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/system.h>
  36#include <asm/mipsregs.h>
  37#include <asm/processor.h>
  38#include <asm/uaccess.h>
  39#include <asm/io.h>
  40#include <asm/elf.h>
  41#include <asm/isadep.h>
  42#include <asm/inst.h>
  43#include <asm/stacktrace.h>
  44
  45/*
  46 * The idle thread. There's no useful work to be done, so just try to conserve
  47 * power and have a low exit latency (ie sit in a loop waiting for somebody to
  48 * say that they'd like to reschedule)
  49 */
  50void __noreturn cpu_idle(void)
  51{
  52        int cpu;
  53
  54        /* CPU is going idle. */
  55        cpu = smp_processor_id();
  56
  57        /* endless idle loop with no priority at all */
  58        while (1) {
  59                tick_nohz_stop_sched_tick(1);
  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                tick_nohz_restart_sched_tick();
  81                preempt_enable_no_resched();
  82                schedule();
  83                preempt_disable();
  84        }
  85}
  86
  87asmlinkage void ret_from_fork(void);
  88
  89void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  90{
  91        unsigned long status;
  92
  93        /* New thread loses kernel privileges. */
  94        status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  95#ifdef CONFIG_64BIT
  96        status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  97#endif
  98        status |= KU_USER;
  99        regs->cp0_status = status;
 100        clear_used_math();
 101        clear_fpu_owner();
 102        if (cpu_has_dsp)
 103                __init_dsp();
 104        regs->cp0_epc = pc;
 105        regs->regs[29] = sp;
 106}
 107
 108void exit_thread(void)
 109{
 110}
 111
 112void flush_thread(void)
 113{
 114}
 115
 116int copy_thread(unsigned long clone_flags, unsigned long usp,
 117        unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 118{
 119        struct thread_info *ti = task_thread_info(p);
 120        struct pt_regs *childregs;
 121        unsigned long childksp;
 122        p->set_child_tid = p->clear_child_tid = NULL;
 123
 124        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 125
 126        preempt_disable();
 127
 128        if (is_fpu_owner())
 129                save_fp(p);
 130
 131        if (cpu_has_dsp)
 132                save_dsp(p);
 133
 134        preempt_enable();
 135
 136        /* set up new TSS. */
 137        childregs = (struct pt_regs *) childksp - 1;
 138        /*  Put the stack after the struct pt_regs.  */
 139        childksp = (unsigned long) childregs;
 140        *childregs = *regs;
 141        childregs->regs[7] = 0; /* Clear error flag */
 142
 143        childregs->regs[2] = 0; /* Child gets zero as return value */
 144
 145        if (childregs->cp0_status & ST0_CU0) {
 146                childregs->regs[28] = (unsigned long) ti;
 147                childregs->regs[29] = childksp;
 148                ti->addr_limit = KERNEL_DS;
 149        } else {
 150                childregs->regs[29] = usp;
 151                ti->addr_limit = USER_DS;
 152        }
 153        p->thread.reg29 = (unsigned long) childregs;
 154        p->thread.reg31 = (unsigned long) ret_from_fork;
 155
 156        /*
 157         * New tasks lose permission to use the fpu. This accelerates context
 158         * switching for most programs since they don't use the fpu.
 159         */
 160        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 161        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 162
 163#ifdef CONFIG_MIPS_MT_SMTC
 164        /*
 165         * SMTC restores TCStatus after Status, and the CU bits
 166         * are aliased there.
 167         */
 168        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 169#endif
 170        clear_tsk_thread_flag(p, TIF_USEDFPU);
 171
 172#ifdef CONFIG_MIPS_MT_FPAFF
 173        clear_tsk_thread_flag(p, TIF_FPUBOUND);
 174#endif /* CONFIG_MIPS_MT_FPAFF */
 175
 176        if (clone_flags & CLONE_SETTLS)
 177                ti->tp_value = regs->regs[7];
 178
 179        return 0;
 180}
 181
 182/* Fill in the fpu structure for a core dump.. */
 183int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 184{
 185        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 186
 187        return 1;
 188}
 189
 190void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 191{
 192        int i;
 193
 194        for (i = 0; i < EF_R0; i++)
 195                gp[i] = 0;
 196        gp[EF_R0] = 0;
 197        for (i = 1; i <= 31; i++)
 198                gp[EF_R0 + i] = regs->regs[i];
 199        gp[EF_R26] = 0;
 200        gp[EF_R27] = 0;
 201        gp[EF_LO] = regs->lo;
 202        gp[EF_HI] = regs->hi;
 203        gp[EF_CP0_EPC] = regs->cp0_epc;
 204        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 205        gp[EF_CP0_STATUS] = regs->cp0_status;
 206        gp[EF_CP0_CAUSE] = regs->cp0_cause;
 207#ifdef EF_UNUSED0
 208        gp[EF_UNUSED0] = 0;
 209#endif
 210}
 211
 212int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 213{
 214        elf_dump_regs(*regs, task_pt_regs(tsk));
 215        return 1;
 216}
 217
 218int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 219{
 220        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 221
 222        return 1;
 223}
 224
 225/*
 226 * Create a kernel thread
 227 */
 228static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 229{
 230        do_exit(fn(arg));
 231}
 232
 233long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 234{
 235        struct pt_regs regs;
 236
 237        memset(&regs, 0, sizeof(regs));
 238
 239        regs.regs[4] = (unsigned long) arg;
 240        regs.regs[5] = (unsigned long) fn;
 241        regs.cp0_epc = (unsigned long) kernel_thread_helper;
 242        regs.cp0_status = read_c0_status();
 243#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 244        regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 245                          ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 246#else
 247        regs.cp0_status |= ST0_EXL;
 248#endif
 249
 250        /* Ok, create the new process.. */
 251        return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 252}
 253
 254/*
 255 *
 256 */
 257struct mips_frame_info {
 258        void            *func;
 259        unsigned long   func_size;
 260        int             frame_size;
 261        int             pc_offset;
 262};
 263
 264static inline int is_ra_save_ins(union mips_instruction *ip)
 265{
 266        /* sw / sd $ra, offset($sp) */
 267        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 268                ip->i_format.rs == 29 &&
 269                ip->i_format.rt == 31;
 270}
 271
 272static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 273{
 274        if (ip->j_format.opcode == jal_op)
 275                return 1;
 276        if (ip->r_format.opcode != spec_op)
 277                return 0;
 278        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 279}
 280
 281static inline int is_sp_move_ins(union mips_instruction *ip)
 282{
 283        /* addiu/daddiu sp,sp,-imm */
 284        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 285                return 0;
 286        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 287                return 1;
 288        return 0;
 289}
 290
 291static int get_frame_info(struct mips_frame_info *info)
 292{
 293        union mips_instruction *ip = info->func;
 294        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 295        unsigned i;
 296
 297        info->pc_offset = -1;
 298        info->frame_size = 0;
 299
 300        if (!ip)
 301                goto err;
 302
 303        if (max_insns == 0)
 304                max_insns = 128U;       /* unknown function size */
 305        max_insns = min(128U, max_insns);
 306
 307        for (i = 0; i < max_insns; i++, ip++) {
 308
 309                if (is_jal_jalr_jr_ins(ip))
 310                        break;
 311                if (!info->frame_size) {
 312                        if (is_sp_move_ins(ip))
 313                                info->frame_size = - ip->i_format.simmediate;
 314                        continue;
 315                }
 316                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 317                        info->pc_offset =
 318                                ip->i_format.simmediate / sizeof(long);
 319                        break;
 320                }
 321        }
 322        if (info->frame_size && info->pc_offset >= 0) /* nested */
 323                return 0;
 324        if (info->pc_offset < 0) /* leaf */
 325                return 1;
 326        /* prologue seems boggus... */
 327err:
 328        return -1;
 329}
 330
 331static struct mips_frame_info schedule_mfi __read_mostly;
 332
 333static int __init frame_info_init(void)
 334{
 335        unsigned long size = 0;
 336#ifdef CONFIG_KALLSYMS
 337        unsigned long ofs;
 338
 339        kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 340#endif
 341        schedule_mfi.func = schedule;
 342        schedule_mfi.func_size = size;
 343
 344        get_frame_info(&schedule_mfi);
 345
 346        /*
 347         * Without schedule() frame info, result given by
 348         * thread_saved_pc() and get_wchan() are not reliable.
 349         */
 350        if (schedule_mfi.pc_offset < 0)
 351                printk("Can't analyze schedule() prologue at %p\n", schedule);
 352
 353        return 0;
 354}
 355
 356arch_initcall(frame_info_init);
 357
 358/*
 359 * Return saved PC of a blocked thread.
 360 */
 361unsigned long thread_saved_pc(struct task_struct *tsk)
 362{
 363        struct thread_struct *t = &tsk->thread;
 364
 365        /* New born processes are a special case */
 366        if (t->reg31 == (unsigned long) ret_from_fork)
 367                return t->reg31;
 368        if (schedule_mfi.pc_offset < 0)
 369                return 0;
 370        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 371}
 372
 373
 374#ifdef CONFIG_KALLSYMS
 375/* generic stack unwinding function */
 376unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 377                                              unsigned long *sp,
 378                                              unsigned long pc,
 379                                              unsigned long *ra)
 380{
 381        struct mips_frame_info info;
 382        unsigned long size, ofs;
 383        int leaf;
 384        extern void ret_from_irq(void);
 385        extern void ret_from_exception(void);
 386
 387        if (!stack_page)
 388                return 0;
 389
 390        /*
 391         * If we reached the bottom of interrupt context,
 392         * return saved pc in pt_regs.
 393         */
 394        if (pc == (unsigned long)ret_from_irq ||
 395            pc == (unsigned long)ret_from_exception) {
 396                struct pt_regs *regs;
 397                if (*sp >= stack_page &&
 398                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 399                        regs = (struct pt_regs *)*sp;
 400                        pc = regs->cp0_epc;
 401                        if (__kernel_text_address(pc)) {
 402                                *sp = regs->regs[29];
 403                                *ra = regs->regs[31];
 404                                return pc;
 405                        }
 406                }
 407                return 0;
 408        }
 409        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 410                return 0;
 411        /*
 412         * Return ra if an exception occurred at the first instruction
 413         */
 414        if (unlikely(ofs == 0)) {
 415                pc = *ra;
 416                *ra = 0;
 417                return pc;
 418        }
 419
 420        info.func = (void *)(pc - ofs);
 421        info.func_size = ofs;   /* analyze from start to ofs */
 422        leaf = get_frame_info(&info);
 423        if (leaf < 0)
 424                return 0;
 425
 426        if (*sp < stack_page ||
 427            *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 428                return 0;
 429
 430        if (leaf)
 431                /*
 432                 * For some extreme cases, get_frame_info() can
 433                 * consider wrongly a nested function as a leaf
 434                 * one. In that cases avoid to return always the
 435                 * same value.
 436                 */
 437                pc = pc != *ra ? *ra : 0;
 438        else
 439                pc = ((unsigned long *)(*sp))[info.pc_offset];
 440
 441        *sp += info.frame_size;
 442        *ra = 0;
 443        return __kernel_text_address(pc) ? pc : 0;
 444}
 445EXPORT_SYMBOL(unwind_stack_by_address);
 446
 447/* used by show_backtrace() */
 448unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 449                           unsigned long pc, unsigned long *ra)
 450{
 451        unsigned long stack_page = (unsigned long)task_stack_page(task);
 452        return unwind_stack_by_address(stack_page, sp, pc, ra);
 453}
 454#endif
 455
 456/*
 457 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 458 */
 459unsigned long get_wchan(struct task_struct *task)
 460{
 461        unsigned long pc = 0;
 462#ifdef CONFIG_KALLSYMS
 463        unsigned long sp;
 464        unsigned long ra = 0;
 465#endif
 466
 467        if (!task || task == current || task->state == TASK_RUNNING)
 468                goto out;
 469        if (!task_stack_page(task))
 470                goto out;
 471
 472        pc = thread_saved_pc(task);
 473
 474#ifdef CONFIG_KALLSYMS
 475        sp = task->thread.reg29 + schedule_mfi.frame_size;
 476
 477        while (in_sched_functions(pc))
 478                pc = unwind_stack(task, &sp, pc, &ra);
 479#endif
 480
 481out:
 482        return pc;
 483}
 484
 485/*
 486 * Don't forget that the stack pointer must be aligned on a 8 bytes
 487 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 488 */
 489unsigned long arch_align_stack(unsigned long sp)
 490{
 491        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 492                sp -= get_random_int() & ~PAGE_MASK;
 493
 494        return sp & ALMASK;
 495}
 496