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 42 #include <asm/pgtable.h> 43 #include <asm/system.h> 44 #include <asm/ldt.h> 45 #include <asm/processor.h> 46 #include <asm/i387.h> 47 #include <asm/desc.h> 48 #ifdef CONFIG_MATH_EMULATION 49 #include <asm/math_emu.h> 50 #endif 51 52 #include <linux/err.h> 53 54 #include <asm/tlbflush.h> 55 #include <asm/cpu.h> 56 #include <asm/idle.h> 57 #include <asm/syscalls.h> 58 #include <asm/ds.h> 59 #include <asm/debugreg.h> 60 61 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); 62 63 /* 64 * Return saved PC of a blocked thread. 65 */ 66 unsigned long thread_saved_pc(struct task_struct *tsk) 67 { 68 return ((unsigned long *)tsk->thread.sp)[3]; 69 } 70 71 #ifndef CONFIG_SMP 72 static inline void play_dead(void) 73 { 74 BUG(); 75 } 76 #endif 77 78 /* 79 * The idle thread. There's no useful work to be 80 * done, so just try to conserve power and have a 81 * low exit latency (ie sit in a loop waiting for 82 * somebody to say that they'd like to reschedule) 83 */ 84 void cpu_idle(void) 85 { 86 int cpu = smp_processor_id(); 87 88 /* 89 * If we're the non-boot CPU, nothing set the stack canary up 90 * for us. CPU0 already has it initialized but no harm in 91 * doing it again. This is a good place for updating it, as 92 * we wont ever return from this function (so the invalid 93 * canaries already on the stack wont ever trigger). 94 */ 95 boot_init_stack_canary(); 96 97 current_thread_info()->status |= TS_POLLING; 98 99 /* endless idle loop with no priority at all */ 100 while (1) { 101 tick_nohz_stop_sched_tick(1); 102 while (!need_resched()) { 103 104 check_pgt_cache(); 105 rmb(); 106 107 if (cpu_is_offline(cpu)) 108 play_dead(); 109 110 local_irq_disable(); 111 /* Don't trace irqs off for idle */ 112 stop_critical_timings(); 113 pm_idle(); 114 start_critical_timings(); 115 } 116 tick_nohz_restart_sched_tick(); 117 preempt_enable_no_resched(); 118 schedule(); 119 preempt_disable(); 120 } 121 } 122 123 void __show_regs(struct pt_regs *regs, int all) 124 { 125 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 126 unsigned long d0, d1, d2, d3, d6, d7; 127 unsigned long sp; 128 unsigned short ss, gs; 129 130 if (user_mode_vm(regs)) { 131 sp = regs->sp; 132 ss = regs->ss & 0xffff; 133 gs = get_user_gs(regs); 134 } else { 135 sp = kernel_stack_pointer(regs); 136 savesegment(ss, ss); 137 savesegment(gs, gs); 138 } 139 140 show_regs_common(); 141 142 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 143 (u16)regs->cs, regs->ip, regs->flags, 144 smp_processor_id()); 145 print_symbol("EIP is at %s\n", regs->ip); 146 147 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 148 regs->ax, regs->bx, regs->cx, regs->dx); 149 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 150 regs->si, regs->di, regs->bp, sp); 151 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 152 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 153 154 if (!all) 155 return; 156 157 cr0 = read_cr0(); 158 cr2 = read_cr2(); 159 cr3 = read_cr3(); 160 cr4 = read_cr4_safe(); 161 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 162 cr0, cr2, cr3, cr4); 163 164 get_debugreg(d0, 0); 165 get_debugreg(d1, 1); 166 get_debugreg(d2, 2); 167 get_debugreg(d3, 3); 168 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 169 d0, d1, d2, d3); 170 171 get_debugreg(d6, 6); 172 get_debugreg(d7, 7); 173 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 174 d6, d7); 175 } 176 177 void show_regs(struct pt_regs *regs) 178 { 179 show_registers(regs); 180 show_trace(NULL, regs, ®s->sp, regs->bp); 181 } 182 183 void release_thread(struct task_struct *dead_task) 184 { 185 BUG_ON(dead_task->mm); 186 release_vm86_irqs(dead_task); 187 } 188 189 /* 190 * This gets called before we allocate a new thread and copy 191 * the current task into it. 192 */ 193 void prepare_to_copy(struct task_struct *tsk) 194 { 195 unlazy_fpu(tsk); 196 } 197 198 int copy_thread(unsigned long clone_flags, unsigned long sp, 199 unsigned long unused, 200 struct task_struct *p, struct pt_regs *regs) 201 { 202 struct pt_regs *childregs; 203 struct task_struct *tsk; 204 int err; 205 206 childregs = task_pt_regs(p); 207 *childregs = *regs; 208 childregs->ax = 0; 209 childregs->sp = sp; 210 211 p->thread.sp = (unsigned long) childregs; 212 p->thread.sp0 = (unsigned long) (childregs+1); 213 214 p->thread.ip = (unsigned long) ret_from_fork; 215 216 task_user_gs(p) = get_user_gs(regs); 217 218 p->thread.io_bitmap_ptr = NULL; 219 tsk = current; 220 err = -ENOMEM; 221 222 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 223 224 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 225 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 226 IO_BITMAP_BYTES, GFP_KERNEL); 227 if (!p->thread.io_bitmap_ptr) { 228 p->thread.io_bitmap_max = 0; 229 return -ENOMEM; 230 } 231 set_tsk_thread_flag(p, TIF_IO_BITMAP); 232 } 233 234 err = 0; 235 236 /* 237 * Set a new TLS for the child thread? 238 */ 239 if (clone_flags & CLONE_SETTLS) 240 err = do_set_thread_area(p, -1, 241 (struct user_desc __user *)childregs->si, 0); 242 243 if (err && p->thread.io_bitmap_ptr) { 244 kfree(p->thread.io_bitmap_ptr); 245 p->thread.io_bitmap_max = 0; 246 } 247 248 clear_tsk_thread_flag(p, TIF_DS_AREA_MSR); 249 p->thread.ds_ctx = NULL; 250 251 clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR); 252 p->thread.debugctlmsr = 0; 253 254 return err; 255 } 256 257 void 258 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 259 { 260 set_user_gs(regs, 0); 261 regs->fs = 0; 262 set_fs(USER_DS); 263 regs->ds = __USER_DS; 264 regs->es = __USER_DS; 265 regs->ss = __USER_DS; 266 regs->cs = __USER_CS; 267 regs->ip = new_ip; 268 regs->sp = new_sp; 269 /* 270 * Free the old FP and other extended state 271 */ 272 free_thread_xstate(current); 273 } 274 EXPORT_SYMBOL_GPL(start_thread); 275 276 277 /* 278 * switch_to(x,yn) should switch tasks from x to y. 279 * 280 * We fsave/fwait so that an exception goes off at the right time 281 * (as a call from the fsave or fwait in effect) rather than to 282 * the wrong process. Lazy FP saving no longer makes any sense 283 * with modern CPU's, and this simplifies a lot of things (SMP 284 * and UP become the same). 285 * 286 * NOTE! We used to use the x86 hardware context switching. The 287 * reason for not using it any more becomes apparent when you 288 * try to recover gracefully from saved state that is no longer 289 * valid (stale segment register values in particular). With the 290 * hardware task-switch, there is no way to fix up bad state in 291 * a reasonable manner. 292 * 293 * The fact that Intel documents the hardware task-switching to 294 * be slow is a fairly red herring - this code is not noticeably 295 * faster. However, there _is_ some room for improvement here, 296 * so the performance issues may eventually be a valid point. 297 * More important, however, is the fact that this allows us much 298 * more flexibility. 299 * 300 * The return value (in %ax) will be the "prev" task after 301 * the task-switch, and shows up in ret_from_fork in entry.S, 302 * for example. 303 */ 304 __notrace_funcgraph struct task_struct * 305 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 306 { 307 struct thread_struct *prev = &prev_p->thread, 308 *next = &next_p->thread; 309 int cpu = smp_processor_id(); 310 struct tss_struct *tss = &per_cpu(init_tss, cpu); 311 bool preload_fpu; 312 313 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 314 315 /* 316 * If the task has used fpu the last 5 timeslices, just do a full 317 * restore of the math state immediately to avoid the trap; the 318 * chances of needing FPU soon are obviously high now 319 */ 320 preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5; 321 322 __unlazy_fpu(prev_p); 323 324 /* we're going to use this soon, after a few expensive things */ 325 if (preload_fpu) 326 prefetch(next->xstate); 327 328 /* 329 * Reload esp0. 330 */ 331 load_sp0(tss, next); 332 333 /* 334 * Save away %gs. No need to save %fs, as it was saved on the 335 * stack on entry. No need to save %es and %ds, as those are 336 * always kernel segments while inside the kernel. Doing this 337 * before setting the new TLS descriptors avoids the situation 338 * where we temporarily have non-reloadable segments in %fs 339 * and %gs. This could be an issue if the NMI handler ever 340 * used %fs or %gs (it does not today), or if the kernel is 341 * running inside of a hypervisor layer. 342 */ 343 lazy_save_gs(prev->gs); 344 345 /* 346 * Load the per-thread Thread-Local Storage descriptor. 347 */ 348 load_TLS(next, cpu); 349 350 /* 351 * Restore IOPL if needed. In normal use, the flags restore 352 * in the switch assembly will handle this. But if the kernel 353 * is running virtualized at a non-zero CPL, the popf will 354 * not restore flags, so it must be done in a separate step. 355 */ 356 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 357 set_iopl_mask(next->iopl); 358 359 /* 360 * Now maybe handle debug registers and/or IO bitmaps 361 */ 362 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 363 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 364 __switch_to_xtra(prev_p, next_p, tss); 365 366 /* If we're going to preload the fpu context, make sure clts 367 is run while we're batching the cpu state updates. */ 368 if (preload_fpu) 369 clts(); 370 371 /* 372 * Leave lazy mode, flushing any hypercalls made here. 373 * This must be done before restoring TLS segments so 374 * the GDT and LDT are properly updated, and must be 375 * done before math_state_restore, so the TS bit is up 376 * to date. 377 */ 378 arch_end_context_switch(next_p); 379 380 if (preload_fpu) 381 __math_state_restore(); 382 383 /* 384 * Restore %gs if needed (which is common) 385 */ 386 if (prev->gs | next->gs) 387 lazy_load_gs(next->gs); 388 389 percpu_write(current_task, next_p); 390 391 return prev_p; 392 } 393 394 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 395 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 396 397 unsigned long get_wchan(struct task_struct *p) 398 { 399 unsigned long bp, sp, ip; 400 unsigned long stack_page; 401 int count = 0; 402 if (!p || p == current || p->state == TASK_RUNNING) 403 return 0; 404 stack_page = (unsigned long)task_stack_page(p); 405 sp = p->thread.sp; 406 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 407 return 0; 408 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 409 bp = *(unsigned long *) sp; 410 do { 411 if (bp < stack_page || bp > top_ebp+stack_page) 412 return 0; 413 ip = *(unsigned long *) (bp+4); 414 if (!in_sched_functions(ip)) 415 return ip; 416 bp = *(unsigned long *) bp; 417 } while (count++ < 16); 418 return 0; 419 } 420 421