Root/arch/s390/kernel/process.c

1/*
2 * This file handles the architecture dependent parts of process handling.
3 *
4 * Copyright IBM Corp. 1999,2009
5 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
6 * Hartmut Penner <hp@de.ibm.com>,
7 * Denis Joseph Barrow,
8 */
9
10#include <linux/compiler.h>
11#include <linux/cpu.h>
12#include <linux/errno.h>
13#include <linux/sched.h>
14#include <linux/kernel.h>
15#include <linux/mm.h>
16#include <linux/fs.h>
17#include <linux/smp.h>
18#include <linux/stddef.h>
19#include <linux/slab.h>
20#include <linux/unistd.h>
21#include <linux/ptrace.h>
22#include <linux/vmalloc.h>
23#include <linux/user.h>
24#include <linux/interrupt.h>
25#include <linux/delay.h>
26#include <linux/reboot.h>
27#include <linux/init.h>
28#include <linux/module.h>
29#include <linux/notifier.h>
30#include <linux/tick.h>
31#include <linux/elfcore.h>
32#include <linux/kernel_stat.h>
33#include <linux/syscalls.h>
34#include <linux/compat.h>
35#include <asm/compat.h>
36#include <asm/uaccess.h>
37#include <asm/pgtable.h>
38#include <asm/system.h>
39#include <asm/io.h>
40#include <asm/processor.h>
41#include <asm/irq.h>
42#include <asm/timer.h>
43#include <asm/nmi.h>
44#include "entry.h"
45
46asmlinkage void ret_from_fork(void) asm ("ret_from_fork");
47
48/*
49 * Return saved PC of a blocked thread. used in kernel/sched.
50 * resume in entry.S does not create a new stack frame, it
51 * just stores the registers %r6-%r15 to the frame given by
52 * schedule. We want to return the address of the caller of
53 * schedule, so we have to walk the backchain one time to
54 * find the frame schedule() store its return address.
55 */
56unsigned long thread_saved_pc(struct task_struct *tsk)
57{
58    struct stack_frame *sf, *low, *high;
59
60    if (!tsk || !task_stack_page(tsk))
61        return 0;
62    low = task_stack_page(tsk);
63    high = (struct stack_frame *) task_pt_regs(tsk);
64    sf = (struct stack_frame *) (tsk->thread.ksp & PSW_ADDR_INSN);
65    if (sf <= low || sf > high)
66        return 0;
67    sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
68    if (sf <= low || sf > high)
69        return 0;
70    return sf->gprs[8];
71}
72
73/*
74 * The idle loop on a S390...
75 */
76static void default_idle(void)
77{
78    /* CPU is going idle. */
79#ifdef CONFIG_HOTPLUG_CPU
80    if (cpu_is_offline(smp_processor_id())) {
81        preempt_enable_no_resched();
82        cpu_die();
83    }
84#endif
85    local_irq_disable();
86    if (need_resched()) {
87        local_irq_enable();
88        return;
89    }
90    local_mcck_disable();
91    if (test_thread_flag(TIF_MCCK_PENDING)) {
92        local_mcck_enable();
93        local_irq_enable();
94        s390_handle_mcck();
95        return;
96    }
97    trace_hardirqs_on();
98    /* Don't trace preempt off for idle. */
99    stop_critical_timings();
100    /* Stop virtual timer and halt the cpu. */
101    vtime_stop_cpu();
102    /* Reenable preemption tracer. */
103    start_critical_timings();
104}
105
106void cpu_idle(void)
107{
108    for (;;) {
109        tick_nohz_stop_sched_tick(1);
110        while (!need_resched())
111            default_idle();
112        tick_nohz_restart_sched_tick();
113        preempt_enable_no_resched();
114        schedule();
115        preempt_disable();
116    }
117}
118
119extern void kernel_thread_starter(void);
120
121asm(
122    ".align 4\n"
123    "kernel_thread_starter:\n"
124    " la 2,0(10)\n"
125    " basr 14,9\n"
126    " la 2,0\n"
127    " br 11\n");
128
129int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
130{
131    struct pt_regs regs;
132
133    memset(&regs, 0, sizeof(regs));
134    regs.psw.mask = psw_kernel_bits | PSW_MASK_IO | PSW_MASK_EXT;
135    regs.psw.addr = (unsigned long) kernel_thread_starter | PSW_ADDR_AMODE;
136    regs.gprs[9] = (unsigned long) fn;
137    regs.gprs[10] = (unsigned long) arg;
138    regs.gprs[11] = (unsigned long) do_exit;
139    regs.orig_gpr2 = -1;
140
141    /* Ok, create the new process.. */
142    return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
143               0, &regs, 0, NULL, NULL);
144}
145EXPORT_SYMBOL(kernel_thread);
146
147/*
148 * Free current thread data structures etc..
149 */
150void exit_thread(void)
151{
152}
153
154void flush_thread(void)
155{
156}
157
158void release_thread(struct task_struct *dead_task)
159{
160}
161
162int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
163        unsigned long unused,
164        struct task_struct *p, struct pt_regs *regs)
165{
166    struct thread_info *ti;
167    struct fake_frame
168    {
169        struct stack_frame sf;
170        struct pt_regs childregs;
171    } *frame;
172
173    frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
174    p->thread.ksp = (unsigned long) frame;
175    /* Store access registers to kernel stack of new process. */
176    frame->childregs = *regs;
177    frame->childregs.gprs[2] = 0; /* child returns 0 on fork. */
178    frame->childregs.gprs[15] = new_stackp;
179    frame->sf.back_chain = 0;
180
181    /* new return point is ret_from_fork */
182    frame->sf.gprs[8] = (unsigned long) ret_from_fork;
183
184    /* fake return stack for resume(), don't go back to schedule */
185    frame->sf.gprs[9] = (unsigned long) frame;
186
187    /* Save access registers to new thread structure. */
188    save_access_regs(&p->thread.acrs[0]);
189
190#ifndef CONFIG_64BIT
191    /*
192     * save fprs to current->thread.fp_regs to merge them with
193     * the emulated registers and then copy the result to the child.
194     */
195    save_fp_regs(&current->thread.fp_regs);
196    memcpy(&p->thread.fp_regs, &current->thread.fp_regs,
197           sizeof(s390_fp_regs));
198    /* Set a new TLS ? */
199    if (clone_flags & CLONE_SETTLS)
200        p->thread.acrs[0] = regs->gprs[6];
201#else /* CONFIG_64BIT */
202    /* Save the fpu registers to new thread structure. */
203    save_fp_regs(&p->thread.fp_regs);
204    /* Set a new TLS ? */
205    if (clone_flags & CLONE_SETTLS) {
206        if (is_compat_task()) {
207            p->thread.acrs[0] = (unsigned int) regs->gprs[6];
208        } else {
209            p->thread.acrs[0] = (unsigned int)(regs->gprs[6] >> 32);
210            p->thread.acrs[1] = (unsigned int) regs->gprs[6];
211        }
212    }
213#endif /* CONFIG_64BIT */
214    /* start new process with ar4 pointing to the correct address space */
215    p->thread.mm_segment = get_fs();
216    /* Don't copy debug registers */
217    memset(&p->thread.per_info, 0, sizeof(p->thread.per_info));
218    clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
219    /* Initialize per thread user and system timer values */
220    ti = task_thread_info(p);
221    ti->user_timer = 0;
222    ti->system_timer = 0;
223    return 0;
224}
225
226SYSCALL_DEFINE0(fork)
227{
228    struct pt_regs *regs = task_pt_regs(current);
229    return do_fork(SIGCHLD, regs->gprs[15], regs, 0, NULL, NULL);
230}
231
232SYSCALL_DEFINE4(clone, unsigned long, newsp, unsigned long, clone_flags,
233        int __user *, parent_tidptr, int __user *, child_tidptr)
234{
235    struct pt_regs *regs = task_pt_regs(current);
236
237    if (!newsp)
238        newsp = regs->gprs[15];
239    return do_fork(clone_flags, newsp, regs, 0,
240               parent_tidptr, child_tidptr);
241}
242
243/*
244 * This is trivial, and on the face of it looks like it
245 * could equally well be done in user mode.
246 *
247 * Not so, for quite unobvious reasons - register pressure.
248 * In user mode vfork() cannot have a stack frame, and if
249 * done by calling the "clone()" system call directly, you
250 * do not have enough call-clobbered registers to hold all
251 * the information you need.
252 */
253SYSCALL_DEFINE0(vfork)
254{
255    struct pt_regs *regs = task_pt_regs(current);
256    return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD,
257               regs->gprs[15], regs, 0, NULL, NULL);
258}
259
260asmlinkage void execve_tail(void)
261{
262    current->thread.fp_regs.fpc = 0;
263    if (MACHINE_HAS_IEEE)
264        asm volatile("sfpc %0,%0" : : "d" (0));
265}
266
267/*
268 * sys_execve() executes a new program.
269 */
270SYSCALL_DEFINE3(execve, const char __user *, name,
271        const char __user *const __user *, argv,
272        const char __user *const __user *, envp)
273{
274    struct pt_regs *regs = task_pt_regs(current);
275    char *filename;
276    long rc;
277
278    filename = getname(name);
279    rc = PTR_ERR(filename);
280    if (IS_ERR(filename))
281        return rc;
282    rc = do_execve(filename, argv, envp, regs);
283    if (rc)
284        goto out;
285    execve_tail();
286    rc = regs->gprs[2];
287out:
288    putname(filename);
289    return rc;
290}
291
292/*
293 * fill in the FPU structure for a core dump.
294 */
295int dump_fpu (struct pt_regs * regs, s390_fp_regs *fpregs)
296{
297#ifndef CONFIG_64BIT
298    /*
299     * save fprs to current->thread.fp_regs to merge them with
300     * the emulated registers and then copy the result to the dump.
301     */
302    save_fp_regs(&current->thread.fp_regs);
303    memcpy(fpregs, &current->thread.fp_regs, sizeof(s390_fp_regs));
304#else /* CONFIG_64BIT */
305    save_fp_regs(fpregs);
306#endif /* CONFIG_64BIT */
307    return 1;
308}
309EXPORT_SYMBOL(dump_fpu);
310
311unsigned long get_wchan(struct task_struct *p)
312{
313    struct stack_frame *sf, *low, *high;
314    unsigned long return_address;
315    int count;
316
317    if (!p || p == current || p->state == TASK_RUNNING || !task_stack_page(p))
318        return 0;
319    low = task_stack_page(p);
320    high = (struct stack_frame *) task_pt_regs(p);
321    sf = (struct stack_frame *) (p->thread.ksp & PSW_ADDR_INSN);
322    if (sf <= low || sf > high)
323        return 0;
324    for (count = 0; count < 16; count++) {
325        sf = (struct stack_frame *) (sf->back_chain & PSW_ADDR_INSN);
326        if (sf <= low || sf > high)
327            return 0;
328        return_address = sf->gprs[8] & PSW_ADDR_INSN;
329        if (!in_sched_functions(return_address))
330            return return_address;
331    }
332    return 0;
333}
334

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