arch/hexagon/kernel/process.c

   1 /*
   2  * Process creation support for Hexagon
   3  *
   4  * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 and
   8  * only version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA.
  19  */
  20
  21 #include <linux/sched.h>
  22 #include <linux/types.h>
  23 #include <linux/module.h>
  24 #include <linux/tick.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/slab.h>
  27
  28 /*
  29  * Program thread launch.  Often defined as a macro in processor.h,
  30  * but we're shooting for a small footprint and it's not an inner-loop
  31  * performance-critical operation.
  32  *
  33  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  34  * so that gets automatically done here.  If we ever stop doing that here,
  35  * we'll probably want to define the ELF_PLAT_INIT macro.
  36  */
  37 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  38 {
  39         /* Set to run with user-mode data segmentation */
  40         set_fs(USER_DS);
  41         /* We want to zero all data-containing registers. Is this overkill? */
  42         memset(regs, 0, sizeof(*regs));
  43         /* We might want to also zero all Processor registers here */
  44         pt_set_usermode(regs);
  45         pt_set_elr(regs, pc);
  46         pt_set_rte_sp(regs, sp);
  47 }
  48
  49 /*
  50  *  Spin, or better still, do a hardware or VM wait instruction
  51  *  If hardware or VM offer wait termination even though interrupts
  52  *  are disabled.
  53  */
  54 static void default_idle(void)
  55 {
  56         __vmwait();
  57 }
  58
  59 void (*idle_sleep)(void) = default_idle;
  60
  61 void cpu_idle(void)
  62 {
  63         while (1) {
  64                 tick_nohz_idle_enter();
  65                 local_irq_disable();
  66                 while (!need_resched()) {
  67                         idle_sleep();
  68                         /*  interrupts wake us up, but aren't serviced  */
  69                         local_irq_enable();     /* service interrupt   */
  70                         local_irq_disable();
  71                 }
  72                 local_irq_enable();
  73                 tick_nohz_idle_exit();
  74                 schedule();
  75         }
  76 }
  77
  78 /*
  79  *  Return saved PC of a blocked thread
  80  */
  81 unsigned long thread_saved_pc(struct task_struct *tsk)
  82 {
  83         return 0;
  84 }
  85
  86 /*
  87  * Copy architecture-specific thread state
  88  */
  89 int copy_thread(unsigned long clone_flags, unsigned long usp,
  90                 unsigned long arg, struct task_struct *p)
  91 {
  92         struct thread_info *ti = task_thread_info(p);
  93         struct hexagon_switch_stack *ss;
  94         struct pt_regs *childregs;
  95         asmlinkage void ret_from_fork(void);
  96
  97         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  98                                         sizeof(*childregs));
  99
 100         ti->regs = childregs;
 101
 102         /*
 103          * Establish kernel stack pointer and initial PC for new thread
 104          * Note that unlike the usual situation, we do not copy the
 105          * parent's callee-saved here; those are in pt_regs and whatever
 106          * we leave here will be overridden on return to userland.
 107          */
 108         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
 109                                                     sizeof(*ss));
 110         ss->lr = (unsigned long)ret_from_fork;
 111         p->thread.switch_sp = ss;
 112         if (unlikely(p->flags & PF_KTHREAD)) {
 113                 memset(childregs, 0, sizeof(struct pt_regs));
 114                 /* r24 <- fn, r25 <- arg */
 115                 ss->r2524 = usp | ((u64)arg << 32);
 116                 pt_set_kmode(childregs);
 117                 return 0;
 118         }
 119         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
 120         ss->r2524 = 0;
 121
 122         if (usp)
 123                 pt_set_rte_sp(childregs, usp);
 124
 125         /* Child sees zero return value */
 126         childregs->r00 = 0;
 127
 128         /*
 129          * The clone syscall has the C signature:
 130          * int [r0] clone(int flags [r0],
 131          *           void *child_frame [r1],
 132          *           void *parent_tid [r2],
 133          *           void *child_tid [r3],
 134          *           void *thread_control_block [r4]);
 135          * ugp is used to provide TLS support.
 136          */
 137         if (clone_flags & CLONE_SETTLS)
 138                 childregs->ugp = childregs->r04;
 139
 140         /*
 141          * Parent sees new pid -- not necessary, not even possible at
 142          * this point in the fork process
 143          * Might also want to set things like ti->addr_limit
 144          */
 145
 146         return 0;
 147 }
 148
 149 /*
 150  * Release any architecture-specific resources locked by thread
 151  */
 152 void release_thread(struct task_struct *dead_task)
 153 {
 154 }
 155
 156 /*
 157  * Free any architecture-specific thread data structures, etc.
 158  */
 159 void exit_thread(void)
 160 {
 161 }
 162
 163 /*
 164  * Some archs flush debug and FPU info here
 165  */
 166 void flush_thread(void)
 167 {
 168 }
 169
 170 /*
 171  * The "wait channel" terminology is archaic, but what we want
 172  * is an identification of the point at which the scheduler
 173  * was invoked by a blocked thread.
 174  */
 175 unsigned long get_wchan(struct task_struct *p)
 176 {
 177         unsigned long fp, pc;
 178         unsigned long stack_page;
 179         int count = 0;
 180         if (!p || p == current || p->state == TASK_RUNNING)
 181                 return 0;
 182
 183         stack_page = (unsigned long)task_stack_page(p);
 184         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 185         do {
 186                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 187                         fp >= (THREAD_SIZE - 8 + stack_page))
 188                         return 0;
 189                 pc = ((unsigned long *)fp)[1];
 190                 if (!in_sched_functions(pc))
 191                         return pc;
 192                 fp = *(unsigned long *) fp;
 193         } while (count++ < 16);
 194
 195         return 0;
 196 }
 197
 198 /*
 199  * Required placeholder.
 200  */
 201 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 202 {
 203         return 0;
 204 }