| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* | 
|  | 2 | * arch/alpha/kernel/entry.S | 
|  | 3 | * | 
|  | 4 | * Kernel entry-points. | 
|  | 5 | */ | 
|  | 6 |  | 
|  | 7 | #include <linux/config.h> | 
|  | 8 | #include <asm/asm_offsets.h> | 
|  | 9 | #include <asm/thread_info.h> | 
|  | 10 | #include <asm/pal.h> | 
|  | 11 | #include <asm/errno.h> | 
|  | 12 | #include <asm/unistd.h> | 
|  | 13 |  | 
|  | 14 | .text | 
|  | 15 | .set noat | 
|  | 16 |  | 
|  | 17 | /* Stack offsets.  */ | 
|  | 18 | #define SP_OFF			184 | 
|  | 19 | #define SWITCH_STACK_SIZE	320 | 
|  | 20 |  | 
|  | 21 | /* | 
|  | 22 | * This defines the normal kernel pt-regs layout. | 
|  | 23 | * | 
|  | 24 | * regs 9-15 preserved by C code | 
|  | 25 | * regs 16-18 saved by PAL-code | 
|  | 26 | * regs 29-30 saved and set up by PAL-code | 
|  | 27 | * JRP - Save regs 16-18 in a special area of the stack, so that | 
|  | 28 | * the palcode-provided values are available to the signal handler. | 
|  | 29 | */ | 
|  | 30 |  | 
|  | 31 | #define SAVE_ALL			\ | 
|  | 32 | subq	$sp, SP_OFF, $sp;	\ | 
|  | 33 | stq	$0, 0($sp);		\ | 
|  | 34 | stq	$1, 8($sp);		\ | 
|  | 35 | stq	$2, 16($sp);		\ | 
|  | 36 | stq	$3, 24($sp);		\ | 
|  | 37 | stq	$4, 32($sp);		\ | 
|  | 38 | stq	$28, 144($sp);		\ | 
|  | 39 | lda	$2, alpha_mv;		\ | 
|  | 40 | stq	$5, 40($sp);		\ | 
|  | 41 | stq	$6, 48($sp);		\ | 
|  | 42 | stq	$7, 56($sp);		\ | 
|  | 43 | stq	$8, 64($sp);		\ | 
|  | 44 | stq	$19, 72($sp);		\ | 
|  | 45 | stq	$20, 80($sp);		\ | 
|  | 46 | stq	$21, 88($sp);		\ | 
|  | 47 | ldq	$2, HAE_CACHE($2);	\ | 
|  | 48 | stq	$22, 96($sp);		\ | 
|  | 49 | stq	$23, 104($sp);		\ | 
|  | 50 | stq	$24, 112($sp);		\ | 
|  | 51 | stq	$25, 120($sp);		\ | 
|  | 52 | stq	$26, 128($sp);		\ | 
|  | 53 | stq	$27, 136($sp);		\ | 
|  | 54 | stq	$2, 152($sp);		\ | 
|  | 55 | stq	$16, 160($sp);		\ | 
|  | 56 | stq	$17, 168($sp);		\ | 
|  | 57 | stq	$18, 176($sp) | 
|  | 58 |  | 
|  | 59 | #define RESTORE_ALL			\ | 
|  | 60 | lda	$19, alpha_mv;		\ | 
|  | 61 | ldq	$0, 0($sp);		\ | 
|  | 62 | ldq	$1, 8($sp);		\ | 
|  | 63 | ldq	$2, 16($sp);		\ | 
|  | 64 | ldq	$3, 24($sp);		\ | 
|  | 65 | ldq	$21, 152($sp);		\ | 
|  | 66 | ldq	$20, HAE_CACHE($19);	\ | 
|  | 67 | ldq	$4, 32($sp);		\ | 
|  | 68 | ldq	$5, 40($sp);		\ | 
|  | 69 | ldq	$6, 48($sp);		\ | 
|  | 70 | ldq	$7, 56($sp);		\ | 
|  | 71 | subq	$20, $21, $20;		\ | 
|  | 72 | ldq	$8, 64($sp);		\ | 
|  | 73 | beq	$20, 99f;		\ | 
|  | 74 | ldq	$20, HAE_REG($19);	\ | 
|  | 75 | stq	$21, HAE_CACHE($19);	\ | 
|  | 76 | stq	$21, 0($20);		\ | 
|  | 77 | ldq	$0, 0($sp);		\ | 
|  | 78 | ldq	$1, 8($sp);		\ | 
|  | 79 | 99:;					\ | 
|  | 80 | ldq	$19, 72($sp);		\ | 
|  | 81 | ldq	$20, 80($sp);		\ | 
|  | 82 | ldq	$21, 88($sp);		\ | 
|  | 83 | ldq	$22, 96($sp);		\ | 
|  | 84 | ldq	$23, 104($sp);		\ | 
|  | 85 | ldq	$24, 112($sp);		\ | 
|  | 86 | ldq	$25, 120($sp);		\ | 
|  | 87 | ldq	$26, 128($sp);		\ | 
|  | 88 | ldq	$27, 136($sp);		\ | 
|  | 89 | ldq	$28, 144($sp);		\ | 
|  | 90 | addq	$sp, SP_OFF, $sp | 
|  | 91 |  | 
|  | 92 | /* | 
|  | 93 | * Non-syscall kernel entry points. | 
|  | 94 | */ | 
|  | 95 |  | 
|  | 96 | .align	4 | 
|  | 97 | .globl	entInt | 
|  | 98 | .ent	entInt | 
|  | 99 | entInt: | 
|  | 100 | SAVE_ALL | 
|  | 101 | lda	$8, 0x3fff | 
|  | 102 | lda	$26, ret_from_sys_call | 
|  | 103 | bic	$sp, $8, $8 | 
|  | 104 | mov	$sp, $19 | 
|  | 105 | jsr	$31, do_entInt | 
|  | 106 | .end entInt | 
|  | 107 |  | 
|  | 108 | .align	4 | 
|  | 109 | .globl	entArith | 
|  | 110 | .ent	entArith | 
|  | 111 | entArith: | 
|  | 112 | SAVE_ALL | 
|  | 113 | lda	$8, 0x3fff | 
|  | 114 | lda	$26, ret_from_sys_call | 
|  | 115 | bic	$sp, $8, $8 | 
|  | 116 | mov	$sp, $18 | 
|  | 117 | jsr	$31, do_entArith | 
|  | 118 | .end entArith | 
|  | 119 |  | 
|  | 120 | .align	4 | 
|  | 121 | .globl	entMM | 
|  | 122 | .ent	entMM | 
|  | 123 | entMM: | 
|  | 124 | SAVE_ALL | 
|  | 125 | /* save $9 - $15 so the inline exception code can manipulate them.  */ | 
|  | 126 | subq	$sp, 56, $sp | 
|  | 127 | stq	$9, 0($sp) | 
|  | 128 | stq	$10, 8($sp) | 
|  | 129 | stq	$11, 16($sp) | 
|  | 130 | stq	$12, 24($sp) | 
|  | 131 | stq	$13, 32($sp) | 
|  | 132 | stq	$14, 40($sp) | 
|  | 133 | stq	$15, 48($sp) | 
|  | 134 | addq	$sp, 56, $19 | 
|  | 135 | /* handle the fault */ | 
|  | 136 | lda	$8, 0x3fff | 
|  | 137 | bic	$sp, $8, $8 | 
|  | 138 | jsr	$26, do_page_fault | 
|  | 139 | /* reload the registers after the exception code played.  */ | 
|  | 140 | ldq	$9, 0($sp) | 
|  | 141 | ldq	$10, 8($sp) | 
|  | 142 | ldq	$11, 16($sp) | 
|  | 143 | ldq	$12, 24($sp) | 
|  | 144 | ldq	$13, 32($sp) | 
|  | 145 | ldq	$14, 40($sp) | 
|  | 146 | ldq	$15, 48($sp) | 
|  | 147 | addq	$sp, 56, $sp | 
|  | 148 | /* finish up the syscall as normal.  */ | 
|  | 149 | br	ret_from_sys_call | 
|  | 150 | .end entMM | 
|  | 151 |  | 
|  | 152 | .align	4 | 
|  | 153 | .globl	entIF | 
|  | 154 | .ent	entIF | 
|  | 155 | entIF: | 
|  | 156 | SAVE_ALL | 
|  | 157 | lda	$8, 0x3fff | 
|  | 158 | lda	$26, ret_from_sys_call | 
|  | 159 | bic	$sp, $8, $8 | 
|  | 160 | mov	$sp, $17 | 
|  | 161 | jsr	$31, do_entIF | 
|  | 162 | .end entIF | 
|  | 163 |  | 
|  | 164 | .align	4 | 
|  | 165 | .globl	entUna | 
|  | 166 | .ent	entUna | 
|  | 167 | entUna: | 
|  | 168 | lda	$sp, -256($sp) | 
|  | 169 | stq	$0, 0($sp) | 
|  | 170 | ldq	$0, 256($sp)	/* get PS */ | 
|  | 171 | stq	$1, 8($sp) | 
|  | 172 | stq	$2, 16($sp) | 
|  | 173 | stq	$3, 24($sp) | 
|  | 174 | and	$0, 8, $0		/* user mode? */ | 
|  | 175 | stq	$4, 32($sp) | 
|  | 176 | bne	$0, entUnaUser	/* yup -> do user-level unaligned fault */ | 
|  | 177 | stq	$5, 40($sp) | 
|  | 178 | stq	$6, 48($sp) | 
|  | 179 | stq	$7, 56($sp) | 
|  | 180 | stq	$8, 64($sp) | 
|  | 181 | stq	$9, 72($sp) | 
|  | 182 | stq	$10, 80($sp) | 
|  | 183 | stq	$11, 88($sp) | 
|  | 184 | stq	$12, 96($sp) | 
|  | 185 | stq	$13, 104($sp) | 
|  | 186 | stq	$14, 112($sp) | 
|  | 187 | stq	$15, 120($sp) | 
|  | 188 | /* 16-18 PAL-saved */ | 
|  | 189 | stq	$19, 152($sp) | 
|  | 190 | stq	$20, 160($sp) | 
|  | 191 | stq	$21, 168($sp) | 
|  | 192 | stq	$22, 176($sp) | 
|  | 193 | stq	$23, 184($sp) | 
|  | 194 | stq	$24, 192($sp) | 
|  | 195 | stq	$25, 200($sp) | 
|  | 196 | stq	$26, 208($sp) | 
|  | 197 | stq	$27, 216($sp) | 
|  | 198 | stq	$28, 224($sp) | 
|  | 199 | stq	$gp, 232($sp) | 
|  | 200 | lda	$8, 0x3fff | 
|  | 201 | stq	$31, 248($sp) | 
|  | 202 | bic	$sp, $8, $8 | 
|  | 203 | jsr	$26, do_entUna | 
|  | 204 | ldq	$0, 0($sp) | 
|  | 205 | ldq	$1, 8($sp) | 
|  | 206 | ldq	$2, 16($sp) | 
|  | 207 | ldq	$3, 24($sp) | 
|  | 208 | ldq	$4, 32($sp) | 
|  | 209 | ldq	$5, 40($sp) | 
|  | 210 | ldq	$6, 48($sp) | 
|  | 211 | ldq	$7, 56($sp) | 
|  | 212 | ldq	$8, 64($sp) | 
|  | 213 | ldq	$9, 72($sp) | 
|  | 214 | ldq	$10, 80($sp) | 
|  | 215 | ldq	$11, 88($sp) | 
|  | 216 | ldq	$12, 96($sp) | 
|  | 217 | ldq	$13, 104($sp) | 
|  | 218 | ldq	$14, 112($sp) | 
|  | 219 | ldq	$15, 120($sp) | 
|  | 220 | /* 16-18 PAL-saved */ | 
|  | 221 | ldq	$19, 152($sp) | 
|  | 222 | ldq	$20, 160($sp) | 
|  | 223 | ldq	$21, 168($sp) | 
|  | 224 | ldq	$22, 176($sp) | 
|  | 225 | ldq	$23, 184($sp) | 
|  | 226 | ldq	$24, 192($sp) | 
|  | 227 | ldq	$25, 200($sp) | 
|  | 228 | ldq	$26, 208($sp) | 
|  | 229 | ldq	$27, 216($sp) | 
|  | 230 | ldq	$28, 224($sp) | 
|  | 231 | ldq	$gp, 232($sp) | 
|  | 232 | lda	$sp, 256($sp) | 
|  | 233 | call_pal PAL_rti | 
|  | 234 | .end entUna | 
|  | 235 |  | 
|  | 236 | .align	4 | 
|  | 237 | .ent	entUnaUser | 
|  | 238 | entUnaUser: | 
|  | 239 | ldq	$0, 0($sp)	/* restore original $0 */ | 
|  | 240 | lda	$sp, 256($sp)	/* pop entUna's stack frame */ | 
|  | 241 | SAVE_ALL		/* setup normal kernel stack */ | 
|  | 242 | lda	$sp, -56($sp) | 
|  | 243 | stq	$9, 0($sp) | 
|  | 244 | stq	$10, 8($sp) | 
|  | 245 | stq	$11, 16($sp) | 
|  | 246 | stq	$12, 24($sp) | 
|  | 247 | stq	$13, 32($sp) | 
|  | 248 | stq	$14, 40($sp) | 
|  | 249 | stq	$15, 48($sp) | 
|  | 250 | lda	$8, 0x3fff | 
|  | 251 | addq	$sp, 56, $19 | 
|  | 252 | bic	$sp, $8, $8 | 
|  | 253 | jsr	$26, do_entUnaUser | 
|  | 254 | ldq	$9, 0($sp) | 
|  | 255 | ldq	$10, 8($sp) | 
|  | 256 | ldq	$11, 16($sp) | 
|  | 257 | ldq	$12, 24($sp) | 
|  | 258 | ldq	$13, 32($sp) | 
|  | 259 | ldq	$14, 40($sp) | 
|  | 260 | ldq	$15, 48($sp) | 
|  | 261 | lda	$sp, 56($sp) | 
|  | 262 | br	ret_from_sys_call | 
|  | 263 | .end entUnaUser | 
|  | 264 |  | 
|  | 265 | .align	4 | 
|  | 266 | .globl	entDbg | 
|  | 267 | .ent	entDbg | 
|  | 268 | entDbg: | 
|  | 269 | SAVE_ALL | 
|  | 270 | lda	$8, 0x3fff | 
|  | 271 | lda	$26, ret_from_sys_call | 
|  | 272 | bic	$sp, $8, $8 | 
|  | 273 | mov	$sp, $16 | 
|  | 274 | jsr	$31, do_entDbg | 
|  | 275 | .end entDbg | 
|  | 276 |  | 
|  | 277 | /* | 
|  | 278 | * The system call entry point is special.  Most importantly, it looks | 
|  | 279 | * like a function call to userspace as far as clobbered registers.  We | 
|  | 280 | * do preserve the argument registers (for syscall restarts) and $26 | 
|  | 281 | * (for leaf syscall functions). | 
|  | 282 | * | 
|  | 283 | * So much for theory.  We don't take advantage of this yet. | 
|  | 284 | * | 
|  | 285 | * Note that a0-a2 are not saved by PALcode as with the other entry points. | 
|  | 286 | */ | 
|  | 287 |  | 
|  | 288 | .align	4 | 
|  | 289 | .globl	entSys | 
|  | 290 | .globl	ret_from_sys_call | 
|  | 291 | .ent	entSys | 
|  | 292 | entSys: | 
|  | 293 | SAVE_ALL | 
|  | 294 | lda	$8, 0x3fff | 
|  | 295 | bic	$sp, $8, $8 | 
|  | 296 | lda	$4, NR_SYSCALLS($31) | 
|  | 297 | stq	$16, SP_OFF+24($sp) | 
|  | 298 | lda	$5, sys_call_table | 
|  | 299 | lda	$27, sys_ni_syscall | 
|  | 300 | cmpult	$0, $4, $4 | 
|  | 301 | ldl	$3, TI_FLAGS($8) | 
|  | 302 | stq	$17, SP_OFF+32($sp) | 
|  | 303 | s8addq	$0, $5, $5 | 
|  | 304 | stq	$18, SP_OFF+40($sp) | 
|  | 305 | blbs	$3, strace | 
|  | 306 | beq	$4, 1f | 
|  | 307 | ldq	$27, 0($5) | 
|  | 308 | 1:	jsr	$26, ($27), alpha_ni_syscall | 
|  | 309 | ldgp	$gp, 0($26) | 
|  | 310 | blt	$0, $syscall_error	/* the call failed */ | 
|  | 311 | stq	$0, 0($sp) | 
|  | 312 | stq	$31, 72($sp)		/* a3=0 => no error */ | 
|  | 313 |  | 
|  | 314 | .align	4 | 
|  | 315 | ret_from_sys_call: | 
|  | 316 | cmovne	$26, 0, $19		/* $19 = 0 => non-restartable */ | 
|  | 317 | ldq	$0, SP_OFF($sp) | 
|  | 318 | and	$0, 8, $0 | 
|  | 319 | beq	$0, restore_all | 
|  | 320 | ret_from_reschedule: | 
|  | 321 | /* Make sure need_resched and sigpending don't change between | 
|  | 322 | sampling and the rti.  */ | 
|  | 323 | lda	$16, 7 | 
|  | 324 | call_pal PAL_swpipl | 
|  | 325 | ldl	$5, TI_FLAGS($8) | 
|  | 326 | and	$5, _TIF_WORK_MASK, $2 | 
|  | 327 | bne	$5, work_pending | 
|  | 328 | restore_all: | 
|  | 329 | RESTORE_ALL | 
|  | 330 | call_pal PAL_rti | 
|  | 331 |  | 
|  | 332 | .align 3 | 
|  | 333 | $syscall_error: | 
|  | 334 | /* | 
|  | 335 | * Some system calls (e.g., ptrace) can return arbitrary | 
|  | 336 | * values which might normally be mistaken as error numbers. | 
|  | 337 | * Those functions must zero $0 (v0) directly in the stack | 
|  | 338 | * frame to indicate that a negative return value wasn't an | 
|  | 339 | * error number.. | 
|  | 340 | */ | 
|  | 341 | ldq	$19, 0($sp)	/* old syscall nr (zero if success) */ | 
|  | 342 | beq	$19, $ret_success | 
|  | 343 |  | 
|  | 344 | ldq	$20, 72($sp)	/* .. and this a3 */ | 
|  | 345 | subq	$31, $0, $0	/* with error in v0 */ | 
|  | 346 | addq	$31, 1, $1	/* set a3 for errno return */ | 
|  | 347 | stq	$0, 0($sp) | 
|  | 348 | mov	$31, $26	/* tell "ret_from_sys_call" we can restart */ | 
|  | 349 | stq	$1, 72($sp)	/* a3 for return */ | 
|  | 350 | br	ret_from_sys_call | 
|  | 351 |  | 
|  | 352 | $ret_success: | 
|  | 353 | stq	$0, 0($sp) | 
|  | 354 | stq	$31, 72($sp)	/* a3=0 => no error */ | 
|  | 355 | br	ret_from_sys_call | 
|  | 356 | .end entSys | 
|  | 357 |  | 
|  | 358 | /* | 
|  | 359 | * Do all cleanup when returning from all interrupts and system calls. | 
|  | 360 | * | 
|  | 361 | * Arguments: | 
|  | 362 | *       $5: TI_FLAGS. | 
|  | 363 | *       $8: current. | 
|  | 364 | *      $19: The old syscall number, or zero if this is not a return | 
|  | 365 | *           from a syscall that errored and is possibly restartable. | 
|  | 366 | *      $20: Error indication. | 
|  | 367 | */ | 
|  | 368 |  | 
|  | 369 | .align	4 | 
|  | 370 | .ent	work_pending | 
|  | 371 | work_pending: | 
|  | 372 | and	$5, _TIF_NEED_RESCHED, $2 | 
|  | 373 | beq	$2, $work_notifysig | 
|  | 374 |  | 
|  | 375 | $work_resched: | 
|  | 376 | subq	$sp, 16, $sp | 
|  | 377 | stq	$19, 0($sp)              /* save syscall nr */ | 
|  | 378 | stq	$20, 8($sp)              /* and error indication (a3) */ | 
|  | 379 | jsr	$26, schedule | 
|  | 380 | ldq	$19, 0($sp) | 
|  | 381 | ldq	$20, 8($sp) | 
|  | 382 | addq	$sp, 16, $sp | 
|  | 383 | /* Make sure need_resched and sigpending don't change between | 
|  | 384 | sampling and the rti.  */ | 
|  | 385 | lda	$16, 7 | 
|  | 386 | call_pal PAL_swpipl | 
|  | 387 | ldl	$5, TI_FLAGS($8) | 
|  | 388 | and	$5, _TIF_WORK_MASK, $2 | 
|  | 389 | beq	$2, restore_all | 
|  | 390 | and	$5, _TIF_NEED_RESCHED, $2 | 
|  | 391 | bne	$2, $work_resched | 
|  | 392 |  | 
|  | 393 | $work_notifysig: | 
|  | 394 | mov	$sp, $17 | 
|  | 395 | br	$1, do_switch_stack | 
|  | 396 | mov	$5, $21 | 
|  | 397 | mov	$sp, $18 | 
|  | 398 | mov	$31, $16 | 
|  | 399 | jsr	$26, do_notify_resume | 
|  | 400 | bsr	$1, undo_switch_stack | 
|  | 401 | br	restore_all | 
|  | 402 | .end work_pending | 
|  | 403 |  | 
|  | 404 | /* | 
|  | 405 | * PTRACE syscall handler | 
|  | 406 | */ | 
|  | 407 |  | 
|  | 408 | .align	4 | 
|  | 409 | .ent	strace | 
|  | 410 | strace: | 
|  | 411 | /* set up signal stack, call syscall_trace */ | 
|  | 412 | bsr	$1, do_switch_stack | 
|  | 413 | jsr	$26, syscall_trace | 
|  | 414 | bsr	$1, undo_switch_stack | 
|  | 415 |  | 
|  | 416 | /* get the system call number and the arguments back.. */ | 
|  | 417 | ldq	$0, 0($sp) | 
|  | 418 | ldq	$16, SP_OFF+24($sp) | 
|  | 419 | ldq	$17, SP_OFF+32($sp) | 
|  | 420 | ldq	$18, SP_OFF+40($sp) | 
|  | 421 | ldq	$19, 72($sp) | 
|  | 422 | ldq	$20, 80($sp) | 
|  | 423 | ldq	$21, 88($sp) | 
|  | 424 |  | 
|  | 425 | /* get the system call pointer.. */ | 
|  | 426 | lda	$1, NR_SYSCALLS($31) | 
|  | 427 | lda	$2, sys_call_table | 
|  | 428 | lda	$27, alpha_ni_syscall | 
|  | 429 | cmpult	$0, $1, $1 | 
|  | 430 | s8addq	$0, $2, $2 | 
|  | 431 | beq	$1, 1f | 
|  | 432 | ldq	$27, 0($2) | 
|  | 433 | 1:	jsr	$26, ($27), sys_gettimeofday | 
|  | 434 | ldgp	$gp, 0($26) | 
|  | 435 |  | 
|  | 436 | /* check return.. */ | 
|  | 437 | blt	$0, $strace_error	/* the call failed */ | 
|  | 438 | stq	$31, 72($sp)		/* a3=0 => no error */ | 
|  | 439 | $strace_success: | 
|  | 440 | stq	$0, 0($sp)		/* save return value */ | 
|  | 441 |  | 
|  | 442 | bsr	$1, do_switch_stack | 
|  | 443 | jsr	$26, syscall_trace | 
|  | 444 | bsr	$1, undo_switch_stack | 
|  | 445 | br	$31, ret_from_sys_call | 
|  | 446 |  | 
|  | 447 | .align	3 | 
|  | 448 | $strace_error: | 
|  | 449 | ldq	$19, 0($sp)	/* old syscall nr (zero if success) */ | 
|  | 450 | beq	$19, $strace_success | 
|  | 451 | ldq	$20, 72($sp)	/* .. and this a3 */ | 
|  | 452 |  | 
|  | 453 | subq	$31, $0, $0	/* with error in v0 */ | 
|  | 454 | addq	$31, 1, $1	/* set a3 for errno return */ | 
|  | 455 | stq	$0, 0($sp) | 
|  | 456 | stq	$1, 72($sp)	/* a3 for return */ | 
|  | 457 |  | 
|  | 458 | bsr	$1, do_switch_stack | 
|  | 459 | mov	$19, $9		/* save old syscall number */ | 
|  | 460 | mov	$20, $10	/* save old a3 */ | 
|  | 461 | jsr	$26, syscall_trace | 
|  | 462 | mov	$9, $19 | 
|  | 463 | mov	$10, $20 | 
|  | 464 | bsr	$1, undo_switch_stack | 
|  | 465 |  | 
|  | 466 | mov	$31, $26	/* tell "ret_from_sys_call" we can restart */ | 
|  | 467 | br	ret_from_sys_call | 
|  | 468 | .end strace | 
|  | 469 |  | 
|  | 470 | /* | 
|  | 471 | * Save and restore the switch stack -- aka the balance of the user context. | 
|  | 472 | */ | 
|  | 473 |  | 
|  | 474 | .align	4 | 
|  | 475 | .ent	do_switch_stack | 
|  | 476 | do_switch_stack: | 
|  | 477 | lda	$sp, -SWITCH_STACK_SIZE($sp) | 
|  | 478 | stq	$9, 0($sp) | 
|  | 479 | stq	$10, 8($sp) | 
|  | 480 | stq	$11, 16($sp) | 
|  | 481 | stq	$12, 24($sp) | 
|  | 482 | stq	$13, 32($sp) | 
|  | 483 | stq	$14, 40($sp) | 
|  | 484 | stq	$15, 48($sp) | 
|  | 485 | stq	$26, 56($sp) | 
|  | 486 | stt	$f0, 64($sp) | 
|  | 487 | stt	$f1, 72($sp) | 
|  | 488 | stt	$f2, 80($sp) | 
|  | 489 | stt	$f3, 88($sp) | 
|  | 490 | stt	$f4, 96($sp) | 
|  | 491 | stt	$f5, 104($sp) | 
|  | 492 | stt	$f6, 112($sp) | 
|  | 493 | stt	$f7, 120($sp) | 
|  | 494 | stt	$f8, 128($sp) | 
|  | 495 | stt	$f9, 136($sp) | 
|  | 496 | stt	$f10, 144($sp) | 
|  | 497 | stt	$f11, 152($sp) | 
|  | 498 | stt	$f12, 160($sp) | 
|  | 499 | stt	$f13, 168($sp) | 
|  | 500 | stt	$f14, 176($sp) | 
|  | 501 | stt	$f15, 184($sp) | 
|  | 502 | stt	$f16, 192($sp) | 
|  | 503 | stt	$f17, 200($sp) | 
|  | 504 | stt	$f18, 208($sp) | 
|  | 505 | stt	$f19, 216($sp) | 
|  | 506 | stt	$f20, 224($sp) | 
|  | 507 | stt	$f21, 232($sp) | 
|  | 508 | stt	$f22, 240($sp) | 
|  | 509 | stt	$f23, 248($sp) | 
|  | 510 | stt	$f24, 256($sp) | 
|  | 511 | stt	$f25, 264($sp) | 
|  | 512 | stt	$f26, 272($sp) | 
|  | 513 | stt	$f27, 280($sp) | 
|  | 514 | mf_fpcr	$f0		# get fpcr | 
|  | 515 | stt	$f28, 288($sp) | 
|  | 516 | stt	$f29, 296($sp) | 
|  | 517 | stt	$f30, 304($sp) | 
|  | 518 | stt	$f0, 312($sp)	# save fpcr in slot of $f31 | 
|  | 519 | ldt	$f0, 64($sp)	# dont let "do_switch_stack" change fp state. | 
|  | 520 | ret	$31, ($1), 1 | 
|  | 521 | .end do_switch_stack | 
|  | 522 |  | 
|  | 523 | .align	4 | 
|  | 524 | .ent	undo_switch_stack | 
|  | 525 | undo_switch_stack: | 
|  | 526 | ldq	$9, 0($sp) | 
|  | 527 | ldq	$10, 8($sp) | 
|  | 528 | ldq	$11, 16($sp) | 
|  | 529 | ldq	$12, 24($sp) | 
|  | 530 | ldq	$13, 32($sp) | 
|  | 531 | ldq	$14, 40($sp) | 
|  | 532 | ldq	$15, 48($sp) | 
|  | 533 | ldq	$26, 56($sp) | 
|  | 534 | ldt	$f30, 312($sp)	# get saved fpcr | 
|  | 535 | ldt	$f0, 64($sp) | 
|  | 536 | ldt	$f1, 72($sp) | 
|  | 537 | ldt	$f2, 80($sp) | 
|  | 538 | ldt	$f3, 88($sp) | 
|  | 539 | mt_fpcr	$f30		# install saved fpcr | 
|  | 540 | ldt	$f4, 96($sp) | 
|  | 541 | ldt	$f5, 104($sp) | 
|  | 542 | ldt	$f6, 112($sp) | 
|  | 543 | ldt	$f7, 120($sp) | 
|  | 544 | ldt	$f8, 128($sp) | 
|  | 545 | ldt	$f9, 136($sp) | 
|  | 546 | ldt	$f10, 144($sp) | 
|  | 547 | ldt	$f11, 152($sp) | 
|  | 548 | ldt	$f12, 160($sp) | 
|  | 549 | ldt	$f13, 168($sp) | 
|  | 550 | ldt	$f14, 176($sp) | 
|  | 551 | ldt	$f15, 184($sp) | 
|  | 552 | ldt	$f16, 192($sp) | 
|  | 553 | ldt	$f17, 200($sp) | 
|  | 554 | ldt	$f18, 208($sp) | 
|  | 555 | ldt	$f19, 216($sp) | 
|  | 556 | ldt	$f20, 224($sp) | 
|  | 557 | ldt	$f21, 232($sp) | 
|  | 558 | ldt	$f22, 240($sp) | 
|  | 559 | ldt	$f23, 248($sp) | 
|  | 560 | ldt	$f24, 256($sp) | 
|  | 561 | ldt	$f25, 264($sp) | 
|  | 562 | ldt	$f26, 272($sp) | 
|  | 563 | ldt	$f27, 280($sp) | 
|  | 564 | ldt	$f28, 288($sp) | 
|  | 565 | ldt	$f29, 296($sp) | 
|  | 566 | ldt	$f30, 304($sp) | 
|  | 567 | lda	$sp, SWITCH_STACK_SIZE($sp) | 
|  | 568 | ret	$31, ($1), 1 | 
|  | 569 | .end undo_switch_stack | 
|  | 570 |  | 
|  | 571 | /* | 
|  | 572 | * The meat of the context switch code. | 
|  | 573 | */ | 
|  | 574 |  | 
|  | 575 | .align	4 | 
|  | 576 | .globl	alpha_switch_to | 
|  | 577 | .ent	alpha_switch_to | 
|  | 578 | alpha_switch_to: | 
|  | 579 | .prologue 0 | 
|  | 580 | bsr	$1, do_switch_stack | 
|  | 581 | call_pal PAL_swpctx | 
|  | 582 | lda	$8, 0x3fff | 
|  | 583 | bsr	$1, undo_switch_stack | 
|  | 584 | bic	$sp, $8, $8 | 
|  | 585 | mov	$17, $0 | 
|  | 586 | ret | 
|  | 587 | .end alpha_switch_to | 
|  | 588 |  | 
|  | 589 | /* | 
|  | 590 | * New processes begin life here. | 
|  | 591 | */ | 
|  | 592 |  | 
|  | 593 | .globl	ret_from_fork | 
|  | 594 | .align	4 | 
|  | 595 | .ent	ret_from_fork | 
|  | 596 | ret_from_fork: | 
|  | 597 | lda	$26, ret_from_sys_call | 
|  | 598 | mov	$17, $16 | 
|  | 599 | jmp	$31, schedule_tail | 
|  | 600 | .end ret_from_fork | 
|  | 601 |  | 
|  | 602 | /* | 
|  | 603 | * kernel_thread(fn, arg, clone_flags) | 
|  | 604 | */ | 
|  | 605 | .align 4 | 
|  | 606 | .globl	kernel_thread | 
|  | 607 | .ent	kernel_thread | 
|  | 608 | kernel_thread: | 
|  | 609 | /* We can be called from a module.  */ | 
|  | 610 | ldgp	$gp, 0($27) | 
|  | 611 | .prologue 1 | 
|  | 612 | subq	$sp, SP_OFF+6*8, $sp | 
|  | 613 | br	$1, 2f		/* load start address */ | 
|  | 614 |  | 
|  | 615 | /* We've now "returned" from a fake system call.  */ | 
|  | 616 | unop | 
|  | 617 | blt	$0, 1f		/* error?  */ | 
|  | 618 | ldi	$1, 0x3fff | 
|  | 619 | beq	$20, 1f		/* parent or child?  */ | 
|  | 620 |  | 
|  | 621 | bic	$sp, $1, $8	/* in child.  */ | 
|  | 622 | jsr	$26, ($27) | 
|  | 623 | ldgp	$gp, 0($26) | 
|  | 624 | mov	$0, $16 | 
|  | 625 | mov	$31, $26 | 
|  | 626 | jmp	$31, sys_exit | 
|  | 627 |  | 
|  | 628 | 1:	ret			/* in parent.  */ | 
|  | 629 |  | 
|  | 630 | .align 4 | 
|  | 631 | 2:	/* Fake a system call stack frame, as we can't do system calls | 
|  | 632 | from kernel space.  Note that we store FN and ARG as they | 
|  | 633 | need to be set up in the child for the call.  Also store $8 | 
|  | 634 | and $26 for use in the parent.  */ | 
|  | 635 | stq	$31, SP_OFF($sp)	/* ps */ | 
|  | 636 | stq	$1, SP_OFF+8($sp)	/* pc */ | 
|  | 637 | stq	$gp, SP_OFF+16($sp)	/* gp */ | 
|  | 638 | stq	$16, 136($sp)		/* $27; FN for child */ | 
|  | 639 | stq	$17, SP_OFF+24($sp)	/* $16; ARG for child */ | 
|  | 640 | stq	$8, 64($sp)		/* $8 */ | 
|  | 641 | stq	$26, 128($sp)		/* $26 */ | 
|  | 642 | /* Avoid the HAE being gratuitously wrong, to avoid restoring it.  */ | 
|  | 643 | ldq	$2, alpha_mv+HAE_CACHE | 
|  | 644 | stq	$2, 152($sp)		/* HAE */ | 
|  | 645 |  | 
|  | 646 | /* Shuffle FLAGS to the front; add CLONE_VM.  */ | 
|  | 647 | ldi	$1, CLONE_VM|CLONE_UNTRACED | 
|  | 648 | or	$18, $1, $16 | 
|  | 649 | bsr	$26, sys_clone | 
|  | 650 |  | 
|  | 651 | /* We don't actually care for a3 success widgetry in the kernel. | 
|  | 652 | Not for positive errno values.  */ | 
|  | 653 | stq	$0, 0($sp)		/* $0 */ | 
|  | 654 | br	restore_all | 
|  | 655 | .end kernel_thread | 
|  | 656 |  | 
|  | 657 | /* | 
|  | 658 | * execve(path, argv, envp) | 
|  | 659 | */ | 
|  | 660 | .align	4 | 
|  | 661 | .globl	execve | 
|  | 662 | .ent	execve | 
|  | 663 | execve: | 
|  | 664 | /* We can be called from a module.  */ | 
|  | 665 | ldgp	$gp, 0($27) | 
|  | 666 | lda	$sp, -(32+SIZEOF_PT_REGS+8)($sp) | 
|  | 667 | .frame	$sp, 32+SIZEOF_PT_REGS+8, $26, 0 | 
|  | 668 | stq	$26, 0($sp) | 
|  | 669 | stq	$16, 8($sp) | 
|  | 670 | stq	$17, 16($sp) | 
|  | 671 | stq	$18, 24($sp) | 
|  | 672 | .prologue 1 | 
|  | 673 |  | 
|  | 674 | lda	$16, 32($sp) | 
|  | 675 | lda	$17, 0 | 
|  | 676 | lda	$18, SIZEOF_PT_REGS | 
|  | 677 | bsr	$26, memset		!samegp | 
|  | 678 |  | 
|  | 679 | /* Avoid the HAE being gratuitously wrong, which would cause us | 
|  | 680 | to do the whole turn off interrupts thing and restore it.  */ | 
|  | 681 | ldq	$2, alpha_mv+HAE_CACHE | 
|  | 682 | stq	$2, 152+32($sp) | 
|  | 683 |  | 
|  | 684 | ldq	$16, 8($sp) | 
|  | 685 | ldq	$17, 16($sp) | 
|  | 686 | ldq	$18, 24($sp) | 
|  | 687 | lda	$19, 32($sp) | 
|  | 688 | bsr	$26, do_execve		!samegp | 
|  | 689 |  | 
|  | 690 | ldq	$26, 0($sp) | 
|  | 691 | bne	$0, 1f			/* error! */ | 
|  | 692 |  | 
|  | 693 | /* Move the temporary pt_regs struct from its current location | 
|  | 694 | to the top of the kernel stack frame.  See copy_thread for | 
|  | 695 | details for a normal process.  */ | 
|  | 696 | lda	$16, 0x4000 - SIZEOF_PT_REGS($8) | 
|  | 697 | lda	$17, 32($sp) | 
|  | 698 | lda	$18, SIZEOF_PT_REGS | 
|  | 699 | bsr	$26, memmove		!samegp | 
|  | 700 |  | 
|  | 701 | /* Take that over as our new stack frame and visit userland!  */ | 
|  | 702 | lda	$sp, 0x4000 - SIZEOF_PT_REGS($8) | 
|  | 703 | br	$31, ret_from_sys_call | 
|  | 704 |  | 
|  | 705 | 1:	lda	$sp, 32+SIZEOF_PT_REGS+8($sp) | 
|  | 706 | ret | 
|  | 707 | .end execve | 
|  | 708 |  | 
|  | 709 |  | 
|  | 710 | /* | 
|  | 711 | * Special system calls.  Most of these are special in that they either | 
|  | 712 | * have to play switch_stack games or in some way use the pt_regs struct. | 
|  | 713 | */ | 
|  | 714 | .align	4 | 
|  | 715 | .globl	sys_fork | 
|  | 716 | .ent	sys_fork | 
|  | 717 | sys_fork: | 
|  | 718 | .prologue 0 | 
|  | 719 | mov	$sp, $21 | 
|  | 720 | bsr	$1, do_switch_stack | 
|  | 721 | bis	$31, SIGCHLD, $16 | 
|  | 722 | mov	$31, $17 | 
|  | 723 | mov	$31, $18 | 
|  | 724 | mov	$31, $19 | 
|  | 725 | mov	$31, $20 | 
|  | 726 | jsr	$26, alpha_clone | 
|  | 727 | bsr	$1, undo_switch_stack | 
|  | 728 | ret | 
|  | 729 | .end sys_fork | 
|  | 730 |  | 
|  | 731 | .align	4 | 
|  | 732 | .globl	sys_clone | 
|  | 733 | .ent	sys_clone | 
|  | 734 | sys_clone: | 
|  | 735 | .prologue 0 | 
|  | 736 | mov	$sp, $21 | 
|  | 737 | bsr	$1, do_switch_stack | 
|  | 738 | /* $16, $17, $18, $19, $20 come from the user.  */ | 
|  | 739 | jsr	$26, alpha_clone | 
|  | 740 | bsr	$1, undo_switch_stack | 
|  | 741 | ret | 
|  | 742 | .end sys_clone | 
|  | 743 |  | 
|  | 744 | .align	4 | 
|  | 745 | .globl	sys_vfork | 
|  | 746 | .ent	sys_vfork | 
|  | 747 | sys_vfork: | 
|  | 748 | .prologue 0 | 
|  | 749 | mov	$sp, $16 | 
|  | 750 | bsr	$1, do_switch_stack | 
|  | 751 | jsr	$26, alpha_vfork | 
|  | 752 | bsr	$1, undo_switch_stack | 
|  | 753 | ret | 
|  | 754 | .end sys_vfork | 
|  | 755 |  | 
|  | 756 | .align	4 | 
|  | 757 | .globl	sys_sigreturn | 
|  | 758 | .ent	sys_sigreturn | 
|  | 759 | sys_sigreturn: | 
|  | 760 | .prologue 0 | 
|  | 761 | mov	$sp, $17 | 
|  | 762 | lda	$18, -SWITCH_STACK_SIZE($sp) | 
|  | 763 | lda	$sp, -SWITCH_STACK_SIZE($sp) | 
|  | 764 | jsr	$26, do_sigreturn | 
|  | 765 | br	$1, undo_switch_stack | 
|  | 766 | br	ret_from_sys_call | 
|  | 767 | .end sys_sigreturn | 
|  | 768 |  | 
|  | 769 | .align	4 | 
|  | 770 | .globl	sys_rt_sigreturn | 
|  | 771 | .ent	sys_rt_sigreturn | 
|  | 772 | sys_rt_sigreturn: | 
|  | 773 | .prologue 0 | 
|  | 774 | mov	$sp, $17 | 
|  | 775 | lda	$18, -SWITCH_STACK_SIZE($sp) | 
|  | 776 | lda	$sp, -SWITCH_STACK_SIZE($sp) | 
|  | 777 | jsr	$26, do_rt_sigreturn | 
|  | 778 | br	$1, undo_switch_stack | 
|  | 779 | br	ret_from_sys_call | 
|  | 780 | .end sys_rt_sigreturn | 
|  | 781 |  | 
|  | 782 | .align	4 | 
|  | 783 | .globl	sys_sigsuspend | 
|  | 784 | .ent	sys_sigsuspend | 
|  | 785 | sys_sigsuspend: | 
|  | 786 | .prologue 0 | 
|  | 787 | mov	$sp, $17 | 
|  | 788 | br	$1, do_switch_stack | 
|  | 789 | mov	$sp, $18 | 
|  | 790 | subq	$sp, 16, $sp | 
|  | 791 | stq	$26, 0($sp) | 
|  | 792 | jsr	$26, do_sigsuspend | 
|  | 793 | ldq	$26, 0($sp) | 
|  | 794 | lda	$sp, SWITCH_STACK_SIZE+16($sp) | 
|  | 795 | ret | 
|  | 796 | .end sys_sigsuspend | 
|  | 797 |  | 
|  | 798 | .align	4 | 
|  | 799 | .globl	sys_rt_sigsuspend | 
|  | 800 | .ent	sys_rt_sigsuspend | 
|  | 801 | sys_rt_sigsuspend: | 
|  | 802 | .prologue 0 | 
|  | 803 | mov	$sp, $18 | 
|  | 804 | br	$1, do_switch_stack | 
|  | 805 | mov	$sp, $19 | 
|  | 806 | subq	$sp, 16, $sp | 
|  | 807 | stq	$26, 0($sp) | 
|  | 808 | jsr	$26, do_rt_sigsuspend | 
|  | 809 | ldq	$26, 0($sp) | 
|  | 810 | lda	$sp, SWITCH_STACK_SIZE+16($sp) | 
|  | 811 | ret | 
|  | 812 | .end sys_rt_sigsuspend | 
|  | 813 |  | 
|  | 814 | .align	4 | 
|  | 815 | .globl	sys_sethae | 
|  | 816 | .ent	sys_sethae | 
|  | 817 | sys_sethae: | 
|  | 818 | .prologue 0 | 
|  | 819 | stq	$16, 152($sp) | 
|  | 820 | ret | 
|  | 821 | .end sys_sethae | 
|  | 822 |  | 
|  | 823 | .align	4 | 
|  | 824 | .globl	osf_getpriority | 
|  | 825 | .ent	osf_getpriority | 
|  | 826 | osf_getpriority: | 
|  | 827 | lda	$sp, -16($sp) | 
|  | 828 | stq	$26, 0($sp) | 
|  | 829 | .prologue 0 | 
|  | 830 |  | 
|  | 831 | jsr	$26, sys_getpriority | 
|  | 832 |  | 
|  | 833 | ldq	$26, 0($sp) | 
|  | 834 | blt	$0, 1f | 
|  | 835 |  | 
|  | 836 | /* Return value is the unbiased priority, i.e. 20 - prio. | 
|  | 837 | This does result in negative return values, so signal | 
|  | 838 | no error by writing into the R0 slot.  */ | 
|  | 839 | lda	$1, 20 | 
|  | 840 | stq	$31, 16($sp) | 
|  | 841 | subl	$1, $0, $0 | 
|  | 842 | unop | 
|  | 843 |  | 
|  | 844 | 1:	lda	$sp, 16($sp) | 
|  | 845 | ret | 
|  | 846 | .end osf_getpriority | 
|  | 847 |  | 
|  | 848 | .align	4 | 
|  | 849 | .globl	sys_getxuid | 
|  | 850 | .ent	sys_getxuid | 
|  | 851 | sys_getxuid: | 
|  | 852 | .prologue 0 | 
|  | 853 | ldq	$2, TI_TASK($8) | 
|  | 854 | ldl	$0, TASK_UID($2) | 
|  | 855 | ldl	$1, TASK_EUID($2) | 
|  | 856 | stq	$1, 80($sp) | 
|  | 857 | ret | 
|  | 858 | .end sys_getxuid | 
|  | 859 |  | 
|  | 860 | .align	4 | 
|  | 861 | .globl	sys_getxgid | 
|  | 862 | .ent	sys_getxgid | 
|  | 863 | sys_getxgid: | 
|  | 864 | .prologue 0 | 
|  | 865 | ldq	$2, TI_TASK($8) | 
|  | 866 | ldl	$0, TASK_GID($2) | 
|  | 867 | ldl	$1, TASK_EGID($2) | 
|  | 868 | stq	$1, 80($sp) | 
|  | 869 | ret | 
|  | 870 | .end sys_getxgid | 
|  | 871 |  | 
|  | 872 | .align	4 | 
|  | 873 | .globl	sys_getxpid | 
|  | 874 | .ent	sys_getxpid | 
|  | 875 | sys_getxpid: | 
|  | 876 | .prologue 0 | 
|  | 877 | ldq	$2, TI_TASK($8) | 
|  | 878 |  | 
|  | 879 | /* See linux/kernel/timer.c sys_getppid for discussion | 
|  | 880 | about this loop.  */ | 
|  | 881 | ldq	$3, TASK_REAL_PARENT($2) | 
|  | 882 | 1:	ldl	$1, TASK_TGID($3) | 
|  | 883 | #ifdef CONFIG_SMP | 
|  | 884 | mov	$3, $4 | 
|  | 885 | mb | 
|  | 886 | ldq	$3, TASK_REAL_PARENT($2) | 
|  | 887 | cmpeq	$3, $4, $4 | 
|  | 888 | beq	$4, 1b | 
|  | 889 | #endif | 
|  | 890 | stq	$1, 80($sp) | 
|  | 891 | ldl	$0, TASK_TGID($2) | 
|  | 892 | ret | 
|  | 893 | .end sys_getxpid | 
|  | 894 |  | 
|  | 895 | .align	4 | 
|  | 896 | .globl	sys_pipe | 
|  | 897 | .ent	sys_pipe | 
|  | 898 | sys_pipe: | 
|  | 899 | lda	$sp, -16($sp) | 
|  | 900 | stq	$26, 0($sp) | 
|  | 901 | .prologue 0 | 
|  | 902 |  | 
|  | 903 | lda	$16, 8($sp) | 
|  | 904 | jsr	$26, do_pipe | 
|  | 905 |  | 
|  | 906 | ldq	$26, 0($sp) | 
|  | 907 | bne	$0, 1f | 
|  | 908 |  | 
|  | 909 | /* The return values are in $0 and $20.  */ | 
|  | 910 | ldl	$1, 12($sp) | 
|  | 911 | ldl	$0, 8($sp) | 
|  | 912 |  | 
|  | 913 | stq	$1, 80+16($sp) | 
|  | 914 | 1:	lda	$sp, 16($sp) | 
|  | 915 | ret | 
|  | 916 | .end sys_pipe | 
|  | 917 |  | 
|  | 918 | .align	4 | 
|  | 919 | .globl	sys_ptrace | 
|  | 920 | .ent	sys_ptrace | 
|  | 921 | sys_ptrace: | 
|  | 922 | .prologue 0 | 
|  | 923 | mov	$sp, $20 | 
|  | 924 | jmp	$31, do_sys_ptrace | 
|  | 925 | .end sys_ptrace | 
|  | 926 |  | 
|  | 927 | .align	4 | 
|  | 928 | .globl	sys_execve | 
|  | 929 | .ent	sys_execve | 
|  | 930 | sys_execve: | 
|  | 931 | .prologue 0 | 
|  | 932 | mov	$sp, $19 | 
|  | 933 | jmp	$31, do_sys_execve | 
|  | 934 | .end sys_execve | 
|  | 935 |  | 
|  | 936 | .align	4 | 
|  | 937 | .globl	osf_sigprocmask | 
|  | 938 | .ent	osf_sigprocmask | 
|  | 939 | osf_sigprocmask: | 
|  | 940 | .prologue 0 | 
|  | 941 | mov	$sp, $18 | 
|  | 942 | jmp	$31, do_osf_sigprocmask | 
|  | 943 | .end osf_sigprocmask | 
|  | 944 |  | 
|  | 945 | .align	4 | 
|  | 946 | .globl	alpha_ni_syscall | 
|  | 947 | .ent	alpha_ni_syscall | 
|  | 948 | alpha_ni_syscall: | 
|  | 949 | .prologue 0 | 
|  | 950 | /* Special because it also implements overflow handling via | 
|  | 951 | syscall number 0.  And if you recall, zero is a special | 
|  | 952 | trigger for "not an error".  Store large non-zero there.  */ | 
|  | 953 | lda	$0, -ENOSYS | 
|  | 954 | unop | 
|  | 955 | stq	$0, 0($sp) | 
|  | 956 | ret | 
|  | 957 | .end alpha_ni_syscall |