xref: /linux/arch/loongarch/kernel/process.c (revision 223981db9bafb80f558162c148f261e2ff043dbe) 
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 
89 	clear_thread_flag(TIF_LSX_CTX_LIVE);
90 	clear_thread_flag(TIF_LASX_CTX_LIVE);
91 	clear_thread_flag(TIF_LBT_CTX_LIVE);
92 	clear_used_math();
93 	regs->csr_era = pc;
94 	regs->regs[3] = sp;
95 }
96 
97 void flush_thread(void)
98 {
99 	flush_ptrace_hw_breakpoint(current);
100 }
101 
102 void exit_thread(struct task_struct *tsk)
103 {
104 }
105 
106 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
107 {
108 	/*
109 	 * Save any process state which is live in hardware registers to the
110 	 * parent context prior to duplication. This prevents the new child
111 	 * state becoming stale if the parent is preempted before copy_thread()
112 	 * gets a chance to save the parent's live hardware registers to the
113 	 * child context.
114 	 */
115 	preempt_disable();
116 
117 	if (is_fpu_owner()) {
118 		if (is_lasx_enabled())
119 			save_lasx(current);
120 		else if (is_lsx_enabled())
121 			save_lsx(current);
122 		else
123 			save_fp(current);
124 	}
125 
126 	preempt_enable();
127 
128 	if (!used_math())
129 		memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
130 	else
131 		memcpy(dst, src, offsetof(struct task_struct, thread.lbt.scr0));
132 
133 #ifdef CONFIG_CPU_HAS_LBT
134 	memcpy(&dst->thread.lbt, &src->thread.lbt, sizeof(struct loongarch_lbt));
135 #endif
136 
137 	return 0;
138 }
139 
140 /*
141  * Copy architecture-specific thread state
142  */
143 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
144 {
145 	unsigned long childksp;
146 	unsigned long tls = args->tls;
147 	unsigned long usp = args->stack;
148 	unsigned long clone_flags = args->flags;
149 	struct pt_regs *childregs, *regs = current_pt_regs();
150 
151 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
152 
153 	/* set up new TSS. */
154 	childregs = (struct pt_regs *) childksp - 1;
155 	/*  Put the stack after the struct pt_regs.  */
156 	childksp = (unsigned long) childregs;
157 	p->thread.sched_cfa = 0;
158 	p->thread.csr_euen = 0;
159 	p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
160 	p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
161 	p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
162 	if (unlikely(args->fn)) {
163 		/* kernel thread */
164 		p->thread.reg03 = childksp;
165 		p->thread.reg23 = (unsigned long)args->fn;
166 		p->thread.reg24 = (unsigned long)args->fn_arg;
167 		p->thread.reg01 = (unsigned long)ret_from_kernel_thread;
168 		p->thread.sched_ra = (unsigned long)ret_from_kernel_thread;
169 		memset(childregs, 0, sizeof(struct pt_regs));
170 		childregs->csr_euen = p->thread.csr_euen;
171 		childregs->csr_crmd = p->thread.csr_crmd;
172 		childregs->csr_prmd = p->thread.csr_prmd;
173 		childregs->csr_ecfg = p->thread.csr_ecfg;
174 		goto out;
175 	}
176 
177 	/* user thread */
178 	*childregs = *regs;
179 	childregs->regs[4] = 0; /* Child gets zero as return value */
180 	if (usp)
181 		childregs->regs[3] = usp;
182 
183 	p->thread.reg03 = (unsigned long) childregs;
184 	p->thread.reg01 = (unsigned long) ret_from_fork;
185 	p->thread.sched_ra = (unsigned long) ret_from_fork;
186 
187 	/*
188 	 * New tasks lose permission to use the fpu. This accelerates context
189 	 * switching for most programs since they don't use the fpu.
190 	 */
191 	childregs->csr_euen = 0;
192 
193 	if (clone_flags & CLONE_SETTLS)
194 		childregs->regs[2] = tls;
195 
196 out:
197 	ptrace_hw_copy_thread(p);
198 	clear_tsk_thread_flag(p, TIF_USEDFPU);
199 	clear_tsk_thread_flag(p, TIF_USEDSIMD);
200 	clear_tsk_thread_flag(p, TIF_USEDLBT);
201 	clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
202 	clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
203 	clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);
204 
205 	return 0;
206 }
207 
208 unsigned long __get_wchan(struct task_struct *task)
209 {
210 	unsigned long pc = 0;
211 	struct unwind_state state;
212 
213 	if (!try_get_task_stack(task))
214 		return 0;
215 
216 	for (unwind_start(&state, task, NULL);
217 	     !unwind_done(&state); unwind_next_frame(&state)) {
218 		pc = unwind_get_return_address(&state);
219 		if (!pc)
220 			break;
221 		if (in_sched_functions(pc))
222 			continue;
223 		break;
224 	}
225 
226 	put_task_stack(task);
227 
228 	return pc;
229 }
230 
231 bool in_irq_stack(unsigned long stack, struct stack_info *info)
232 {
233 	unsigned long nextsp;
234 	unsigned long begin = (unsigned long)this_cpu_read(irq_stack);
235 	unsigned long end = begin + IRQ_STACK_START;
236 
237 	if (stack < begin || stack >= end)
238 		return false;
239 
240 	nextsp = *(unsigned long *)end;
241 	if (nextsp & (SZREG - 1))
242 		return false;
243 
244 	info->begin = begin;
245 	info->end = end;
246 	info->next_sp = nextsp;
247 	info->type = STACK_TYPE_IRQ;
248 
249 	return true;
250 }
251 
252 bool in_task_stack(unsigned long stack, struct task_struct *task,
253 			struct stack_info *info)
254 {
255 	unsigned long begin = (unsigned long)task_stack_page(task);
256 	unsigned long end = begin + THREAD_SIZE;
257 
258 	if (stack < begin || stack >= end)
259 		return false;
260 
261 	info->begin = begin;
262 	info->end = end;
263 	info->next_sp = 0;
264 	info->type = STACK_TYPE_TASK;
265 
266 	return true;
267 }
268 
269 int get_stack_info(unsigned long stack, struct task_struct *task,
270 		   struct stack_info *info)
271 {
272 	task = task ? : current;
273 
274 	if (!stack || stack & (SZREG - 1))
275 		goto unknown;
276 
277 	if (in_task_stack(stack, task, info))
278 		return 0;
279 
280 	if (task != current)
281 		goto unknown;
282 
283 	if (in_irq_stack(stack, info))
284 		return 0;
285 
286 unknown:
287 	info->type = STACK_TYPE_UNKNOWN;
288 	return -EINVAL;
289 }
290 
291 unsigned long stack_top(void)
292 {
293 	unsigned long top = TASK_SIZE & PAGE_MASK;
294 
295 	/* Space for the VDSO & data page */
296 	top -= PAGE_ALIGN(current->thread.vdso->size);
297 	top -= VVAR_SIZE;
298 
299 	/* Space to randomize the VDSO base */
300 	if (current->flags & PF_RANDOMIZE)
301 		top -= VDSO_RANDOMIZE_SIZE;
302 
303 	return top;
304 }
305 
306 /*
307  * Don't forget that the stack pointer must be aligned on a 8 bytes
308  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
309  */
310 unsigned long arch_align_stack(unsigned long sp)
311 {
312 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
313 		sp -= get_random_u32_below(PAGE_SIZE);
314 
315 	return sp & STACK_ALIGN;
316 }
317 
318 static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
319 static struct cpumask backtrace_csd_busy;
320 
321 static void handle_backtrace(void *info)
322 {
323 	nmi_cpu_backtrace(get_irq_regs());
324 	cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
325 }
326 
327 static void raise_backtrace(cpumask_t *mask)
328 {
329 	call_single_data_t *csd;
330 	int cpu;
331 
332 	for_each_cpu(cpu, mask) {
333 		/*
334 		 * If we previously sent an IPI to the target CPU & it hasn't
335 		 * cleared its bit in the busy cpumask then it didn't handle
336 		 * our previous IPI & it's not safe for us to reuse the
337 		 * call_single_data_t.
338 		 */
339 		if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
340 			pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
341 				cpu);
342 			continue;
343 		}
344 
345 		csd = &per_cpu(backtrace_csd, cpu);
346 		csd->func = handle_backtrace;
347 		smp_call_function_single_async(cpu, csd);
348 	}
349 }
350 
351 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
352 {
353 	nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace);
354 }
355 
356 #ifdef CONFIG_64BIT
357 void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
358 {
359 	unsigned int i;
360 
361 	for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
362 		uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
363 	}
364 
365 	uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
366 	uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
367 	uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
368 	uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
369 	uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
370 	uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
371 	uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
372 	uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
373 }
374 #endif /* CONFIG_64BIT */
375