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 #include <linux/tracehook.h>
  28
  29 /*
  30  * Program thread launch.  Often defined as a macro in processor.h,
  31  * but we're shooting for a small footprint and it's not an inner-loop
  32  * performance-critical operation.
  33  *
  34  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  35  * so that gets automatically done here.  If we ever stop doing that here,
  36  * we'll probably want to define the ELF_PLAT_INIT macro.
  37  */
  38 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  39 {
  40         /* We want to zero all data-containing registers. Is this overkill? */
  41         memset(regs, 0, sizeof(*regs));
  42         /* We might want to also zero all Processor registers here */
  43         pt_set_usermode(regs);
  44         pt_set_elr(regs, pc);
  45         pt_set_rte_sp(regs, sp);
  46 }
  47
  48 /*
  49  *  Spin, or better still, do a hardware or VM wait instruction
  50  *  If hardware or VM offer wait termination even though interrupts
  51  *  are disabled.
  52  */
  53 void arch_cpu_idle(void)
  54 {
  55         __vmwait();
  56         /*  interrupts wake us up, but irqs are still disabled */
  57         local_irq_enable();
  58 }
  59
  60 /*
  61  *  Return saved PC of a blocked thread
  62  */
  63 unsigned long thread_saved_pc(struct task_struct *tsk)
  64 {
  65         return 0;
  66 }
  67
  68 /*
  69  * Copy architecture-specific thread state
  70  */
  71 int copy_thread(unsigned long clone_flags, unsigned long usp,
  72                 unsigned long arg, struct task_struct *p)
  73 {
  74         struct thread_info *ti = task_thread_info(p);
  75         struct hexagon_switch_stack *ss;
  76         struct pt_regs *childregs;
  77         asmlinkage void ret_from_fork(void);
  78
  79         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  80                                         sizeof(*childregs));
  81
  82         ti->regs = childregs;
  83
  84         /*
  85          * Establish kernel stack pointer and initial PC for new thread
  86          * Note that unlike the usual situation, we do not copy the
  87          * parent's callee-saved here; those are in pt_regs and whatever
  88          * we leave here will be overridden on return to userland.
  89          */
  90         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  91                                                     sizeof(*ss));
  92         ss->lr = (unsigned long)ret_from_fork;
  93         p->thread.switch_sp = ss;
  94         if (unlikely(p->flags & PF_KTHREAD)) {
  95                 memset(childregs, 0, sizeof(struct pt_regs));
  96                 /* r24 <- fn, r25 <- arg */
  97                 ss->r24 = usp;
  98                 ss->r25 = arg;
  99                 pt_set_kmode(childregs);
 100                 return 0;
 101         }
 102         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
 103         ss->r2524 = 0;
 104
 105         if (usp)
 106                 pt_set_rte_sp(childregs, usp);
 107
 108         /* Child sees zero return value */
 109         childregs->r00 = 0;
 110
 111         /*
 112          * The clone syscall has the C signature:
 113          * int [r0] clone(int flags [r0],
 114          *           void *child_frame [r1],
 115          *           void *parent_tid [r2],
 116          *           void *child_tid [r3],
 117          *           void *thread_control_block [r4]);
 118          * ugp is used to provide TLS support.
 119          */
 120         if (clone_flags & CLONE_SETTLS)
 121                 childregs->ugp = childregs->r04;
 122
 123         /*
 124          * Parent sees new pid -- not necessary, not even possible at
 125          * this point in the fork process
 126          * Might also want to set things like ti->addr_limit
 127          */
 128
 129         return 0;
 130 }
 131
 132 /*
 133  * Release any architecture-specific resources locked by thread
 134  */
 135 void release_thread(struct task_struct *dead_task)
 136 {
 137 }
 138
 139 /*
 140  * Some archs flush debug and FPU info here
 141  */
 142 void flush_thread(void)
 143 {
 144 }
 145
 146 /*
 147  * The "wait channel" terminology is archaic, but what we want
 148  * is an identification of the point at which the scheduler
 149  * was invoked by a blocked thread.
 150  */
 151 unsigned long get_wchan(struct task_struct *p)
 152 {
 153         unsigned long fp, pc;
 154         unsigned long stack_page;
 155         int count = 0;
 156         if (!p || p == current || p->state == TASK_RUNNING)
 157                 return 0;
 158
 159         stack_page = (unsigned long)task_stack_page(p);
 160         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 161         do {
 162                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 163                         fp >= (THREAD_SIZE - 8 + stack_page))
 164                         return 0;
 165                 pc = ((unsigned long *)fp)[1];
 166                 if (!in_sched_functions(pc))
 167                         return pc;
 168                 fp = *(unsigned long *) fp;
 169         } while (count++ < 16);
 170
 171         return 0;
 172 }
 173
 174 /*
 175  * Required placeholder.
 176  */
 177 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 178 {
 179         return 0;
 180 }
 181
 182
 183 /*
 184  * Called on the exit path of event entry; see vm_entry.S
 185  *
 186  * Interrupts will already be disabled.
 187  *
 188  * Returns 0 if there's no need to re-check for more work.
 189  */
 190
 191 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 192 {
 193         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 194                 return 0;
 195         }  /* shortcut -- no work to be done */
 196
 197         local_irq_enable();
 198
 199         if (thread_info_flags & _TIF_NEED_RESCHED) {
 200                 schedule();
 201                 return 1;
 202         }
 203
 204         if (thread_info_flags & _TIF_SIGPENDING) {
 205                 do_signal(regs);
 206                 return 1;
 207         }
 208
 209         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 210                 clear_thread_flag(TIF_NOTIFY_RESUME);
 211                 tracehook_notify_resume(regs);
 212                 return 1;
 213         }
 214
 215         /* Should not even reach here */
 216         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 217                 thread_info_flags);
 218 }