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 release_thread(struct task_struct *dead_task) 178 { 179 BUG_ON(dead_task->mm); 180 release_vm86_irqs(dead_task); 181 } 182 183 /* 184 * This gets called before we allocate a new thread and copy 185 * the current task into it. 186 */ 187 void prepare_to_copy(struct task_struct *tsk) 188 { 189 unlazy_fpu(tsk); 190 } 191 192 int copy_thread(unsigned long clone_flags, unsigned long sp, 193 unsigned long unused, 194 struct task_struct *p, struct pt_regs *regs) 195 { 196 struct pt_regs *childregs; 197 struct task_struct *tsk; 198 int err; 199 200 childregs = task_pt_regs(p); 201 *childregs = *regs; 202 childregs->ax = 0; 203 childregs->sp = sp; 204 205 p->thread.sp = (unsigned long) childregs; 206 p->thread.sp0 = (unsigned long) (childregs+1); 207 208 p->thread.ip = (unsigned long) ret_from_fork; 209 210 task_user_gs(p) = get_user_gs(regs); 211 212 p->thread.io_bitmap_ptr = NULL; 213 tsk = current; 214 err = -ENOMEM; 215 216 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 217 218 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 219 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 220 IO_BITMAP_BYTES, GFP_KERNEL); 221 if (!p->thread.io_bitmap_ptr) { 222 p->thread.io_bitmap_max = 0; 223 return -ENOMEM; 224 } 225 set_tsk_thread_flag(p, TIF_IO_BITMAP); 226 } 227 228 err = 0; 229 230 /* 231 * Set a new TLS for the child thread? 232 */ 233 if (clone_flags & CLONE_SETTLS) 234 err = do_set_thread_area(p, -1, 235 (struct user_desc __user *)childregs->si, 0); 236 237 if (err && p->thread.io_bitmap_ptr) { 238 kfree(p->thread.io_bitmap_ptr); 239 p->thread.io_bitmap_max = 0; 240 } 241 242 clear_tsk_thread_flag(p, TIF_DS_AREA_MSR); 243 p->thread.ds_ctx = NULL; 244 245 clear_tsk_thread_flag(p, TIF_DEBUGCTLMSR); 246 p->thread.debugctlmsr = 0; 247 248 return err; 249 } 250 251 void 252 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 253 { 254 set_user_gs(regs, 0); 255 regs->fs = 0; 256 set_fs(USER_DS); 257 regs->ds = __USER_DS; 258 regs->es = __USER_DS; 259 regs->ss = __USER_DS; 260 regs->cs = __USER_CS; 261 regs->ip = new_ip; 262 regs->sp = new_sp; 263 /* 264 * Free the old FP and other extended state 265 */ 266 free_thread_xstate(current); 267 } 268 EXPORT_SYMBOL_GPL(start_thread); 269 270 271 /* 272 * switch_to(x,yn) should switch tasks from x to y. 273 * 274 * We fsave/fwait so that an exception goes off at the right time 275 * (as a call from the fsave or fwait in effect) rather than to 276 * the wrong process. Lazy FP saving no longer makes any sense 277 * with modern CPU's, and this simplifies a lot of things (SMP 278 * and UP become the same). 279 * 280 * NOTE! We used to use the x86 hardware context switching. The 281 * reason for not using it any more becomes apparent when you 282 * try to recover gracefully from saved state that is no longer 283 * valid (stale segment register values in particular). With the 284 * hardware task-switch, there is no way to fix up bad state in 285 * a reasonable manner. 286 * 287 * The fact that Intel documents the hardware task-switching to 288 * be slow is a fairly red herring - this code is not noticeably 289 * faster. However, there _is_ some room for improvement here, 290 * so the performance issues may eventually be a valid point. 291 * More important, however, is the fact that this allows us much 292 * more flexibility. 293 * 294 * The return value (in %ax) will be the "prev" task after 295 * the task-switch, and shows up in ret_from_fork in entry.S, 296 * for example. 297 */ 298 __notrace_funcgraph struct task_struct * 299 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 300 { 301 struct thread_struct *prev = &prev_p->thread, 302 *next = &next_p->thread; 303 int cpu = smp_processor_id(); 304 struct tss_struct *tss = &per_cpu(init_tss, cpu); 305 bool preload_fpu; 306 307 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 308 309 /* 310 * If the task has used fpu the last 5 timeslices, just do a full 311 * restore of the math state immediately to avoid the trap; the 312 * chances of needing FPU soon are obviously high now 313 */ 314 preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5; 315 316 __unlazy_fpu(prev_p); 317 318 /* we're going to use this soon, after a few expensive things */ 319 if (preload_fpu) 320 prefetch(next->xstate); 321 322 /* 323 * Reload esp0. 324 */ 325 load_sp0(tss, next); 326 327 /* 328 * Save away %gs. No need to save %fs, as it was saved on the 329 * stack on entry. No need to save %es and %ds, as those are 330 * always kernel segments while inside the kernel. Doing this 331 * before setting the new TLS descriptors avoids the situation 332 * where we temporarily have non-reloadable segments in %fs 333 * and %gs. This could be an issue if the NMI handler ever 334 * used %fs or %gs (it does not today), or if the kernel is 335 * running inside of a hypervisor layer. 336 */ 337 lazy_save_gs(prev->gs); 338 339 /* 340 * Load the per-thread Thread-Local Storage descriptor. 341 */ 342 load_TLS(next, cpu); 343 344 /* 345 * Restore IOPL if needed. In normal use, the flags restore 346 * in the switch assembly will handle this. But if the kernel 347 * is running virtualized at a non-zero CPL, the popf will 348 * not restore flags, so it must be done in a separate step. 349 */ 350 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 351 set_iopl_mask(next->iopl); 352 353 /* 354 * Now maybe handle debug registers and/or IO bitmaps 355 */ 356 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 357 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 358 __switch_to_xtra(prev_p, next_p, tss); 359 360 /* If we're going to preload the fpu context, make sure clts 361 is run while we're batching the cpu state updates. */ 362 if (preload_fpu) 363 clts(); 364 365 /* 366 * Leave lazy mode, flushing any hypercalls made here. 367 * This must be done before restoring TLS segments so 368 * the GDT and LDT are properly updated, and must be 369 * done before math_state_restore, so the TS bit is up 370 * to date. 371 */ 372 arch_end_context_switch(next_p); 373 374 if (preload_fpu) 375 __math_state_restore(); 376 377 /* 378 * Restore %gs if needed (which is common) 379 */ 380 if (prev->gs | next->gs) 381 lazy_load_gs(next->gs); 382 383 percpu_write(current_task, next_p); 384 385 return prev_p; 386 } 387 388 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 389 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 390 391 unsigned long get_wchan(struct task_struct *p) 392 { 393 unsigned long bp, sp, ip; 394 unsigned long stack_page; 395 int count = 0; 396 if (!p || p == current || p->state == TASK_RUNNING) 397 return 0; 398 stack_page = (unsigned long)task_stack_page(p); 399 sp = p->thread.sp; 400 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 401 return 0; 402 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 403 bp = *(unsigned long *) sp; 404 do { 405 if (bp < stack_page || bp > top_ebp+stack_page) 406 return 0; 407 ip = *(unsigned long *) (bp+4); 408 if (!in_sched_functions(ip)) 409 return ip; 410 bp = *(unsigned long *) bp; 411 } while (count++ < 16); 412 return 0; 413 } 414 415