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