summaryrefslogtreecommitdiff
path: root/arch/hexagon/kernel/process.c
blob: e15eeaebd78530e90eace2211582a1bb2bf1f32b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Process creation support for Hexagon
 *
 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
 */

#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task.h>
#include <linux/sched/task_stack.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/tick.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/resume_user_mode.h>

/*
 * Program thread launch.  Often defined as a macro in processor.h,
 * but we're shooting for a small footprint and it's not an inner-loop
 * performance-critical operation.
 *
 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
 * so that gets automatically done here.  If we ever stop doing that here,
 * we'll probably want to define the ELF_PLAT_INIT macro.
 */
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
	/* We want to zero all data-containing registers. Is this overkill? */
	memset(regs, 0, sizeof(*regs));
	/* We might want to also zero all Processor registers here */
	pt_set_usermode(regs);
	pt_set_elr(regs, pc);
	pt_set_rte_sp(regs, sp);
}

/*
 *  Spin, or better still, do a hardware or VM wait instruction
 *  If hardware or VM offer wait termination even though interrupts
 *  are disabled.
 */
void arch_cpu_idle(void)
{
	__vmwait();
	/*  interrupts wake us up, but irqs are still disabled */
	raw_local_irq_enable();
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
	unsigned long clone_flags = args->flags;
	unsigned long usp = args->stack;
	unsigned long tls = args->tls;
	struct thread_info *ti = task_thread_info(p);
	struct hexagon_switch_stack *ss;
	struct pt_regs *childregs;
	asmlinkage void ret_from_fork(void);

	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
					sizeof(*childregs));

	ti->regs = childregs;

	/*
	 * Establish kernel stack pointer and initial PC for new thread
	 * Note that unlike the usual situation, we do not copy the
	 * parent's callee-saved here; those are in pt_regs and whatever
	 * we leave here will be overridden on return to userland.
	 */
	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
						    sizeof(*ss));
	ss->lr = (unsigned long)ret_from_fork;
	p->thread.switch_sp = ss;
	if (unlikely(args->fn)) {
		memset(childregs, 0, sizeof(struct pt_regs));
		/* r24 <- fn, r25 <- arg */
		ss->r24 = (unsigned long)args->fn;
		ss->r25 = (unsigned long)args->fn_arg;
		pt_set_kmode(childregs);
		return 0;
	}
	memcpy(childregs, current_pt_regs(), sizeof(*childregs));
	ss->r2524 = 0;

	if (usp)
		pt_set_rte_sp(childregs, usp);

	/* Child sees zero return value */
	childregs->r00 = 0;

	/*
	 * The clone syscall has the C signature:
	 * int [r0] clone(int flags [r0],
	 *           void *child_frame [r1],
	 *           void *parent_tid [r2],
	 *           void *child_tid [r3],
	 *           void *thread_control_block [r4]);
	 * ugp is used to provide TLS support.
	 */
	if (clone_flags & CLONE_SETTLS)
		childregs->ugp = tls;

	/*
	 * Parent sees new pid -- not necessary, not even possible at
	 * this point in the fork process
	 */

	return 0;
}

/*
 * Some archs flush debug and FPU info here
 */
void flush_thread(void)
{
}

/*
 * The "wait channel" terminology is archaic, but what we want
 * is an identification of the point at which the scheduler
 * was invoked by a blocked thread.
 */
unsigned long __get_wchan(struct task_struct *p)
{
	unsigned long fp, pc;
	unsigned long stack_page;
	int count = 0;

	stack_page = (unsigned long)task_stack_page(p);
	fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
	do {
		if (fp < (stack_page + sizeof(struct thread_info)) ||
			fp >= (THREAD_SIZE - 8 + stack_page))
			return 0;
		pc = ((unsigned long *)fp)[1];
		if (!in_sched_functions(pc))
			return pc;
		fp = *(unsigned long *) fp;
	} while (count++ < 16);

	return 0;
}

/*
 * Called on the exit path of event entry; see vm_entry.S
 *
 * Interrupts will already be disabled.
 *
 * Returns 0 if there's no need to re-check for more work.
 */

int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
{
	if (!(thread_info_flags & _TIF_WORK_MASK)) {
		return 0;
	}  /* shortcut -- no work to be done */

	local_irq_enable();

	if (thread_info_flags & _TIF_NEED_RESCHED) {
		schedule();
		return 1;
	}

	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
		do_signal(regs);
		return 1;
	}

	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
		resume_user_mode_work(regs);
		return 1;
	}

	/* Should not even reach here */
	panic("%s: bad thread_info flags 0x%08x\n", __func__,
		thread_info_flags);
}