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