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(tsk: p, flag: 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(task: p))
218 return 0;
219
220 if (!try_get_task_stack(tsk: 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: &state);
230 if (!ip)
231 break;
232
233 if (!in_sched_functions(ip))
234 break;
235 }
236
237 put_task_stack(tsk: 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

source code of linux/arch/s390/kernel/process.c