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/sched/debug.h>
  21 #include <linux/sched/task.h>
  22 #include <linux/sched/task_stack.h>
  23 #include <linux/kernel.h>
  24 #include <linux/mm.h>
  25 #include <linux/smp.h>
  26 #include <linux/stddef.h>
  27 #include <linux/unistd.h>
  28 #include <linux/ptrace.h>
  29 #include <linux/elf.h>
  30 #include <linux/hw_breakpoint.h>
  31 #include <linux/init.h>
  32 #include <linux/prctl.h>
  33 #include <linux/init_task.h>
  34 #include <linux/module.h>
  35 #include <linux/mqueue.h>
  36 #include <linux/fs.h>
  37 #include <linux/slab.h>
  38 #include <linux/rcupdate.h>
  39
  40 #include <asm/pgtable.h>
  41 #include <linux/uaccess.h>
  42 #include <asm/io.h>
  43 #include <asm/processor.h>
  44 #include <asm/platform.h>
  45 #include <asm/mmu.h>
  46 #include <asm/irq.h>
  47 #include <linux/atomic.h>
  48 #include <asm/asm-offsets.h>
  49 #include <asm/regs.h>
  50 #include <asm/hw_breakpoint.h>
  51
  52 extern void ret_from_fork(void);
  53 extern void ret_from_kernel_thread(void);
  54
  55 struct task_struct *current_set[NR_CPUS] = {&init_task, };
  56
  57 void (*pm_power_off)(void) = NULL;
  58 EXPORT_SYMBOL(pm_power_off);
  59
  60
  61 #if XTENSA_HAVE_COPROCESSORS
  62
  63 void coprocessor_release_all(struct thread_info *ti)
  64 {
  65         unsigned long cpenable;
  66         int i;
  67
  68         /* Make sure we don't switch tasks during this operation. */
  69
  70         preempt_disable();
  71
  72         /* Walk through all cp owners and release it for the requested one. */
  73
  74         cpenable = ti->cpenable;
  75
  76         for (i = 0; i < XCHAL_CP_MAX; i++) {
  77                 if (coprocessor_owner[i] == ti) {
  78                         coprocessor_owner[i] = 0;
  79                         cpenable &= ~(1 << i);
  80                 }
  81         }
  82
  83         ti->cpenable = cpenable;
  84         coprocessor_clear_cpenable();
  85
  86         preempt_enable();
  87 }
  88
  89 void coprocessor_flush_all(struct thread_info *ti)
  90 {
  91         unsigned long cpenable;
  92         int i;
  93
  94         preempt_disable();
  95
  96         cpenable = ti->cpenable;
  97
  98         for (i = 0; i < XCHAL_CP_MAX; i++) {
  99                 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
 100                         coprocessor_flush(ti, i);
 101                 cpenable >>= 1;
 102         }
 103
 104         preempt_enable();
 105 }
 106
 107 #endif
 108
 109
 110 /*
 111  * Powermanagement idle function, if any is provided by the platform.
 112  */
 113 void arch_cpu_idle(void)
 114 {
 115         platform_idle();
 116 }
 117
 118 /*
 119  * This is called when the thread calls exit().
 120  */
 121 void exit_thread(struct task_struct *tsk)
 122 {
 123 #if XTENSA_HAVE_COPROCESSORS
 124         coprocessor_release_all(task_thread_info(tsk));
 125 #endif
 126 }
 127
 128 /*
 129  * Flush thread state. This is called when a thread does an execve()
 130  * Note that we flush coprocessor registers for the case execve fails.
 131  */
 132 void flush_thread(void)
 133 {
 134 #if XTENSA_HAVE_COPROCESSORS
 135         struct thread_info *ti = current_thread_info();
 136         coprocessor_flush_all(ti);
 137         coprocessor_release_all(ti);
 138 #endif
 139         flush_ptrace_hw_breakpoint(current);
 140 }
 141
 142 /*
 143  * this gets called so that we can store coprocessor state into memory and
 144  * copy the current task into the new thread.
 145  */
 146 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 147 {
 148 #if XTENSA_HAVE_COPROCESSORS
 149         coprocessor_flush_all(task_thread_info(src));
 150 #endif
 151         *dst = *src;
 152         return 0;
 153 }
 154
 155 /*
 156  * Copy thread.
 157  *
 158  * There are two modes in which this function is called:
 159  * 1) Userspace thread creation,
 160  *    regs != NULL, usp_thread_fn is userspace stack pointer.
 161  *    It is expected to copy parent regs (in case CLONE_VM is not set
 162  *    in the clone_flags) and set up passed usp in the childregs.
 163  * 2) Kernel thread creation,
 164  *    regs == NULL, usp_thread_fn is the function to run in the new thread
 165  *    and thread_fn_arg is its parameter.
 166  *    childregs are not used for the kernel threads.
 167  *
 168  * The stack layout for the new thread looks like this:
 169  *
 170  *      +------------------------+
 171  *      |       childregs        |
 172  *      +------------------------+ <- thread.sp = sp in dummy-frame
 173  *      |      dummy-frame       |    (saved in dummy-frame spill-area)
 174  *      +------------------------+
 175  *
 176  * We create a dummy frame to return to either ret_from_fork or
 177  *   ret_from_kernel_thread:
 178  *   a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
 179  *   sp points to itself (thread.sp)
 180  *   a2, a3 are unused for userspace threads,
 181  *   a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
 182  *
 183  * Note: This is a pristine frame, so we don't need any spill region on top of
 184  *       childregs.
 185  *
 186  * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
 187  * not an entire process), we're normally given a new usp, and we CANNOT share
 188  * any live address register windows.  If we just copy those live frames over,
 189  * the two threads (parent and child) will overflow the same frames onto the
 190  * parent stack at different times, likely corrupting the parent stack (esp.
 191  * if the parent returns from functions that called clone() and calls new
 192  * ones, before the child overflows its now old copies of its parent windows).
 193  * One solution is to spill windows to the parent stack, but that's fairly
 194  * involved.  Much simpler to just not copy those live frames across.
 195  */
 196
 197 int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn,
 198                 unsigned long thread_fn_arg, struct task_struct *p)
 199 {
 200         struct pt_regs *childregs = task_pt_regs(p);
 201
 202 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
 203         struct thread_info *ti;
 204 #endif
 205
 206         /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
 207         *((int*)childregs - 3) = (unsigned long)childregs;
 208         *((int*)childregs - 4) = 0;
 209
 210         p->thread.sp = (unsigned long)childregs;
 211
 212         if (!(p->flags & PF_KTHREAD)) {
 213                 struct pt_regs *regs = current_pt_regs();
 214                 unsigned long usp = usp_thread_fn ?
 215                         usp_thread_fn : regs->areg[1];
 216
 217                 p->thread.ra = MAKE_RA_FOR_CALL(
 218                                 (unsigned long)ret_from_fork, 0x1);
 219
 220                 /* This does not copy all the regs.
 221                  * In a bout of brilliance or madness,
 222                  * ARs beyond a0-a15 exist past the end of the struct.
 223                  */
 224                 *childregs = *regs;
 225                 childregs->areg[1] = usp;
 226                 childregs->areg[2] = 0;
 227
 228                 /* When sharing memory with the parent thread, the child
 229                    usually starts on a pristine stack, so we have to reset
 230                    windowbase, windowstart and wmask.
 231                    (Note that such a new thread is required to always create
 232                    an initial call4 frame)
 233                    The exception is vfork, where the new thread continues to
 234                    run on the parent's stack until it calls execve. This could
 235                    be a call8 or call12, which requires a legal stack frame
 236                    of the previous caller for the overflow handlers to work.
 237                    (Note that it's always legal to overflow live registers).
 238                    In this case, ensure to spill at least the stack pointer
 239                    of that frame. */
 240
 241                 if (clone_flags & CLONE_VM) {
 242                         /* check that caller window is live and same stack */
 243                         int len = childregs->wmask & ~0xf;
 244                         if (regs->areg[1] == usp && len != 0) {
 245                                 int callinc = (regs->areg[0] >> 30) & 3;
 246                                 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
 247                                 put_user(regs->areg[caller_ars+1],
 248                                          (unsigned __user*)(usp - 12));
 249                         }
 250                         childregs->wmask = 1;
 251                         childregs->windowstart = 1;
 252                         childregs->windowbase = 0;
 253                 } else {
 254                         int len = childregs->wmask & ~0xf;
 255                         memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
 256                                &regs->areg[XCHAL_NUM_AREGS - len/4], len);
 257                 }
 258
 259                 /* The thread pointer is passed in the '4th argument' (= a5) */
 260                 if (clone_flags & CLONE_SETTLS)
 261                         childregs->threadptr = childregs->areg[5];
 262         } else {
 263                 p->thread.ra = MAKE_RA_FOR_CALL(
 264                                 (unsigned long)ret_from_kernel_thread, 1);
 265
 266                 /* pass parameters to ret_from_kernel_thread:
 267                  * a2 = thread_fn, a3 = thread_fn arg
 268                  */
 269                 *((int *)childregs - 1) = thread_fn_arg;
 270                 *((int *)childregs - 2) = usp_thread_fn;
 271
 272                 /* Childregs are only used when we're going to userspace
 273                  * in which case start_thread will set them up.
 274                  */
 275         }
 276
 277 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
 278         ti = task_thread_info(p);
 279         ti->cpenable = 0;
 280 #endif
 281
 282         clear_ptrace_hw_breakpoint(p);
 283
 284         return 0;
 285 }
 286
 287
 288 /*
 289  * These bracket the sleeping functions..
 290  */
 291
 292 unsigned long get_wchan(struct task_struct *p)
 293 {
 294         unsigned long sp, pc;
 295         unsigned long stack_page = (unsigned long) task_stack_page(p);
 296         int count = 0;
 297
 298         if (!p || p == current || p->state == TASK_RUNNING)
 299                 return 0;
 300
 301         sp = p->thread.sp;
 302         pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
 303
 304         do {
 305                 if (sp < stack_page + sizeof(struct task_struct) ||
 306                     sp >= (stack_page + THREAD_SIZE) ||
 307                     pc == 0)
 308                         return 0;
 309                 if (!in_sched_functions(pc))
 310                         return pc;
 311
 312                 /* Stack layout: sp-4: ra, sp-3: sp' */
 313
 314                 pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
 315                 sp = *(unsigned long *)sp - 3;
 316         } while (count++ < 16);
 317         return 0;
 318 }
 319
 320 /*
 321  * xtensa_gregset_t and 'struct pt_regs' are vastly different formats
 322  * of processor registers.  Besides different ordering,
 323  * xtensa_gregset_t contains non-live register information that
 324  * 'struct pt_regs' does not.  Exception handling (primarily) uses
 325  * 'struct pt_regs'.  Core files and ptrace use xtensa_gregset_t.
 326  *
 327  */
 328
 329 void xtensa_elf_core_copy_regs (xtensa_gregset_t *elfregs, struct pt_regs *regs)
 330 {
 331         unsigned long wb, ws, wm;
 332         int live, last;
 333
 334         wb = regs->windowbase;
 335         ws = regs->windowstart;
 336         wm = regs->wmask;
 337         ws = ((ws >> wb) | (ws << (WSBITS - wb))) & ((1 << WSBITS) - 1);
 338
 339         /* Don't leak any random bits. */
 340
 341         memset(elfregs, 0, sizeof(*elfregs));
 342
 343         /* Note:  PS.EXCM is not set while user task is running; its
 344          * being set in regs->ps is for exception handling convenience.
 345          */
 346
 347         elfregs->pc             = regs->pc;
 348         elfregs->ps             = (regs->ps & ~(1 << PS_EXCM_BIT));
 349         elfregs->lbeg           = regs->lbeg;
 350         elfregs->lend           = regs->lend;
 351         elfregs->lcount         = regs->lcount;
 352         elfregs->sar            = regs->sar;
 353         elfregs->windowstart    = ws;
 354
 355         live = (wm & 2) ? 4 : (wm & 4) ? 8 : (wm & 8) ? 12 : 16;
 356         last = XCHAL_NUM_AREGS - (wm >> 4) * 4;
 357         memcpy(elfregs->a, regs->areg, live * 4);
 358         memcpy(elfregs->a + last, regs->areg + last, (wm >> 4) * 16);
 359 }
 360
 361 int dump_fpu(void)
 362 {
 363         return 0;
 364 }