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