process.c

  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 */
 46struct task_struct *cpu_tasks[NR_CPUS] = {
 47	[0 ... NR_CPUS - 1] = &init_task,
 48};
 49EXPORT_SYMBOL(cpu_tasks);
 50
 51void free_stack(unsigned long stack, int order)
 52{
 53	free_pages(stack, order);
 54}
 55
 56unsigned long alloc_stack(int order, int atomic)
 57{
 58	unsigned long page;
 59	gfp_t flags = GFP_KERNEL;
 60
 61	if (atomic)
 62		flags = GFP_ATOMIC;
 63	page = __get_free_pages(flags, order);
 64
 65	return page;
 66}
 67
 68static inline void set_current(struct task_struct *task)
 69{
 70	cpu_tasks[task_thread_info(task)->cpu] = task;
 71}
 72
 73struct task_struct *__switch_to(struct task_struct *from, struct task_struct *to)
 74{
 75	to->thread.prev_sched = from;
 76	set_current(to);
 77
 78	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
 79	arch_switch_to(current);
 80
 81	return current->thread.prev_sched;
 82}
 83
 84void interrupt_end(void)
 85{
 86	struct pt_regs *regs = &current->thread.regs;
 87	unsigned long thread_flags;
 88
 89	thread_flags = read_thread_flags();
 90	while (thread_flags & _TIF_WORK_MASK) {
 91		if (thread_flags & _TIF_NEED_RESCHED)
 92			schedule();
 93		if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
 94			do_signal(regs);
 95		if (thread_flags & _TIF_NOTIFY_RESUME)
 96			resume_user_mode_work(regs);
 97		thread_flags = read_thread_flags();
 98	}
 99}
100
101int get_current_pid(void)
102{
103	return task_pid_nr(current);
104}
105
106/*
107 * This is called magically, by its address being stuffed in a jmp_buf
108 * and being longjmp-d to.
109 */
110void new_thread_handler(void)
111{
112	int (*fn)(void *);
113	void *arg;
114
115	if (current->thread.prev_sched != NULL)
116		schedule_tail(current->thread.prev_sched);
117	current->thread.prev_sched = NULL;
118
119	fn = current->thread.request.thread.proc;
120	arg = current->thread.request.thread.arg;
121
122	/*
123	 * callback returns only if the kernel thread execs a process
124	 */
125	fn(arg);
126	userspace(&current->thread.regs.regs);
127}
128
129/* Called magically, see new_thread_handler above */
130static void fork_handler(void)
131{
132	schedule_tail(current->thread.prev_sched);
133
134	/*
135	 * XXX: if interrupt_end() calls schedule, this call to
136	 * arch_switch_to isn't needed. We could want to apply this to
137	 * improve performance. -bb
138	 */
139	arch_switch_to(current);
140
141	current->thread.prev_sched = NULL;
142
143	userspace(&current->thread.regs.regs);
144}
145
146int copy_thread(struct task_struct * p, const struct kernel_clone_args *args)
147{
148	u64 clone_flags = args->flags;
149	unsigned long sp = args->stack;
150	unsigned long tls = args->tls;
151	void (*handler)(void);
152	int ret = 0;
153
154	p->thread = (struct thread_struct) INIT_THREAD;
155
156	if (!args->fn) {
157	  	memcpy(&p->thread.regs.regs, current_pt_regs(),
158		       sizeof(p->thread.regs.regs));
159		PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
160		if (sp != 0)
161			REGS_SP(p->thread.regs.regs.gp) = sp;
162
163		handler = fork_handler;
164
165		arch_copy_thread(&current->thread.arch, &p->thread.arch);
166	} else {
167		get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
168		p->thread.request.thread.proc = args->fn;
169		p->thread.request.thread.arg = args->fn_arg;
170		handler = new_thread_handler;
171	}
172
173	new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
174
175	if (!args->fn) {
176		clear_flushed_tls(p);
177
178		/*
179		 * Set a new TLS for the child thread?
180		 */
181		if (clone_flags & CLONE_SETTLS)
182			ret = arch_set_tls(p, tls);
183	}
184
185	return ret;
186}
187
188void initial_thread_cb(void (*proc)(void *), void *arg)
189{
190	initial_thread_cb_skas(proc, arg);
191}
192
193int arch_dup_task_struct(struct task_struct *dst,
194			 struct task_struct *src)
195{
196	/* init_task is not dynamically sized (missing FPU state) */
197	if (unlikely(src == &init_task)) {
198		memcpy(dst, src, sizeof(init_task));
199		memset((void *)dst + sizeof(init_task), 0,
200		       arch_task_struct_size - sizeof(init_task));
201	} else {
202		memcpy(dst, src, arch_task_struct_size);
203	}
204
205	return 0;
206}
207
208void um_idle_sleep(void)
209{
210	if (time_travel_mode != TT_MODE_OFF)
211		time_travel_sleep();
212	else
213		os_idle_sleep();
214}
215
216void arch_cpu_idle(void)
217{
218	um_idle_sleep();
219}
220
221void arch_cpu_idle_prepare(void)
222{
223	os_idle_prepare();
224}
225
226int __uml_cant_sleep(void) {
227	return in_atomic() || irqs_disabled() || in_interrupt();
228	/* Is in_interrupt() really needed? */
229}
230
231int uml_need_resched(void)
232{
233	return need_resched();
234}
235
236extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
237
238void do_uml_exitcalls(void)
239{
240	exitcall_t *call;
241
242	call = &__uml_exitcall_end;
243	while (--call >= &__uml_exitcall_begin)
244		(*call)();
245}
246
247char *uml_strdup(const char *string)
248{
249	return kstrdup(string, GFP_KERNEL);
250}
251EXPORT_SYMBOL(uml_strdup);
252
253int copy_from_user_proc(void *to, void __user *from, int size)
254{
255	return copy_from_user(to, from, size);
256}
257
258int singlestepping(void)
259{
260	return test_thread_flag(TIF_SINGLESTEP);
261}
262
263/*
264 * Only x86 and x86_64 have an arch_align_stack().
265 * All other arches have "#define arch_align_stack(x) (x)"
266 * in their asm/exec.h
267 * As this is included in UML from asm-um/system-generic.h,
268 * we can use it to behave as the subarch does.
269 */
270#ifndef arch_align_stack
271unsigned long arch_align_stack(unsigned long sp)
272{
273	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
274		sp -= get_random_u32_below(8192);
275	return sp & ~0xf;
276}
277#endif
278
279unsigned long __get_wchan(struct task_struct *p)
280{
281	unsigned long stack_page, sp, ip;
282	bool seen_sched = 0;
283
284	stack_page = (unsigned long) task_stack_page(p);
285	/* Bail if the process has no kernel stack for some reason */
286	if (stack_page == 0)
287		return 0;
288
289	sp = p->thread.switch_buf->JB_SP;
290	/*
291	 * Bail if the stack pointer is below the bottom of the kernel
292	 * stack for some reason
293	 */
294	if (sp < stack_page)
295		return 0;
296
297	while (sp < stack_page + THREAD_SIZE) {
298		ip = *((unsigned long *) sp);
299		if (in_sched_functions(ip))
300			/* Ignore everything until we're above the scheduler */
301			seen_sched = 1;
302		else if (kernel_text_address(ip) && seen_sched)
303			return ip;
304
305		sp += sizeof(unsigned long);
306	}
307
308	return 0;
309}