arch/mips/kernel/process.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
   7  * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
   8  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
   9  * Copyright (C) 2004 Thiemo Seufer
  10  */
  11 #include <linux/errno.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/tick.h>
  15 #include <linux/kernel.h>
  16 #include <linux/mm.h>
  17 #include <linux/stddef.h>
  18 #include <linux/unistd.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/slab.h>
  21 #include <linux/mman.h>
  22 #include <linux/personality.h>
  23 #include <linux/sys.h>
  24 #include <linux/user.h>
  25 #include <linux/init.h>
  26 #include <linux/completion.h>
  27 #include <linux/kallsyms.h>
  28 #include <linux/random.h>
  29
  30 #include <asm/asm.h>
  31 #include <asm/bootinfo.h>
  32 #include <asm/cpu.h>
  33 #include <asm/dsp.h>
  34 #include <asm/fpu.h>
  35 #include <asm/pgtable.h>
  36 #include <asm/system.h>
  37 #include <asm/mipsregs.h>
  38 #include <asm/processor.h>
  39 #include <asm/uaccess.h>
  40 #include <asm/io.h>
  41 #include <asm/elf.h>
  42 #include <asm/isadep.h>
  43 #include <asm/inst.h>
  44 #include <asm/stacktrace.h>
  45
  46 /*
  47  * The idle thread. There's no useful work to be done, so just try to conserve
  48  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  49  * say that they'd like to reschedule)
  50  */
  51 void __noreturn cpu_idle(void)
  52 {
  53         int cpu;
  54
  55         /* CPU is going idle. */
  56         cpu = smp_processor_id();
  57
  58         /* endless idle loop with no priority at all */
  59         while (1) {
  60                 tick_nohz_stop_sched_tick(1);
  61                 while (!need_resched() && cpu_online(cpu)) {
  62 #ifdef CONFIG_MIPS_MT_SMTC
  63                         extern void smtc_idle_loop_hook(void);
  64
  65                         smtc_idle_loop_hook();
  66 #endif
  67                         if (cpu_wait)
  68                                 (*cpu_wait)();
  69                 }
  70 #ifdef CONFIG_HOTPLUG_CPU
  71                 if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
  72                     (system_state == SYSTEM_RUNNING ||
  73                      system_state == SYSTEM_BOOTING))
  74                         play_dead();
  75 #endif
  76                 tick_nohz_restart_sched_tick();
  77                 preempt_enable_no_resched();
  78                 schedule();
  79                 preempt_disable();
  80         }
  81 }
  82
  83 asmlinkage void ret_from_fork(void);
  84
  85 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  86 {
  87         unsigned long status;
  88
  89         /* New thread loses kernel privileges. */
  90         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  91 #ifdef CONFIG_64BIT
  92         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  93 #endif
  94         status |= KU_USER;
  95         regs->cp0_status = status;
  96         clear_used_math();
  97         clear_fpu_owner();
  98         if (cpu_has_dsp)
  99                 __init_dsp();
 100         regs->cp0_epc = pc;
 101         regs->regs[29] = sp;
 102         current_thread_info()->addr_limit = USER_DS;
 103 }
 104
 105 void exit_thread(void)
 106 {
 107 }
 108
 109 void flush_thread(void)
 110 {
 111 }
 112
 113 int copy_thread(unsigned long clone_flags, unsigned long usp,
 114         unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 115 {
 116         struct thread_info *ti = task_thread_info(p);
 117         struct pt_regs *childregs;
 118         unsigned long childksp;
 119         p->set_child_tid = p->clear_child_tid = NULL;
 120
 121         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 122
 123         preempt_disable();
 124
 125         if (is_fpu_owner())
 126                 save_fp(p);
 127
 128         if (cpu_has_dsp)
 129                 save_dsp(p);
 130
 131         preempt_enable();
 132
 133         /* set up new TSS. */
 134         childregs = (struct pt_regs *) childksp - 1;
 135         /*  Put the stack after the struct pt_regs.  */
 136         childksp = (unsigned long) childregs;
 137         *childregs = *regs;
 138         childregs->regs[7] = 0; /* Clear error flag */
 139
 140         childregs->regs[2] = 0; /* Child gets zero as return value */
 141         regs->regs[2] = p->pid;
 142
 143         if (childregs->cp0_status & ST0_CU0) {
 144                 childregs->regs[28] = (unsigned long) ti;
 145                 childregs->regs[29] = childksp;
 146                 ti->addr_limit = KERNEL_DS;
 147         } else {
 148                 childregs->regs[29] = usp;
 149                 ti->addr_limit = USER_DS;
 150         }
 151         p->thread.reg29 = (unsigned long) childregs;
 152         p->thread.reg31 = (unsigned long) ret_from_fork;
 153
 154         /*
 155          * New tasks lose permission to use the fpu. This accelerates context
 156          * switching for most programs since they don't use the fpu.
 157          */
 158         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 159         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 160
 161 #ifdef CONFIG_MIPS_MT_SMTC
 162         /*
 163          * SMTC restores TCStatus after Status, and the CU bits
 164          * are aliased there.
 165          */
 166         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 167 #endif
 168         clear_tsk_thread_flag(p, TIF_USEDFPU);
 169
 170 #ifdef CONFIG_MIPS_MT_FPAFF
 171         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 172 #endif /* CONFIG_MIPS_MT_FPAFF */
 173
 174         if (clone_flags & CLONE_SETTLS)
 175                 ti->tp_value = regs->regs[7];
 176
 177         return 0;
 178 }
 179
 180 /* Fill in the fpu structure for a core dump.. */
 181 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 182 {
 183         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 184
 185         return 1;
 186 }
 187
 188 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 189 {
 190         int i;
 191
 192         for (i = 0; i < EF_R0; i++)
 193                 gp[i] = 0;
 194         gp[EF_R0] = 0;
 195         for (i = 1; i <= 31; i++)
 196                 gp[EF_R0 + i] = regs->regs[i];
 197         gp[EF_R26] = 0;
 198         gp[EF_R27] = 0;
 199         gp[EF_LO] = regs->lo;
 200         gp[EF_HI] = regs->hi;
 201         gp[EF_CP0_EPC] = regs->cp0_epc;
 202         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 203         gp[EF_CP0_STATUS] = regs->cp0_status;
 204         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 205 #ifdef EF_UNUSED0
 206         gp[EF_UNUSED0] = 0;
 207 #endif
 208 }
 209
 210 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 211 {
 212         elf_dump_regs(*regs, task_pt_regs(tsk));
 213         return 1;
 214 }
 215
 216 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 217 {
 218         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 219
 220         return 1;
 221 }
 222
 223 /*
 224  * Create a kernel thread
 225  */
 226 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 227 {
 228         do_exit(fn(arg));
 229 }
 230
 231 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 232 {
 233         struct pt_regs regs;
 234
 235         memset(&regs, 0, sizeof(regs));
 236
 237         regs.regs[4] = (unsigned long) arg;
 238         regs.regs[5] = (unsigned long) fn;
 239         regs.cp0_epc = (unsigned long) kernel_thread_helper;
 240         regs.cp0_status = read_c0_status();
 241 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 242         regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 243                           ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 244 #else
 245         regs.cp0_status |= ST0_EXL;
 246 #endif
 247
 248         /* Ok, create the new process.. */
 249         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 250 }
 251
 252 /*
 253  *
 254  */
 255 struct mips_frame_info {
 256         void            *func;
 257         unsigned long   func_size;
 258         int             frame_size;
 259         int             pc_offset;
 260 };
 261
 262 static inline int is_ra_save_ins(union mips_instruction *ip)
 263 {
 264         /* sw / sd $ra, offset($sp) */
 265         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 266                 ip->i_format.rs == 29 &&
 267                 ip->i_format.rt == 31;
 268 }
 269
 270 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 271 {
 272         if (ip->j_format.opcode == jal_op)
 273                 return 1;
 274         if (ip->r_format.opcode != spec_op)
 275                 return 0;
 276         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 277 }
 278
 279 static inline int is_sp_move_ins(union mips_instruction *ip)
 280 {
 281         /* addiu/daddiu sp,sp,-imm */
 282         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 283                 return 0;
 284         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 285                 return 1;
 286         return 0;
 287 }
 288
 289 static int get_frame_info(struct mips_frame_info *info)
 290 {
 291         union mips_instruction *ip = info->func;
 292         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 293         unsigned i;
 294
 295         info->pc_offset = -1;
 296         info->frame_size = 0;
 297
 298         if (!ip)
 299                 goto err;
 300
 301         if (max_insns == 0)
 302                 max_insns = 128U;       /* unknown function size */
 303         max_insns = min(128U, max_insns);
 304
 305         for (i = 0; i < max_insns; i++, ip++) {
 306
 307                 if (is_jal_jalr_jr_ins(ip))
 308                         break;
 309                 if (!info->frame_size) {
 310                         if (is_sp_move_ins(ip))
 311                                 info->frame_size = - ip->i_format.simmediate;
 312                         continue;
 313                 }
 314                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 315                         info->pc_offset =
 316                                 ip->i_format.simmediate / sizeof(long);
 317                         break;
 318                 }
 319         }
 320         if (info->frame_size && info->pc_offset >= 0) /* nested */
 321                 return 0;
 322         if (info->pc_offset < 0) /* leaf */
 323                 return 1;
 324         /* prologue seems boggus... */
 325 err:
 326         return -1;
 327 }
 328
 329 static struct mips_frame_info schedule_mfi __read_mostly;
 330
 331 static int __init frame_info_init(void)
 332 {
 333         unsigned long size = 0;
 334 #ifdef CONFIG_KALLSYMS
 335         unsigned long ofs;
 336
 337         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 338 #endif
 339         schedule_mfi.func = schedule;
 340         schedule_mfi.func_size = size;
 341
 342         get_frame_info(&schedule_mfi);
 343
 344         /*
 345          * Without schedule() frame info, result given by
 346          * thread_saved_pc() and get_wchan() are not reliable.
 347          */
 348         if (schedule_mfi.pc_offset < 0)
 349                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 350
 351         return 0;
 352 }
 353
 354 arch_initcall(frame_info_init);
 355
 356 /*
 357  * Return saved PC of a blocked thread.
 358  */
 359 unsigned long thread_saved_pc(struct task_struct *tsk)
 360 {
 361         struct thread_struct *t = &tsk->thread;
 362
 363         /* New born processes are a special case */
 364         if (t->reg31 == (unsigned long) ret_from_fork)
 365                 return t->reg31;
 366         if (schedule_mfi.pc_offset < 0)
 367                 return 0;
 368         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 369 }
 370
 371
 372 #ifdef CONFIG_KALLSYMS
 373 /* used by show_backtrace() */
 374 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 375                            unsigned long pc, unsigned long *ra)
 376 {
 377         unsigned long stack_page;
 378         struct mips_frame_info info;
 379         unsigned long size, ofs;
 380         int leaf;
 381         extern void ret_from_irq(void);
 382         extern void ret_from_exception(void);
 383
 384         stack_page = (unsigned long)task_stack_page(task);
 385         if (!stack_page)
 386                 return 0;
 387
 388         /*
 389          * If we reached the bottom of interrupt context,
 390          * return saved pc in pt_regs.
 391          */
 392         if (pc == (unsigned long)ret_from_irq ||
 393             pc == (unsigned long)ret_from_exception) {
 394                 struct pt_regs *regs;
 395                 if (*sp >= stack_page &&
 396                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 397                         regs = (struct pt_regs *)*sp;
 398                         pc = regs->cp0_epc;
 399                         if (__kernel_text_address(pc)) {
 400                                 *sp = regs->regs[29];
 401                                 *ra = regs->regs[31];
 402                                 return pc;
 403                         }
 404                 }
 405                 return 0;
 406         }
 407         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 408                 return 0;
 409         /*
 410          * Return ra if an exception occured at the first instruction
 411          */
 412         if (unlikely(ofs == 0)) {
 413                 pc = *ra;
 414                 *ra = 0;
 415                 return pc;
 416         }
 417
 418         info.func = (void *)(pc - ofs);
 419         info.func_size = ofs;   /* analyze from start to ofs */
 420         leaf = get_frame_info(&info);
 421         if (leaf < 0)
 422                 return 0;
 423
 424         if (*sp < stack_page ||
 425             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 426                 return 0;
 427
 428         if (leaf)
 429                 /*
 430                  * For some extreme cases, get_frame_info() can
 431                  * consider wrongly a nested function as a leaf
 432                  * one. In that cases avoid to return always the
 433                  * same value.
 434                  */
 435                 pc = pc != *ra ? *ra : 0;
 436         else
 437                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 438
 439         *sp += info.frame_size;
 440         *ra = 0;
 441         return __kernel_text_address(pc) ? pc : 0;
 442 }
 443 #endif
 444
 445 /*
 446  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 447  */
 448 unsigned long get_wchan(struct task_struct *task)
 449 {
 450         unsigned long pc = 0;
 451 #ifdef CONFIG_KALLSYMS
 452         unsigned long sp;
 453         unsigned long ra = 0;
 454 #endif
 455
 456         if (!task || task == current || task->state == TASK_RUNNING)
 457                 goto out;
 458         if (!task_stack_page(task))
 459                 goto out;
 460
 461         pc = thread_saved_pc(task);
 462
 463 #ifdef CONFIG_KALLSYMS
 464         sp = task->thread.reg29 + schedule_mfi.frame_size;
 465
 466         while (in_sched_functions(pc))
 467                 pc = unwind_stack(task, &sp, pc, &ra);
 468 #endif
 469
 470 out:
 471         return pc;
 472 }
 473
 474 /*
 475  * Don't forget that the stack pointer must be aligned on a 8 bytes
 476  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 477  */
 478 unsigned long arch_align_stack(unsigned long sp)
 479 {
 480         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 481                 sp -= get_random_int() & ~PAGE_MASK;
 482
 483         return sp & ALMASK;
 484 }