process.c

  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/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/vtimer.h>
 39#include <asm/exec.h>
 40#include <asm/fpu.h>
 41#include <asm/irq.h>
 42#include <asm/nmi.h>
 43#include <asm/smp.h>
 44#include <asm/stacktrace.h>
 45#include <asm/runtime_instr.h>
 46#include <asm/unwind.h>
 47#include "entry.h"
 48
 49void ret_from_fork(void) asm("ret_from_fork");
 50
 51void __ret_from_fork(struct task_struct *prev, struct pt_regs *regs)
 52{
 53	void (*func)(void *arg);
 54
 55	schedule_tail(prev);
 56
 57	if (!user_mode(regs)) {
 58		/* Kernel thread */
 59		func = (void *)regs->gprs[9];
 60		func((void *)regs->gprs[10]);
 61	}
 62	clear_pt_regs_flag(regs, PIF_SYSCALL);
 63	syscall_exit_to_user_mode(regs);
 64}
 65
 66void flush_thread(void)
 67{
 68}
 69
 70void arch_setup_new_exec(void)
 71{
 72	if (get_lowcore()->current_pid != current->pid) {
 73		get_lowcore()->current_pid = current->pid;
 74		if (test_facility(40))
 75			lpp(&get_lowcore()->lpp);
 76	}
 77}
 78
 79void arch_release_task_struct(struct task_struct *tsk)
 80{
 81	runtime_instr_release(tsk);
 82	guarded_storage_release(tsk);
 83}
 84
 85int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 86{
 87	save_user_fpu_regs();
 88
 89	*dst = *src;
 90	dst->thread.kfpu_flags = 0;
 91
 92	/*
 93	 * Don't transfer over the runtime instrumentation or the guarded
 94	 * storage control block pointers. These fields are cleared here instead
 95	 * of in copy_thread() to avoid premature freeing of associated memory
 96	 * on fork() failure. Wait to clear the RI flag because ->stack still
 97	 * refers to the source thread.
 98	 */
 99	dst->thread.ri_cb = NULL;
100	dst->thread.gs_cb = NULL;
101	dst->thread.gs_bc_cb = NULL;
102
103	return 0;
104}
105
106int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
107{
108	u64 clone_flags = args->flags;
109	unsigned long new_stackp = args->stack;
110	unsigned long tls = args->tls;
111	struct fake_frame
112	{
113		struct stack_frame sf;
114		struct pt_regs childregs;
115	} *frame;
116
117	frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
118	p->thread.ksp = (unsigned long) frame;
119	/* Save access registers to new thread structure. */
120	save_access_regs(&p->thread.acrs[0]);
121	/* start new process with ar4 pointing to the correct address space */
122	/* Don't copy debug registers */
123	memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
124	memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
125	clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
126	p->thread.per_flags = 0;
127	/* Initialize per thread user and system timer values */
128	p->thread.user_timer = 0;
129	p->thread.guest_timer = 0;
130	p->thread.system_timer = 0;
131	p->thread.hardirq_timer = 0;
132	p->thread.softirq_timer = 0;
133	p->thread.last_break = 1;
134
135	frame->sf.back_chain = 0;
136	frame->sf.gprs[11 - 6] = (unsigned long)&frame->childregs;
137	frame->sf.gprs[12 - 6] = (unsigned long)p;
138	/* new return point is ret_from_fork */
139	frame->sf.gprs[14 - 6] = (unsigned long)ret_from_fork;
140	/* fake return stack for resume(), don't go back to schedule */
141	frame->sf.gprs[15 - 6] = (unsigned long)frame;
142
143	/* Store access registers to kernel stack of new process. */
144	if (unlikely(args->fn)) {
145		/* kernel thread */
146		memset(&frame->childregs, 0, sizeof(struct pt_regs));
147		frame->childregs.psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO |
148					    PSW_MASK_EXT | PSW_MASK_MCHECK;
149		frame->childregs.gprs[9] = (unsigned long)args->fn;
150		frame->childregs.gprs[10] = (unsigned long)args->fn_arg;
151		frame->childregs.orig_gpr2 = -1;
152		frame->childregs.last_break = 1;
153		return 0;
154	}
155	frame->childregs = *current_pt_regs();
156	frame->childregs.gprs[2] = 0;	/* child returns 0 on fork. */
157	frame->childregs.flags = 0;
158	if (new_stackp)
159		frame->childregs.gprs[15] = new_stackp;
160	/*
161	 * Clear the runtime instrumentation flag after the above childregs
162	 * copy. The CB pointer was already cleared in arch_dup_task_struct().
163	 */
164	frame->childregs.psw.mask &= ~PSW_MASK_RI;
165
166	/* Set a new TLS ?  */
167	if (clone_flags & CLONE_SETTLS) {
168		p->thread.acrs[0] = (unsigned int)(tls >> 32);
169		p->thread.acrs[1] = (unsigned int)tls;
170	}
171	/*
172	 * s390 stores the svc return address in arch_data when calling
173	 * sigreturn()/restart_syscall() via vdso. 1 means no valid address
174	 * stored.
175	 */
176	p->restart_block.arch_data = 1;
177	return 0;
178}
179
180void execve_tail(void)
181{
182	current->thread.ufpu.fpc = 0;
183	fpu_sfpc(0);
184}
185
186struct task_struct *__switch_to(struct task_struct *prev, struct task_struct *next)
187{
188	save_user_fpu_regs();
189	save_kernel_fpu_regs(&prev->thread);
190	save_access_regs(&prev->thread.acrs[0]);
191	save_ri_cb(prev->thread.ri_cb);
192	save_gs_cb(prev->thread.gs_cb);
193	update_cr_regs(next);
194	restore_kernel_fpu_regs(&next->thread);
195	restore_access_regs(&next->thread.acrs[0]);
196	restore_ri_cb(next->thread.ri_cb, prev->thread.ri_cb);
197	restore_gs_cb(next->thread.gs_cb);
198	return __switch_to_asm(prev, next);
199}
200
201unsigned long __get_wchan(struct task_struct *p)
202{
203	struct unwind_state state;
204	unsigned long ip = 0;
205
206	if (!task_stack_page(p))
207		return 0;
208
209	if (!try_get_task_stack(p))
210		return 0;
211
212	unwind_for_each_frame(&state, p, NULL, 0) {
213		if (state.stack_info.type != STACK_TYPE_TASK) {
214			ip = 0;
215			break;
216		}
217
218		ip = unwind_get_return_address(&state);
219		if (!ip)
220			break;
221
222		if (!in_sched_functions(ip))
223			break;
224	}
225
226	put_task_stack(p);
227	return ip;
228}
229
230unsigned long arch_align_stack(unsigned long sp)
231{
232	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
233		sp -= get_random_u32_below(PAGE_SIZE);
234	return sp & ~0xf;
235}
236
237static inline unsigned long brk_rnd(void)
238{
239	return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT;
240}
241
242unsigned long arch_randomize_brk(struct mm_struct *mm)
243{
244	unsigned long ret;
245
246	ret = PAGE_ALIGN(mm->brk + brk_rnd());
247	return (ret > mm->brk) ? ret : mm->brk;
248}