arch/xtensa/kernel/process.c

   1 /*
   2  * arch/xtensa/kernel/process.c
   3  *
   4  * Xtensa Processor version.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  *
  10  * Copyright (C) 2001 - 2005 Tensilica Inc.
  11  *
  12  * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
  13  * Chris Zankel <chris@zankel.net>
  14  * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
  15  * Kevin Chea
  16  */
  17
  18 #include <linux/errno.h>
  19 #include <linux/sched.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/smp.h>
  23 #include <linux/stddef.h>
  24 #include <linux/unistd.h>
  25 #include <linux/ptrace.h>
  26 #include <linux/elf.h>
  27 #include <linux/init.h>
  28 #include <linux/prctl.h>
  29 #include <linux/init_task.h>
  30 #include <linux/module.h>
  31 #include <linux/mqueue.h>
  32 #include <linux/fs.h>
  33 #include <linux/slab.h>
  34 #include <linux/rcupdate.h>
  35
  36 #include <asm/pgtable.h>
  37 #include <asm/uaccess.h>
  38 #include <asm/io.h>
  39 #include <asm/processor.h>
  40 #include <asm/platform.h>
  41 #include <asm/mmu.h>
  42 #include <asm/irq.h>
  43 #include <linux/atomic.h>
  44 #include <asm/asm-offsets.h>
  45 #include <asm/regs.h>
  46
  47 extern void ret_from_fork(void);
  48
  49 struct task_struct *current_set[NR_CPUS] = {&init_task, };
  50
  51 void (*pm_power_off)(void) = NULL;
  52 EXPORT_SYMBOL(pm_power_off);
  53
  54
  55 #if XTENSA_HAVE_COPROCESSORS
  56
  57 void coprocessor_release_all(struct thread_info *ti)
  58 {
  59         unsigned long cpenable;
  60         int i;
  61
  62         /* Make sure we don't switch tasks during this operation. */
  63
  64         preempt_disable();
  65
  66         /* Walk through all cp owners and release it for the requested one. */
  67
  68         cpenable = ti->cpenable;
  69
  70         for (i = 0; i < XCHAL_CP_MAX; i++) {
  71                 if (coprocessor_owner[i] == ti) {
  72                         coprocessor_owner[i] = 0;
  73                         cpenable &= ~(1 << i);
  74                 }
  75         }
  76
  77         ti->cpenable = cpenable;
  78         coprocessor_clear_cpenable();
  79
  80         preempt_enable();
  81 }
  82
  83 void coprocessor_flush_all(struct thread_info *ti)
  84 {
  85         unsigned long cpenable;
  86         int i;
  87
  88         preempt_disable();
  89
  90         cpenable = ti->cpenable;
  91
  92         for (i = 0; i < XCHAL_CP_MAX; i++) {
  93                 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
  94                         coprocessor_flush(ti, i);
  95                 cpenable >>= 1;
  96         }
  97
  98         preempt_enable();
  99 }
 100
 101 #endif
 102
 103
 104 /*
 105  * Powermanagement idle function, if any is provided by the platform.
 106  */
 107
 108 void cpu_idle(void)
 109 {
 110         local_irq_enable();
 111
 112         /* endless idle loop with no priority at all */
 113         while (1) {
 114                 rcu_idle_enter();
 115                 while (!need_resched())
 116                         platform_idle();
 117                 rcu_idle_exit();
 118                 schedule_preempt_disabled();
 119         }
 120 }
 121
 122 /*
 123  * This is called when the thread calls exit().
 124  */
 125 void exit_thread(void)
 126 {
 127 #if XTENSA_HAVE_COPROCESSORS
 128         coprocessor_release_all(current_thread_info());
 129 #endif
 130 }
 131
 132 /*
 133  * Flush thread state. This is called when a thread does an execve()
 134  * Note that we flush coprocessor registers for the case execve fails.
 135  */
 136 void flush_thread(void)
 137 {
 138 #if XTENSA_HAVE_COPROCESSORS
 139         struct thread_info *ti = current_thread_info();
 140         coprocessor_flush_all(ti);
 141         coprocessor_release_all(ti);
 142 #endif
 143 }
 144
 145 /*
 146  * this gets called so that we can store coprocessor state into memory and
 147  * copy the current task into the new thread.
 148  */
 149 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 150 {
 151 #if XTENSA_HAVE_COPROCESSORS
 152         coprocessor_flush_all(task_thread_info(src));
 153 #endif
 154         *dst = *src;
 155         return 0;
 156 }
 157
 158 /*
 159  * Copy thread.
 160  *
 161  * The stack layout for the new thread looks like this:
 162  *
 163  *      +------------------------+ <- sp in childregs (= tos)
 164  *      |       childregs        |
 165  *      +------------------------+ <- thread.sp = sp in dummy-frame
 166  *      |      dummy-frame       |    (saved in dummy-frame spill-area)
 167  *      +------------------------+
 168  *
 169  * We create a dummy frame to return to ret_from_fork:
 170  *   a0 points to ret_from_fork (simulating a call4)
 171  *   sp points to itself (thread.sp)
 172  *   a2, a3 are unused.
 173  *
 174  * Note: This is a pristine frame, so we don't need any spill region on top of
 175  *       childregs.
 176  *
 177  * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
 178  * not an entire process), we're normally given a new usp, and we CANNOT share
 179  * any live address register windows.  If we just copy those live frames over,
 180  * the two threads (parent and child) will overflow the same frames onto the
 181  * parent stack at different times, likely corrupting the parent stack (esp.
 182  * if the parent returns from functions that called clone() and calls new
 183  * ones, before the child overflows its now old copies of its parent windows).
 184  * One solution is to spill windows to the parent stack, but that's fairly
 185  * involved.  Much simpler to just not copy those live frames across.
 186  */
 187
 188 int copy_thread(unsigned long clone_flags, unsigned long usp,
 189                 unsigned long unused,
 190                 struct task_struct * p, struct pt_regs * regs)
 191 {
 192         struct pt_regs *childregs;
 193         struct thread_info *ti;
 194         unsigned long tos;
 195         int user_mode = user_mode(regs);
 196
 197         /* Set up new TSS. */
 198         tos = (unsigned long)task_stack_page(p) + THREAD_SIZE;
 199         if (user_mode)
 200                 childregs = (struct pt_regs*)(tos - PT_USER_SIZE);
 201         else
 202                 childregs = (struct pt_regs*)tos - 1;
 203
 204         /* This does not copy all the regs.  In a bout of brilliance or madness,
 205            ARs beyond a0-a15 exist past the end of the struct. */
 206         *childregs = *regs;
 207
 208         /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
 209         *((int*)childregs - 3) = (unsigned long)childregs;
 210         *((int*)childregs - 4) = 0;
 211
 212         childregs->areg[2] = 0;
 213         p->set_child_tid = p->clear_child_tid = NULL;
 214         p->thread.ra = MAKE_RA_FOR_CALL((unsigned long)ret_from_fork, 0x1);
 215         p->thread.sp = (unsigned long)childregs;
 216
 217         if (user_mode(regs)) {
 218
 219                 childregs->areg[1] = usp;
 220                 if (clone_flags & CLONE_VM) {
 221                         childregs->wmask = 1;   /* can't share live windows */
 222                 } else {
 223                         int len = childregs->wmask & ~0xf;
 224                         memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
 225                                &regs->areg[XCHAL_NUM_AREGS - len/4], len);
 226                 }
 227 // FIXME: we need to set THREADPTR in thread_info...
 228                 if (clone_flags & CLONE_SETTLS)
 229                         childregs->areg[2] = childregs->areg[6];
 230
 231         } else {
 232                 /* In kernel space, we start a new thread with a new stack. */
 233                 childregs->wmask = 1;
 234                 childregs->areg[1] = tos;
 235         }
 236
 237 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
 238         ti = task_thread_info(p);
 239         ti->cpenable = 0;
 240 #endif
 241
 242         return 0;
 243 }
 244
 245
 246 /*
 247  * These bracket the sleeping functions..
 248  */
 249
 250 unsigned long get_wchan(struct task_struct *p)
 251 {
 252         unsigned long sp, pc;
 253         unsigned long stack_page = (unsigned long) task_stack_page(p);
 254         int count = 0;
 255
 256         if (!p || p == current || p->state == TASK_RUNNING)
 257                 return 0;
 258
 259         sp = p->thread.sp;
 260         pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
 261
 262         do {
 263                 if (sp < stack_page + sizeof(struct task_struct) ||
 264                     sp >= (stack_page + THREAD_SIZE) ||
 265                     pc == 0)
 266                         return 0;
 267                 if (!in_sched_functions(pc))
 268                         return pc;
 269
 270                 /* Stack layout: sp-4: ra, sp-3: sp' */
 271
 272                 pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
 273                 sp = *(unsigned long *)sp - 3;
 274         } while (count++ < 16);
 275         return 0;
 276 }
 277
 278 /*
 279  * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
 280  * of processor registers.  Besides different ordering,
 281  * xtensa_gregset_t contains non-live register information that
 282  * 'struct pt_regs' does not.  Exception handling (primarily) uses
 283  * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
 284  *
 285  */
 286
 287 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
 288 {
 289         unsigned long wb, ws, wm;
 290         int live, last;
 291
 292         wb = regs->windowbase;
 293         ws = regs->windowstart;
 294         wm = regs->wmask;
 295         ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
 296
 297         /* Don't leak any random bits. */
 298
 299         memset(elfregs, 0, sizeof(*elfregs));
 300
 301         /* Note:  PS.EXCM is not set while user task is running; its
 302          * being set in regs->ps is for exception handling convenience.
 303          */
 304
 305         elfregs->pc             = regs->pc;
 306         elfregs->ps             = (regs->ps & ~(1 << PS_EXCM_BIT));
 307         elfregs->lbeg           = regs->lbeg;
 308         elfregs->lend           = regs->lend;
 309         elfregs->lcount         = regs->lcount;
 310         elfregs->sar            = regs->sar;
 311         elfregs->windowstart    = ws;
 312
 313         live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
 314         last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
 315         memcpy(elfregs->a, regs->areg, live * 4);
 316         memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
 317 }
 318
 319 int dump_fpu(void)
 320 {
 321         return 0;
 322 }
 323
 324 asmlinkage
 325 long xtensa_clone(unsigned long clone_flags, unsigned long newsp,
 326                   void __user *parent_tid, void *child_tls,
 327                   void __user *child_tid, long a5,
 328                   struct pt_regs *regs)
 329 {
 330         if (!newsp)
 331                 newsp = regs->areg[1];
 332         return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 333 }
 334
 335 /*
 336  * xtensa_execve() executes a new program.
 337  */
 338
 339 asmlinkage
 340 long xtensa_execve(const char __user *name,
 341                    const char __user *const __user *argv,
 342                    const char __user *const __user *envp,
 343                    long a3, long a4, long a5,
 344                    struct pt_regs *regs)
 345 {
 346         long error;
 347         struct filename *filename;
 348
 349         filename = getname(name);
 350         error = PTR_ERR(filename);
 351         if (IS_ERR(filename))
 352                 goto out;
 353         error = do_execve(filename->name, argv, envp, regs);
 354         putname(filename);
 355 out:
 356         return error;
 357 }
 358