process.c

  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>
 37unsigned long __stack_chk_guard __read_mostly;
 38EXPORT_SYMBOL(__stack_chk_guard);
 39#endif
 40
 41extern asmlinkage void ret_from_fork_kernel_asm(void);
 42extern asmlinkage void ret_from_fork_user_asm(void);
 43
 44void noinstr arch_cpu_idle(void)
 45{
 46	cpu_do_idle();
 47}
 48
 49int 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
 58int 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
 66void __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}
101void 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
108unsigned 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
116static bool compat_mode_supported __read_mostly;
117
118bool 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
125static 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}
140early_initcall(compat_mode_detect);
141#endif
142
143void 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
168void 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
193void 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
200int 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
212asmlinkage 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
219asmlinkage void ret_from_fork_user(struct pt_regs *regs)
220{
221	syscall_exit_to_user_mode(regs);
222}
223
224int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
225{
226	u64 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
265void __init arch_task_cache_init(void)
266{
267	riscv_v_setup_ctx_cache();
268}
269
270#ifdef CONFIG_RISCV_ISA_SUPM
271enum {
272	PMLEN_0 = 0,
273	PMLEN_7 = 7,
274	PMLEN_16 = 16,
275};
276
277static bool have_user_pmlen_7;
278static bool have_user_pmlen_16;
279
280/*
281 * Control the relaxed ABI allowing tagged user addresses into the kernel.
282 */
283static unsigned int tagged_addr_disabled;
284
285long 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		pmm = ENVCFG_PMM_PMLEN_0;
330	}
331
332	if (mmap_write_lock_killable(mm))
333		return -EINTR;
334
335	if (test_bit(MM_CONTEXT_LOCK_PMLEN, &mm->context.flags) && mm->context.pmlen != pmlen) {
336		mmap_write_unlock(mm);
337		return -EBUSY;
338	}
339
340	envcfg_update_bits(task, ENVCFG_PMM, pmm);
341	mm->context.pmlen = pmlen;
342
343	mmap_write_unlock(mm);
344
345	return 0;
346}
347
348long get_tagged_addr_ctrl(struct task_struct *task)
349{
350	struct thread_info *ti = task_thread_info(task);
351	long ret = 0;
352
353	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
354		return -EINVAL;
355
356	if (is_compat_thread(ti))
357		return -EINVAL;
358
359	/*
360	 * The mm context's pmlen is set only when the tagged address ABI is
361	 * enabled, so the effective PMLEN must be extracted from envcfg.PMM.
362	 */
363	switch (task->thread.envcfg & ENVCFG_PMM) {
364	case ENVCFG_PMM_PMLEN_7:
365		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_7);
366		break;
367	case ENVCFG_PMM_PMLEN_16:
368		ret = FIELD_PREP(PR_PMLEN_MASK, PMLEN_16);
369		break;
370	}
371
372	if (task->mm->context.pmlen)
373		ret |= PR_TAGGED_ADDR_ENABLE;
374
375	return ret;
376}
377
378static bool try_to_set_pmm(unsigned long value)
379{
380	csr_set(CSR_ENVCFG, value);
381	return (csr_read_clear(CSR_ENVCFG, ENVCFG_PMM) & ENVCFG_PMM) == value;
382}
383
384/*
385 * Global sysctl to disable the tagged user addresses support. This control
386 * only prevents the tagged address ABI enabling via prctl() and does not
387 * disable it for tasks that already opted in to the relaxed ABI.
388 */
389
390static const struct ctl_table tagged_addr_sysctl_table[] = {
391	{
392		.procname	= "tagged_addr_disabled",
393		.mode		= 0644,
394		.data		= &tagged_addr_disabled,
395		.maxlen		= sizeof(int),
396		.proc_handler	= proc_dointvec_minmax,
397		.extra1		= SYSCTL_ZERO,
398		.extra2		= SYSCTL_ONE,
399	},
400};
401
402static int __init tagged_addr_init(void)
403{
404	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
405		return 0;
406
407	/*
408	 * envcfg.PMM is a WARL field. Detect which values are supported.
409	 * Assume the supported PMLEN values are the same on all harts.
410	 */
411	csr_clear(CSR_ENVCFG, ENVCFG_PMM);
412	have_user_pmlen_7 = try_to_set_pmm(ENVCFG_PMM_PMLEN_7);
413	have_user_pmlen_16 = try_to_set_pmm(ENVCFG_PMM_PMLEN_16);
414
415	if (!register_sysctl("abi", tagged_addr_sysctl_table))
416		return -EINVAL;
417
418	return 0;
419}
420core_initcall(tagged_addr_init);
421#endif	/* CONFIG_RISCV_ISA_SUPM */