LXR linux/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 */
  49void __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                    (system_state == SYSTEM_RUNNING ||
  77                     system_state == SYSTEM_BOOTING))
  78                        play_dead();
  79#endif
  80                rcu_idle_exit();
  81                tick_nohz_idle_exit();
  82                schedule_preempt_disabled();
  83        }
  84}
  85
  86asmlinkage void ret_from_fork(void);
  87
  88void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  89{
  90        unsigned long status;
  91
  92        /* New thread loses kernel privileges. */
  93        status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  94#ifdef CONFIG_64BIT
  95        status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  96#endif
  97        status |= KU_USER;
  98        regs->cp0_status = status;
  99        clear_used_math();
 100        clear_fpu_owner();
 101        if (cpu_has_dsp)
 102                __init_dsp();
 103        regs->cp0_epc = pc;
 104        regs->regs[29] = sp;
 105}
 106
 107void exit_thread(void)
 108{
 109}
 110
 111void flush_thread(void)
 112{
 113}
 114
 115int copy_thread(unsigned long clone_flags, unsigned long usp,
 116        unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 117{
 118        struct thread_info *ti = task_thread_info(p);
 119        struct pt_regs *childregs;
 120        unsigned long childksp;
 121        p->set_child_tid = p->clear_child_tid = NULL;
 122
 123        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 124
 125        preempt_disable();
 126
 127        if (is_fpu_owner())
 128                save_fp(p);
 129
 130        if (cpu_has_dsp)
 131                save_dsp(p);
 132
 133        preempt_enable();
 134
 135        /* set up new TSS. */
 136        childregs = (struct pt_regs *) childksp - 1;
 137        /*  Put the stack after the struct pt_regs.  */
 138        childksp = (unsigned long) childregs;
 139        *childregs = *regs;
 140        childregs->regs[7] = 0; /* Clear error flag */
 141
 142        childregs->regs[2] = 0; /* Child gets zero as return value */
 143
 144        if (childregs->cp0_status & ST0_CU0) {
 145                childregs->regs[28] = (unsigned long) ti;
 146                childregs->regs[29] = childksp;
 147                ti->addr_limit = KERNEL_DS;
 148        } else {
 149                childregs->regs[29] = usp;
 150                ti->addr_limit = USER_DS;
 151        }
 152        p->thread.reg29 = (unsigned long) childregs;
 153        p->thread.reg31 = (unsigned long) ret_from_fork;
 154
 155        /*
 156         * New tasks lose permission to use the fpu. This accelerates context
 157         * switching for most programs since they don't use the fpu.
 158         */
 159        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 160        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 161
 162#ifdef CONFIG_MIPS_MT_SMTC
 163        /*
 164         * SMTC restores TCStatus after Status, and the CU bits
 165         * are aliased there.
 166         */
 167        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 168#endif
 169        clear_tsk_thread_flag(p, TIF_USEDFPU);
 170
 171#ifdef CONFIG_MIPS_MT_FPAFF
 172        clear_tsk_thread_flag(p, TIF_FPUBOUND);
 173#endif /* CONFIG_MIPS_MT_FPAFF */
 174
 175        if (clone_flags & CLONE_SETTLS)
 176                ti->tp_value = regs->regs[7];
 177
 178        return 0;
 179}
 180
 181/* Fill in the fpu structure for a core dump.. */
 182int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 183{
 184        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 185
 186        return 1;
 187}
 188
 189void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 190{
 191        int i;
 192
 193        for (i = 0; i < EF_R0; i++)
 194                gp[i] = 0;
 195        gp[EF_R0] = 0;
 196        for (i = 1; i <= 31; i++)
 197                gp[EF_R0 + i] = regs->regs[i];
 198        gp[EF_R26] = 0;
 199        gp[EF_R27] = 0;
 200        gp[EF_LO] = regs->lo;
 201        gp[EF_HI] = regs->hi;
 202        gp[EF_CP0_EPC] = regs->cp0_epc;
 203        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 204        gp[EF_CP0_STATUS] = regs->cp0_status;
 205        gp[EF_CP0_CAUSE] = regs->cp0_cause;
 206#ifdef EF_UNUSED0
 207        gp[EF_UNUSED0] = 0;
 208#endif
 209}
 210
 211int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 212{
 213        elf_dump_regs(*regs, task_pt_regs(tsk));
 214        return 1;
 215}
 216
 217int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 218{
 219        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 220
 221        return 1;
 222}
 223
 224/*
 225 * Create a kernel thread
 226 */
 227static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 228{
 229        do_exit(fn(arg));
 230}
 231
 232long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 233{
 234        struct pt_regs regs;
 235
 236        memset(&regs, 0, sizeof(regs));
 237
 238        regs.regs[4] = (unsigned long) arg;
 239        regs.regs[5] = (unsigned long) fn;
 240        regs.cp0_epc = (unsigned long) kernel_thread_helper;
 241        regs.cp0_status = read_c0_status();
 242#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 243        regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 244                          ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 245#else
 246        regs.cp0_status |= ST0_EXL;
 247#endif
 248
 249        /* Ok, create the new process.. */
 250        return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 251}
 252
 253/*
 254 *
 255 */
 256struct mips_frame_info {
 257        void            *func;
 258        unsigned long   func_size;
 259        int             frame_size;
 260        int             pc_offset;
 261};
 262
 263static inline int is_ra_save_ins(union mips_instruction *ip)
 264{
 265        /* sw / sd $ra, offset($sp) */
 266        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 267                ip->i_format.rs == 29 &&
 268                ip->i_format.rt == 31;
 269}
 270
 271static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 272{
 273        if (ip->j_format.opcode == jal_op)
 274                return 1;
 275        if (ip->r_format.opcode != spec_op)
 276                return 0;
 277        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 278}
 279
 280static inline int is_sp_move_ins(union mips_instruction *ip)
 281{
 282        /* addiu/daddiu sp,sp,-imm */
 283        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 284                return 0;
 285        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 286                return 1;
 287        return 0;
 288}
 289
 290static int get_frame_info(struct mips_frame_info *info)
 291{
 292        union mips_instruction *ip = info->func;
 293        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 294        unsigned i;
 295
 296        info->pc_offset = -1;
 297        info->frame_size = 0;
 298
 299        if (!ip)
 300                goto err;
 301
 302        if (max_insns == 0)
 303                max_insns = 128U;       /* unknown function size */
 304        max_insns = min(128U, max_insns);
 305
 306        for (i = 0; i < max_insns; i++, ip++) {
 307
 308                if (is_jal_jalr_jr_ins(ip))
 309                        break;
 310                if (!info->frame_size) {
 311                        if (is_sp_move_ins(ip))
 312                                info->frame_size = - ip->i_format.simmediate;
 313                        continue;
 314                }
 315                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 316                        info->pc_offset =
 317                                ip->i_format.simmediate / sizeof(long);
 318                        break;
 319                }
 320        }
 321        if (info->frame_size && info->pc_offset >= 0) /* nested */
 322                return 0;
 323        if (info->pc_offset < 0) /* leaf */
 324                return 1;
 325        /* prologue seems boggus... */
 326err:
 327        return -1;
 328}
 329
 330static struct mips_frame_info schedule_mfi __read_mostly;
 331
 332static int __init frame_info_init(void)
 333{
 334        unsigned long size = 0;
 335#ifdef CONFIG_KALLSYMS
 336        unsigned long ofs;
 337
 338        kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 339#endif
 340        schedule_mfi.func = schedule;
 341        schedule_mfi.func_size = size;
 342
 343        get_frame_info(&schedule_mfi);
 344
 345        /*
 346         * Without schedule() frame info, result given by
 347         * thread_saved_pc() and get_wchan() are not reliable.
 348         */
 349        if (schedule_mfi.pc_offset < 0)
 350                printk("Can't analyze schedule() prologue at %p\n", schedule);
 351
 352        return 0;
 353}
 354
 355arch_initcall(frame_info_init);
 356
 357/*
 358 * Return saved PC of a blocked thread.
 359 */
 360unsigned long thread_saved_pc(struct task_struct *tsk)
 361{
 362        struct thread_struct *t = &tsk->thread;
 363
 364        /* New born processes are a special case */
 365        if (t->reg31 == (unsigned long) ret_from_fork)
 366                return t->reg31;
 367        if (schedule_mfi.pc_offset < 0)
 368                return 0;
 369        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 370}
 371
 372
 373#ifdef CONFIG_KALLSYMS
 374/* generic stack unwinding function */
 375unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 376                                              unsigned long *sp,
 377                                              unsigned long pc,
 378                                              unsigned long *ra)
 379{
 380        struct mips_frame_info info;
 381        unsigned long size, ofs;
 382        int leaf;
 383        extern void ret_from_irq(void);
 384        extern void ret_from_exception(void);
 385
 386        if (!stack_page)
 387                return 0;
 388
 389        /*
 390         * If we reached the bottom of interrupt context,
 391         * return saved pc in pt_regs.
 392         */
 393        if (pc == (unsigned long)ret_from_irq ||
 394            pc == (unsigned long)ret_from_exception) {
 395                struct pt_regs *regs;
 396                if (*sp >= stack_page &&
 397                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 398                        regs = (struct pt_regs *)*sp;
 399                        pc = regs->cp0_epc;
 400                        if (__kernel_text_address(pc)) {
 401                                *sp = regs->regs[29];
 402                                *ra = regs->regs[31];
 403                                return pc;
 404                        }
 405                }
 406                return 0;
 407        }
 408        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 409                return 0;
 410        /*
 411         * Return ra if an exception occurred at the first instruction
 412         */
 413        if (unlikely(ofs == 0)) {
 414                pc = *ra;
 415                *ra = 0;
 416                return pc;
 417        }
 418
 419        info.func = (void *)(pc - ofs);
 420        info.func_size = ofs;   /* analyze from start to ofs */
 421        leaf = get_frame_info(&info);
 422        if (leaf < 0)
 423                return 0;
 424
 425        if (*sp < stack_page ||
 426            *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 427                return 0;
 428
 429        if (leaf)
 430                /*
 431                 * For some extreme cases, get_frame_info() can
 432                 * consider wrongly a nested function as a leaf
 433                 * one. In that cases avoid to return always the
 434                 * same value.
 435                 */
 436                pc = pc != *ra ? *ra : 0;
 437        else
 438                pc = ((unsigned long *)(*sp))[info.pc_offset];
 439
 440        *sp += info.frame_size;
 441        *ra = 0;
 442        return __kernel_text_address(pc) ? pc : 0;
 443}
 444EXPORT_SYMBOL(unwind_stack_by_address);
 445
 446/* used by show_backtrace() */
 447unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 448                           unsigned long pc, unsigned long *ra)
 449{
 450        unsigned long stack_page = (unsigned long)task_stack_page(task);
 451        return unwind_stack_by_address(stack_page, sp, pc, ra);
 452}
 453#endif
 454
 455/*
 456 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 457 */
 458unsigned long get_wchan(struct task_struct *task)
 459{
 460        unsigned long pc = 0;
 461#ifdef CONFIG_KALLSYMS
 462        unsigned long sp;
 463        unsigned long ra = 0;
 464#endif
 465
 466        if (!task || task == current || task->state == TASK_RUNNING)
 467                goto out;
 468        if (!task_stack_page(task))
 469                goto out;
 470
 471        pc = thread_saved_pc(task);
 472
 473#ifdef CONFIG_KALLSYMS
 474        sp = task->thread.reg29 + schedule_mfi.frame_size;
 475
 476        while (in_sched_functions(pc))
 477                pc = unwind_stack(task, &sp, pc, &ra);
 478#endif
 479
 480out:
 481        return pc;
 482}
 483
 484/*
 485 * Don't forget that the stack pointer must be aligned on a 8 bytes
 486 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 487 */
 488unsigned long arch_align_stack(unsigned long sp)
 489{
 490        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 491                sp -= get_random_int() & ~PAGE_MASK;
 492
 493        return sp & ALMASK;
 494}
 495