Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/i386/i386/locore.S
Version:
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1 /*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * William Jolitz. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * from: @(#)locore.s 7.3 (Berkeley) 5/13/91 33 * $FreeBSD$ 34 * 35 * originally from: locore.s, by William F. Jolitz 36 * 37 * Substantially rewritten by David Greenman, Rod Grimes, 38 * Bruce Evans, Wolfgang Solfrank, Poul-Henning Kamp 39 * and many others. 40 */ 41 42 #include "opt_bootp.h" 43 #include "opt_nfsroot.h" 44 #include "opt_pmap.h" 45 46 #include <sys/reboot.h> 47 48 #include <machine/asmacros.h> 49 #include <machine/cputypes.h> 50 #include <machine/psl.h> 51 #include <machine/pmap.h> 52 #include <machine/specialreg.h> 53 54 #include "assym.inc" 55 56 /* 57 * Compiled KERNBASE location and the kernel load address, now identical. 58 */ 59 .globl kernbase 60 .set kernbase,KERNBASE 61 .globl kernload 62 .set kernload,KERNLOAD 63 64 /* 65 * Globals 66 */ 67 .data 68 ALIGN_DATA /* just to be sure */ 69 70 .space 0x2000 /* space for tmpstk - temporary stack */ 71 tmpstk: 72 73 .globl bootinfo 74 bootinfo: .space BOOTINFO_SIZE /* bootinfo that we can handle */ 75 76 .text 77 /********************************************************************** 78 * 79 * This is where the bootblocks start us, set the ball rolling... 80 * 81 */ 82 ENTRY(btext) 83 84 /* Tell the bios to warmboot next time */ 85 movw $0x1234,0x472 86 87 /* Set up a real frame in case the double return in newboot is executed. */ 88 xorl %ebp,%ebp 89 pushl %ebp 90 movl %esp, %ebp 91 92 /* Don't trust what the BIOS gives for eflags. */ 93 pushl $PSL_KERNEL 94 popfl 95 96 /* 97 * Don't trust what the BIOS gives for %fs and %gs. Trust the bootstrap 98 * to set %cs, %ds, %es and %ss. 99 */ 100 mov %ds, %ax 101 mov %ax, %fs 102 mov %ax, %gs 103 104 /* 105 * Clear the bss. Not all boot programs do it, and it is our job anyway. 106 * 107 * XXX we don't check that there is memory for our bss and page tables 108 * before using it. 109 * 110 * Note: we must be careful to not overwrite an active gdt or idt. They 111 * inactive from now until we switch to new ones, since we don't load any 112 * more segment registers or permit interrupts until after the switch. 113 */ 114 movl $__bss_end,%ecx 115 movl $__bss_start,%edi 116 subl %edi,%ecx 117 xorl %eax,%eax 118 cld 119 rep 120 stosb 121 122 call recover_bootinfo 123 124 /* Get onto a stack that we can trust. */ 125 /* 126 * XXX this step is delayed in case recover_bootinfo needs to return via 127 * the old stack, but it need not be, since recover_bootinfo actually 128 * returns via the old frame. 129 */ 130 movl $tmpstk,%esp 131 132 call identify_cpu 133 call pmap_cold 134 135 /* set up bootstrap stack */ 136 movl proc0kstack,%eax /* location of in-kernel stack */ 137 138 /* 139 * Only use bottom page for init386(). init386() calculates the 140 * PCB + FPU save area size and returns the true top of stack. 141 */ 142 leal PAGE_SIZE(%eax),%esp 143 144 xorl %ebp,%ebp /* mark end of frames */ 145 146 pushl physfree /* value of first for init386(first) */ 147 call init386 /* wire 386 chip for unix operation */ 148 149 /* 150 * Clean up the stack in a way that db_numargs() understands, so 151 * that backtraces in ddb don't underrun the stack. Traps for 152 * inaccessible memory are more fatal than usual this early. 153 */ 154 addl $4,%esp 155 156 /* Switch to true top of stack. */ 157 movl %eax,%esp 158 159 call mi_startup /* autoconfiguration, mountroot etc */ 160 /* NOTREACHED */ 161 addl $0,%esp /* for db_numargs() again */ 162 163 /********************************************************************** 164 * 165 * Recover the bootinfo passed to us from the boot program 166 * 167 */ 168 recover_bootinfo: 169 /* 170 * This code is called in different ways depending on what loaded 171 * and started the kernel. This is used to detect how we get the 172 * arguments from the other code and what we do with them. 173 * 174 * Old disk boot blocks: 175 * (*btext)(howto, bootdev, cyloffset, esym); 176 * [return address == 0, and can NOT be returned to] 177 * [cyloffset was not supported by the FreeBSD boot code 178 * and always passed in as 0] 179 * [esym is also known as total in the boot code, and 180 * was never properly supported by the FreeBSD boot code] 181 * This code from 1.x/2.x doesn't supply now-required metadata and 182 * likely will fail (we test for it to avoid dereferencing stack 183 * garbage here). 184 * 185 * Old diskless netboot code: 186 * (*btext)(0,0,0,0,&nfsdiskless,0,0,0); 187 * [return address != 0, and can NOT be returned to] 188 * If we are being booted by this code it will NOT work, 189 * so we are just going to halt if we find this case. 190 * 191 * New uniform boot code: 192 * (*btext)(howto, bootdev, 0, 0, 0, &bootinfo) 193 * [return address != 0, and can be returned to] 194 * 195 * There may seem to be a lot of wasted arguments in here, but 196 * that is so the newer boot code can still load very old kernels 197 * and old boot code can load new kernels. 198 */ 199 200 /* 201 * The old style disk boot blocks fake a frame on the stack and did an 202 * lret to get here. The frame on the stack has a return address of 0. 203 * This style of boot (from 1.x / 2.x) almost certainly won't work, 204 * since the kernel has required metadata since about 7.x or so and none 205 * are present. 206 */ 207 cmpl $0,4(%ebp) 208 je olddiskboot 209 210 /* 211 * We have some form of return address, so this is either the 212 * old diskless netboot code, or the new uniform code. That can 213 * be detected by looking at the 5th argument, if it is 0 214 * we are being booted by the new uniform boot code. 215 */ 216 cmpl $0,24(%ebp) 217 je newboot 218 219 /* 220 * Seems we have been loaded by the old 1.x/2.x diskless boot code, we 221 * don't stand a chance of running as the diskless structure changed 222 * considerably between the two, so just halt. 223 */ 224 hlt 225 226 /* 227 * We have been loaded by the new uniform boot code. 228 * Let's check the bootinfo version, and if we do not understand 229 * it we return to the loader with a status of 1 to indicate this error 230 */ 231 newboot: 232 movl 28(%ebp),%ebx /* &bootinfo.version */ 233 movl BI_VERSION(%ebx),%eax 234 cmpl $1,%eax /* We only understand version 1 */ 235 je 1f 236 testl $RB_BOOTINFO,8(%ebp) /* bi_size (and bootinfo) valid? */ 237 jne 1f 238 movl $1,%eax /* Return status */ 239 leave 240 /* 241 * XXX this returns to our caller's caller (as is required) since 242 * we didn't set up a frame and our caller did. 243 */ 244 ret 245 246 1: 247 /* 248 * If we have a kernelname copy it in 249 */ 250 movl BI_KERNELNAME(%ebx),%esi 251 cmpl $0,%esi 252 je 2f /* No kernelname */ 253 movl $MAXPATHLEN,%ecx /* Brute force!!! */ 254 movl $kernelname,%edi 255 cmpb $'/',(%esi) /* Make sure it starts with a slash */ 256 je 1f 257 movb $'/',(%edi) 258 incl %edi 259 decl %ecx 260 1: 261 cld 262 rep 263 movsb 264 265 2: 266 /* 267 * Determine the size of the boot loader's copy of the bootinfo 268 * struct. Copy min(our size, loader's size) into our bootinfo. 269 * Incompatible with really old boot loaders from FreeBSD 1.x and 2.0. 270 */ 271 movl %ebx,%esi 272 movl $bootinfo,%edi 273 movl BI_SIZE(%ebx),%ecx 274 cmpl $BOOTINFO_SIZE,%ecx 275 jbe got_common_bi_size 276 movl $BOOTINFO_SIZE,%ecx 277 got_common_bi_size: 278 cld 279 rep 280 movsb 281 282 #ifdef NFS_ROOT 283 #ifndef BOOTP_NFSV3 284 /* 285 * If we have a nfs_diskless structure copy it in 286 */ 287 movl BI_NFS_DISKLESS(%ebx),%esi 288 cmpl $0,%esi 289 je olddiskboot 290 movl $nfs_diskless,%edi 291 movl $NFSDISKLESS_SIZE,%ecx 292 cld 293 rep 294 movsb 295 movl $nfs_diskless_valid,%edi 296 movl $1,(%edi) 297 #endif 298 #endif 299 300 /* 301 * The old style disk boot. 302 * (*btext)(howto, bootdev, cyloffset, esym); 303 * Note that the newer boot code just falls into here to pick 304 * up howto and bootdev, cyloffset and esym are no longer used 305 */ 306 olddiskboot: 307 movl 8(%ebp),%eax 308 movl %eax,boothowto 309 movl 12(%ebp),%eax 310 movl %eax,bootdev 311 312 ret 313 314 315 /********************************************************************** 316 * 317 * Identify the CPU and initialize anything special about it 318 * 319 */ 320 ENTRY(identify_cpu) 321 322 pushl %ebx 323 324 /* Try to toggle alignment check flag; does not exist on 386. */ 325 pushfl 326 popl %eax 327 movl %eax,%ecx 328 orl $PSL_AC,%eax 329 pushl %eax 330 popfl 331 pushfl 332 popl %eax 333 xorl %ecx,%eax 334 andl $PSL_AC,%eax 335 pushl %ecx 336 popfl 337 338 testl %eax,%eax 339 jnz try486 340 341 /* NexGen CPU does not have alignment check flag. */ 342 pushfl 343 movl $0x5555, %eax 344 xorl %edx, %edx 345 movl $2, %ecx 346 clc 347 divl %ecx 348 jz trynexgen 349 popfl 350 movl $CPU_386,cpu 351 jmp 3f 352 353 trynexgen: 354 popfl 355 movl $CPU_NX586,cpu 356 movl $0x4778654e,cpu_vendor # store vendor string 357 movl $0x72446e65,cpu_vendor+4 358 movl $0x6e657669,cpu_vendor+8 359 movl $0,cpu_vendor+12 360 jmp 3f 361 362 try486: /* Try to toggle identification flag; does not exist on early 486s. */ 363 pushfl 364 popl %eax 365 movl %eax,%ecx 366 xorl $PSL_ID,%eax 367 pushl %eax 368 popfl 369 pushfl 370 popl %eax 371 xorl %ecx,%eax 372 andl $PSL_ID,%eax 373 pushl %ecx 374 popfl 375 376 testl %eax,%eax 377 jnz trycpuid 378 movl $CPU_486,cpu 379 380 /* 381 * Check Cyrix CPU 382 * Cyrix CPUs do not change the undefined flags following 383 * execution of the divide instruction which divides 5 by 2. 384 * 385 * Note: CPUID is enabled on M2, so it passes another way. 386 */ 387 pushfl 388 movl $0x5555, %eax 389 xorl %edx, %edx 390 movl $2, %ecx 391 clc 392 divl %ecx 393 jnc trycyrix 394 popfl 395 jmp 3f /* You may use Intel CPU. */ 396 397 trycyrix: 398 popfl 399 /* 400 * IBM Bluelighting CPU also doesn't change the undefined flags. 401 * Because IBM doesn't disclose the information for Bluelighting 402 * CPU, we couldn't distinguish it from Cyrix's (including IBM 403 * brand of Cyrix CPUs). 404 */ 405 movl $0x69727943,cpu_vendor # store vendor string 406 movl $0x736e4978,cpu_vendor+4 407 movl $0x64616574,cpu_vendor+8 408 jmp 3f 409 410 trycpuid: /* Use the `cpuid' instruction. */ 411 xorl %eax,%eax 412 cpuid # cpuid 0 413 movl %eax,cpu_high # highest capability 414 movl %ebx,cpu_vendor # store vendor string 415 movl %edx,cpu_vendor+4 416 movl %ecx,cpu_vendor+8 417 movb $0,cpu_vendor+12 418 419 movl $1,%eax 420 cpuid # cpuid 1 421 movl %eax,cpu_id # store cpu_id 422 movl %ebx,cpu_procinfo # store cpu_procinfo 423 movl %edx,cpu_feature # store cpu_feature 424 movl %ecx,cpu_feature2 # store cpu_feature2 425 rorl $8,%eax # extract family type 426 andl $15,%eax 427 cmpl $5,%eax 428 jae 1f 429 430 /* less than Pentium; must be 486 */ 431 movl $CPU_486,cpu 432 jmp 3f 433 1: 434 /* a Pentium? */ 435 cmpl $5,%eax 436 jne 2f 437 movl $CPU_586,cpu 438 jmp 3f 439 2: 440 /* Greater than Pentium...call it a Pentium Pro */ 441 movl $CPU_686,cpu 442 3: 443 popl %ebx 444 ret 445 END(identify_cpu) 446 447 #ifdef XENHVM 448 /* Xen Hypercall page */ 449 .text 450 .p2align PAGE_SHIFT, 0x90 /* Hypercall_page needs to be PAGE aligned */ 451 452 ENTRY(hypercall_page) 453 .skip 0x1000, 0x90 /* Fill with "nop"s */ 454 #endif
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