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                        play_dead();
  77#endif
  78                rcu_idle_exit();
  79                tick_nohz_idle_exit();
  80                schedule_preempt_disabled();
  81        }
  82}
  83
  84asmlinkage void ret_from_fork(void);
  85asmlinkage void ret_from_kernel_thread(void);
  86
  87void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  88{
  89        unsigned long status;
  90
  91        /* New thread loses kernel privileges. */
  92        status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  93#ifdef CONFIG_64BIT
  94        status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  95#endif
  96        status |= KU_USER;
  97        regs->cp0_status = status;
  98        clear_used_math();
  99        clear_fpu_owner();
 100        if (cpu_has_dsp)
 101                __init_dsp();
 102        regs->cp0_epc = pc;
 103        regs->regs[29] = sp;
 104}
 105
 106void exit_thread(void)
 107{
 108}
 109
 110void flush_thread(void)
 111{
 112}
 113
 114int copy_thread(unsigned long clone_flags, unsigned long usp,
 115        unsigned long arg, struct task_struct *p)
 116{
 117        struct thread_info *ti = task_thread_info(p);
 118        struct pt_regs *childregs, *regs = current_pt_regs();
 119        unsigned long childksp;
 120        p->set_child_tid = p->clear_child_tid = NULL;
 121
 122        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 123
 124        preempt_disable();
 125
 126        if (is_fpu_owner())
 127                save_fp(p);
 128
 129        if (cpu_has_dsp)
 130                save_dsp(p);
 131
 132        preempt_enable();
 133
 134        /* set up new TSS. */
 135        childregs = (struct pt_regs *) childksp - 1;
 136        /*  Put the stack after the struct pt_regs.  */
 137        childksp = (unsigned long) childregs;
 138        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 139        if (unlikely(p->flags & PF_KTHREAD)) {
 140                unsigned long status = p->thread.cp0_status;
 141                memset(childregs, 0, sizeof(struct pt_regs));
 142                ti->addr_limit = KERNEL_DS;
 143                p->thread.reg16 = usp; /* fn */
 144                p->thread.reg17 = arg;
 145                p->thread.reg29 = childksp;
 146                p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
 147#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 148                status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 149                         ((status & (ST0_KUC | ST0_IEC)) << 2);
 150#else
 151                status |= ST0_EXL;
 152#endif
 153                childregs->cp0_status = status;
 154                return 0;
 155        }
 156        *childregs = *regs;
 157        childregs->regs[7] = 0; /* Clear error flag */
 158        childregs->regs[2] = 0; /* Child gets zero as return value */
 159        childregs->regs[29] = usp;
 160        ti->addr_limit = USER_DS;
 161
 162        p->thread.reg29 = (unsigned long) childregs;
 163        p->thread.reg31 = (unsigned long) ret_from_fork;
 164
 165        /*
 166         * New tasks lose permission to use the fpu. This accelerates context
 167         * switching for most programs since they don't use the fpu.
 168         */
 169        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 170
 171#ifdef CONFIG_MIPS_MT_SMTC
 172        /*
 173         * SMTC restores TCStatus after Status, and the CU bits
 174         * are aliased there.
 175         */
 176        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 177#endif
 178        clear_tsk_thread_flag(p, TIF_USEDFPU);
 179
 180#ifdef CONFIG_MIPS_MT_FPAFF
 181        clear_tsk_thread_flag(p, TIF_FPUBOUND);
 182#endif /* CONFIG_MIPS_MT_FPAFF */
 183
 184        if (clone_flags & CLONE_SETTLS)
 185                ti->tp_value = regs->regs[7];
 186
 187        return 0;
 188}
 189
 190/* Fill in the fpu structure for a core dump.. */
 191int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 192{
 193        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 194
 195        return 1;
 196}
 197
 198void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 199{
 200        int i;
 201
 202        for (i = 0; i < EF_R0; i++)
 203                gp[i] = 0;
 204        gp[EF_R0] = 0;
 205        for (i = 1; i <= 31; i++)
 206                gp[EF_R0 + i] = regs->regs[i];
 207        gp[EF_R26] = 0;
 208        gp[EF_R27] = 0;
 209        gp[EF_LO] = regs->lo;
 210        gp[EF_HI] = regs->hi;
 211        gp[EF_CP0_EPC] = regs->cp0_epc;
 212        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 213        gp[EF_CP0_STATUS] = regs->cp0_status;
 214        gp[EF_CP0_CAUSE] = regs->cp0_cause;
 215#ifdef EF_UNUSED0
 216        gp[EF_UNUSED0] = 0;
 217#endif
 218}
 219
 220int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 221{
 222        elf_dump_regs(*regs, task_pt_regs(tsk));
 223        return 1;
 224}
 225
 226int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 227{
 228        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 229
 230        return 1;
 231}
 232
 233/*
 234 *
 235 */
 236struct mips_frame_info {
 237        void            *func;
 238        unsigned long   func_size;
 239        int             frame_size;
 240        int             pc_offset;
 241};
 242
 243static inline int is_ra_save_ins(union mips_instruction *ip)
 244{
 245        /* sw / sd $ra, offset($sp) */
 246        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 247                ip->i_format.rs == 29 &&
 248                ip->i_format.rt == 31;
 249}
 250
 251static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 252{
 253        if (ip->j_format.opcode == jal_op)
 254                return 1;
 255        if (ip->r_format.opcode != spec_op)
 256                return 0;
 257        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 258}
 259
 260static inline int is_sp_move_ins(union mips_instruction *ip)
 261{
 262        /* addiu/daddiu sp,sp,-imm */
 263        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 264                return 0;
 265        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 266                return 1;
 267        return 0;
 268}
 269
 270static int get_frame_info(struct mips_frame_info *info)
 271{
 272        union mips_instruction *ip = info->func;
 273        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 274        unsigned i;
 275
 276        info->pc_offset = -1;
 277        info->frame_size = 0;
 278
 279        if (!ip)
 280                goto err;
 281
 282        if (max_insns == 0)
 283                max_insns = 128U;       /* unknown function size */
 284        max_insns = min(128U, max_insns);
 285
 286        for (i = 0; i < max_insns; i++, ip++) {
 287
 288                if (is_jal_jalr_jr_ins(ip))
 289                        break;
 290                if (!info->frame_size) {
 291                        if (is_sp_move_ins(ip))
 292                                info->frame_size = - ip->i_format.simmediate;
 293                        continue;
 294                }
 295                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 296                        info->pc_offset =
 297                                ip->i_format.simmediate / sizeof(long);
 298                        break;
 299                }
 300        }
 301        if (info->frame_size && info->pc_offset >= 0) /* nested */
 302                return 0;
 303        if (info->pc_offset < 0) /* leaf */
 304                return 1;
 305        /* prologue seems boggus... */
 306err:
 307        return -1;
 308}
 309
 310static struct mips_frame_info schedule_mfi __read_mostly;
 311
 312static int __init frame_info_init(void)
 313{
 314        unsigned long size = 0;
 315#ifdef CONFIG_KALLSYMS
 316        unsigned long ofs;
 317
 318        kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 319#endif
 320        schedule_mfi.func = schedule;
 321        schedule_mfi.func_size = size;
 322
 323        get_frame_info(&schedule_mfi);
 324
 325        /*
 326         * Without schedule() frame info, result given by
 327         * thread_saved_pc() and get_wchan() are not reliable.
 328         */
 329        if (schedule_mfi.pc_offset < 0)
 330                printk("Can't analyze schedule() prologue at %p\n", schedule);
 331
 332        return 0;
 333}
 334
 335arch_initcall(frame_info_init);
 336
 337/*
 338 * Return saved PC of a blocked thread.
 339 */
 340unsigned long thread_saved_pc(struct task_struct *tsk)
 341{
 342        struct thread_struct *t = &tsk->thread;
 343
 344        /* New born processes are a special case */
 345        if (t->reg31 == (unsigned long) ret_from_fork)
 346                return t->reg31;
 347        if (schedule_mfi.pc_offset < 0)
 348                return 0;
 349        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 350}
 351
 352
 353#ifdef CONFIG_KALLSYMS
 354/* generic stack unwinding function */
 355unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 356                                              unsigned long *sp,
 357                                              unsigned long pc,
 358                                              unsigned long *ra)
 359{
 360        struct mips_frame_info info;
 361        unsigned long size, ofs;
 362        int leaf;
 363        extern void ret_from_irq(void);
 364        extern void ret_from_exception(void);
 365
 366        if (!stack_page)
 367                return 0;
 368
 369        /*
 370         * If we reached the bottom of interrupt context,
 371         * return saved pc in pt_regs.
 372         */
 373        if (pc == (unsigned long)ret_from_irq ||
 374            pc == (unsigned long)ret_from_exception) {
 375                struct pt_regs *regs;
 376                if (*sp >= stack_page &&
 377                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 378                        regs = (struct pt_regs *)*sp;
 379                        pc = regs->cp0_epc;
 380                        if (__kernel_text_address(pc)) {
 381                                *sp = regs->regs[29];
 382                                *ra = regs->regs[31];
 383                                return pc;
 384                        }
 385                }
 386                return 0;
 387        }
 388        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 389                return 0;
 390        /*
 391         * Return ra if an exception occurred at the first instruction
 392         */
 393        if (unlikely(ofs == 0)) {
 394                pc = *ra;
 395                *ra = 0;
 396                return pc;
 397        }
 398
 399        info.func = (void *)(pc - ofs);
 400        info.func_size = ofs;   /* analyze from start to ofs */
 401        leaf = get_frame_info(&info);
 402        if (leaf < 0)
 403                return 0;
 404
 405        if (*sp < stack_page ||
 406            *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 407                return 0;
 408
 409        if (leaf)
 410                /*
 411                 * For some extreme cases, get_frame_info() can
 412                 * consider wrongly a nested function as a leaf
 413                 * one. In that cases avoid to return always the
 414                 * same value.
 415                 */
 416                pc = pc != *ra ? *ra : 0;
 417        else
 418                pc = ((unsigned long *)(*sp))[info.pc_offset];
 419
 420        *sp += info.frame_size;
 421        *ra = 0;
 422        return __kernel_text_address(pc) ? pc : 0;
 423}
 424EXPORT_SYMBOL(unwind_stack_by_address);
 425
 426/* used by show_backtrace() */
 427unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 428                           unsigned long pc, unsigned long *ra)
 429{
 430        unsigned long stack_page = (unsigned long)task_stack_page(task);
 431        return unwind_stack_by_address(stack_page, sp, pc, ra);
 432}
 433#endif
 434
 435/*
 436 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 437 */
 438unsigned long get_wchan(struct task_struct *task)
 439{
 440        unsigned long pc = 0;
 441#ifdef CONFIG_KALLSYMS
 442        unsigned long sp;
 443        unsigned long ra = 0;
 444#endif
 445
 446        if (!task || task == current || task->state == TASK_RUNNING)
 447                goto out;
 448        if (!task_stack_page(task))
 449                goto out;
 450
 451        pc = thread_saved_pc(task);
 452
 453#ifdef CONFIG_KALLSYMS
 454        sp = task->thread.reg29 + schedule_mfi.frame_size;
 455
 456        while (in_sched_functions(pc))
 457                pc = unwind_stack(task, &sp, pc, &ra);
 458#endif
 459
 460out:
 461        return pc;
 462}
 463
 464/*
 465 * Don't forget that the stack pointer must be aligned on a 8 bytes
 466 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 467 */
 468unsigned long arch_align_stack(unsigned long sp)
 469{
 470        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 471                sp -= get_random_int() & ~PAGE_MASK;
 472
 473        return sp & ALMASK;
 474}
 475