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  *  Return saved PC of a blocked thread
  65  */
  66 unsigned long thread_saved_pc(struct task_struct *tsk)
  67 {
  68         return 0;
  69 }
  70
  71 /*
  72  * Copy architecture-specific thread state
  73  */
  74 int copy_thread(unsigned long clone_flags, unsigned long usp,
  75                 unsigned long arg, struct task_struct *p)
  76 {
  77         struct thread_info *ti = task_thread_info(p);
  78         struct hexagon_switch_stack *ss;
  79         struct pt_regs *childregs;
  80         asmlinkage void ret_from_fork(void);
  81
  82         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  83                                         sizeof(*childregs));
  84
  85         ti->regs = childregs;
  86
  87         /*
  88          * Establish kernel stack pointer and initial PC for new thread
  89          * Note that unlike the usual situation, we do not copy the
  90          * parent's callee-saved here; those are in pt_regs and whatever
  91          * we leave here will be overridden on return to userland.
  92          */
  93         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  94                                                     sizeof(*ss));
  95         ss->lr = (unsigned long)ret_from_fork;
  96         p->thread.switch_sp = ss;
  97         if (unlikely(p->flags & PF_KTHREAD)) {
  98                 memset(childregs, 0, sizeof(struct pt_regs));
  99                 /* r24 <- fn, r25 <- arg */
 100                 ss->r24 = usp;
 101                 ss->r25 = arg;
 102                 pt_set_kmode(childregs);
 103                 return 0;
 104         }
 105         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
 106         ss->r2524 = 0;
 107
 108         if (usp)
 109                 pt_set_rte_sp(childregs, usp);
 110
 111         /* Child sees zero return value */
 112         childregs->r00 = 0;
 113
 114         /*
 115          * The clone syscall has the C signature:
 116          * int [r0] clone(int flags [r0],
 117          *           void *child_frame [r1],
 118          *           void *parent_tid [r2],
 119          *           void *child_tid [r3],
 120          *           void *thread_control_block [r4]);
 121          * ugp is used to provide TLS support.
 122          */
 123         if (clone_flags & CLONE_SETTLS)
 124                 childregs->ugp = childregs->r04;
 125
 126         /*
 127          * Parent sees new pid -- not necessary, not even possible at
 128          * this point in the fork process
 129          * Might also want to set things like ti->addr_limit
 130          */
 131
 132         return 0;
 133 }
 134
 135 /*
 136  * Release any architecture-specific resources locked by thread
 137  */
 138 void release_thread(struct task_struct *dead_task)
 139 {
 140 }
 141
 142 /*
 143  * Some archs flush debug and FPU info here
 144  */
 145 void flush_thread(void)
 146 {
 147 }
 148
 149 /*
 150  * The "wait channel" terminology is archaic, but what we want
 151  * is an identification of the point at which the scheduler
 152  * was invoked by a blocked thread.
 153  */
 154 unsigned long get_wchan(struct task_struct *p)
 155 {
 156         unsigned long fp, pc;
 157         unsigned long stack_page;
 158         int count = 0;
 159         if (!p || p == current || p->state == TASK_RUNNING)
 160                 return 0;
 161
 162         stack_page = (unsigned long)task_stack_page(p);
 163         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 164         do {
 165                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 166                         fp >= (THREAD_SIZE - 8 + stack_page))
 167                         return 0;
 168                 pc = ((unsigned long *)fp)[1];
 169                 if (!in_sched_functions(pc))
 170                         return pc;
 171                 fp = *(unsigned long *) fp;
 172         } while (count++ < 16);
 173
 174         return 0;
 175 }
 176
 177 /*
 178  * Required placeholder.
 179  */
 180 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 181 {
 182         return 0;
 183 }
 184
 185
 186 /*
 187  * Called on the exit path of event entry; see vm_entry.S
 188  *
 189  * Interrupts will already be disabled.
 190  *
 191  * Returns 0 if there's no need to re-check for more work.
 192  */
 193
 194 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 195 {
 196         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 197                 return 0;
 198         }  /* shortcut -- no work to be done */
 199
 200         local_irq_enable();
 201
 202         if (thread_info_flags & _TIF_NEED_RESCHED) {
 203                 schedule();
 204                 return 1;
 205         }
 206
 207         if (thread_info_flags & _TIF_SIGPENDING) {
 208                 do_signal(regs);
 209                 return 1;
 210         }
 211
 212         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 213                 clear_thread_flag(TIF_NOTIFY_RESUME);
 214                 tracehook_notify_resume(regs);
 215                 return 1;
 216         }
 217
 218         /* Should not even reach here */
 219         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 220                 thread_info_flags);
 221 }