1 /* 2 * Copyright (C) 1995 Linus Torvalds 3 * 4 * Pentium III FXSR, SSE support 5 * Gareth Hughes <gareth@valinux.com>, May 2000 6 */ 7 8 /* 9 * This file handles the architecture-dependent parts of process handling.. 10 */ 11 12 #include <linux/stackprotector.h> 13 #include <linux/cpu.h> 14 #include <linux/errno.h> 15 #include <linux/sched.h> 16 #include <linux/fs.h> 17 #include <linux/kernel.h> 18 #include <linux/mm.h> 19 #include <linux/elfcore.h> 20 #include <linux/smp.h> 21 #include <linux/stddef.h> 22 #include <linux/slab.h> 23 #include <linux/vmalloc.h> 24 #include <linux/user.h> 25 #include <linux/interrupt.h> 26 #include <linux/utsname.h> 27 #include <linux/delay.h> 28 #include <linux/reboot.h> 29 #include <linux/init.h> 30 #include <linux/mc146818rtc.h> 31 #include <linux/module.h> 32 #include <linux/kallsyms.h> 33 #include <linux/ptrace.h> 34 #include <linux/personality.h> 35 #include <linux/tick.h> 36 #include <linux/percpu.h> 37 #include <linux/prctl.h> 38 #include <linux/dmi.h> 39 #include <linux/ftrace.h> 40 #include <linux/uaccess.h> 41 #include <linux/io.h> 42 #include <linux/kdebug.h> 43 44 #include <asm/pgtable.h> 45 #include <asm/system.h> 46 #include <asm/ldt.h> 47 #include <asm/processor.h> 48 #include <asm/i387.h> 49 #include <asm/desc.h> 50 #ifdef CONFIG_MATH_EMULATION 51 #include <asm/math_emu.h> 52 #endif 53 54 #include <linux/err.h> 55 56 #include <asm/tlbflush.h> 57 #include <asm/cpu.h> 58 #include <asm/idle.h> 59 #include <asm/syscalls.h> 60 #include <asm/ds.h> 61 62 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); 63 64 DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task; 65 EXPORT_PER_CPU_SYMBOL(current_task); 66 67 /* 68 * Return saved PC of a blocked thread. 69 */ 70 unsigned long thread_saved_pc(struct task_struct *tsk) 71 { 72 return ((unsigned long *)tsk->thread.sp)[3]; 73 } 74 75 #ifndef CONFIG_SMP 76 static inline void play_dead(void) 77 { 78 BUG(); 79 } 80 #endif 81 82 /* 83 * The idle thread. There's no useful work to be 84 * done, so just try to conserve power and have a 85 * low exit latency (ie sit in a loop waiting for 86 * somebody to say that they'd like to reschedule) 87 */ 88 void cpu_idle(void) 89 { 90 int cpu = smp_processor_id(); 91 92 /* 93 * If we're the non-boot CPU, nothing set the stack canary up 94 * for us. CPU0 already has it initialized but no harm in 95 * doing it again. This is a good place for updating it, as 96 * we wont ever return from this function (so the invalid 97 * canaries already on the stack wont ever trigger). 98 */ 99 boot_init_stack_canary(); 100 101 current_thread_info()->status |= TS_POLLING; 102 103 /* endless idle loop with no priority at all */ 104 while (1) { 105 tick_nohz_stop_sched_tick(1); 106 while (!need_resched()) { 107 108 check_pgt_cache(); 109 rmb(); 110 111 if (cpu_is_offline(cpu)) 112 play_dead(); 113 114 local_irq_disable(); 115 /* Don't trace irqs off for idle */ 116 stop_critical_timings(); 117 pm_idle(); 118 start_critical_timings(); 119 } 120 tick_nohz_restart_sched_tick(); 121 preempt_enable_no_resched(); 122 schedule(); 123 preempt_disable(); 124 } 125 } 126 127 void __show_regs(struct pt_regs *regs, int all) 128 { 129 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 130 unsigned long d0, d1, d2, d3, d6, d7; 131 unsigned long sp; 132 unsigned short ss, gs; 133 const char *board; 134 135 if (user_mode_vm(regs)) { 136 sp = regs->sp; 137 ss = regs->ss & 0xffff; 138 gs = get_user_gs(regs); 139 } else { 140 sp = (unsigned long) (®s->sp); 141 savesegment(ss, ss); 142 savesegment(gs, gs); 143 } 144 145 printk("\n"); 146 147 board = dmi_get_system_info(DMI_PRODUCT_NAME); 148 if (!board) 149 board = ""; 150 printk("Pid: %d, comm: %s %s (%s %.*s) %s\n", 151 task_pid_nr(current), current->comm, 152 print_tainted(), init_utsname()->release, 153 (int)strcspn(init_utsname()->version, " "), 154 init_utsname()->version, board); 155 156 printk("EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 157 (u16)regs->cs, regs->ip, regs->flags, 158 smp_processor_id()); 159 print_symbol("EIP is at %s\n", regs->ip); 160 161 printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 162 regs->ax, regs->bx, regs->cx, regs->dx); 163 printk("ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 164 regs->si, regs->di, regs->bp, sp); 165 printk(" DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 166 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 167 168 if (!all) 169 return; 170 171 cr0 = read_cr0(); 172 cr2 = read_cr2(); 173 cr3 = read_cr3(); 174 cr4 = read_cr4_safe(); 175 printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 176 cr0, cr2, cr3, cr4); 177 178 get_debugreg(d0, 0); 179 get_debugreg(d1, 1); 180 get_debugreg(d2, 2); 181 get_debugreg(d3, 3); 182 printk("DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 183 d0, d1, d2, d3); 184 185 get_debugreg(d6, 6); 186 get_debugreg(d7, 7); 187 printk("DR6: %08lx DR7: %08lx\n", 188 d6, d7); 189 } 190 191 void show_regs(struct pt_regs *regs) 192 { 193 __show_regs(regs, 1); 194 show_trace(NULL, regs, ®s->sp, regs->bp); 195 } 196 197 /* 198 * This gets run with %bx containing the 199 * function to call, and %dx containing 200 * the "args". 201 */ 202 extern void kernel_thread_helper(void); 203 204 /* 205 * Create a kernel thread 206 */ 207 int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags) 208 { 209 struct pt_regs regs; 210 211 memset(®s, 0, sizeof(regs)); 212 213 regs.bx = (unsigned long) fn; 214 regs.dx = (unsigned long) arg; 215 216 regs.ds = __USER_DS; 217 regs.es = __USER_DS; 218 regs.fs = __KERNEL_PERCPU; 219 regs.gs = __KERNEL_STACK_CANARY; 220 regs.orig_ax = -1; 221 regs.ip = (unsigned long) kernel_thread_helper; 222 regs.cs = __KERNEL_CS | get_kernel_rpl(); 223 regs.flags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2; 224 225 /* Ok, create the new process.. */ 226 return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL, NULL); 227 } 228 EXPORT_SYMBOL(kernel_thread); 229 230 void release_thread(struct task_struct *dead_task) 231 { 232 BUG_ON(dead_task->mm); 233 release_vm86_irqs(dead_task); 234 } 235 236 /* 237 * This gets called before we allocate a new thread and copy 238 * the current task into it. 239 */ 240 void prepare_to_copy(struct task_struct *tsk) 241 { 242 unlazy_fpu(tsk); 243 } 244 245 int copy_thread(unsigned long clone_flags, unsigned long sp, 246 unsigned long unused, 247 struct task_struct *p, struct pt_regs *regs) 248 { 249 struct pt_regs *childregs; 250 struct task_struct *tsk; 251 int err; 252 253 childregs = task_pt_regs(p); 254 *childregs = *regs; 255 childregs->ax = 0; 256 childregs->sp = sp; 257 258 p->thread.sp = (unsigned long) childregs; 259 p->thread.sp0 = (unsigned long) (childregs+1); 260 261 p->thread.ip = (unsigned long) ret_from_fork; 262 263 task_user_gs(p) = get_user_gs(regs); 264 265 tsk = current; 266 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 267 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 268 IO_BITMAP_BYTES, GFP_KERNEL); 269 if (!p->thread.io_bitmap_ptr) { 270 p->thread.io_bitmap_max = 0; 271 return -ENOMEM; 272 } 273 set_tsk_thread_flag(p, TIF_IO_BITMAP); 274 } 275 276 err = 0; 277 278 /* 279 * Set a new TLS for the child thread? 280 */ 281 if (clone_flags & CLONE_SETTLS) 282 err = do_set_thread_area(p, -1, 283 (struct user_desc __user *)childregs->si, 0); 284 285 if (err && p->thread.io_bitmap_ptr) { 286 kfree(p->thread.io_bitmap_ptr); 287 p->thread.io_bitmap_max = 0; 288 } 289 290 clear_tsk_thread_flag(p, TIF_DS_AREA_MSR); 291 p->thread.ds_ctx = NULL; 292 293 clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR); 294 p->thread.debugctlmsr = 0; 295 296 return err; 297 } 298 299 void 300 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 301 { 302 set_user_gs(regs, 0); 303 regs->fs = 0; 304 set_fs(USER_DS); 305 regs->ds = __USER_DS; 306 regs->es = __USER_DS; 307 regs->ss = __USER_DS; 308 regs->cs = __USER_CS; 309 regs->ip = new_ip; 310 regs->sp = new_sp; 311 /* 312 * Free the old FP and other extended state 313 */ 314 free_thread_xstate(current); 315 } 316 EXPORT_SYMBOL_GPL(start_thread); 317 318 319 /* 320 * switch_to(x,yn) should switch tasks from x to y. 321 * 322 * We fsave/fwait so that an exception goes off at the right time 323 * (as a call from the fsave or fwait in effect) rather than to 324 * the wrong process. Lazy FP saving no longer makes any sense 325 * with modern CPU's, and this simplifies a lot of things (SMP 326 * and UP become the same). 327 * 328 * NOTE! We used to use the x86 hardware context switching. The 329 * reason for not using it any more becomes apparent when you 330 * try to recover gracefully from saved state that is no longer 331 * valid (stale segment register values in particular). With the 332 * hardware task-switch, there is no way to fix up bad state in 333 * a reasonable manner. 334 * 335 * The fact that Intel documents the hardware task-switching to 336 * be slow is a fairly red herring - this code is not noticeably 337 * faster. However, there _is_ some room for improvement here, 338 * so the performance issues may eventually be a valid point. 339 * More important, however, is the fact that this allows us much 340 * more flexibility. 341 * 342 * The return value (in %ax) will be the "prev" task after 343 * the task-switch, and shows up in ret_from_fork in entry.S, 344 * for example. 345 */ 346 __notrace_funcgraph struct task_struct * 347 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 348 { 349 struct thread_struct *prev = &prev_p->thread, 350 *next = &next_p->thread; 351 int cpu = smp_processor_id(); 352 struct tss_struct *tss = &per_cpu(init_tss, cpu); 353 354 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 355 356 __unlazy_fpu(prev_p); 357 358 359 /* we're going to use this soon, after a few expensive things */ 360 if (next_p->fpu_counter > 5) 361 prefetch(next->xstate); 362 363 /* 364 * Reload esp0. 365 */ 366 load_sp0(tss, next); 367 368 /* 369 * Save away %gs. No need to save %fs, as it was saved on the 370 * stack on entry. No need to save %es and %ds, as those are 371 * always kernel segments while inside the kernel. Doing this 372 * before setting the new TLS descriptors avoids the situation 373 * where we temporarily have non-reloadable segments in %fs 374 * and %gs. This could be an issue if the NMI handler ever 375 * used %fs or %gs (it does not today), or if the kernel is 376 * running inside of a hypervisor layer. 377 */ 378 lazy_save_gs(prev->gs); 379 380 /* 381 * Load the per-thread Thread-Local Storage descriptor. 382 */ 383 load_TLS(next, cpu); 384 385 /* 386 * Restore IOPL if needed. In normal use, the flags restore 387 * in the switch assembly will handle this. But if the kernel 388 * is running virtualized at a non-zero CPL, the popf will 389 * not restore flags, so it must be done in a separate step. 390 */ 391 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 392 set_iopl_mask(next->iopl); 393 394 /* 395 * Now maybe handle debug registers and/or IO bitmaps 396 */ 397 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 398 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 399 __switch_to_xtra(prev_p, next_p, tss); 400 401 /* 402 * Leave lazy mode, flushing any hypercalls made here. 403 * This must be done before restoring TLS segments so 404 * the GDT and LDT are properly updated, and must be 405 * done before math_state_restore, so the TS bit is up 406 * to date. 407 */ 408 arch_end_context_switch(next_p); 409 410 /* If the task has used fpu the last 5 timeslices, just do a full 411 * restore of the math state immediately to avoid the trap; the 412 * chances of needing FPU soon are obviously high now 413 * 414 * tsk_used_math() checks prevent calling math_state_restore(), 415 * which can sleep in the case of !tsk_used_math() 416 */ 417 if (tsk_used_math(next_p) && next_p->fpu_counter > 5) 418 math_state_restore(); 419 420 /* 421 * Restore %gs if needed (which is common) 422 */ 423 if (prev->gs | next->gs) 424 lazy_load_gs(next->gs); 425 426 percpu_write(current_task, next_p); 427 428 return prev_p; 429 } 430 431 int sys_clone(struct pt_regs *regs) 432 { 433 unsigned long clone_flags; 434 unsigned long newsp; 435 int __user *parent_tidptr, *child_tidptr; 436 437 clone_flags = regs->bx; 438 newsp = regs->cx; 439 parent_tidptr = (int __user *)regs->dx; 440 child_tidptr = (int __user *)regs->di; 441 if (!newsp) 442 newsp = regs->sp; 443 return do_fork(clone_flags, newsp, regs, 0, parent_tidptr, child_tidptr); 444 } 445 446 /* 447 * sys_execve() executes a new program. 448 */ 449 int sys_execve(struct pt_regs *regs) 450 { 451 int error; 452 char *filename; 453 454 filename = getname((char __user *) regs->bx); 455 error = PTR_ERR(filename); 456 if (IS_ERR(filename)) 457 goto out; 458 error = do_execve(filename, 459 (char __user * __user *) regs->cx, 460 (char __user * __user *) regs->dx, 461 regs); 462 if (error == 0) { 463 /* Make sure we don't return using sysenter.. */ 464 set_thread_flag(TIF_IRET); 465 } 466 putname(filename); 467 out: 468 return error; 469 } 470 471 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 472 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 473 474 unsigned long get_wchan(struct task_struct *p) 475 { 476 unsigned long bp, sp, ip; 477 unsigned long stack_page; 478 int count = 0; 479 if (!p || p == current || p->state == TASK_RUNNING) 480 return 0; 481 stack_page = (unsigned long)task_stack_page(p); 482 sp = p->thread.sp; 483 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 484 return 0; 485 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 486 bp = *(unsigned long *) sp; 487 do { 488 if (bp < stack_page || bp > top_ebp+stack_page) 489 return 0; 490 ip = *(unsigned long *) (bp+4); 491 if (!in_sched_functions(ip)) 492 return ip; 493 bp = *(unsigned long *) bp; 494 } while (count++ < 16); 495 return 0; 496 } 497 498