xref: /linux/arch/loongarch/kernel/process.c (revision e91c37f1) 
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/hw_breakpoint.h>
22 #include <linux/mm.h>
23 #include <linux/stddef.h>
24 #include <linux/unistd.h>
25 #include <linux/export.h>
26 #include <linux/ptrace.h>
27 #include <linux/mman.h>
28 #include <linux/personality.h>
29 #include <linux/sys.h>
30 #include <linux/completion.h>
31 #include <linux/kallsyms.h>
32 #include <linux/random.h>
33 #include <linux/prctl.h>
34 #include <linux/nmi.h>
35 
36 #include <asm/asm.h>
37 #include <asm/bootinfo.h>
38 #include <asm/cpu.h>
39 #include <asm/elf.h>
40 #include <asm/exec.h>
41 #include <asm/fpu.h>
42 #include <asm/lbt.h>
43 #include <asm/io.h>
44 #include <asm/irq.h>
45 #include <asm/irq_regs.h>
46 #include <asm/loongarch.h>
47 #include <asm/pgtable.h>
48 #include <asm/processor.h>
49 #include <asm/reg.h>
50 #include <asm/unwind.h>
51 #include <asm/vdso.h>
52 
53 #ifdef CONFIG_STACKPROTECTOR
54 #include <linux/stackprotector.h>
55 unsigned long __stack_chk_guard __read_mostly;
56 EXPORT_SYMBOL(__stack_chk_guard);
57 #endif
58 
59 /*
60  * Idle related variables and functions
61  */
62 
63 unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
64 EXPORT_SYMBOL(boot_option_idle_override);
65 
66 asmlinkage void ret_from_fork(void);
67 asmlinkage void ret_from_kernel_thread(void);
68 
69 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
70 {
71 	unsigned long crmd;
72 	unsigned long prmd;
73 	unsigned long euen;
74 
75 	/* New thread loses kernel privileges. */
76 	crmd = regs->csr_crmd & ~(PLV_MASK);
77 	crmd |= PLV_USER;
78 	regs->csr_crmd = crmd;
79 
80 	prmd = regs->csr_prmd & ~(PLV_MASK);
81 	prmd |= PLV_USER;
82 	regs->csr_prmd = prmd;
83 
84 	euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
85 	regs->csr_euen = euen;
86 	lose_fpu(0);
87 	lose_lbt(0);
88 	current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;
89 
90 	clear_thread_flag(TIF_LSX_CTX_LIVE);
91 	clear_thread_flag(TIF_LASX_CTX_LIVE);
92 	clear_thread_flag(TIF_LBT_CTX_LIVE);
93 	clear_used_math();
94 	regs->csr_era = pc;
95 	regs->regs[3] = sp;
96 }
97 
98 void flush_thread(void)
99 {
100 	flush_ptrace_hw_breakpoint(current);
101 }
102 
103 void exit_thread(struct task_struct *tsk)
104 {
105 }
106 
107 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
108 {
109 	/*
110 	 * Save any process state which is live in hardware registers to the
111 	 * parent context prior to duplication. This prevents the new child
112 	 * state becoming stale if the parent is preempted before copy_thread()
113 	 * gets a chance to save the parent's live hardware registers to the
114 	 * child context.
115 	 */
116 	preempt_disable();
117 
118 	if (is_fpu_owner()) {
119 		if (is_lasx_enabled())
120 			save_lasx(current);
121 		else if (is_lsx_enabled())
122 			save_lsx(current);
123 		else
124 			save_fp(current);
125 	}
126 
127 	preempt_enable();
128 
129 	if (!used_math())
130 		memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
131 	else
132 		memcpy(dst, src, offsetof(struct task_struct, thread.lbt.scr0));
133 
134 #ifdef CONFIG_CPU_HAS_LBT
135 	memcpy(&dst->thread.lbt, &src->thread.lbt, sizeof(struct loongarch_lbt));
136 #endif
137 
138 	return 0;
139 }
140 
141 /*
142  * Copy architecture-specific thread state
143  */
144 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
145 {
146 	unsigned long childksp;
147 	unsigned long tls = args->tls;
148 	unsigned long usp = args->stack;
149 	unsigned long clone_flags = args->flags;
150 	struct pt_regs *childregs, *regs = current_pt_regs();
151 
152 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
153 
154 	/* set up new TSS. */
155 	childregs = (struct pt_regs *) childksp - 1;
156 	/*  Put the stack after the struct pt_regs.  */
157 	childksp = (unsigned long) childregs;
158 	p->thread.sched_cfa = 0;
159 	p->thread.csr_euen = 0;
160 	p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
161 	p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
162 	p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
163 	if (unlikely(args->fn)) {
164 		/* kernel thread */
165 		p->thread.reg03 = childksp;
166 		p->thread.reg23 = (unsigned long)args->fn;
167 		p->thread.reg24 = (unsigned long)args->fn_arg;
168 		p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
169 		p->thread.sched_ra = (unsigned long)ret_from_kernel_thread;
170 		memset(childregs, 0, sizeof(struct pt_regs));
171 		childregs->csr_euen = p->thread.csr_euen;
172 		childregs->csr_crmd = p->thread.csr_crmd;
173 		childregs->csr_prmd = p->thread.csr_prmd;
174 		childregs->csr_ecfg = p->thread.csr_ecfg;
175 		goto out;
176 	}
177 
178 	/* user thread */
179 	*childregs = *regs;
180 	childregs->regs[4] = 0; /* Child gets zero as return value */
181 	if (usp)
182 		childregs->regs[3] = usp;
183 
184 	p->thread.reg03 = (unsigned long) childregs;
185 	p->thread.reg01 = (unsigned long) ret_from_fork;
186 	p->thread.sched_ra = (unsigned long) ret_from_fork;
187 
188 	/*
189 	 * New tasks lose permission to use the fpu. This accelerates context
190 	 * switching for most programs since they don't use the fpu.
191 	 */
192 	childregs->csr_euen = 0;
193 
194 	if (clone_flags & CLONE_SETTLS)
195 		childregs->regs[2] = tls;
196 
197 out:
198 	ptrace_hw_copy_thread(p);
199 	clear_tsk_thread_flag(p, TIF_USEDFPU);
200 	clear_tsk_thread_flag(p, TIF_USEDSIMD);
201 	clear_tsk_thread_flag(p, TIF_USEDLBT);
202 	clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
203 	clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
204 	clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);
205 
206 	return 0;
207 }
208 
209 unsigned long __get_wchan(struct task_struct *task)
210 {
211 	unsigned long pc = 0;
212 	struct unwind_state state;
213 
214 	if (!try_get_task_stack(task))
215 		return 0;
216 
217 	for (unwind_start(&state, task, NULL);
218 	     !unwind_done(&state); unwind_next_frame(&state)) {
219 		pc = unwind_get_return_address(&state);
220 		if (!pc)
221 			break;
222 		if (in_sched_functions(pc))
223 			continue;
224 		break;
225 	}
226 
227 	put_task_stack(task);
228 
229 	return pc;
230 }
231 
232 bool in_irq_stack(unsigned long stack, struct stack_info *info)
233 {
234 	unsigned long nextsp;
235 	unsigned long begin = (unsigned long)this_cpu_read(irq_stack);
236 	unsigned long end = begin + IRQ_STACK_START;
237 
238 	if (stack < begin || stack >= end)
239 		return false;
240 
241 	nextsp = *(unsigned long *)end;
242 	if (nextsp & (SZREG - 1))
243 		return false;
244 
245 	info->begin = begin;
246 	info->end = end;
247 	info->next_sp = nextsp;
248 	info->type = STACK_TYPE_IRQ;
249 
250 	return true;
251 }
252 
253 bool in_task_stack(unsigned long stack, struct task_struct *task,
254 			struct stack_info *info)
255 {
256 	unsigned long begin = (unsigned long)task_stack_page(task);
257 	unsigned long end = begin + THREAD_SIZE;
258 
259 	if (stack < begin || stack >= end)
260 		return false;
261 
262 	info->begin = begin;
263 	info->end = end;
264 	info->next_sp = 0;
265 	info->type = STACK_TYPE_TASK;
266 
267 	return true;
268 }
269 
270 int get_stack_info(unsigned long stack, struct task_struct *task,
271 		   struct stack_info *info)
272 {
273 	task = task ? : current;
274 
275 	if (!stack || stack & (SZREG - 1))
276 		goto unknown;
277 
278 	if (in_task_stack(stack, task, info))
279 		return 0;
280 
281 	if (task != current)
282 		goto unknown;
283 
284 	if (in_irq_stack(stack, info))
285 		return 0;
286 
287 unknown:
288 	info->type = STACK_TYPE_UNKNOWN;
289 	return -EINVAL;
290 }
291 
292 unsigned long stack_top(void)
293 {
294 	unsigned long top = TASK_SIZE & PAGE_MASK;
295 
296 	/* Space for the VDSO & data page */
297 	top -= PAGE_ALIGN(current->thread.vdso->size);
298 	top -= VVAR_SIZE;
299 
300 	/* Space to randomize the VDSO base */
301 	if (current->flags & PF_RANDOMIZE)
302 		top -= VDSO_RANDOMIZE_SIZE;
303 
304 	return top;
305 }
306 
307 /*
308  * Don't forget that the stack pointer must be aligned on a 8 bytes
309  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
310  */
311 unsigned long arch_align_stack(unsigned long sp)
312 {
313 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
314 		sp -= get_random_u32_below(PAGE_SIZE);
315 
316 	return sp & STACK_ALIGN;
317 }
318 
319 static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
320 static struct cpumask backtrace_csd_busy;
321 
322 static void handle_backtrace(void *info)
323 {
324 	nmi_cpu_backtrace(get_irq_regs());
325 	cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
326 }
327 
328 static void raise_backtrace(cpumask_t *mask)
329 {
330 	call_single_data_t *csd;
331 	int cpu;
332 
333 	for_each_cpu(cpu, mask) {
334 		/*
335 		 * If we previously sent an IPI to the target CPU & it hasn't
336 		 * cleared its bit in the busy cpumask then it didn't handle
337 		 * our previous IPI & it's not safe for us to reuse the
338 		 * call_single_data_t.
339 		 */
340 		if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
341 			pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
342 				cpu);
343 			continue;
344 		}
345 
346 		csd = &per_cpu(backtrace_csd, cpu);
347 		csd->func = handle_backtrace;
348 		smp_call_function_single_async(cpu, csd);
349 	}
350 }
351 
352 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
353 {
354 	nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace);
355 }
356 
357 #ifdef CONFIG_64BIT
358 void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
359 {
360 	unsigned int i;
361 
362 	for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
363 		uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
364 	}
365 
366 	uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
367 	uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
368 	uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
369 	uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
370 	uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
371 	uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
372 	uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
373 	uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
374 }
375 #endif /* CONFIG_64BIT */
376