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 void (*pm_power_off)(void) = NULL;
  56 EXPORT_SYMBOL(pm_power_off);
  57
  58
  59 #ifdef CONFIG_STACKPROTECTOR
  60 #include <linux/stackprotector.h>
  61 unsigned long __stack_chk_guard __read_mostly;
  62 EXPORT_SYMBOL(__stack_chk_guard);
  63 #endif
  64
  65 #if XTENSA_HAVE_COPROCESSORS
  66
  67 void coprocessor_release_all(struct thread_info *ti)
  68 {
  69         unsigned long cpenable;
  70         int i;
  71
  72         /* Make sure we don't switch tasks during this operation. */
  73
  74         preempt_disable();
  75
  76         /* Walk through all cp owners and release it for the requested one. */
  77
  78         cpenable = ti->cpenable;
  79
  80         for (i = 0; i < XCHAL_CP_MAX; i++) {
  81                 if (coprocessor_owner[i] == ti) {
  82                         coprocessor_owner[i] = 0;
  83                         cpenable &= ~(1 << i);
  84                 }
  85         }
  86
  87         ti->cpenable = cpenable;
  88         if (ti == current_thread_info())
  89                 xtensa_set_sr(0, cpenable);
  90
  91         preempt_enable();
  92 }
  93
  94 void coprocessor_flush_all(struct thread_info *ti)
  95 {
  96         unsigned long cpenable, old_cpenable;
  97         int i;
  98
  99         preempt_disable();
 100
 101         old_cpenable = xtensa_get_sr(cpenable);
 102         cpenable = ti->cpenable;
 103         xtensa_set_sr(cpenable, cpenable);
 104
 105         for (i = 0; i < XCHAL_CP_MAX; i++) {
 106                 if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
 107                         coprocessor_flush(ti, i);
 108                 cpenable >>= 1;
 109         }
 110         xtensa_set_sr(old_cpenable, cpenable);
 111
 112         preempt_enable();
 113 }
 114
 115 #endif
 116
 117
 118 /*
 119  * Powermanagement idle function, if any is provided by the platform.
 120  */
 121 void arch_cpu_idle(void)
 122 {
 123         platform_idle();
 124 }
 125
 126 /*
 127  * This is called when the thread calls exit().
 128  */
 129 void exit_thread(struct task_struct *tsk)
 130 {
 131 #if XTENSA_HAVE_COPROCESSORS
 132         coprocessor_release_all(task_thread_info(tsk));
 133 #endif
 134 }
 135
 136 /*
 137  * Flush thread state. This is called when a thread does an execve()
 138  * Note that we flush coprocessor registers for the case execve fails.
 139  */
 140 void flush_thread(void)
 141 {
 142 #if XTENSA_HAVE_COPROCESSORS
 143         struct thread_info *ti = current_thread_info();
 144         coprocessor_flush_all(ti);
 145         coprocessor_release_all(ti);
 146 #endif
 147         flush_ptrace_hw_breakpoint(current);
 148 }
 149
 150 /*
 151  * this gets called so that we can store coprocessor state into memory and
 152  * copy the current task into the new thread.
 153  */
 154 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 155 {
 156 #if XTENSA_HAVE_COPROCESSORS
 157         coprocessor_flush_all(task_thread_info(src));
 158 #endif
 159         *dst = *src;
 160         return 0;
 161 }
 162
 163 /*
 164  * Copy thread.
 165  *
 166  * There are two modes in which this function is called:
 167  * 1) Userspace thread creation,
 168  *    regs != NULL, usp_thread_fn is userspace stack pointer.
 169  *    It is expected to copy parent regs (in case CLONE_VM is not set
 170  *    in the clone_flags) and set up passed usp in the childregs.
 171  * 2) Kernel thread creation,
 172  *    regs == NULL, usp_thread_fn is the function to run in the new thread
 173  *    and thread_fn_arg is its parameter.
 174  *    childregs are not used for the kernel threads.
 175  *
 176  * The stack layout for the new thread looks like this:
 177  *
 178  *      +------------------------+
 179  *      |       childregs        |
 180  *      +------------------------+ <- thread.sp = sp in dummy-frame
 181  *      |      dummy-frame       |    (saved in dummy-frame spill-area)
 182  *      +------------------------+
 183  *
 184  * We create a dummy frame to return to either ret_from_fork or
 185  *   ret_from_kernel_thread:
 186  *   a0 points to ret_from_fork/ret_from_kernel_thread (simulating a call4)
 187  *   sp points to itself (thread.sp)
 188  *   a2, a3 are unused for userspace threads,
 189  *   a2 points to thread_fn, a3 holds thread_fn arg for kernel threads.
 190  *
 191  * Note: This is a pristine frame, so we don't need any spill region on top of
 192  *       childregs.
 193  *
 194  * The fun part:  if we're keeping the same VM (i.e. cloning a thread,
 195  * not an entire process), we're normally given a new usp, and we CANNOT share
 196  * any live address register windows.  If we just copy those live frames over,
 197  * the two threads (parent and child) will overflow the same frames onto the
 198  * parent stack at different times, likely corrupting the parent stack (esp.
 199  * if the parent returns from functions that called clone() and calls new
 200  * ones, before the child overflows its now old copies of its parent windows).
 201  * One solution is to spill windows to the parent stack, but that's fairly
 202  * involved.  Much simpler to just not copy those live frames across.
 203  */
 204
 205 int copy_thread_tls(unsigned long clone_flags, unsigned long usp_thread_fn,
 206                 unsigned long thread_fn_arg, struct task_struct *p,
 207                 unsigned long tls)
 208 {
 209         struct pt_regs *childregs = task_pt_regs(p);
 210
 211 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
 212         struct thread_info *ti;
 213 #endif
 214
 215         /* Create a call4 dummy-frame: a0 = 0, a1 = childregs. */
 216         SPILL_SLOT(childregs, 1) = (unsigned long)childregs;
 217         SPILL_SLOT(childregs, 0) = 0;
 218
 219         p->thread.sp = (unsigned long)childregs;
 220
 221         if (!(p->flags & PF_KTHREAD)) {
 222                 struct pt_regs *regs = current_pt_regs();
 223                 unsigned long usp = usp_thread_fn ?
 224                         usp_thread_fn : regs->areg[1];
 225
 226                 p->thread.ra = MAKE_RA_FOR_CALL(
 227                                 (unsigned long)ret_from_fork, 0x1);
 228
 229                 /* This does not copy all the regs.
 230                  * In a bout of brilliance or madness,
 231                  * ARs beyond a0-a15 exist past the end of the struct.
 232                  */
 233                 *childregs = *regs;
 234                 childregs->areg[1] = usp;
 235                 childregs->areg[2] = 0;
 236
 237                 /* When sharing memory with the parent thread, the child
 238                    usually starts on a pristine stack, so we have to reset
 239                    windowbase, windowstart and wmask.
 240                    (Note that such a new thread is required to always create
 241                    an initial call4 frame)
 242                    The exception is vfork, where the new thread continues to
 243                    run on the parent's stack until it calls execve. This could
 244                    be a call8 or call12, which requires a legal stack frame
 245                    of the previous caller for the overflow handlers to work.
 246                    (Note that it's always legal to overflow live registers).
 247                    In this case, ensure to spill at least the stack pointer
 248                    of that frame. */
 249
 250                 if (clone_flags & CLONE_VM) {
 251                         /* check that caller window is live and same stack */
 252                         int len = childregs->wmask & ~0xf;
 253                         if (regs->areg[1] == usp && len != 0) {
 254                                 int callinc = (regs->areg[0] >> 30) & 3;
 255                                 int caller_ars = XCHAL_NUM_AREGS - callinc * 4;
 256                                 put_user(regs->areg[caller_ars+1],
 257                                          (unsigned __user*)(usp - 12));
 258                         }
 259                         childregs->wmask = 1;
 260                         childregs->windowstart = 1;
 261                         childregs->windowbase = 0;
 262                 } else {
 263                         int len = childregs->wmask & ~0xf;
 264                         memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],
 265                                &regs->areg[XCHAL_NUM_AREGS - len/4], len);
 266                 }
 267
 268                 childregs->syscall = regs->syscall;
 269
 270                 if (clone_flags & CLONE_SETTLS)
 271                         childregs->threadptr = tls;
 272         } else {
 273                 p->thread.ra = MAKE_RA_FOR_CALL(
 274                                 (unsigned long)ret_from_kernel_thread, 1);
 275
 276                 /* pass parameters to ret_from_kernel_thread:
 277                  * a2 = thread_fn, a3 = thread_fn arg
 278                  */
 279                 SPILL_SLOT(childregs, 3) = thread_fn_arg;
 280                 SPILL_SLOT(childregs, 2) = usp_thread_fn;
 281
 282                 /* Childregs are only used when we're going to userspace
 283                  * in which case start_thread will set them up.
 284                  */
 285         }
 286
 287 #if (XTENSA_HAVE_COPROCESSORS || XTENSA_HAVE_IO_PORTS)
 288         ti = task_thread_info(p);
 289         ti->cpenable = 0;
 290 #endif
 291
 292         clear_ptrace_hw_breakpoint(p);
 293
 294         return 0;
 295 }
 296
 297
 298 /*
 299  * These bracket the sleeping functions..
 300  */
 301
 302 unsigned long get_wchan(struct task_struct *p)
 303 {
 304         unsigned long sp, pc;
 305         unsigned long stack_page = (unsigned long) task_stack_page(p);
 306         int count = 0;
 307
 308         if (!p || p == current || p->state == TASK_RUNNING)
 309                 return 0;
 310
 311         sp = p->thread.sp;
 312         pc = MAKE_PC_FROM_RA(p->thread.ra, p->thread.sp);
 313
 314         do {
 315                 if (sp < stack_page + sizeof(struct task_struct) ||
 316                     sp >= (stack_page + THREAD_SIZE) ||
 317                     pc == 0)
 318                         return 0;
 319                 if (!in_sched_functions(pc))
 320                         return pc;
 321
 322                 /* Stack layout: sp-4: ra, sp-3: sp' */
 323
 324                 pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
 325                 sp = SPILL_SLOT(sp, 1);
 326         } while (count++ < 16);
 327         return 0;
 328 }