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         if (usp)
 160                 childregs->regs[29] = usp;
 161         ti->addr_limit = USER_DS;
 162
 163         p->thread.reg29 = (unsigned long) childregs;
 164         p->thread.reg31 = (unsigned long) ret_from_fork;
 165
 166         /*
 167          * New tasks lose permission to use the fpu. This accelerates context
 168          * switching for most programs since they don't use the fpu.
 169          */
 170         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 171
 172 #ifdef CONFIG_MIPS_MT_SMTC
 173         /*
 174          * SMTC restores TCStatus after Status, and the CU bits
 175          * are aliased there.
 176          */
 177         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 178 #endif
 179         clear_tsk_thread_flag(p, TIF_USEDFPU);
 180
 181 #ifdef CONFIG_MIPS_MT_FPAFF
 182         clear_tsk_thread_flag(p, TIF_FPUBOUND);
 183 #endif /* CONFIG_MIPS_MT_FPAFF */
 184
 185         if (clone_flags & CLONE_SETTLS)
 186                 ti->tp_value = regs->regs[7];
 187
 188         return 0;
 189 }
 190
 191 /* Fill in the fpu structure for a core dump.. */
 192 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 193 {
 194         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 195
 196         return 1;
 197 }
 198
 199 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 200 {
 201         int i;
 202
 203         for (i = 0; i < EF_R0; i++)
 204                 gp[i] = 0;
 205         gp[EF_R0] = 0;
 206         for (i = 1; i <= 31; i++)
 207                 gp[EF_R0 + i] = regs->regs[i];
 208         gp[EF_R26] = 0;
 209         gp[EF_R27] = 0;
 210         gp[EF_LO] = regs->lo;
 211         gp[EF_HI] = regs->hi;
 212         gp[EF_CP0_EPC] = regs->cp0_epc;
 213         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 214         gp[EF_CP0_STATUS] = regs->cp0_status;
 215         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 216 #ifdef EF_UNUSED0
 217         gp[EF_UNUSED0] = 0;
 218 #endif
 219 }
 220
 221 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 222 {
 223         elf_dump_regs(*regs, task_pt_regs(tsk));
 224         return 1;
 225 }
 226
 227 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 228 {
 229         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 230
 231         return 1;
 232 }
 233
 234 /*
 235  *
 236  */
 237 struct mips_frame_info {
 238         void            *func;
 239         unsigned long   func_size;
 240         int             frame_size;
 241         int             pc_offset;
 242 };
 243
 244 static inline int is_ra_save_ins(union mips_instruction *ip)
 245 {
 246         /* sw / sd $ra, offset($sp) */
 247         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 248                 ip->i_format.rs == 29 &&
 249                 ip->i_format.rt == 31;
 250 }
 251
 252 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 253 {
 254         if (ip->j_format.opcode == jal_op)
 255                 return 1;
 256         if (ip->r_format.opcode != spec_op)
 257                 return 0;
 258         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 259 }
 260
 261 static inline int is_sp_move_ins(union mips_instruction *ip)
 262 {
 263         /* addiu/daddiu sp,sp,-imm */
 264         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 265                 return 0;
 266         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 267                 return 1;
 268         return 0;
 269 }
 270
 271 static int get_frame_info(struct mips_frame_info *info)
 272 {
 273         union mips_instruction *ip = info->func;
 274         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 275         unsigned i;
 276
 277         info->pc_offset = -1;
 278         info->frame_size = 0;
 279
 280         if (!ip)
 281                 goto err;
 282
 283         if (max_insns == 0)
 284                 max_insns = 128U;       /* unknown function size */
 285         max_insns = min(128U, max_insns);
 286
 287         for (i = 0; i < max_insns; i++, ip++) {
 288
 289                 if (is_jal_jalr_jr_ins(ip))
 290                         break;
 291                 if (!info->frame_size) {
 292                         if (is_sp_move_ins(ip))
 293                                 info->frame_size = - ip->i_format.simmediate;
 294                         continue;
 295                 }
 296                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 297                         info->pc_offset =
 298                                 ip->i_format.simmediate / sizeof(long);
 299                         break;
 300                 }
 301         }
 302         if (info->frame_size && info->pc_offset >= 0) /* nested */
 303                 return 0;
 304         if (info->pc_offset < 0) /* leaf */
 305                 return 1;
 306         /* prologue seems boggus... */
 307 err:
 308         return -1;
 309 }
 310
 311 static struct mips_frame_info schedule_mfi __read_mostly;
 312
 313 static int __init frame_info_init(void)
 314 {
 315         unsigned long size = 0;
 316 #ifdef CONFIG_KALLSYMS
 317         unsigned long ofs;
 318
 319         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 320 #endif
 321         schedule_mfi.func = schedule;
 322         schedule_mfi.func_size = size;
 323
 324         get_frame_info(&schedule_mfi);
 325
 326         /*
 327          * Without schedule() frame info, result given by
 328          * thread_saved_pc() and get_wchan() are not reliable.
 329          */
 330         if (schedule_mfi.pc_offset < 0)
 331                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 332
 333         return 0;
 334 }
 335
 336 arch_initcall(frame_info_init);
 337
 338 /*
 339  * Return saved PC of a blocked thread.
 340  */
 341 unsigned long thread_saved_pc(struct task_struct *tsk)
 342 {
 343         struct thread_struct *t = &tsk->thread;
 344
 345         /* New born processes are a special case */
 346         if (t->reg31 == (unsigned long) ret_from_fork)
 347                 return t->reg31;
 348         if (schedule_mfi.pc_offset < 0)
 349                 return 0;
 350         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 351 }
 352
 353
 354 #ifdef CONFIG_KALLSYMS
 355 /* generic stack unwinding function */
 356 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 357                                               unsigned long *sp,
 358                                               unsigned long pc,
 359                                               unsigned long *ra)
 360 {
 361         struct mips_frame_info info;
 362         unsigned long size, ofs;
 363         int leaf;
 364         extern void ret_from_irq(void);
 365         extern void ret_from_exception(void);
 366
 367         if (!stack_page)
 368                 return 0;
 369
 370         /*
 371          * If we reached the bottom of interrupt context,
 372          * return saved pc in pt_regs.
 373          */
 374         if (pc == (unsigned long)ret_from_irq ||
 375             pc == (unsigned long)ret_from_exception) {
 376                 struct pt_regs *regs;
 377                 if (*sp >= stack_page &&
 378                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 379                         regs = (struct pt_regs *)*sp;
 380                         pc = regs->cp0_epc;
 381                         if (__kernel_text_address(pc)) {
 382                                 *sp = regs->regs[29];
 383                                 *ra = regs->regs[31];
 384                                 return pc;
 385                         }
 386                 }
 387                 return 0;
 388         }
 389         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 390                 return 0;
 391         /*
 392          * Return ra if an exception occurred at the first instruction
 393          */
 394         if (unlikely(ofs == 0)) {
 395                 pc = *ra;
 396                 *ra = 0;
 397                 return pc;
 398         }
 399
 400         info.func = (void *)(pc - ofs);
 401         info.func_size = ofs;   /* analyze from start to ofs */
 402         leaf = get_frame_info(&info);
 403         if (leaf < 0)
 404                 return 0;
 405
 406         if (*sp < stack_page ||
 407             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 408                 return 0;
 409
 410         if (leaf)
 411                 /*
 412                  * For some extreme cases, get_frame_info() can
 413                  * consider wrongly a nested function as a leaf
 414                  * one. In that cases avoid to return always the
 415                  * same value.
 416                  */
 417                 pc = pc != *ra ? *ra : 0;
 418         else
 419                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 420
 421         *sp += info.frame_size;
 422         *ra = 0;
 423         return __kernel_text_address(pc) ? pc : 0;
 424 }
 425 EXPORT_SYMBOL(unwind_stack_by_address);
 426
 427 /* used by show_backtrace() */
 428 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 429                            unsigned long pc, unsigned long *ra)
 430 {
 431         unsigned long stack_page = (unsigned long)task_stack_page(task);
 432         return unwind_stack_by_address(stack_page, sp, pc, ra);
 433 }
 434 #endif
 435
 436 /*
 437  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 438  */
 439 unsigned long get_wchan(struct task_struct *task)
 440 {
 441         unsigned long pc = 0;
 442 #ifdef CONFIG_KALLSYMS
 443         unsigned long sp;
 444         unsigned long ra = 0;
 445 #endif
 446
 447         if (!task || task == current || task->state == TASK_RUNNING)
 448                 goto out;
 449         if (!task_stack_page(task))
 450                 goto out;
 451
 452         pc = thread_saved_pc(task);
 453
 454 #ifdef CONFIG_KALLSYMS
 455         sp = task->thread.reg29 + schedule_mfi.frame_size;
 456
 457         while (in_sched_functions(pc))
 458                 pc = unwind_stack(task, &sp, pc, &ra);
 459 #endif
 460
 461 out:
 462         return pc;
 463 }
 464
 465 /*
 466  * Don't forget that the stack pointer must be aligned on a 8 bytes
 467  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 468  */
 469 unsigned long arch_align_stack(unsigned long sp)
 470 {
 471         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 472                 sp -= get_random_int() & ~PAGE_MASK;
 473
 474         return sp & ALMASK;
 475 }