xref: /linux/arch/loongarch/kernel/process.c (revision 2a1ea59de83bf367215e2a4dd9bf8bbd061349b3) 
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/entry-common.h>
17 #include <linux/errno.h>
18 #include <linux/sched.h>
19 #include <linux/sched/debug.h>
20 #include <linux/sched/task.h>
21 #include <linux/sched/task_stack.h>
22 #include <linux/hw_breakpoint.h>
23 #include <linux/mm.h>
24 #include <linux/stddef.h>
25 #include <linux/unistd.h>
26 #include <linux/export.h>
27 #include <linux/ptrace.h>
28 #include <linux/mman.h>
29 #include <linux/personality.h>
30 #include <linux/sys.h>
31 #include <linux/completion.h>
32 #include <linux/kallsyms.h>
33 #include <linux/random.h>
34 #include <linux/prctl.h>
35 #include <linux/nmi.h>
36 
37 #include <asm/asm.h>
38 #include <asm/asm-prototypes.h>
39 #include <asm/bootinfo.h>
40 #include <asm/cpu.h>
41 #include <asm/elf.h>
42 #include <asm/exec.h>
43 #include <asm/fpu.h>
44 #include <asm/lbt.h>
45 #include <asm/io.h>
46 #include <asm/irq.h>
47 #include <asm/irq_regs.h>
48 #include <asm/loongarch.h>
49 #include <asm/pgtable.h>
50 #include <asm/processor.h>
51 #include <asm/reg.h>
52 #include <asm/switch_to.h>
53 #include <asm/unwind.h>
54 #include <asm/vdso.h>
55 
56 #ifdef CONFIG_STACKPROTECTOR
57 #include <linux/stackprotector.h>
58 unsigned long __stack_chk_guard __read_mostly;
59 EXPORT_SYMBOL(__stack_chk_guard);
60 #endif
61 
62 /*
63  * Idle related variables and functions
64  */
65 
66 unsigned long boot_option_idle_override = IDLE_NO_OVERRIDE;
67 EXPORT_SYMBOL(boot_option_idle_override);
68 
69 asmlinkage void restore_and_ret(void);
70 asmlinkage void ret_from_fork_asm(void);
71 asmlinkage void ret_from_kernel_thread_asm(void);
72 
73 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
74 {
75 	unsigned long crmd;
76 	unsigned long prmd;
77 	unsigned long euen;
78 
79 	/* New thread loses kernel privileges. */
80 	crmd = regs->csr_crmd & ~(PLV_MASK);
81 	crmd |= PLV_USER;
82 	regs->csr_crmd = crmd;
83 
84 	prmd = regs->csr_prmd & ~(PLV_MASK);
85 	prmd |= PLV_USER;
86 	regs->csr_prmd = prmd;
87 
88 	euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
89 	regs->csr_euen = euen;
90 	lose_fpu(0);
91 	lose_lbt(0);
92 	current->thread.fpu.fcsr = boot_cpu_data.fpu_csr0;
93 
94 	clear_thread_flag(TIF_LSX_CTX_LIVE);
95 	clear_thread_flag(TIF_LASX_CTX_LIVE);
96 	clear_thread_flag(TIF_LBT_CTX_LIVE);
97 	clear_used_math();
98 	regs->csr_era = pc;
99 	regs->regs[3] = sp;
100 }
101 
102 void flush_thread(void)
103 {
104 	flush_ptrace_hw_breakpoint(current);
105 }
106 
107 void exit_thread(struct task_struct *tsk)
108 {
109 }
110 
111 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
112 {
113 	/*
114 	 * Save any process state which is live in hardware registers to the
115 	 * parent context prior to duplication. This prevents the new child
116 	 * state becoming stale if the parent is preempted before copy_thread()
117 	 * gets a chance to save the parent's live hardware registers to the
118 	 * child context.
119 	 */
120 	preempt_disable();
121 
122 	if (is_fpu_owner()) {
123 		if (is_lasx_enabled())
124 			save_lasx(current);
125 		else if (is_lsx_enabled())
126 			save_lsx(current);
127 		else
128 			save_fp(current);
129 	}
130 
131 	preempt_enable();
132 
133 	if (!used_math())
134 		memcpy(dst, src, offsetof(struct task_struct, thread.fpu.fpr));
135 	else
136 		memcpy(dst, src, offsetof(struct task_struct, thread.lbt.scr0));
137 
138 #ifdef CONFIG_CPU_HAS_LBT
139 	memcpy(&dst->thread.lbt, &src->thread.lbt, sizeof(struct loongarch_lbt));
140 #endif
141 
142 	return 0;
143 }
144 
145 asmlinkage void noinstr __no_stack_protector ret_from_fork(struct task_struct *prev,
146 							   struct pt_regs *regs)
147 {
148 	schedule_tail(prev);
149 	syscall_exit_to_user_mode(regs);
150 }
151 
152 asmlinkage void noinstr __no_stack_protector ret_from_kernel_thread(struct task_struct *prev,
153 								    struct pt_regs *regs,
154 								    int (*fn)(void *),
155 								    void *fn_arg)
156 {
157 	schedule_tail(prev);
158 	fn(fn_arg);
159 	syscall_exit_to_user_mode(regs);
160 }
161 
162 /*
163  * Copy architecture-specific thread state
164  */
165 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
166 {
167 	unsigned long childksp;
168 	unsigned long tls = args->tls;
169 	unsigned long usp = args->stack;
170 	unsigned long clone_flags = args->flags;
171 	struct pt_regs *childregs, *regs = current_pt_regs();
172 
173 	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
174 
175 	/* set up new TSS. */
176 	childregs = (struct pt_regs *) childksp - 1;
177 	/*  Put the stack after the struct pt_regs.  */
178 	childksp = (unsigned long) childregs;
179 	p->thread.sched_cfa = 0;
180 	p->thread.csr_euen = 0;
181 	p->thread.csr_crmd = csr_read32(LOONGARCH_CSR_CRMD);
182 	p->thread.csr_prmd = csr_read32(LOONGARCH_CSR_PRMD);
183 	p->thread.csr_ecfg = csr_read32(LOONGARCH_CSR_ECFG);
184 	if (unlikely(args->fn)) {
185 		/* kernel thread */
186 		p->thread.reg03 = childksp;
187 		p->thread.reg23 = (unsigned long)args->fn;
188 		p->thread.reg24 = (unsigned long)args->fn_arg;
189 		p->thread.reg01 = (unsigned long)ret_from_kernel_thread_asm;
190 		p->thread.sched_ra = (unsigned long)ret_from_kernel_thread_asm;
191 		memset(childregs, 0, sizeof(struct pt_regs));
192 		childregs->csr_euen = p->thread.csr_euen;
193 		childregs->csr_crmd = p->thread.csr_crmd;
194 		childregs->csr_prmd = p->thread.csr_prmd;
195 		childregs->csr_ecfg = p->thread.csr_ecfg;
196 		goto out;
197 	}
198 
199 	/* user thread */
200 	*childregs = *regs;
201 	childregs->regs[4] = 0; /* Child gets zero as return value */
202 	if (usp)
203 		childregs->regs[3] = usp;
204 
205 	p->thread.reg03 = (unsigned long) childregs;
206 	p->thread.reg01 = (unsigned long) ret_from_fork_asm;
207 	p->thread.sched_ra = (unsigned long) ret_from_fork_asm;
208 
209 	/*
210 	 * New tasks lose permission to use the fpu. This accelerates context
211 	 * switching for most programs since they don't use the fpu.
212 	 */
213 	childregs->csr_euen = 0;
214 
215 	if (clone_flags & CLONE_SETTLS)
216 		childregs->regs[2] = tls;
217 
218 out:
219 	ptrace_hw_copy_thread(p);
220 	clear_tsk_thread_flag(p, TIF_USEDFPU);
221 	clear_tsk_thread_flag(p, TIF_USEDSIMD);
222 	clear_tsk_thread_flag(p, TIF_USEDLBT);
223 	clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
224 	clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
225 	clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);
226 
227 	return 0;
228 }
229 
230 unsigned long __get_wchan(struct task_struct *task)
231 {
232 	unsigned long pc = 0;
233 	struct unwind_state state;
234 
235 	if (!try_get_task_stack(task))
236 		return 0;
237 
238 	for (unwind_start(&state, task, NULL);
239 	     !unwind_done(&state); unwind_next_frame(&state)) {
240 		pc = unwind_get_return_address(&state);
241 		if (!pc)
242 			break;
243 		if (in_sched_functions(pc))
244 			continue;
245 		break;
246 	}
247 
248 	put_task_stack(task);
249 
250 	return pc;
251 }
252 
253 bool in_irq_stack(unsigned long stack, struct stack_info *info)
254 {
255 	unsigned long nextsp;
256 	unsigned long begin = (unsigned long)this_cpu_read(irq_stack);
257 	unsigned long end = begin + IRQ_STACK_START;
258 
259 	if (stack < begin || stack >= end)
260 		return false;
261 
262 	nextsp = *(unsigned long *)end;
263 	if (nextsp & (SZREG - 1))
264 		return false;
265 
266 	info->begin = begin;
267 	info->end = end;
268 	info->next_sp = nextsp;
269 	info->type = STACK_TYPE_IRQ;
270 
271 	return true;
272 }
273 
274 bool in_task_stack(unsigned long stack, struct task_struct *task,
275 			struct stack_info *info)
276 {
277 	unsigned long begin = (unsigned long)task_stack_page(task);
278 	unsigned long end = begin + THREAD_SIZE;
279 
280 	if (stack < begin || stack >= end)
281 		return false;
282 
283 	info->begin = begin;
284 	info->end = end;
285 	info->next_sp = 0;
286 	info->type = STACK_TYPE_TASK;
287 
288 	return true;
289 }
290 
291 int get_stack_info(unsigned long stack, struct task_struct *task,
292 		   struct stack_info *info)
293 {
294 	task = task ? : current;
295 
296 	if (!stack || stack & (SZREG - 1))
297 		goto unknown;
298 
299 	if (in_task_stack(stack, task, info))
300 		return 0;
301 
302 	if (task != current)
303 		goto unknown;
304 
305 	if (in_irq_stack(stack, info))
306 		return 0;
307 
308 unknown:
309 	info->type = STACK_TYPE_UNKNOWN;
310 	return -EINVAL;
311 }
312 
313 unsigned long stack_top(void)
314 {
315 	unsigned long top = TASK_SIZE & PAGE_MASK;
316 
317 	if (current->thread.vdso) {
318 		/* Space for the VDSO & data page */
319 		top -= PAGE_ALIGN(current->thread.vdso->size);
320 		top -= VVAR_SIZE;
321 
322 		/* Space to randomize the VDSO base */
323 		if (current->flags & PF_RANDOMIZE)
324 			top -= VDSO_RANDOMIZE_SIZE;
325 	}
326 
327 	return top;
328 }
329 
330 /*
331  * Don't forget that the stack pointer must be aligned on a 8 bytes
332  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
333  */
334 unsigned long arch_align_stack(unsigned long sp)
335 {
336 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
337 		sp -= get_random_u32_below(PAGE_SIZE);
338 
339 	return sp & STACK_ALIGN;
340 }
341 
342 static DEFINE_PER_CPU(call_single_data_t, backtrace_csd);
343 static struct cpumask backtrace_csd_busy;
344 
345 static void handle_backtrace(void *info)
346 {
347 	nmi_cpu_backtrace(get_irq_regs());
348 	cpumask_clear_cpu(smp_processor_id(), &backtrace_csd_busy);
349 }
350 
351 static void raise_backtrace(cpumask_t *mask)
352 {
353 	call_single_data_t *csd;
354 	int cpu;
355 
356 	for_each_cpu(cpu, mask) {
357 		/*
358 		 * If we previously sent an IPI to the target CPU & it hasn't
359 		 * cleared its bit in the busy cpumask then it didn't handle
360 		 * our previous IPI & it's not safe for us to reuse the
361 		 * call_single_data_t.
362 		 */
363 		if (cpumask_test_and_set_cpu(cpu, &backtrace_csd_busy)) {
364 			pr_warn("Unable to send backtrace IPI to CPU%u - perhaps it hung?\n",
365 				cpu);
366 			continue;
367 		}
368 
369 		csd = &per_cpu(backtrace_csd, cpu);
370 		csd->func = handle_backtrace;
371 		smp_call_function_single_async(cpu, csd);
372 	}
373 }
374 
375 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
376 {
377 	nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace);
378 }
379 
380 #ifdef CONFIG_64BIT
381 void loongarch_dump_regs64(u64 *uregs, const struct pt_regs *regs)
382 {
383 	unsigned int i;
384 
385 	for (i = LOONGARCH_EF_R1; i <= LOONGARCH_EF_R31; i++) {
386 		uregs[i] = regs->regs[i - LOONGARCH_EF_R0];
387 	}
388 
389 	uregs[LOONGARCH_EF_ORIG_A0] = regs->orig_a0;
390 	uregs[LOONGARCH_EF_CSR_ERA] = regs->csr_era;
391 	uregs[LOONGARCH_EF_CSR_BADV] = regs->csr_badvaddr;
392 	uregs[LOONGARCH_EF_CSR_CRMD] = regs->csr_crmd;
393 	uregs[LOONGARCH_EF_CSR_PRMD] = regs->csr_prmd;
394 	uregs[LOONGARCH_EF_CSR_EUEN] = regs->csr_euen;
395 	uregs[LOONGARCH_EF_CSR_ECFG] = regs->csr_ecfg;
396 	uregs[LOONGARCH_EF_CSR_ESTAT] = regs->csr_estat;
397 }
398 #endif /* CONFIG_64BIT */
399