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 */
 29void 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 */
 44void 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 */
 53int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 54{
 55	u64 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 */
118void 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 */
127unsigned 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
156int do_work_pending(struct pt_regs *regs, u32 thread_info_flags);
157int 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}