arch/hexagon/kernel/process.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Process creation support for Hexagon
   4  *
   5  * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
   6  */
   7
   8 #include <linux/cpu.h>
   9 #include <linux/sched.h>
  10 #include <linux/sched/debug.h>
  11 #include <linux/sched/task.h>
  12 #include <linux/sched/task_stack.h>
  13 #include <linux/types.h>
  14 #include <linux/module.h>
  15 #include <linux/tick.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/slab.h>
  18 #include <linux/resume_user_mode.h>
  19
  20 /*
  21  * Program thread launch.  Often defined as a macro in processor.h,
  22  * but we're shooting for a small footprint and it's not an inner-loop
  23  * performance-critical operation.
  24  *
  25  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  26  * so that gets automatically done here.  If we ever stop doing that here,
  27  * we'll probably want to define the ELF_PLAT_INIT macro.
  28  */
  29 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  30 {
  31         /* We want to zero all data-containing registers. Is this overkill? */
  32         memset(regs, 0, sizeof(*regs));
  33         /* We might want to also zero all Processor registers here */
  34         pt_set_usermode(regs);
  35         pt_set_elr(regs, pc);
  36         pt_set_rte_sp(regs, sp);
  37 }
  38
  39 /*
  40  *  Spin, or better still, do a hardware or VM wait instruction
  41  *  If hardware or VM offer wait termination even though interrupts
  42  *  are disabled.
  43  */
  44 void arch_cpu_idle(void)
  45 {
  46         __vmwait();
  47         /*  interrupts wake us up, but irqs are still disabled */
  48 }
  49
  50 /*
  51  * Copy architecture-specific thread state
  52  */
  53 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
  54 {
  55         unsigned long clone_flags = args->flags;
  56         unsigned long usp = args->stack;
  57         unsigned long tls = args->tls;
  58         struct thread_info *ti = task_thread_info(p);
  59         struct hexagon_switch_stack *ss;
  60         struct pt_regs *childregs;
  61         asmlinkage void ret_from_fork(void);
  62
  63         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  64                                         sizeof(*childregs));
  65
  66         ti->regs = childregs;
  67
  68         /*
  69          * Establish kernel stack pointer and initial PC for new thread
  70          * Note that unlike the usual situation, we do not copy the
  71          * parent's callee-saved here; those are in pt_regs and whatever
  72          * we leave here will be overridden on return to userland.
  73          */
  74         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  75                                                     sizeof(*ss));
  76         ss->lr = (unsigned long)ret_from_fork;
  77         p->thread.switch_sp = ss;
  78         if (unlikely(args->fn)) {
  79                 memset(childregs, 0, sizeof(struct pt_regs));
  80                 /* r24 <- fn, r25 <- arg */
  81                 ss->r24 = (unsigned long)args->fn;
  82                 ss->r25 = (unsigned long)args->fn_arg;
  83                 pt_set_kmode(childregs);
  84                 return 0;
  85         }
  86         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
  87         ss->r2524 = 0;
  88
  89         if (usp)
  90                 pt_set_rte_sp(childregs, usp);
  91
  92         /* Child sees zero return value */
  93         childregs->r00 = 0;
  94
  95         /*
  96          * The clone syscall has the C signature:
  97          * int [r0] clone(int flags [r0],
  98          *           void *child_frame [r1],
  99          *           void *parent_tid [r2],
 100          *           void *child_tid [r3],
 101          *           void *thread_control_block [r4]);
 102          * ugp is used to provide TLS support.
 103          */
 104         if (clone_flags & CLONE_SETTLS)
 105                 childregs->ugp = tls;
 106
 107         /*
 108          * Parent sees new pid -- not necessary, not even possible at
 109          * this point in the fork process
 110          */
 111
 112         return 0;
 113 }
 114
 115 /*
 116  * Some archs flush debug and FPU info here
 117  */
 118 void flush_thread(void)
 119 {
 120 }
 121
 122 /*
 123  * The "wait channel" terminology is archaic, but what we want
 124  * is an identification of the point at which the scheduler
 125  * was invoked by a blocked thread.
 126  */
 127 unsigned long __get_wchan(struct task_struct *p)
 128 {
 129         unsigned long fp, pc;
 130         unsigned long stack_page;
 131         int count = 0;
 132
 133         stack_page = (unsigned long)task_stack_page(p);
 134         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 135         do {
 136                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 137                         fp >= (THREAD_SIZE - 8 + stack_page))
 138                         return 0;
 139                 pc = ((unsigned long *)fp)[1];
 140                 if (!in_sched_functions(pc))
 141                         return pc;
 142                 fp = *(unsigned long *) fp;
 143         } while (count++ < 16);
 144
 145         return 0;
 146 }
 147
 148 /*
 149  * Called on the exit path of event entry; see vm_entry.S
 150  *
 151  * Interrupts will already be disabled.
 152  *
 153  * Returns 0 if there's no need to re-check for more work.
 154  */
 155
 156 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags);
 157 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 158 {
 159         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 160                 return 0;
 161         }  /* shortcut -- no work to be done */
 162
 163         local_irq_enable();
 164
 165         if (thread_info_flags & _TIF_NEED_RESCHED) {
 166                 schedule();
 167                 return 1;
 168         }
 169
 170         if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
 171                 do_signal(regs);
 172                 return 1;
 173         }
 174
 175         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 176                 resume_user_mode_work(regs);
 177                 return 1;
 178         }
 179
 180         /* Should not even reach here */
 181         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 182                 thread_info_flags);
 183 }