1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
4  *  Chen Liqin <liqin.chen@sunplusct.com>
5  *  Lennox Wu <lennox.wu@sunplusct.com>
6  * Copyright (C) 2012 Regents of the University of California
7  * Copyright (C) 2017 SiFive
8  */
9 
10 #include <linux/bitfield.h>
11 #include <linux/cpu.h>
12 #include <linux/kernel.h>
13 #include <linux/sched.h>
14 #include <linux/sched/debug.h>
15 #include <linux/sched/task_stack.h>
16 #include <linux/tick.h>
17 #include <linux/ptrace.h>
18 #include <linux/uaccess.h>
19 #include <linux/personality.h>
20 #include <linux/entry-common.h>
21 
22 #include <asm/asm-prototypes.h>
23 #include <asm/unistd.h>
24 #include <asm/processor.h>
25 #include <asm/csr.h>
26 #include <asm/stacktrace.h>
27 #include <asm/string.h>
28 #include <asm/switch_to.h>
29 #include <asm/thread_info.h>
30 #include <asm/cpuidle.h>
31 #include <asm/vector.h>
32 #include <asm/cpufeature.h>
33 #include <asm/exec.h>
34 
35 #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
36 #include <linux/stackprotector.h>
37 unsigned long __stack_chk_guard __read_mostly;
38 EXPORT_SYMBOL(__stack_chk_guard);
39 #endif
40 
41 extern asmlinkage void ret_from_fork_kernel_asm(void);
42 extern asmlinkage void ret_from_fork_user_asm(void);
43 
44 void noinstr arch_cpu_idle(void)
45 {
46 	cpu_do_idle();
47 }
48 
49 int set_unalign_ctl(struct task_struct *tsk, unsigned int val)
50 {
51 	if (!unaligned_ctl_available())
52 		return -EINVAL;
53 
54 	tsk->thread.align_ctl = val;
55 	return 0;
56 }
57 
58 int get_unalign_ctl(struct task_struct *tsk, unsigned long adr)
59 {
60 	if (!unaligned_ctl_available())
61 		return -EINVAL;
62 
63 	return put_user(tsk->thread.align_ctl, (unsigned int __user *)adr);
64 }
65 
66 void __show_regs(struct pt_regs *regs)
67 {
68 	show_regs_print_info(KERN_DEFAULT);
69 
70 	if (!user_mode(regs)) {
71 		pr_cont("epc : %pS\n", (void *)regs->epc);
72 		pr_cont(" ra : %pS\n", (void *)regs->ra);
73 	}
74 
75 	pr_cont("epc : " REG_FMT " ra : " REG_FMT " sp : " REG_FMT "\n",
76 		regs->epc, regs->ra, regs->sp);
77 	pr_cont(" gp : " REG_FMT " tp : " REG_FMT " t0 : " REG_FMT "\n",
78 		regs->gp, regs->tp, regs->t0);
79 	pr_cont(" t1 : " REG_FMT " t2 : " REG_FMT " s0 : " REG_FMT "\n",
80 		regs->t1, regs->t2, regs->s0);
81 	pr_cont(" s1 : " REG_FMT " a0 : " REG_FMT " a1 : " REG_FMT "\n",
82 		regs->s1, regs->a0, regs->a1);
83 	pr_cont(" a2 : " REG_FMT " a3 : " REG_FMT " a4 : " REG_FMT "\n",
84 		regs->a2, regs->a3, regs->a4);
85 	pr_cont(" a5 : " REG_FMT " a6 : " REG_FMT " a7 : " REG_FMT "\n",
86 		regs->a5, regs->a6, regs->a7);
87 	pr_cont(" s2 : " REG_FMT " s3 : " REG_FMT " s4 : " REG_FMT "\n",
88 		regs->s2, regs->s3, regs->s4);
89 	pr_cont(" s5 : " REG_FMT " s6 : " REG_FMT " s7 : " REG_FMT "\n",
90 		regs->s5, regs->s6, regs->s7);
91 	pr_cont(" s8 : " REG_FMT " s9 : " REG_FMT " s10: " REG_FMT "\n",
92 		regs->s8, regs->s9, regs->s10);
93 	pr_cont(" s11: " REG_FMT " t3 : " REG_FMT " t4 : " REG_FMT "\n",
94 		regs->s11, regs->t3, regs->t4);
95 	pr_cont(" t5 : " REG_FMT " t6 : " REG_FMT "\n",
96 		regs->t5, regs->t6);
97 
98 	pr_cont("status: " REG_FMT " badaddr: " REG_FMT " cause: " REG_FMT "\n",
99 		regs->status, regs->badaddr, regs->cause);
100 }
101 void show_regs(struct pt_regs *regs)
102 {
103 	__show_regs(regs);
104 	if (!user_mode(regs))
105 		dump_backtrace(regs, NULL, KERN_DEFAULT);
106 }
107 
108 unsigned long arch_align_stack(unsigned long sp)
109 {
110 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
111 		sp -= get_random_u32_below(PAGE_SIZE);
112 	return sp & ~0xf;
113 }
114 
115 #ifdef CONFIG_COMPAT
116 static bool compat_mode_supported __read_mostly;
117 
118 bool compat_elf_check_arch(Elf32_Ehdr *hdr)
119 {
120 	return compat_mode_supported &&
121 	       hdr->e_machine == EM_RISCV &&
122 	       hdr->e_ident[EI_CLASS] == ELFCLASS32;
123 }
124 
125 static int __init compat_mode_detect(void)
126 {
127 	unsigned long tmp = csr_read(CSR_STATUS);
128 
129 	csr_write(CSR_STATUS, (tmp & ~SR_UXL) | SR_UXL_32);
130 	compat_mode_supported =
131 			(csr_read(CSR_STATUS) & SR_UXL) == SR_UXL_32;
132 
133 	csr_write(CSR_STATUS, tmp);
134 
135 	pr_info("riscv: ELF compat mode %s",
136 			compat_mode_supported ? "supported" : "unsupported");
137 
138 	return 0;
139 }
140 early_initcall(compat_mode_detect);
141 #endif
142 
143 void start_thread(struct pt_regs *regs, unsigned long pc,
144 	unsigned long sp)
145 {
146 	regs->status = SR_PIE;
147 	if (has_fpu()) {
148 		regs->status |= SR_FS_INITIAL;
149 		/*
150 		 * Restore the initial value to the FP register
151 		 * before starting the user program.
152 		 */
153 		fstate_restore(current, regs);
154 	}
155 	regs->epc = pc;
156 	regs->sp = sp;
157 
158 #ifdef CONFIG_64BIT
159 	regs->status &= ~SR_UXL;
160 
161 	if (is_compat_task())
162 		regs->status |= SR_UXL_32;
163 	else
164 		regs->status |= SR_UXL_64;
165 #endif
166 }
167 
168 void flush_thread(void)
169 {
170 #ifdef CONFIG_FPU
171 	/*
172 	 * Reset FPU state and context
173 	 *	frm: round to nearest, ties to even (IEEE default)
174 	 *	fflags: accrued exceptions cleared
175 	 */
176 	fstate_off(current, task_pt_regs(current));
177 	memset(&current->thread.fstate, 0, sizeof(current->thread.fstate));
178 #endif
179 #ifdef CONFIG_RISCV_ISA_V
180 	/* Reset vector state */
181 	riscv_v_vstate_ctrl_init(current);
182 	riscv_v_vstate_off(task_pt_regs(current));
183 	kfree(current->thread.vstate.datap);
184 	memset(&current->thread.vstate, 0, sizeof(struct __riscv_v_ext_state));
185 	clear_tsk_thread_flag(current, TIF_RISCV_V_DEFER_RESTORE);
186 #endif
187 #ifdef CONFIG_RISCV_ISA_SUPM
188 	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
189 		envcfg_update_bits(current, ENVCFG_PMM, ENVCFG_PMM_PMLEN_0);
190 #endif
191 }
192 
193 void arch_release_task_struct(struct task_struct *tsk)
194 {
195 	/* Free the vector context of datap. */
196 	if (has_vector() || has_xtheadvector())
197 		riscv_v_thread_free(tsk);
198 }
199 
200 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
201 {
202 	fstate_save(src, task_pt_regs(src));
203 	*dst = *src;
204 	/* clear entire V context, including datap for a new task */
205 	memset(&dst->thread.vstate, 0, sizeof(struct __riscv_v_ext_state));
206 	memset(&dst->thread.kernel_vstate, 0, sizeof(struct __riscv_v_ext_state));
207 	clear_tsk_thread_flag(dst, TIF_RISCV_V_DEFER_RESTORE);
208 
209 	return 0;
210 }
211 
212 asmlinkage void ret_from_fork_kernel(void *fn_arg, int (*fn)(void *), struct pt_regs *regs)
213 {
214 	fn(fn_arg);
215 
216 	syscall_exit_to_user_mode(regs);
217 }
218 
219 asmlinkage void ret_from_fork_user(struct pt_regs *regs)
220 {
221 	syscall_exit_to_user_mode(regs);
222 }
223 
224 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
225 {
226 	unsigned long clone_flags = args->flags;
227 	unsigned long usp = args->stack;
228 	unsigned long tls = args->tls;
229 	struct pt_regs *childregs = task_pt_regs(p);
230 
231 	/* Ensure all threads in this mm have the same pointer masking mode. */
232 	if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM) && p->mm && (clone_flags & CLONE_VM))
233 		set_bit(MM_CONTEXT_LOCK_PMLEN, &p->mm->context.flags);
234 
235 	memset(&p->thread.s, 0, sizeof(p->thread.s));
236 
237 	/* p->thread holds context to be restored by __switch_to() */
238 	if (unlikely(args->fn)) {
239 		/* Kernel thread */
240 		memset(childregs, 0, sizeof(struct pt_regs));
241 		/* Supervisor/Machine, irqs on: */
242 		childregs->status = SR_PP | SR_PIE;
243 
244 		p->thread.s[0] = (unsigned long)args->fn;
245 		p->thread.s[1] = (unsigned long)args->fn_arg;
246 		p->thread.ra = (unsigned long)ret_from_fork_kernel_asm;
247 	} else {
248 		*childregs = *(current_pt_regs());
249 		/* Turn off status.VS */
250 		riscv_v_vstate_off(childregs);
251 		if (usp) /* User fork */
252 			childregs->sp = usp;
253 		if (clone_flags & CLONE_SETTLS)
254 			childregs->tp = tls;
255 		childregs->a0 = 0; /* Return value of fork() */
256 		p->thread.ra = (unsigned long)ret_from_fork_user_asm;
257 	}
258 	p->thread.riscv_v_flags = 0;
259 	if (has_vector() || has_xtheadvector())
260 		riscv_v_thread_alloc(p);
261 	p->thread.sp = (unsigned long)childregs; /* kernel sp */
262 	return 0;
263 }
264 
265 void __init arch_task_cache_init(void)
266 {
267 	riscv_v_setup_ctx_cache();
268 }
269 
270 #ifdef CONFIG_RISCV_ISA_SUPM
271 enum {
272 	PMLEN_0 = 0,
273 	PMLEN_7 = 7,
274 	PMLEN_16 = 16,
275 };
276 
277 static bool have_user_pmlen_7;
278 static bool have_user_pmlen_16;
279 
280 /*
281  * Control the relaxed ABI allowing tagged user addresses into the kernel.
282  */
283 static unsigned int tagged_addr_disabled;
284 
285 long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
286 {
287 	unsigned long valid_mask = PR_PMLEN_MASK | PR_TAGGED_ADDR_ENABLE;
288 	struct thread_info *ti = task_thread_info(task);
289 	struct mm_struct *mm = task->mm;
290 	unsigned long pmm;
291 	u8 pmlen;
292 
293 	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
294 		return -EINVAL;
295 
296 	if (is_compat_thread(ti))
297 		return -EINVAL;
298 
299 	if (arg & ~valid_mask)
300 		return -EINVAL;
301 
302 	/*
303 	 * Prefer the smallest PMLEN that satisfies the user's request,
304 	 * in case choosing a larger PMLEN has a performance impact.
305 	 */
306 	pmlen = FIELD_GET(PR_PMLEN_MASK, arg);
307 	if (pmlen == PMLEN_0) {
308 		pmm = ENVCFG_PMM_PMLEN_0;
309 	} else if (pmlen <= PMLEN_7 && have_user_pmlen_7) {
310 		pmlen = PMLEN_7;
311 		pmm = ENVCFG_PMM_PMLEN_7;
312 	} else if (pmlen <= PMLEN_16 && have_user_pmlen_16) {
313 		pmlen = PMLEN_16;
314 		pmm = ENVCFG_PMM_PMLEN_16;
315 	} else {
316 		return -EINVAL;
317 	}
318 
319 	/*
320 	 * Do not allow the enabling of the tagged address ABI if globally
321 	 * disabled via sysctl abi.tagged_addr_disabled, if pointer masking
322 	 * is disabled for userspace.
323 	 */
324 	if (arg & PR_TAGGED_ADDR_ENABLE && (tagged_addr_disabled || !pmlen))
325 		return -EINVAL;
326 
327 	if (!(arg & PR_TAGGED_ADDR_ENABLE))
328 		pmlen = PMLEN_0;
329 
330 	if (mmap_write_lock_killable(mm))
331 		return -EINTR;
332 
333 	if (test_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags) && mm->context.pmlen != pmlen) {
334 		mmap_write_unlock(mm);
335 		return -EBUSY;
336 	}
337 
338 	envcfg_update_bits(task, ENVCFG_PMM, pmm);
339 	mm->context.pmlen = pmlen;
340 
341 	mmap_write_unlock(mm);
342 
343 	return 0;
344 }
345 
346 long get_tagged_addr_ctrl(struct task_struct *task)
347 {
348 	struct thread_info *ti = task_thread_info(task);
349 	long ret = 0;
350 
351 	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
352 		return -EINVAL;
353 
354 	if (is_compat_thread(ti))
355 		return -EINVAL;
356 
357 	/*
358 	 * The mm context's pmlen is set only when the tagged address ABI is
359 	 * enabled, so the effective PMLEN must be extracted from envcfg.PMM.
360 	 */
361 	switch (task->thread.envcfg & ENVCFG_PMM) {
362 	case ENVCFG_PMM_PMLEN_7:
363 		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_7);
364 		break;
365 	case ENVCFG_PMM_PMLEN_16:
366 		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_16);
367 		break;
368 	}
369 
370 	if (task->mm->context.pmlen)
371 		ret |= PR_TAGGED_ADDR_ENABLE;
372 
373 	return ret;
374 }
375 
376 static bool try_to_set_pmm(unsigned long value)
377 {
378 	csr_set(CSR_ENVCFG, value);
379 	return (csr_read_clear(CSR_ENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
380 }
381 
382 /*
383  * Global sysctl to disable the tagged user addresses support. This control
384  * only prevents the tagged address ABI enabling via prctl() and does not
385  * disable it for tasks that already opted in to the relaxed ABI.
386  */
387 
388 static const struct ctl_table tagged_addr_sysctl_table[] = {
389 	{
390 		.procname	= "tagged_addr_disabled",
391 		.mode		= 0644,
392 		.data		= &tagged_addr_disabled,
393 		.maxlen		= sizeof(int),
394 		.proc_handler	= proc_dointvec_minmax,
395 		.extra1		= SYSCTL_ZERO,
396 		.extra2		= SYSCTL_ONE,
397 	},
398 };
399 
400 static int __init tagged_addr_init(void)
401 {
402 	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
403 		return 0;
404 
405 	/*
406 	 * envcfg.PMM is a WARL field. Detect which values are supported.
407 	 * Assume the supported PMLEN values are the same on all harts.
408 	 */
409 	csr_clear(CSR_ENVCFG, ENVCFG_PMM);
410 	have_user_pmlen_7 = try_to_set_pmm(ENVCFG_PMM_PMLEN_7);
411 	have_user_pmlen_16 = try_to_set_pmm(ENVCFG_PMM_PMLEN_16);
412 
413 	if (!register_sysctl("abi", tagged_addr_sysctl_table))
414 		return -EINVAL;
415 
416 	return 0;
417 }
418 core_initcall(tagged_addr_init);
419 #endif	/* CONFIG_RISCV_ISA_SUPM */
420