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