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