1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This file handles the architecture dependent parts of process handling.
4 *
5 *    Copyright IBM Corp. 1999, 2009
6 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
7 *		 Hartmut Penner <hp@de.ibm.com>,
8 *		 Denis Joseph Barrow,
9 */
10
11#include <linux/elf-randomize.h>
12#include <linux/compiler.h>
13#include <linux/cpu.h>
14#include <linux/sched.h>
15#include <linux/sched/debug.h>
16#include <linux/sched/task.h>
17#include <linux/sched/task_stack.h>
18#include <linux/kernel.h>
19#include <linux/mm.h>
20#include <linux/elfcore.h>
21#include <linux/smp.h>
22#include <linux/slab.h>
23#include <linux/interrupt.h>
24#include <linux/tick.h>
25#include <linux/personality.h>
26#include <linux/syscalls.h>
27#include <linux/compat.h>
28#include <linux/kprobes.h>
29#include <linux/random.h>
30#include <linux/export.h>
31#include <linux/init_task.h>
32#include <linux/entry-common.h>
33#include <linux/io.h>
34#include <asm/guarded_storage.h>
35#include <asm/access-regs.h>
36#include <asm/switch_to.h>
37#include <asm/cpu_mf.h>
38#include <asm/processor.h>
39#include <asm/ptrace.h>
40#include <asm/vtimer.h>
41#include <asm/exec.h>
42#include <asm/fpu.h>
43#include <asm/irq.h>
44#include <asm/nmi.h>
45#include <asm/smp.h>
46#include <asm/stacktrace.h>
47#include <asm/runtime_instr.h>
48#include <asm/unwind.h>
49#include "entry.h"
50
51void ret_from_fork(void) asm("ret_from_fork");
52
53void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs)
54{
55	void (*func)(void *arg);
56
57	schedule_tail(prev);
58
59	if (!user_mode(regs)) {
60		/* Kernel thread */
61		func = (void *)regs->gprs[9];
62		func((void *)regs->gprs[10]);
63	}
64	clear_pt_regs_flag(regs, PIF_SYSCALL);
65	syscall_exit_to_user_mode(regs);
66}
67
68void flush_thread(void)
69{
70}
71
72void arch_setup_new_exec(void)
73{
74	if (S390_lowcore.current_pid != current->pid) {
75		S390_lowcore.current_pid = current->pid;
76		if (test_facility(40))
77			lpp(&S390_lowcore.lpp);
78	}
79}
80
81void arch_release_task_struct(struct task_struct *tsk)
82{
83	runtime_instr_release(tsk);
84	guarded_storage_release(tsk);
85}
86
87int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
88{
89	/*
90	 * Save the floating-point or vector register state of the current
91	 * task and set the TIF_FPU flag to lazy restore the FPU register
92	 * state when returning to user space.
93	 */
94	save_user_fpu_regs();
95
96	*dst = *src;
97	dst->thread.kfpu_flags = 0;
98
99	/*
100	 * Don't transfer over the runtime instrumentation or the guarded
101	 * storage control block pointers. These fields are cleared here instead
102	 * of in copy_thread() to avoid premature freeing of associated memory
103	 * on fork() failure. Wait to clear the RI flag because ->stack still
104	 * refers to the source thread.
105	 */
106	dst->thread.ri_cb = NULL;
107	dst->thread.gs_cb = NULL;
108	dst->thread.gs_bc_cb = NULL;
109
110	return 0;
111}
112
113int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
114{
115	unsigned long clone_flags = args->flags;
116	unsigned long new_stackp = args->stack;
117	unsigned long tls = args->tls;
118	struct fake_frame
119	{
120		struct stack_frame sf;
121		struct pt_regs childregs;
122	} *frame;
123
124	frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
125	p->thread.ksp = (unsigned long) frame;
126	/* Save access registers to new thread structure. */
127	save_access_regs(&p->thread.acrs[0]);
128	/* start new process with ar4 pointing to the correct address space */
129	/* Don't copy debug registers */
130	memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
131	memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
132	clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
133	p->thread.per_flags = 0;
134	/* Initialize per thread user and system timer values */
135	p->thread.user_timer = 0;
136	p->thread.guest_timer = 0;
137	p->thread.system_timer = 0;
138	p->thread.hardirq_timer = 0;
139	p->thread.softirq_timer = 0;
140	p->thread.last_break = 1;
141
142	frame->sf.back_chain = 0;
143	frame->sf.gprs[11 - 6] = (unsigned long)&frame->childregs;
144	frame->sf.gprs[12 - 6] = (unsigned long)p;
145	/* new return point is ret_from_fork */
146	frame->sf.gprs[14 - 6] = (unsigned long)ret_from_fork;
147	/* fake return stack for resume(), don't go back to schedule */
148	frame->sf.gprs[15 - 6] = (unsigned long)frame;
149
150	/* Store access registers to kernel stack of new process. */
151	if (unlikely(args->fn)) {
152		/* kernel thread */
153		memset(&frame->childregs, 0, sizeof(struct pt_regs));
154		frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO |
155					    PSW_MASK_EXT | PSW_MASK_MCHECK;
156		frame->childregs.gprs[9] = (unsigned long)args->fn;
157		frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
158		frame->childregs.orig_gpr2 = -1;
159		frame->childregs.last_break = 1;
160		return 0;
161	}
162	frame->childregs = *current_pt_regs();
163	frame->childregs.gprs[2] = 0;	/* child returns 0 on fork. */
164	frame->childregs.flags = 0;
165	if (new_stackp)
166		frame->childregs.gprs[15] = new_stackp;
167	/*
168	 * Clear the runtime instrumentation flag after the above childregs
169	 * copy. The CB pointer was already cleared in arch_dup_task_struct().
170	 */
171	frame->childregs.psw.mask &= ~PSW_MASK_RI;
172
173	/* Set a new TLS ?  */
174	if (clone_flags & CLONE_SETTLS) {
175		if (is_compat_task()) {
176			p->thread.acrs[0] = (unsigned int)tls;
177		} else {
178			p->thread.acrs[0] = (unsigned int)(tls >> 32);
179			p->thread.acrs[1] = (unsigned int)tls;
180		}
181	}
182	/*
183	 * s390 stores the svc return address in arch_data when calling
184	 * sigreturn()/restart_syscall() via vdso. 1 means no valid address
185	 * stored.
186	 */
187	p->restart_block.arch_data = 1;
188	return 0;
189}
190
191void execve_tail(void)
192{
193	current->thread.ufpu.fpc = 0;
194	fpu_sfpc(0);
195}
196
197struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
198{
199	save_user_fpu_regs();
200	save_kernel_fpu_regs(&prev->thread);
201	save_access_regs(&prev->thread.acrs[0]);
202	save_ri_cb(prev->thread.ri_cb);
203	save_gs_cb(prev->thread.gs_cb);
204	update_cr_regs(next);
205	restore_kernel_fpu_regs(&next->thread);
206	restore_access_regs(&next->thread.acrs[0]);
207	restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);
208	restore_gs_cb(next->thread.gs_cb);
209	return __switch_to_asm(prev, next);
210}
211
212unsigned long __get_wchan(struct task_struct *p)
213{
214	struct unwind_state state;
215	unsigned long ip = 0;
216
217	if (!task_stack_page(p))
218		return 0;
219
220	if (!try_get_task_stack(p))
221		return 0;
222
223	unwind_for_each_frame(&state, p, NULL, 0) {
224		if (state.stack_info.type != STACK_TYPE_TASK) {
225			ip = 0;
226			break;
227		}
228
229		ip = unwind_get_return_address(&state);
230		if (!ip)
231			break;
232
233		if (!in_sched_functions(ip))
234			break;
235	}
236
237	put_task_stack(p);
238	return ip;
239}
240
241unsigned long arch_align_stack(unsigned long sp)
242{
243	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
244		sp -= get_random_u32_below(PAGE_SIZE);
245	return sp & ~0xf;
246}
247
248static inline unsigned long brk_rnd(void)
249{
250	return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT;
251}
252
253unsigned long arch_randomize_brk(struct mm_struct *mm)
254{
255	unsigned long ret;
256
257	ret = PAGE_ALIGN(mm->brk + brk_rnd());
258	return (ret > mm->brk) ? ret : mm->brk;
259}
260