1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Author: Huacai Chen <chenhuacai@loongson.cn>
4  * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
5  *
6  * Derived from MIPS:
7  * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
8  * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
9  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
10  * Copyright (C) 2004 Thiemo Seufer
11  * Copyright (C) 2013  Imagination Technologies Ltd.
12  */
13 #include <linux/cpu.h>
14 #include <linux/init.h>
15 #include <linux/kernel.h>
16 #include <linux/errno.h>
17 #include <linux/sched.h>
18 #include <linux/sched/debug.h>
19 #include <linux/sched/task.h>
20 #include <linux/sched/task_stack.h>
21 #include <linux/mm.h>
22 #include <linux/stddef.h>
23 #include <linux/unistd.h>
24 #include <linux/export.h>
25 #include <linux/ptrace.h>
26 #include <linux/mman.h>
27 #include <linux/personality.h>
28 #include <linux/sys.h>
29 #include <linux/completion.h>
30 #include <linux/kallsyms.h>
31 #include <linux/random.h>
32 #include <linux/prctl.h>
33 #include <linux/nmi.h>
34 
35 #include <asm/asm.h>
36 #include <asm/bootinfo.h>
37 #include <asm/cpu.h>
38 #include <asm/elf.h>
39 #include <asm/fpu.h>
40 #include <asm/io.h>
41 #include <asm/irq.h>
42 #include <asm/irq_regs.h>
43 #include <asm/loongarch.h>
44 #include <asm/pgtable.h>
45 #include <asm/processor.h>
46 #include <asm/reg.h>
47 #include <asm/vdso.h>
48 
49 /*
50  * Idle related variables and functions
51  */
52 
53 unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
54 EXPORT_SYMBOL(boot_option_idle_override);
55 
56 #ifdef CONFIG_HOTPLUG_CPU
arch_cpu_idle_dead(void)57 void arch_cpu_idle_dead(void)
58 {
59 	play_dead();
60 }
61 #endif
62 
63 asmlinkage void ret_from_fork(void);
64 asmlinkage void ret_from_kernel_thread(void);
65 
start_thread(struct pt_regs * regs,unsigned long pc,unsigned long sp)66 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
67 {
68 	unsigned long crmd;
69 	unsigned long prmd;
70 	unsigned long euen;
71 
72 	/* New thread loses kernel privileges. */
73 	crmd = regs->csr_crmd & ~(PLV_MASK);
74 	crmd |= PLV_USER;
75 	regs->csr_crmd = crmd;
76 
77 	prmd = regs->csr_prmd & ~(PLV_MASK);
78 	prmd |= PLV_USER;
79 	regs->csr_prmd = prmd;
80 
81 	euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
82 	regs->csr_euen = euen;
83 	lose_fpu(0);
84 
85 	clear_thread_flag(TIF_LSX_CTX_LIVE);
86 	clear_thread_flag(TIF_LASX_CTX_LIVE);
87 	clear_used_math();
88 	regs->csr_era = pc;
89 	regs->regs[3] = sp;
90 }
91 
exit_thread(struct task_struct * tsk)92 void exit_thread(struct task_struct *tsk)
93 {
94 }
95 
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)96 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
97 {
98 	/*
99 	 * Save any process state which is live in hardware registers to the
100 	 * parent context prior to duplication. This prevents the new child
101 	 * state becoming stale if the parent is preempted before copy_thread()
102 	 * gets a chance to save the parent's live hardware registers to the
103 	 * child context.
104 	 */
105 	preempt_disable();
106 
107 	if (is_fpu_owner())
108 		save_fp(current);
109 
110 	preempt_enable();
111 
112 	if (used_math())
113 		memcpy(dst, src, sizeof(struct task_struct));
114 	else
115 		memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
116 
117 	return 0;
118 }
119 
120 /*
121  * Copy architecture-specific thread state
122  */
copy_thread(struct task_struct * p,const struct kernel_clone_args * args)123 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
124 {
125 	unsigned long childksp;
126 	unsigned long tls = args->tls;
127 	unsigned long usp = args->stack;
128 	unsigned long clone_flags = args->flags;
129 	struct pt_regs *childregs, *regs = current_pt_regs();
130 
131 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
132 
133 	/* set up new TSS. */
134 	childregs = (struct pt_regs *) childksp - 1;
135 	/*  Put the stack after the struct pt_regs.  */
136 	childksp = (unsigned long) childregs;
137 	p->thread.csr_euen = 0;
138 	p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
139 	p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
140 	p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
141 	if (unlikely(args->fn)) {
142 		/* kernel thread */
143 		p->thread.reg03 = childksp;
144 		p->thread.reg23 = (unsigned long)args->fn;
145 		p->thread.reg24 = (unsigned long)args->fn_arg;
146 		p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
147 		memset(childregs, 0, sizeof(struct pt_regs));
148 		childregs->csr_euen = p->thread.csr_euen;
149 		childregs->csr_crmd = p->thread.csr_crmd;
150 		childregs->csr_prmd = p->thread.csr_prmd;
151 		childregs->csr_ecfg = p->thread.csr_ecfg;
152 		return 0;
153 	}
154 
155 	/* user thread */
156 	*childregs = *regs;
157 	childregs->regs[4] = 0; /* Child gets zero as return value */
158 	if (usp)
159 		childregs->regs[3] = usp;
160 
161 	p->thread.reg03 = (unsigned long) childregs;
162 	p->thread.reg01 = (unsigned long) ret_from_fork;
163 
164 	/*
165 	 * New tasks lose permission to use the fpu. This accelerates context
166 	 * switching for most programs since they don't use the fpu.
167 	 */
168 	childregs->csr_euen = 0;
169 
170 	clear_tsk_thread_flag(p, TIF_USEDFPU);
171 	clear_tsk_thread_flag(p, TIF_USEDSIMD);
172 	clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
173 	clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
174 
175 	if (clone_flags & CLONE_SETTLS)
176 		childregs->regs[2] = tls;
177 
178 	return 0;
179 }
180 
__get_wchan(struct task_struct * task)181 unsigned long __get_wchan(struct task_struct *task)
182 {
183 	return 0;
184 }
185 
stack_top(void)186 unsigned long stack_top(void)
187 {
188 	unsigned long top = TASK_SIZE & PAGE_MASK;
189 
190 	/* Space for the VDSO & data page */
191 	top -= PAGE_ALIGN(current->thread.vdso->size);
192 	top -= PAGE_SIZE;
193 
194 	/* Space to randomize the VDSO base */
195 	if (current->flags & PF_RANDOMIZE)
196 		top -= VDSO_RANDOMIZE_SIZE;
197 
198 	return top;
199 }
200 
201 /*
202  * Don't forget that the stack pointer must be aligned on a 8 bytes
203  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
204  */
arch_align_stack(unsigned long sp)205 unsigned long arch_align_stack(unsigned long sp)
206 {
207 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
208 		sp -= get_random_int() & ~PAGE_MASK;
209 
210 	return sp & STACK_ALIGN;
211 }
212 
213 static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
214 static struct cpumask backtrace_csd_busy;
215 
handle_backtrace(void * info)216 static void handle_backtrace(void *info)
217 {
218 	nmi_cpu_backtrace(get_irq_regs());
219 	cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
220 }
221 
raise_backtrace(cpumask_t * mask)222 static void raise_backtrace(cpumask_t *mask)
223 {
224 	call_single_data_t *csd;
225 	int cpu;
226 
227 	for_each_cpu(cpu, mask) {
228 		/*
229 		 * If we previously sent an IPI to the target CPU & it hasn't
230 		 * cleared its bit in the busy cpumask then it didn't handle
231 		 * our previous IPI & it's not safe for us to reuse the
232 		 * call_single_data_t.
233 		 */
234 		if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
235 			pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
236 				cpu);
237 			continue;
238 		}
239 
240 		csd = &per_cpu(backtrace_csd, cpu);
241 		csd->func = handle_backtrace;
242 		smp_call_function_single_async(cpu, csd);
243 	}
244 }
245 
arch_trigger_cpumask_backtrace(const cpumask_t * mask,bool exclude_self)246 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
247 {
248 	nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace);
249 }
250 
251 #ifdef CONFIG_64BIT
loongarch_dump_regs64(u64 * uregs,const struct pt_regs * regs)252 void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
253 {
254 	unsigned int i;
255 
256 	for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
257 		uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
258 	}
259 
260 	uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
261 	uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
262 	uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
263 	uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
264 	uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
265 	uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
266 	uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
267 	uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
268 }
269 #endif /* CONFIG_64BIT */
270