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/delay.h> 27 #include <linux/reboot.h> 28 #include <linux/init.h> 29 #include <linux/mc146818rtc.h> 30 #include <linux/module.h> 31 #include <linux/kallsyms.h> 32 #include <linux/ptrace.h> 33 #include <linux/personality.h> 34 #include <linux/tick.h> 35 #include <linux/percpu.h> 36 #include <linux/prctl.h> 37 #include <linux/ftrace.h> 38 #include <linux/uaccess.h> 39 #include <linux/io.h> 40 #include <linux/kdebug.h> 41 #include <linux/cpuidle.h> 42 43 #include <asm/pgtable.h> 44 #include <asm/system.h> 45 #include <asm/ldt.h> 46 #include <asm/processor.h> 47 #include <asm/i387.h> 48 #include <asm/desc.h> 49 #ifdef CONFIG_MATH_EMULATION 50 #include <asm/math_emu.h> 51 #endif 52 53 #include <linux/err.h> 54 55 #include <asm/tlbflush.h> 56 #include <asm/cpu.h> 57 #include <asm/idle.h> 58 #include <asm/syscalls.h> 59 #include <asm/debugreg.h> 60 #include <asm/nmi.h> 61 62 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); 63 64 /* 65 * Return saved PC of a blocked thread. 66 */ 67 unsigned long thread_saved_pc(struct task_struct *tsk) 68 { 69 return ((unsigned long *)tsk->thread.sp)[3]; 70 } 71 72 #ifndef CONFIG_SMP 73 static inline void play_dead(void) 74 { 75 BUG(); 76 } 77 #endif 78 79 /* 80 * The idle thread. There's no useful work to be 81 * done, so just try to conserve power and have a 82 * low exit latency (ie sit in a loop waiting for 83 * somebody to say that they'd like to reschedule) 84 */ 85 void cpu_idle(void) 86 { 87 int cpu = smp_processor_id(); 88 89 /* 90 * If we're the non-boot CPU, nothing set the stack canary up 91 * for us. CPU0 already has it initialized but no harm in 92 * doing it again. This is a good place for updating it, as 93 * we wont ever return from this function (so the invalid 94 * canaries already on the stack wont ever trigger). 95 */ 96 boot_init_stack_canary(); 97 98 current_thread_info()->status |= TS_POLLING; 99 100 /* endless idle loop with no priority at all */ 101 while (1) { 102 tick_nohz_idle_enter_norcu(); 103 while (!need_resched()) { 104 105 check_pgt_cache(); 106 rmb(); 107 108 if (cpu_is_offline(cpu)) 109 play_dead(); 110 111 local_touch_nmi(); 112 local_irq_disable(); 113 /* Don't trace irqs off for idle */ 114 stop_critical_timings(); 115 if (cpuidle_idle_call()) 116 pm_idle(); 117 start_critical_timings(); 118 } 119 tick_nohz_idle_exit_norcu(); 120 preempt_enable_no_resched(); 121 schedule(); 122 preempt_disable(); 123 } 124 } 125 126 void __show_regs(struct pt_regs *regs, int all) 127 { 128 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 129 unsigned long d0, d1, d2, d3, d6, d7; 130 unsigned long sp; 131 unsigned short ss, gs; 132 133 if (user_mode_vm(regs)) { 134 sp = regs->sp; 135 ss = regs->ss & 0xffff; 136 gs = get_user_gs(regs); 137 } else { 138 sp = kernel_stack_pointer(regs); 139 savesegment(ss, ss); 140 savesegment(gs, gs); 141 } 142 143 show_regs_common(); 144 145 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 146 (u16)regs->cs, regs->ip, regs->flags, 147 smp_processor_id()); 148 print_symbol("EIP is at %s\n", regs->ip); 149 150 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 151 regs->ax, regs->bx, regs->cx, regs->dx); 152 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 153 regs->si, regs->di, regs->bp, sp); 154 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 155 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 156 157 if (!all) 158 return; 159 160 cr0 = read_cr0(); 161 cr2 = read_cr2(); 162 cr3 = read_cr3(); 163 cr4 = read_cr4_safe(); 164 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 165 cr0, cr2, cr3, cr4); 166 167 get_debugreg(d0, 0); 168 get_debugreg(d1, 1); 169 get_debugreg(d2, 2); 170 get_debugreg(d3, 3); 171 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 172 d0, d1, d2, d3); 173 174 get_debugreg(d6, 6); 175 get_debugreg(d7, 7); 176 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 177 d6, d7); 178 } 179 180 void release_thread(struct task_struct *dead_task) 181 { 182 BUG_ON(dead_task->mm); 183 release_vm86_irqs(dead_task); 184 } 185 186 /* 187 * This gets called before we allocate a new thread and copy 188 * the current task into it. 189 */ 190 void prepare_to_copy(struct task_struct *tsk) 191 { 192 unlazy_fpu(tsk); 193 } 194 195 int copy_thread(unsigned long clone_flags, unsigned long sp, 196 unsigned long unused, 197 struct task_struct *p, struct pt_regs *regs) 198 { 199 struct pt_regs *childregs; 200 struct task_struct *tsk; 201 int err; 202 203 childregs = task_pt_regs(p); 204 *childregs = *regs; 205 childregs->ax = 0; 206 childregs->sp = sp; 207 208 p->thread.sp = (unsigned long) childregs; 209 p->thread.sp0 = (unsigned long) (childregs+1); 210 211 p->thread.ip = (unsigned long) ret_from_fork; 212 213 task_user_gs(p) = get_user_gs(regs); 214 215 p->thread.io_bitmap_ptr = NULL; 216 tsk = current; 217 err = -ENOMEM; 218 219 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 220 221 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 222 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 223 IO_BITMAP_BYTES, GFP_KERNEL); 224 if (!p->thread.io_bitmap_ptr) { 225 p->thread.io_bitmap_max = 0; 226 return -ENOMEM; 227 } 228 set_tsk_thread_flag(p, TIF_IO_BITMAP); 229 } 230 231 err = 0; 232 233 /* 234 * Set a new TLS for the child thread? 235 */ 236 if (clone_flags & CLONE_SETTLS) 237 err = do_set_thread_area(p, -1, 238 (struct user_desc __user *)childregs->si, 0); 239 240 if (err && p->thread.io_bitmap_ptr) { 241 kfree(p->thread.io_bitmap_ptr); 242 p->thread.io_bitmap_max = 0; 243 } 244 return err; 245 } 246 247 void 248 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 249 { 250 set_user_gs(regs, 0); 251 regs->fs = 0; 252 regs->ds = __USER_DS; 253 regs->es = __USER_DS; 254 regs->ss = __USER_DS; 255 regs->cs = __USER_CS; 256 regs->ip = new_ip; 257 regs->sp = new_sp; 258 /* 259 * Free the old FP and other extended state 260 */ 261 free_thread_xstate(current); 262 } 263 EXPORT_SYMBOL_GPL(start_thread); 264 265 266 /* 267 * switch_to(x,y) should switch tasks from x to y. 268 * 269 * We fsave/fwait so that an exception goes off at the right time 270 * (as a call from the fsave or fwait in effect) rather than to 271 * the wrong process. Lazy FP saving no longer makes any sense 272 * with modern CPU's, and this simplifies a lot of things (SMP 273 * and UP become the same). 274 * 275 * NOTE! We used to use the x86 hardware context switching. The 276 * reason for not using it any more becomes apparent when you 277 * try to recover gracefully from saved state that is no longer 278 * valid (stale segment register values in particular). With the 279 * hardware task-switch, there is no way to fix up bad state in 280 * a reasonable manner. 281 * 282 * The fact that Intel documents the hardware task-switching to 283 * be slow is a fairly red herring - this code is not noticeably 284 * faster. However, there _is_ some room for improvement here, 285 * so the performance issues may eventually be a valid point. 286 * More important, however, is the fact that this allows us much 287 * more flexibility. 288 * 289 * The return value (in %ax) will be the "prev" task after 290 * the task-switch, and shows up in ret_from_fork in entry.S, 291 * for example. 292 */ 293 __notrace_funcgraph struct task_struct * 294 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 295 { 296 struct thread_struct *prev = &prev_p->thread, 297 *next = &next_p->thread; 298 int cpu = smp_processor_id(); 299 struct tss_struct *tss = &per_cpu(init_tss, cpu); 300 bool preload_fpu; 301 302 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 303 304 /* 305 * If the task has used fpu the last 5 timeslices, just do a full 306 * restore of the math state immediately to avoid the trap; the 307 * chances of needing FPU soon are obviously high now 308 */ 309 preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5; 310 311 __unlazy_fpu(prev_p); 312 313 /* we're going to use this soon, after a few expensive things */ 314 if (preload_fpu) 315 prefetch(next->fpu.state); 316 317 /* 318 * Reload esp0. 319 */ 320 load_sp0(tss, next); 321 322 /* 323 * Save away %gs. No need to save %fs, as it was saved on the 324 * stack on entry. No need to save %es and %ds, as those are 325 * always kernel segments while inside the kernel. Doing this 326 * before setting the new TLS descriptors avoids the situation 327 * where we temporarily have non-reloadable segments in %fs 328 * and %gs. This could be an issue if the NMI handler ever 329 * used %fs or %gs (it does not today), or if the kernel is 330 * running inside of a hypervisor layer. 331 */ 332 lazy_save_gs(prev->gs); 333 334 /* 335 * Load the per-thread Thread-Local Storage descriptor. 336 */ 337 load_TLS(next, cpu); 338 339 /* 340 * Restore IOPL if needed. In normal use, the flags restore 341 * in the switch assembly will handle this. But if the kernel 342 * is running virtualized at a non-zero CPL, the popf will 343 * not restore flags, so it must be done in a separate step. 344 */ 345 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 346 set_iopl_mask(next->iopl); 347 348 /* 349 * Now maybe handle debug registers and/or IO bitmaps 350 */ 351 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 352 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 353 __switch_to_xtra(prev_p, next_p, tss); 354 355 /* If we're going to preload the fpu context, make sure clts 356 is run while we're batching the cpu state updates. */ 357 if (preload_fpu) 358 clts(); 359 360 /* 361 * Leave lazy mode, flushing any hypercalls made here. 362 * This must be done before restoring TLS segments so 363 * the GDT and LDT are properly updated, and must be 364 * done before math_state_restore, so the TS bit is up 365 * to date. 366 */ 367 arch_end_context_switch(next_p); 368 369 if (preload_fpu) 370 __math_state_restore(); 371 372 /* 373 * Restore %gs if needed (which is common) 374 */ 375 if (prev->gs | next->gs) 376 lazy_load_gs(next->gs); 377 378 percpu_write(current_task, next_p); 379 380 return prev_p; 381 } 382 383 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 384 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 385 386 unsigned long get_wchan(struct task_struct *p) 387 { 388 unsigned long bp, sp, ip; 389 unsigned long stack_page; 390 int count = 0; 391 if (!p || p == current || p->state == TASK_RUNNING) 392 return 0; 393 stack_page = (unsigned long)task_stack_page(p); 394 sp = p->thread.sp; 395 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 396 return 0; 397 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 398 bp = *(unsigned long *) sp; 399 do { 400 if (bp < stack_page || bp > top_ebp+stack_page) 401 return 0; 402 ip = *(unsigned long *) (bp+4); 403 if (!in_sched_functions(ip)) 404 return ip; 405 bp = *(unsigned long *) bp; 406 } while (count++ < 16); 407 return 0; 408 } 409 410