xref: /linux/arch/um/kernel/process.c (revision 001821b0e79716c4e17c71d8e053a23599a7a508) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2015 Anton Ivanov (aivanov@{brocade.com,kot-begemot.co.uk})
4  * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
5  * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
6  * Copyright 2003 PathScale, Inc.
7  */
8 
9 #include <linux/stddef.h>
10 #include <linux/err.h>
11 #include <linux/hardirq.h>
12 #include <linux/mm.h>
13 #include <linux/module.h>
14 #include <linux/personality.h>
15 #include <linux/proc_fs.h>
16 #include <linux/ptrace.h>
17 #include <linux/random.h>
18 #include <linux/cpu.h>
19 #include <linux/slab.h>
20 #include <linux/sched.h>
21 #include <linux/sched/debug.h>
22 #include <linux/sched/task.h>
23 #include <linux/sched/task_stack.h>
24 #include <linux/seq_file.h>
25 #include <linux/tick.h>
26 #include <linux/threads.h>
27 #include <linux/resume_user_mode.h>
28 #include <asm/current.h>
29 #include <asm/mmu_context.h>
30 #include <asm/switch_to.h>
31 #include <asm/exec.h>
32 #include <linux/uaccess.h>
33 #include <as-layout.h>
34 #include <kern_util.h>
35 #include <os.h>
36 #include <skas.h>
37 #include <registers.h>
38 #include <linux/time-internal.h>
39 #include <linux/elfcore.h>
40 
41 /*
42  * This is a per-cpu array.  A processor only modifies its entry and it only
43  * cares about its entry, so it's OK if another processor is modifying its
44  * entry.
45  */
46 struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { NULL } };
47 
48 void free_stack(unsigned long stack, int order)
49 {
50 	free_pages(stack, order);
51 }
52 
53 unsigned long alloc_stack(int order, int atomic)
54 {
55 	unsigned long page;
56 	gfp_t flags = GFP_KERNEL;
57 
58 	if (atomic)
59 		flags = GFP_ATOMIC;
60 	page = __get_free_pages(flags, order);
61 
62 	return page;
63 }
64 
65 static inline void set_current(struct task_struct *task)
66 {
67 	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task) { task });
68 }
69 
70 struct task_struct *__switch_to(struct task_struct *from, struct task_struct *to)
71 {
72 	to->thread.prev_sched = from;
73 	set_current(to);
74 
75 	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
76 	arch_switch_to(current);
77 
78 	return current->thread.prev_sched;
79 }
80 
81 void interrupt_end(void)
82 {
83 	struct pt_regs *regs = &current->thread.regs;
84 
85 	if (need_resched())
86 		schedule();
87 	if (test_thread_flag(TIF_SIGPENDING) ||
88 	    test_thread_flag(TIF_NOTIFY_SIGNAL))
89 		do_signal(regs);
90 	if (test_thread_flag(TIF_NOTIFY_RESUME))
91 		resume_user_mode_work(regs);
92 }
93 
94 int get_current_pid(void)
95 {
96 	return task_pid_nr(current);
97 }
98 
99 /*
100  * This is called magically, by its address being stuffed in a jmp_buf
101  * and being longjmp-d to.
102  */
103 void new_thread_handler(void)
104 {
105 	int (*fn)(void *);
106 	void *arg;
107 
108 	if (current->thread.prev_sched != NULL)
109 		schedule_tail(current->thread.prev_sched);
110 	current->thread.prev_sched = NULL;
111 
112 	fn = current->thread.request.u.thread.proc;
113 	arg = current->thread.request.u.thread.arg;
114 
115 	/*
116 	 * callback returns only if the kernel thread execs a process
117 	 */
118 	fn(arg);
119 	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
120 }
121 
122 /* Called magically, see new_thread_handler above */
123 static void fork_handler(void)
124 {
125 	force_flush_all();
126 
127 	schedule_tail(current->thread.prev_sched);
128 
129 	/*
130 	 * XXX: if interrupt_end() calls schedule, this call to
131 	 * arch_switch_to isn't needed. We could want to apply this to
132 	 * improve performance. -bb
133 	 */
134 	arch_switch_to(current);
135 
136 	current->thread.prev_sched = NULL;
137 
138 	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
139 }
140 
141 int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
142 {
143 	unsigned long clone_flags = args->flags;
144 	unsigned long sp = args->stack;
145 	unsigned long tls = args->tls;
146 	void (*handler)(void);
147 	int ret = 0;
148 
149 	p->thread = (struct thread_struct) INIT_THREAD;
150 
151 	if (!args->fn) {
152 	  	memcpy(&p->thread.regs.regs, current_pt_regs(),
153 		       sizeof(p->thread.regs.regs));
154 		PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
155 		if (sp != 0)
156 			REGS_SP(p->thread.regs.regs.gp) = sp;
157 
158 		handler = fork_handler;
159 
160 		arch_copy_thread(&current->thread.arch, &p->thread.arch);
161 	} else {
162 		get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
163 		p->thread.request.u.thread.proc = args->fn;
164 		p->thread.request.u.thread.arg = args->fn_arg;
165 		handler = new_thread_handler;
166 	}
167 
168 	new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
169 
170 	if (!args->fn) {
171 		clear_flushed_tls(p);
172 
173 		/*
174 		 * Set a new TLS for the child thread?
175 		 */
176 		if (clone_flags & CLONE_SETTLS)
177 			ret = arch_set_tls(p, tls);
178 	}
179 
180 	return ret;
181 }
182 
183 void initial_thread_cb(void (*proc)(void *), void *arg)
184 {
185 	int save_kmalloc_ok = kmalloc_ok;
186 
187 	kmalloc_ok = 0;
188 	initial_thread_cb_skas(proc, arg);
189 	kmalloc_ok = save_kmalloc_ok;
190 }
191 
192 void um_idle_sleep(void)
193 {
194 	if (time_travel_mode != TT_MODE_OFF)
195 		time_travel_sleep();
196 	else
197 		os_idle_sleep();
198 }
199 
200 void arch_cpu_idle(void)
201 {
202 	um_idle_sleep();
203 }
204 
205 int __uml_cant_sleep(void) {
206 	return in_atomic() || irqs_disabled() || in_interrupt();
207 	/* Is in_interrupt() really needed? */
208 }
209 
210 int user_context(unsigned long sp)
211 {
212 	unsigned long stack;
213 
214 	stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
215 	return stack != (unsigned long) current_thread_info();
216 }
217 
218 extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
219 
220 void do_uml_exitcalls(void)
221 {
222 	exitcall_t *call;
223 
224 	call = &__uml_exitcall_end;
225 	while (--call >= &__uml_exitcall_begin)
226 		(*call)();
227 }
228 
229 char *uml_strdup(const char *string)
230 {
231 	return kstrdup(string, GFP_KERNEL);
232 }
233 EXPORT_SYMBOL(uml_strdup);
234 
235 int copy_from_user_proc(void *to, void __user *from, int size)
236 {
237 	return copy_from_user(to, from, size);
238 }
239 
240 static atomic_t using_sysemu = ATOMIC_INIT(0);
241 int sysemu_supported;
242 
243 static void set_using_sysemu(int value)
244 {
245 	if (value > sysemu_supported)
246 		return;
247 	atomic_set(&using_sysemu, value);
248 }
249 
250 static int get_using_sysemu(void)
251 {
252 	return atomic_read(&using_sysemu);
253 }
254 
255 static int sysemu_proc_show(struct seq_file *m, void *v)
256 {
257 	seq_printf(m, "%d\n", get_using_sysemu());
258 	return 0;
259 }
260 
261 static int sysemu_proc_open(struct inode *inode, struct file *file)
262 {
263 	return single_open(file, sysemu_proc_show, NULL);
264 }
265 
266 static ssize_t sysemu_proc_write(struct file *file, const char __user *buf,
267 				 size_t count, loff_t *pos)
268 {
269 	char tmp[2];
270 
271 	if (copy_from_user(tmp, buf, 1))
272 		return -EFAULT;
273 
274 	if (tmp[0] >= '0' && tmp[0] <= '2')
275 		set_using_sysemu(tmp[0] - '0');
276 	/* We use the first char, but pretend to write everything */
277 	return count;
278 }
279 
280 static const struct proc_ops sysemu_proc_ops = {
281 	.proc_open	= sysemu_proc_open,
282 	.proc_read	= seq_read,
283 	.proc_lseek	= seq_lseek,
284 	.proc_release	= single_release,
285 	.proc_write	= sysemu_proc_write,
286 };
287 
288 static int __init make_proc_sysemu(void)
289 {
290 	struct proc_dir_entry *ent;
291 	if (!sysemu_supported)
292 		return 0;
293 
294 	ent = proc_create("sysemu", 0600, NULL, &sysemu_proc_ops);
295 
296 	if (ent == NULL)
297 	{
298 		printk(KERN_WARNING "Failed to register /proc/sysemu\n");
299 		return 0;
300 	}
301 
302 	return 0;
303 }
304 
305 late_initcall(make_proc_sysemu);
306 
307 int singlestepping(void)
308 {
309 	return test_thread_flag(TIF_SINGLESTEP);
310 }
311 
312 /*
313  * Only x86 and x86_64 have an arch_align_stack().
314  * All other arches have "#define arch_align_stack(x) (x)"
315  * in their asm/exec.h
316  * As this is included in UML from asm-um/system-generic.h,
317  * we can use it to behave as the subarch does.
318  */
319 #ifndef arch_align_stack
320 unsigned long arch_align_stack(unsigned long sp)
321 {
322 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
323 		sp -= get_random_u32_below(8192);
324 	return sp & ~0xf;
325 }
326 #endif
327 
328 unsigned long __get_wchan(struct task_struct *p)
329 {
330 	unsigned long stack_page, sp, ip;
331 	bool seen_sched = 0;
332 
333 	stack_page = (unsigned long) task_stack_page(p);
334 	/* Bail if the process has no kernel stack for some reason */
335 	if (stack_page == 0)
336 		return 0;
337 
338 	sp = p->thread.switch_buf->JB_SP;
339 	/*
340 	 * Bail if the stack pointer is below the bottom of the kernel
341 	 * stack for some reason
342 	 */
343 	if (sp < stack_page)
344 		return 0;
345 
346 	while (sp < stack_page + THREAD_SIZE) {
347 		ip = *((unsigned long *) sp);
348 		if (in_sched_functions(ip))
349 			/* Ignore everything until we're above the scheduler */
350 			seen_sched = 1;
351 		else if (kernel_text_address(ip) && seen_sched)
352 			return ip;
353 
354 		sp += sizeof(unsigned long);
355 	}
356 
357 	return 0;
358 }
359 
360 int elf_core_copy_task_fpregs(struct task_struct *t, elf_fpregset_t *fpu)
361 {
362 	int cpu = current_thread_info()->cpu;
363 
364 	return save_i387_registers(userspace_pid[cpu], (unsigned long *) fpu);
365 }
366 
367