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/sched/debug.h>
  23 #include <linux/sched/task.h>
  24 #include <linux/sched/task_stack.h>
  25 #include <linux/types.h>
  26 #include <linux/module.h>
  27 #include <linux/tick.h>
  28 #include <linux/uaccess.h>
  29 #include <linux/slab.h>
  30 #include <linux/tracehook.h>
  31
  32 /*
  33  * Program thread launch.  Often defined as a macro in processor.h,
  34  * but we're shooting for a small footprint and it's not an inner-loop
  35  * performance-critical operation.
  36  *
  37  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  38  * so that gets automatically done here.  If we ever stop doing that here,
  39  * we'll probably want to define the ELF_PLAT_INIT macro.
  40  */
  41 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  42 {
  43         /* We want to zero all data-containing registers. Is this overkill? */
  44         memset(regs, 0, sizeof(*regs));
  45         /* We might want to also zero all Processor registers here */
  46         pt_set_usermode(regs);
  47         pt_set_elr(regs, pc);
  48         pt_set_rte_sp(regs, sp);
  49 }
  50
  51 /*
  52  *  Spin, or better still, do a hardware or VM wait instruction
  53  *  If hardware or VM offer wait termination even though interrupts
  54  *  are disabled.
  55  */
  56 void arch_cpu_idle(void)
  57 {
  58         __vmwait();
  59         /*  interrupts wake us up, but irqs are still disabled */
  60         local_irq_enable();
  61 }
  62
  63 /*
  64  * Copy architecture-specific thread state
  65  */
  66 int copy_thread(unsigned long clone_flags, unsigned long usp,
  67                 unsigned long arg, struct task_struct *p)
  68 {
  69         struct thread_info *ti = task_thread_info(p);
  70         struct hexagon_switch_stack *ss;
  71         struct pt_regs *childregs;
  72         asmlinkage void ret_from_fork(void);
  73
  74         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  75                                         sizeof(*childregs));
  76
  77         ti->regs = childregs;
  78
  79         /*
  80          * Establish kernel stack pointer and initial PC for new thread
  81          * Note that unlike the usual situation, we do not copy the
  82          * parent's callee-saved here; those are in pt_regs and whatever
  83          * we leave here will be overridden on return to userland.
  84          */
  85         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  86                                                     sizeof(*ss));
  87         ss->lr = (unsigned long)ret_from_fork;
  88         p->thread.switch_sp = ss;
  89         if (unlikely(p->flags & PF_KTHREAD)) {
  90                 memset(childregs, 0, sizeof(struct pt_regs));
  91                 /* r24 <- fn, r25 <- arg */
  92                 ss->r24 = usp;
  93                 ss->r25 = arg;
  94                 pt_set_kmode(childregs);
  95                 return 0;
  96         }
  97         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
  98         ss->r2524 = 0;
  99
 100         if (usp)
 101                 pt_set_rte_sp(childregs, usp);
 102
 103         /* Child sees zero return value */
 104         childregs->r00 = 0;
 105
 106         /*
 107          * The clone syscall has the C signature:
 108          * int [r0] clone(int flags [r0],
 109          *           void *child_frame [r1],
 110          *           void *parent_tid [r2],
 111          *           void *child_tid [r3],
 112          *           void *thread_control_block [r4]);
 113          * ugp is used to provide TLS support.
 114          */
 115         if (clone_flags & CLONE_SETTLS)
 116                 childregs->ugp = childregs->r04;
 117
 118         /*
 119          * Parent sees new pid -- not necessary, not even possible at
 120          * this point in the fork process
 121          * Might also want to set things like ti->addr_limit
 122          */
 123
 124         return 0;
 125 }
 126
 127 /*
 128  * Release any architecture-specific resources locked by thread
 129  */
 130 void release_thread(struct task_struct *dead_task)
 131 {
 132 }
 133
 134 /*
 135  * Some archs flush debug and FPU info here
 136  */
 137 void flush_thread(void)
 138 {
 139 }
 140
 141 /*
 142  * The "wait channel" terminology is archaic, but what we want
 143  * is an identification of the point at which the scheduler
 144  * was invoked by a blocked thread.
 145  */
 146 unsigned long get_wchan(struct task_struct *p)
 147 {
 148         unsigned long fp, pc;
 149         unsigned long stack_page;
 150         int count = 0;
 151         if (!p || p == current || p->state == TASK_RUNNING)
 152                 return 0;
 153
 154         stack_page = (unsigned long)task_stack_page(p);
 155         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 156         do {
 157                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 158                         fp >= (THREAD_SIZE - 8 + stack_page))
 159                         return 0;
 160                 pc = ((unsigned long *)fp)[1];
 161                 if (!in_sched_functions(pc))
 162                         return pc;
 163                 fp = *(unsigned long *) fp;
 164         } while (count++ < 16);
 165
 166         return 0;
 167 }
 168
 169 /*
 170  * Required placeholder.
 171  */
 172 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 173 {
 174         return 0;
 175 }
 176
 177
 178 /*
 179  * Called on the exit path of event entry; see vm_entry.S
 180  *
 181  * Interrupts will already be disabled.
 182  *
 183  * Returns 0 if there's no need to re-check for more work.
 184  */
 185
 186 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 187 {
 188         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 189                 return 0;
 190         }  /* shortcut -- no work to be done */
 191
 192         local_irq_enable();
 193
 194         if (thread_info_flags & _TIF_NEED_RESCHED) {
 195                 schedule();
 196                 return 1;
 197         }
 198
 199         if (thread_info_flags & _TIF_SIGPENDING) {
 200                 do_signal(regs);
 201                 return 1;
 202         }
 203
 204         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 205                 clear_thread_flag(TIF_NOTIFY_RESUME);
 206                 tracehook_notify_resume(regs);
 207                 return 1;
 208         }
 209
 210         /* Should not even reach here */
 211         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 212                 thread_info_flags);
 213 }