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/types.h>
  25 #include <linux/module.h>
  26 #include <linux/tick.h>
  27 #include <linux/uaccess.h>
  28 #include <linux/slab.h>
  29 #include <linux/tracehook.h>
  30
  31 /*
  32  * Program thread launch.  Often defined as a macro in processor.h,
  33  * but we're shooting for a small footprint and it's not an inner-loop
  34  * performance-critical operation.
  35  *
  36  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  37  * so that gets automatically done here.  If we ever stop doing that here,
  38  * we'll probably want to define the ELF_PLAT_INIT macro.
  39  */
  40 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  41 {
  42         /* We want to zero all data-containing registers. Is this overkill? */
  43         memset(regs, 0, sizeof(*regs));
  44         /* We might want to also zero all Processor registers here */
  45         pt_set_usermode(regs);
  46         pt_set_elr(regs, pc);
  47         pt_set_rte_sp(regs, sp);
  48 }
  49
  50 /*
  51  *  Spin, or better still, do a hardware or VM wait instruction
  52  *  If hardware or VM offer wait termination even though interrupts
  53  *  are disabled.
  54  */
  55 void arch_cpu_idle(void)
  56 {
  57         __vmwait();
  58         /*  interrupts wake us up, but irqs are still disabled */
  59         local_irq_enable();
  60 }
  61
  62 /*
  63  *  Return saved PC of a blocked thread
  64  */
  65 unsigned long thread_saved_pc(struct task_struct *tsk)
  66 {
  67         return 0;
  68 }
  69
  70 /*
  71  * Copy architecture-specific thread state
  72  */
  73 int copy_thread(unsigned long clone_flags, unsigned long usp,
  74                 unsigned long arg, struct task_struct *p)
  75 {
  76         struct thread_info *ti = task_thread_info(p);
  77         struct hexagon_switch_stack *ss;
  78         struct pt_regs *childregs;
  79         asmlinkage void ret_from_fork(void);
  80
  81         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  82                                         sizeof(*childregs));
  83
  84         ti->regs = childregs;
  85
  86         /*
  87          * Establish kernel stack pointer and initial PC for new thread
  88          * Note that unlike the usual situation, we do not copy the
  89          * parent's callee-saved here; those are in pt_regs and whatever
  90          * we leave here will be overridden on return to userland.
  91          */
  92         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  93                                                     sizeof(*ss));
  94         ss->lr = (unsigned long)ret_from_fork;
  95         p->thread.switch_sp = ss;
  96         if (unlikely(p->flags & PF_KTHREAD)) {
  97                 memset(childregs, 0, sizeof(struct pt_regs));
  98                 /* r24 <- fn, r25 <- arg */
  99                 ss->r24 = usp;
 100                 ss->r25 = arg;
 101                 pt_set_kmode(childregs);
 102                 return 0;
 103         }
 104         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
 105         ss->r2524 = 0;
 106
 107         if (usp)
 108                 pt_set_rte_sp(childregs, usp);
 109
 110         /* Child sees zero return value */
 111         childregs->r00 = 0;
 112
 113         /*
 114          * The clone syscall has the C signature:
 115          * int [r0] clone(int flags [r0],
 116          *           void *child_frame [r1],
 117          *           void *parent_tid [r2],
 118          *           void *child_tid [r3],
 119          *           void *thread_control_block [r4]);
 120          * ugp is used to provide TLS support.
 121          */
 122         if (clone_flags & CLONE_SETTLS)
 123                 childregs->ugp = childregs->r04;
 124
 125         /*
 126          * Parent sees new pid -- not necessary, not even possible at
 127          * this point in the fork process
 128          * Might also want to set things like ti->addr_limit
 129          */
 130
 131         return 0;
 132 }
 133
 134 /*
 135  * Release any architecture-specific resources locked by thread
 136  */
 137 void release_thread(struct task_struct *dead_task)
 138 {
 139 }
 140
 141 /*
 142  * Some archs flush debug and FPU info here
 143  */
 144 void flush_thread(void)
 145 {
 146 }
 147
 148 /*
 149  * The "wait channel" terminology is archaic, but what we want
 150  * is an identification of the point at which the scheduler
 151  * was invoked by a blocked thread.
 152  */
 153 unsigned long get_wchan(struct task_struct *p)
 154 {
 155         unsigned long fp, pc;
 156         unsigned long stack_page;
 157         int count = 0;
 158         if (!p || p == current || p->state == TASK_RUNNING)
 159                 return 0;
 160
 161         stack_page = (unsigned long)task_stack_page(p);
 162         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 163         do {
 164                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 165                         fp >= (THREAD_SIZE - 8 + stack_page))
 166                         return 0;
 167                 pc = ((unsigned long *)fp)[1];
 168                 if (!in_sched_functions(pc))
 169                         return pc;
 170                 fp = *(unsigned long *) fp;
 171         } while (count++ < 16);
 172
 173         return 0;
 174 }
 175
 176 /*
 177  * Required placeholder.
 178  */
 179 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 180 {
 181         return 0;
 182 }
 183
 184
 185 /*
 186  * Called on the exit path of event entry; see vm_entry.S
 187  *
 188  * Interrupts will already be disabled.
 189  *
 190  * Returns 0 if there's no need to re-check for more work.
 191  */
 192
 193 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 194 {
 195         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 196                 return 0;
 197         }  /* shortcut -- no work to be done */
 198
 199         local_irq_enable();
 200
 201         if (thread_info_flags & _TIF_NEED_RESCHED) {
 202                 schedule();
 203                 return 1;
 204         }
 205
 206         if (thread_info_flags & _TIF_SIGPENDING) {
 207                 do_signal(regs);
 208                 return 1;
 209         }
 210
 211         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 212                 clear_thread_flag(TIF_NOTIFY_RESUME);
 213                 tracehook_notify_resume(regs);
 214                 return 1;
 215         }
 216
 217         /* Should not even reach here */
 218         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 219                 thread_info_flags);
 220 }