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 <asm/cpu_mf.h>
34 #include <asm/io.h>
35 #include <asm/processor.h>
36 #include <asm/vtimer.h>
37 #include <asm/exec.h>
38 #include <asm/irq.h>
39 #include <asm/nmi.h>
40 #include <asm/smp.h>
41 #include <asm/stacktrace.h>
42 #include <asm/switch_to.h>
43 #include <asm/runtime_instr.h>
44 #include <asm/unwind.h>
45 #include "entry.h"
46 
47 void ret_from_fork(void) asm("ret_from_fork");
48 
__ret_from_fork(struct task_struct * prev,struct pt_regs * regs)49 void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs)
50 {
51 	void (*func)(void *arg);
52 
53 	schedule_tail(prev);
54 
55 	if (!user_mode(regs)) {
56 		/* Kernel thread */
57 		func = (void *)regs->gprs[9];
58 		func((void *)regs->gprs[10]);
59 	}
60 	clear_pt_regs_flag(regs, PIF_SYSCALL);
61 	syscall_exit_to_user_mode(regs);
62 }
63 
flush_thread(void)64 void flush_thread(void)
65 {
66 }
67 
arch_setup_new_exec(void)68 void arch_setup_new_exec(void)
69 {
70 	if (S390_lowcore.current_pid != current->pid) {
71 		S390_lowcore.current_pid = current->pid;
72 		if (test_facility(40))
73 			lpp(&S390_lowcore.lpp);
74 	}
75 }
76 
arch_release_task_struct(struct task_struct * tsk)77 void arch_release_task_struct(struct task_struct *tsk)
78 {
79 	runtime_instr_release(tsk);
80 	guarded_storage_release(tsk);
81 }
82 
arch_dup_task_struct(struct task_struct * dst,struct task_struct * src)83 int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
84 {
85 	/*
86 	 * Save the floating-point or vector register state of the current
87 	 * task and set the CIF_FPU flag to lazy restore the FPU register
88 	 * state when returning to user space.
89 	 */
90 	save_fpu_regs();
91 
92 	memcpy(dst, src, arch_task_struct_size);
93 	dst->thread.fpu.regs = dst->thread.fpu.fprs;
94 
95 	/*
96 	 * Don't transfer over the runtime instrumentation or the guarded
97 	 * storage control block pointers. These fields are cleared here instead
98 	 * of in copy_thread() to avoid premature freeing of associated memory
99 	 * on fork() failure. Wait to clear the RI flag because ->stack still
100 	 * refers to the source thread.
101 	 */
102 	dst->thread.ri_cb = NULL;
103 	dst->thread.gs_cb = NULL;
104 	dst->thread.gs_bc_cb = NULL;
105 
106 	return 0;
107 }
108 
copy_thread(struct task_struct * p,const struct kernel_clone_args * args)109 int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
110 {
111 	unsigned long clone_flags = args->flags;
112 	unsigned long new_stackp = args->stack;
113 	unsigned long tls = args->tls;
114 	struct fake_frame
115 	{
116 		struct stack_frame sf;
117 		struct pt_regs childregs;
118 	} *frame;
119 
120 	frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
121 	p->thread.ksp = (unsigned long) frame;
122 	/* Save access registers to new thread structure. */
123 	save_access_regs(&p->thread.acrs[0]);
124 	/* start new process with ar4 pointing to the correct address space */
125 	/* Don't copy debug registers */
126 	memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
127 	memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
128 	clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
129 	p->thread.per_flags = 0;
130 	/* Initialize per thread user and system timer values */
131 	p->thread.user_timer = 0;
132 	p->thread.guest_timer = 0;
133 	p->thread.system_timer = 0;
134 	p->thread.hardirq_timer = 0;
135 	p->thread.softirq_timer = 0;
136 	p->thread.last_break = 1;
137 
138 	frame->sf.back_chain = 0;
139 	frame->sf.gprs[5] = (unsigned long)frame + sizeof(struct stack_frame);
140 	frame->sf.gprs[6] = (unsigned long)p;
141 	/* new return point is ret_from_fork */
142 	frame->sf.gprs[8] = (unsigned long)ret_from_fork;
143 	/* fake return stack for resume(), don't go back to schedule */
144 	frame->sf.gprs[9] = (unsigned long)frame;
145 
146 	/* Store access registers to kernel stack of new process. */
147 	if (unlikely(args->fn)) {
148 		/* kernel thread */
149 		memset(&frame->childregs, 0, sizeof(struct pt_regs));
150 		frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_DAT |
151 				PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
152 		frame->childregs.psw.addr =
153 				(unsigned long)__ret_from_fork;
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 		if (is_compat_task()) {
174 			p->thread.acrs[0] = (unsigned int)tls;
175 		} else {
176 			p->thread.acrs[0] = (unsigned int)(tls >> 32);
177 			p->thread.acrs[1] = (unsigned int)tls;
178 		}
179 	}
180 	/*
181 	 * s390 stores the svc return address in arch_data when calling
182 	 * sigreturn()/restart_syscall() via vdso. 1 means no valid address
183 	 * stored.
184 	 */
185 	p->restart_block.arch_data = 1;
186 	return 0;
187 }
188 
execve_tail(void)189 void execve_tail(void)
190 {
191 	current->thread.fpu.fpc = 0;
192 	asm volatile("sfpc %0" : : "d" (0));
193 }
194 
__get_wchan(struct task_struct * p)195 unsigned long __get_wchan(struct task_struct *p)
196 {
197 	struct unwind_state state;
198 	unsigned long ip = 0;
199 
200 	if (!task_stack_page(p))
201 		return 0;
202 
203 	if (!try_get_task_stack(p))
204 		return 0;
205 
206 	unwind_for_each_frame(&state, p, NULL, 0) {
207 		if (state.stack_info.type != STACK_TYPE_TASK) {
208 			ip = 0;
209 			break;
210 		}
211 
212 		ip = unwind_get_return_address(&state);
213 		if (!ip)
214 			break;
215 
216 		if (!in_sched_functions(ip))
217 			break;
218 	}
219 
220 	put_task_stack(p);
221 	return ip;
222 }
223 
arch_align_stack(unsigned long sp)224 unsigned long arch_align_stack(unsigned long sp)
225 {
226 	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
227 		sp -= prandom_u32_max(PAGE_SIZE);
228 	return sp & ~0xf;
229 }
230 
brk_rnd(void)231 static inline unsigned long brk_rnd(void)
232 {
233 	return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT;
234 }
235 
arch_randomize_brk(struct mm_struct * mm)236 unsigned long arch_randomize_brk(struct mm_struct *mm)
237 {
238 	unsigned long ret;
239 
240 	ret = PAGE_ALIGN(mm->brk + brk_rnd());
241 	return (ret > mm->brk) ? ret : mm->brk;
242 }
243