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/sched.h>
  13 #include <linux/tick.h>
  14 #include <linux/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/stddef.h>
  17 #include <linux/unistd.h>
  18 #include <linux/export.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/mman.h>
  21 #include <linux/personality.h>
  22 #include <linux/sys.h>
  23 #include <linux/user.h>
  24 #include <linux/init.h>
  25 #include <linux/completion.h>
  26 #include <linux/kallsyms.h>
  27 #include <linux/random.h>
  28
  29 #include <asm/asm.h>
  30 #include <asm/bootinfo.h>
  31 #include <asm/cpu.h>
  32 #include <asm/dsp.h>
  33 #include <asm/fpu.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/mipsregs.h>
  36 #include <asm/processor.h>
  37 #include <asm/uaccess.h>
  38 #include <asm/io.h>
  39 #include <asm/elf.h>
  40 #include <asm/isadep.h>
  41 #include <asm/inst.h>
  42 #include <asm/stacktrace.h>
  43
  44 /*
  45  * The idle thread. There's no useful work to be done, so just try to conserve
  46  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  47  * say that they'd like to reschedule)
  48  */
  49 void __noreturn cpu_idle(void)
  50 {
  51         int cpu;
  52
  53         /* CPU is going idle. */
  54         cpu = smp_processor_id();
  55
  56         /* endless idle loop with no priority at all */
  57         while (1) {
  58                 tick_nohz_idle_enter();
  59                 rcu_idle_enter();
  60                 while (!need_resched() && cpu_online(cpu)) {
  61 #ifdef CONFIG_MIPS_MT_SMTC
  62                         extern void smtc_idle_loop_hook(void);
  63
  64                         smtc_idle_loop_hook();
  65 #endif
  66
  67                         if (cpu_wait) {
  68                                 /* Don't trace irqs off for idle */
  69                                 stop_critical_timings();
  70                                 (*cpu_wait)();
  71                                 start_critical_timings();
  72                         }
  73                 }
  74 #ifdef CONFIG_HOTPLUG_CPU
  75                 if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map))
  76                         play_dead();
  77 #endif
  78                 rcu_idle_exit();
  79                 tick_nohz_idle_exit();
  80                 schedule_preempt_disabled();
  81         }
  82 }
  83
  84 asmlinkage void ret_from_fork(void);
  85 asmlinkage void ret_from_kernel_thread(void);
  86
  87 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  88 {
  89         unsigned long status;
  90
  91         /* New thread loses kernel privileges. */
  92         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  93 #ifdef CONFIG_64BIT
  94         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  95 #endif
  96         status |= KU_USER;
  97         regs->cp0_status = status;
  98         clear_used_math();
  99         clear_fpu_owner();
 100         if (cpu_has_dsp)
 101                 __init_dsp();
 102         regs->cp0_epc = pc;
 103         regs->regs[29] = sp;
 104 }
 105
 106 void exit_thread(void)
 107 {
 108 }
 109
 110 void flush_thread(void)
 111 {
 112 }
 113
 114 int copy_thread(unsigned long clone_flags, unsigned long usp,
 115         unsigned long arg, struct task_struct *p)
 116 {
 117         struct thread_info *ti = task_thread_info(p);
 118         struct pt_regs *childregs, *regs = current_pt_regs();
 119         unsigned long childksp;
 120         p->set_child_tid = p->clear_child_tid = NULL;
 121
 122         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 123
 124         preempt_disable();
 125
 126         if (is_fpu_owner())
 127                 save_fp(p);
 128
 129         if (cpu_has_dsp)
 130                 save_dsp(p);
 131
 132         preempt_enable();
 133
 134         /* set up new TSS. */
 135         childregs = (struct pt_regs *) childksp - 1;
 136         /*  Put the stack after the struct pt_regs.  */
 137         childksp = (unsigned long) childregs;
 138         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 139         if (unlikely(p->flags & PF_KTHREAD)) {
 140                 unsigned long status = p->thread.cp0_status;
 141                 memset(childregs, 0, sizeof(struct pt_regs));
 142                 ti->addr_limit = KERNEL_DS;
 143                 p->thread.reg16 = usp; /* fn */
 144                 p->thread.reg17 = arg;
 145                 p->thread.reg29 = childksp;
 146                 p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 147 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 148                 status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 149                          ((status & (ST0_KUC | ST0_IEC)) << 2);
 150 #else
 151                 status |= ST0_EXL;
 152 #endif
 153                 childregs->cp0_status = status;
 154                 return 0;
 155         }
 156         *childregs = *regs;
 157         childregs->regs[7] = 0; /* Clear error flag */
 158         childregs->regs[2] = 0; /* Child gets zero as return value */
 159         childregs->regs[29] = usp;
 160         ti->addr_limit = USER_DS;
 161
 162         p->thread.reg29 = (unsigned long) childregs;
 163         p->thread.reg31 = (unsigned long) ret_from_fork;
 164
 165         /*
 166          * New tasks lose permission to use the fpu. This accelerates context
 167          * switching for most programs since they don't use the fpu.
 168          */
 169         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 170
 171 #ifdef CONFIG_MIPS_MT_SMTC
 172         /*
 173          * SMTC restores TCStatus after Status, and the CU bits
 174          * are aliased there.
 175          */
 176         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 177 #endif
 178         clear_tsk_thread_flag(p, TIF_USEDFPU);
 179
 180 #ifdef CONFIG_MIPS_MT_FPAFF
 181         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 182 #endif /* CONFIG_MIPS_MT_FPAFF */
 183
 184         if (clone_flags & CLONE_SETTLS)
 185                 ti->tp_value = regs->regs[7];
 186
 187         return 0;
 188 }
 189
 190 /* Fill in the fpu structure for a core dump.. */
 191 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 192 {
 193         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 194
 195         return 1;
 196 }
 197
 198 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 199 {
 200         int i;
 201
 202         for (i = 0; i < EF_R0; i++)
 203                 gp[i] = 0;
 204         gp[EF_R0] = 0;
 205         for (i = 1; i <= 31; i++)
 206                 gp[EF_R0 + i] = regs->regs[i];
 207         gp[EF_R26] = 0;
 208         gp[EF_R27] = 0;
 209         gp[EF_LO] = regs->lo;
 210         gp[EF_HI] = regs->hi;
 211         gp[EF_CP0_EPC] = regs->cp0_epc;
 212         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 213         gp[EF_CP0_STATUS] = regs->cp0_status;
 214         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 215 #ifdef EF_UNUSED0
 216         gp[EF_UNUSED0] = 0;
 217 #endif
 218 }
 219
 220 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 221 {
 222         elf_dump_regs(*regs, task_pt_regs(tsk));
 223         return 1;
 224 }
 225
 226 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 227 {
 228         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 229
 230         return 1;
 231 }
 232
 233 /*
 234  *
 235  */
 236 struct mips_frame_info {
 237         void            *func;
 238         unsigned long   func_size;
 239         int             frame_size;
 240         int             pc_offset;
 241 };
 242
 243 static inline int is_ra_save_ins(union mips_instruction *ip)
 244 {
 245         /* sw / sd $ra, offset($sp) */
 246         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 247                 ip->i_format.rs == 29 &&
 248                 ip->i_format.rt == 31;
 249 }
 250
 251 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 252 {
 253         if (ip->j_format.opcode == jal_op)
 254                 return 1;
 255         if (ip->r_format.opcode != spec_op)
 256                 return 0;
 257         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 258 }
 259
 260 static inline int is_sp_move_ins(union mips_instruction *ip)
 261 {
 262         /* addiu/daddiu sp,sp,-imm */
 263         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 264                 return 0;
 265         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 266                 return 1;
 267         return 0;
 268 }
 269
 270 static int get_frame_info(struct mips_frame_info *info)
 271 {
 272         union mips_instruction *ip = info->func;
 273         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 274         unsigned i;
 275
 276         info->pc_offset = -1;
 277         info->frame_size = 0;
 278
 279         if (!ip)
 280                 goto err;
 281
 282         if (max_insns == 0)
 283                 max_insns = 128U;       /* unknown function size */
 284         max_insns = min(128U, max_insns);
 285
 286         for (i = 0; i < max_insns; i++, ip++) {
 287
 288                 if (is_jal_jalr_jr_ins(ip))
 289                         break;
 290                 if (!info->frame_size) {
 291                         if (is_sp_move_ins(ip))
 292                                 info->frame_size = - ip->i_format.simmediate;
 293                         continue;
 294                 }
 295                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 296                         info->pc_offset =
 297                                 ip->i_format.simmediate / sizeof(long);
 298                         break;
 299                 }
 300         }
 301         if (info->frame_size && info->pc_offset >= 0) /* nested */
 302                 return 0;
 303         if (info->pc_offset < 0) /* leaf */
 304                 return 1;
 305         /* prologue seems boggus... */
 306 err:
 307         return -1;
 308 }
 309
 310 static struct mips_frame_info schedule_mfi __read_mostly;
 311
 312 static int __init frame_info_init(void)
 313 {
 314         unsigned long size = 0;
 315 #ifdef CONFIG_KALLSYMS
 316         unsigned long ofs;
 317
 318         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 319 #endif
 320         schedule_mfi.func = schedule;
 321         schedule_mfi.func_size = size;
 322
 323         get_frame_info(&schedule_mfi);
 324
 325         /*
 326          * Without schedule() frame info, result given by
 327          * thread_saved_pc() and get_wchan() are not reliable.
 328          */
 329         if (schedule_mfi.pc_offset < 0)
 330                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 331
 332         return 0;
 333 }
 334
 335 arch_initcall(frame_info_init);
 336
 337 /*
 338  * Return saved PC of a blocked thread.
 339  */
 340 unsigned long thread_saved_pc(struct task_struct *tsk)
 341 {
 342         struct thread_struct *t = &tsk->thread;
 343
 344         /* New born processes are a special case */
 345         if (t->reg31 == (unsigned long) ret_from_fork)
 346                 return t->reg31;
 347         if (schedule_mfi.pc_offset < 0)
 348                 return 0;
 349         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 350 }
 351
 352
 353 #ifdef CONFIG_KALLSYMS
 354 /* generic stack unwinding function */
 355 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 356                                               unsigned long *sp,
 357                                               unsigned long pc,
 358                                               unsigned long *ra)
 359 {
 360         struct mips_frame_info info;
 361         unsigned long size, ofs;
 362         int leaf;
 363         extern void ret_from_irq(void);
 364         extern void ret_from_exception(void);
 365
 366         if (!stack_page)
 367                 return 0;
 368
 369         /*
 370          * If we reached the bottom of interrupt context,
 371          * return saved pc in pt_regs.
 372          */
 373         if (pc == (unsigned long)ret_from_irq ||
 374             pc == (unsigned long)ret_from_exception) {
 375                 struct pt_regs *regs;
 376                 if (*sp >= stack_page &&
 377                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 378                         regs = (struct pt_regs *)*sp;
 379                         pc = regs->cp0_epc;
 380                         if (__kernel_text_address(pc)) {
 381                                 *sp = regs->regs[29];
 382                                 *ra = regs->regs[31];
 383                                 return pc;
 384                         }
 385                 }
 386                 return 0;
 387         }
 388         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 389                 return 0;
 390         /*
 391          * Return ra if an exception occurred at the first instruction
 392          */
 393         if (unlikely(ofs == 0)) {
 394                 pc = *ra;
 395                 *ra = 0;
 396                 return pc;
 397         }
 398
 399         info.func = (void *)(pc - ofs);
 400         info.func_size = ofs;   /* analyze from start to ofs */
 401         leaf = get_frame_info(&info);
 402         if (leaf < 0)
 403                 return 0;
 404
 405         if (*sp < stack_page ||
 406             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 407                 return 0;
 408
 409         if (leaf)
 410                 /*
 411                  * For some extreme cases, get_frame_info() can
 412                  * consider wrongly a nested function as a leaf
 413                  * one. In that cases avoid to return always the
 414                  * same value.
 415                  */
 416                 pc = pc != *ra ? *ra : 0;
 417         else
 418                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 419
 420         *sp += info.frame_size;
 421         *ra = 0;
 422         return __kernel_text_address(pc) ? pc : 0;
 423 }
 424 EXPORT_SYMBOL(unwind_stack_by_address);
 425
 426 /* used by show_backtrace() */
 427 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 428                            unsigned long pc, unsigned long *ra)
 429 {
 430         unsigned long stack_page = (unsigned long)task_stack_page(task);
 431         return unwind_stack_by_address(stack_page, sp, pc, ra);
 432 }
 433 #endif
 434
 435 /*
 436  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 437  */
 438 unsigned long get_wchan(struct task_struct *task)
 439 {
 440         unsigned long pc = 0;
 441 #ifdef CONFIG_KALLSYMS
 442         unsigned long sp;
 443         unsigned long ra = 0;
 444 #endif
 445
 446         if (!task || task == current || task->state == TASK_RUNNING)
 447                 goto out;
 448         if (!task_stack_page(task))
 449                 goto out;
 450
 451         pc = thread_saved_pc(task);
 452
 453 #ifdef CONFIG_KALLSYMS
 454         sp = task->thread.reg29 + schedule_mfi.frame_size;
 455
 456         while (in_sched_functions(pc))
 457                 pc = unwind_stack(task, &sp, pc, &ra);
 458 #endif
 459
 460 out:
 461         return pc;
 462 }
 463
 464 /*
 465  * Don't forget that the stack pointer must be aligned on a 8 bytes
 466  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 467  */
 468 unsigned long arch_align_stack(unsigned long sp)
 469 {
 470         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 471                 sp -= get_random_int() & ~PAGE_MASK;
 472
 473         return sp & ALMASK;
 474 }