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/resume_user_mode.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 */
28void 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 */
43void arch_cpu_idle(void)
44{
45	__vmwait();
46	/*  interrupts wake us up, but irqs are still disabled */
47}
48
49/*
50 * Copy architecture-specific thread state
51 */
52int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
53{
54	unsigned long clone_flags = args->flags;
55	unsigned long usp = args->stack;
56	unsigned long tls = args->tls;
57	struct thread_info *ti = task_thread_info(p);
58	struct hexagon_switch_stack *ss;
59	struct pt_regs *childregs;
60	asmlinkage void ret_from_fork(void);
61
62	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
63					sizeof(*childregs));
64
65	ti->regs = childregs;
66
67	/*
68	 * Establish kernel stack pointer and initial PC for new thread
69	 * Note that unlike the usual situation, we do not copy the
70	 * parent's callee-saved here; those are in pt_regs and whatever
71	 * we leave here will be overridden on return to userland.
72	 */
73	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
74						    sizeof(*ss));
75	ss->lr = (unsigned long)ret_from_fork;
76	p->thread.switch_sp = ss;
77	if (unlikely(args->fn)) {
78		memset(childregs, 0, sizeof(struct pt_regs));
79		/* r24 <- fn, r25 <- arg */
80		ss->r24 = (unsigned long)args->fn;
81		ss->r25 = (unsigned long)args->fn_arg;
82		pt_set_kmode(childregs);
83		return 0;
84	}
85	memcpy(childregs, current_pt_regs(), sizeof(*childregs));
86	ss->r2524 = 0;
87
88	if (usp)
89		pt_set_rte_sp(childregs, usp);
90
91	/* Child sees zero return value */
92	childregs->r00 = 0;
93
94	/*
95	 * The clone syscall has the C signature:
96	 * int [r0] clone(int flags [r0],
97	 *           void *child_frame [r1],
98	 *           void *parent_tid [r2],
99	 *           void *child_tid [r3],
100	 *           void *thread_control_block [r4]);
101	 * ugp is used to provide TLS support.
102	 */
103	if (clone_flags & CLONE_SETTLS)
104		childregs->ugp = tls;
105
106	/*
107	 * Parent sees new pid -- not necessary, not even possible at
108	 * this point in the fork process
109	 */
110
111	return 0;
112}
113
114/*
115 * Some archs flush debug and FPU info here
116 */
117void flush_thread(void)
118{
119}
120
121/*
122 * The "wait channel" terminology is archaic, but what we want
123 * is an identification of the point at which the scheduler
124 * was invoked by a blocked thread.
125 */
126unsigned long __get_wchan(struct task_struct *p)
127{
128	unsigned long fp, pc;
129	unsigned long stack_page;
130	int count = 0;
131
132	stack_page = (unsigned long)task_stack_page(p);
133	fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
134	do {
135		if (fp < (stack_page + sizeof(struct thread_info)) ||
136			fp >= (THREAD_SIZE - 8 + stack_page))
137			return 0;
138		pc = ((unsigned long *)fp)[1];
139		if (!in_sched_functions(pc))
140			return pc;
141		fp = *(unsigned long *) fp;
142	} while (count++ < 16);
143
144	return 0;
145}
146
147/*
148 * Called on the exit path of event entry; see vm_entry.S
149 *
150 * Interrupts will already be disabled.
151 *
152 * Returns 0 if there's no need to re-check for more work.
153 */
154
155int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
156{
157	if (!(thread_info_flags & _TIF_WORK_MASK)) {
158		return 0;
159	}  /* shortcut -- no work to be done */
160
161	local_irq_enable();
162
163	if (thread_info_flags & _TIF_NEED_RESCHED) {
164		schedule();
165		return 1;
166	}
167
168	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
169		do_signal(regs);
170		return 1;
171	}
172
173	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
174		resume_user_mode_work(regs);
175		return 1;
176	}
177
178	/* Should not even reach here */
179	panic("%s: bad thread_info flags 0x%08x\n", __func__,
180		thread_info_flags);
181}
182