EDX(%ebx) 319 movl ESI_REGADDR,%eax 320 movl %eax,BIOSCALLREG_ESI(%ebx) 321 movl EDI_REGADDR,%eax 322 movl %eax,BIOSCALLREG_EDI(%ebx) 323 movl EFLAGS_REGADDR,%eax 324 movl %eax,BIOSCALLREG_EFLAGS(%ebx) 325 movl ES_REGADDR, %eax 326 movl %eax,BIOSCALLREG_ES(%ebx) 327 328 # finish up, restore registers, and return 329 popfl 330 popl %gs 331 popl %fs 332 popl %es 333 popl %ds # see above 334 popl %ebx 335 popl %edi 336 popl %esi 337 leave 338 ret 339 340 #ifdef __ELF__ 341 .align 16 342 #else 343 .align 4 344 #endif 345 IDT_bios: # BIOS IDT descriptor (real-mode) 346 .word 1023 347 .long 0 348
Indexes created Tue Sep 30 17:09:57 GMT 2025