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