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/sched.h>
   9 #include <linux/sched/debug.h>
  10 #include <linux/sched/task.h>
  11 #include <linux/sched/task_stack.h>
  12 #include <linux/types.h>
  13 #include <linux/module.h>
  14 #include <linux/tick.h>
  15 #include <linux/uaccess.h>
  16 #include <linux/slab.h>
  17 #include <linux/tracehook.h>
  18
  19 /*
  20  * Program thread launch.  Often defined as a macro in processor.h,
  21  * but we're shooting for a small footprint and it's not an inner-loop
  22  * performance-critical operation.
  23  *
  24  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
  25  * so that gets automatically done here.  If we ever stop doing that here,
  26  * we'll probably want to define the ELF_PLAT_INIT macro.
  27  */
  28 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
  29 {
  30         /* We want to zero all data-containing registers. Is this overkill? */
  31         memset(regs, 0, sizeof(*regs));
  32         /* We might want to also zero all Processor registers here */
  33         pt_set_usermode(regs);
  34         pt_set_elr(regs, pc);
  35         pt_set_rte_sp(regs, sp);
  36 }
  37
  38 /*
  39  *  Spin, or better still, do a hardware or VM wait instruction
  40  *  If hardware or VM offer wait termination even though interrupts
  41  *  are disabled.
  42  */
  43 void arch_cpu_idle(void)
  44 {
  45         __vmwait();
  46         /*  interrupts wake us up, but irqs are still disabled */
  47         local_irq_enable();
  48 }
  49
  50 /*
  51  * Copy architecture-specific thread state
  52  */
  53 int copy_thread(unsigned long clone_flags, unsigned long usp,
  54                 unsigned long arg, struct task_struct *p)
  55 {
  56         struct thread_info *ti = task_thread_info(p);
  57         struct hexagon_switch_stack *ss;
  58         struct pt_regs *childregs;
  59         asmlinkage void ret_from_fork(void);
  60
  61         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
  62                                         sizeof(*childregs));
  63
  64         ti->regs = childregs;
  65
  66         /*
  67          * Establish kernel stack pointer and initial PC for new thread
  68          * Note that unlike the usual situation, we do not copy the
  69          * parent's callee-saved here; those are in pt_regs and whatever
  70          * we leave here will be overridden on return to userland.
  71          */
  72         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
  73                                                     sizeof(*ss));
  74         ss->lr = (unsigned long)ret_from_fork;
  75         p->thread.switch_sp = ss;
  76         if (unlikely(p->flags & PF_KTHREAD)) {
  77                 memset(childregs, 0, sizeof(struct pt_regs));
  78                 /* r24 <- fn, r25 <- arg */
  79                 ss->r24 = usp;
  80                 ss->r25 = arg;
  81                 pt_set_kmode(childregs);
  82                 return 0;
  83         }
  84         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
  85         ss->r2524 = 0;
  86
  87         if (usp)
  88                 pt_set_rte_sp(childregs, usp);
  89
  90         /* Child sees zero return value */
  91         childregs->r00 = 0;
  92
  93         /*
  94          * The clone syscall has the C signature:
  95          * int [r0] clone(int flags [r0],
  96          *           void *child_frame [r1],
  97          *           void *parent_tid [r2],
  98          *           void *child_tid [r3],
  99          *           void *thread_control_block [r4]);
 100          * ugp is used to provide TLS support.
 101          */
 102         if (clone_flags & CLONE_SETTLS)
 103                 childregs->ugp = childregs->r04;
 104
 105         /*
 106          * Parent sees new pid -- not necessary, not even possible at
 107          * this point in the fork process
 108          * Might also want to set things like ti->addr_limit
 109          */
 110
 111         return 0;
 112 }
 113
 114 /*
 115  * Release any architecture-specific resources locked by thread
 116  */
 117 void release_thread(struct task_struct *dead_task)
 118 {
 119 }
 120
 121 /*
 122  * Some archs flush debug and FPU info here
 123  */
 124 void flush_thread(void)
 125 {
 126 }
 127
 128 /*
 129  * The "wait channel" terminology is archaic, but what we want
 130  * is an identification of the point at which the scheduler
 131  * was invoked by a blocked thread.
 132  */
 133 unsigned long get_wchan(struct task_struct *p)
 134 {
 135         unsigned long fp, pc;
 136         unsigned long stack_page;
 137         int count = 0;
 138         if (!p || p == current || p->state == TASK_RUNNING)
 139                 return 0;
 140
 141         stack_page = (unsigned long)task_stack_page(p);
 142         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
 143         do {
 144                 if (fp < (stack_page + sizeof(struct thread_info)) ||
 145                         fp >= (THREAD_SIZE - 8 + stack_page))
 146                         return 0;
 147                 pc = ((unsigned long *)fp)[1];
 148                 if (!in_sched_functions(pc))
 149                         return pc;
 150                 fp = *(unsigned long *) fp;
 151         } while (count++ < 16);
 152
 153         return 0;
 154 }
 155
 156 /*
 157  * Required placeholder.
 158  */
 159 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 160 {
 161         return 0;
 162 }
 163
 164
 165 /*
 166  * Called on the exit path of event entry; see vm_entry.S
 167  *
 168  * Interrupts will already be disabled.
 169  *
 170  * Returns 0 if there's no need to re-check for more work.
 171  */
 172
 173 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
 174 {
 175         if (!(thread_info_flags & _TIF_WORK_MASK)) {
 176                 return 0;
 177         }  /* shortcut -- no work to be done */
 178
 179         local_irq_enable();
 180
 181         if (thread_info_flags & _TIF_NEED_RESCHED) {
 182                 schedule();
 183                 return 1;
 184         }
 185
 186         if (thread_info_flags & _TIF_SIGPENDING) {
 187                 do_signal(regs);
 188                 return 1;
 189         }
 190
 191         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 192                 clear_thread_flag(TIF_NOTIFY_RESUME);
 193                 tracehook_notify_resume(regs);
 194                 return 1;
 195         }
 196
 197         /* Should not even reach here */
 198         panic("%s: bad thread_info flags 0x%08x\n", __func__,
 199                 thread_info_flags);
 200 }