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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 <[email protected]>,
7 * Hartmut Penner <[email protected]>,
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/kprobes.h>
28#include <linux/random.h>
29#include <linux/init_task.h>
30#include <linux/entry-common.h>
31#include <linux/io.h>
32#include <asm/guarded_storage.h>
33#include <asm/access-regs.h>
34#include <asm/switch_to.h>
35#include <asm/cpu_mf.h>
36#include <asm/processor.h>
37#include <asm/ptrace.h>
38#include <asm/exec.h>
39#include <asm/fpu.h>
40#include <asm/irq.h>
41#include <asm/nmi.h>
42#include <asm/smp.h>
43#include <asm/stacktrace.h>
44#include <asm/runtime_instr.h>
45#include <asm/unwind.h>
46#include "entry.h"
47
48void ret_from_fork(void) asm("ret_from_fork");
49
50void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs)
51{
52 int (*func)(void *arg);
53
54 schedule_tail(prev);
55
56 if (!user_mode(regs)) {
57 /* Kernel thread */
58 func = (void *)regs->gprs[9];
59 func((void *)regs->gprs[10]);
60 }
61 clear_pt_regs_flag(regs, PIF_SYSCALL);
62 syscall_exit_to_user_mode(regs);
63}
64
65void flush_thread(void)
66{
67}
68
69void arch_setup_new_exec(void)
70{
71 if (get_lowcore()->current_pid != current->pid) {
72 get_lowcore()->current_pid = current->pid;
73 if (test_facility(40))
74 lpp(&get_lowcore()->lpp);
75 }
76}
77
78void arch_release_task_struct(struct task_struct *tsk)
79{
80 runtime_instr_release(tsk);
81 guarded_storage_release(tsk);
82}
83
84int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
85{
86 save_user_fpu_regs();
87
88 *dst = *src;
89 dst->thread.kfpu_flags = 0;
90
91 /*
92 * Don't transfer over the runtime instrumentation or the guarded
93 * storage control block pointers. These fields are cleared here instead
94 * of in copy_thread() to avoid premature freeing of associated memory
95 * on fork() failure. Wait to clear the RI flag because ->stack still
96 * refers to the source thread.
97 */
98 dst->thread.ri_cb = NULL;
99 dst->thread.gs_cb = NULL;
100 dst->thread.gs_bc_cb = NULL;
101
102 return 0;
103}
104
105int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
106{
107 u64 clone_flags = args->flags;
108 unsigned long new_stackp = args->stack;
109 unsigned long tls = args->tls;
110 struct fake_frame
111 {
112 struct stack_frame sf;
113 struct pt_regs childregs;
114 } *frame;
115
116 frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
117 p->thread.ksp = (unsigned long) frame;
118 /* Save access registers to new thread structure. */
119 save_access_regs(&p->thread.acrs[0]);
120 /* start new process with ar4 pointing to the correct address space */
121 /* Don't copy debug registers */
122 memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
123 memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
124 clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
125 p->thread.per_flags = 0;
126 /* Initialize per thread user and system timer values */
127 p->thread.user_timer = 0;
128 p->thread.guest_timer = 0;
129 p->thread.system_timer = 0;
130 p->thread.hardirq_timer = 0;
131 p->thread.softirq_timer = 0;
132 p->thread.last_break = 1;
133 /*
134 * s390 stores the svc return address in arch_data when calling
135 * sigreturn()/restart_syscall() via vdso. 1 means no valid address
136 * stored.
137 */
138 p->restart_block.arch_data = 1;
139
140 frame->sf.back_chain = 0;
141 frame->sf.gprs[11 - 6] = (unsigned long)&frame->childregs;
142 frame->sf.gprs[12 - 6] = (unsigned long)p;
143 /* new return point is ret_from_fork */
144 frame->sf.gprs[14 - 6] = (unsigned long)ret_from_fork;
145 /* fake return stack for resume(), don't go back to schedule */
146 frame->sf.gprs[15 - 6] = (unsigned long)frame;
147
148 /* Store access registers to kernel stack of new process. */
149 if (unlikely(args->fn)) {
150 /* kernel thread */
151 memset(&frame->childregs, 0, sizeof(struct pt_regs));
152 frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO |
153 PSW_MASK_EXT | PSW_MASK_MCHECK;
154 frame->childregs.gprs[9] = (unsigned long)args->fn;
155 frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
156 frame->childregs.orig_gpr2 = -1;
157 frame->childregs.last_break = 1;
158 return 0;
159 }
160 frame->childregs = *current_pt_regs();
161 frame->childregs.gprs[2] = 0; /* child returns 0 on fork. */
162 frame->childregs.flags = 0;
163 if (new_stackp)
164 frame->childregs.gprs[15] = new_stackp;
165 /*
166 * Clear the runtime instrumentation flag after the above childregs
167 * copy. The CB pointer was already cleared in arch_dup_task_struct().
168 */
169 frame->childregs.psw.mask &= ~PSW_MASK_RI;
170
171 /* Set a new TLS ? */
172 if (clone_flags & CLONE_SETTLS) {
173 p->thread.acrs[0] = (unsigned int)(tls >> 32);
174 p->thread.acrs[1] = (unsigned int)tls;
175 }
176 return 0;
177}
178
179void execve_tail(void)
180{
181 current->thread.ufpu.fpc = 0;
182 fpu_sfpc(0);
183}
184
185struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
186{
187 save_user_fpu_regs();
188 save_kernel_fpu_regs(&prev->thread);
189 save_access_regs(&prev->thread.acrs[0]);
190 save_ri_cb(prev->thread.ri_cb);
191 save_gs_cb(prev->thread.gs_cb);
192 update_cr_regs(next);
193 restore_kernel_fpu_regs(&next->thread);
194 restore_access_regs(&next->thread.acrs[0]);
195 restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);
196 restore_gs_cb(next->thread.gs_cb);
197 return __switch_to_asm(prev, next);
198}
199
200unsigned long __get_wchan(struct task_struct *p)
201{
202 struct unwind_state state;
203 unsigned long ip = 0;
204
205 if (!try_get_task_stack(p))
206 return 0;
207
208 unwind_for_each_frame(&state, p, NULL, 0) {
209 if (state.stack_info.type != STACK_TYPE_TASK) {
210 ip = 0;
211 break;
212 }
213
214 ip = unwind_get_return_address(&state);
215 if (!ip)
216 break;
217
218 if (!in_sched_functions(ip))
219 break;
220 }
221
222 put_task_stack(p);
223 return ip;
224}
225
226unsigned long arch_align_stack(unsigned long sp)
227{
228 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
229 sp -= get_random_u32_below(PAGE_SIZE);
230 return sp & ~0xf;
231}
232
233static inline unsigned long brk_rnd(void)
234{
235 return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT;
236}
237
238unsigned long arch_randomize_brk(struct mm_struct *mm)
239{
240 unsigned long ret;
241
242 ret = PAGE_ALIGN(mm->brk + brk_rnd());
243 return (ret > mm->brk) ? ret : mm->brk;
244}