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Linux/arch/hexagon/kernel/process.c

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  1 /*
  2  * Process creation support for Hexagon
  3  *
  4  * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
  5  *
  6  * This program is free software; you can redistribute it and/or modify
  7  * it under the terms of the GNU General Public License version 2 and
  8  * only version 2 as published by the Free Software Foundation.
  9  *
 10  * This program is distributed in the hope that it will be useful,
 11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 13  * GNU General Public License for more details.
 14  *
 15  * You should have received a copy of the GNU General Public License
 16  * along with this program; if not, write to the Free Software
 17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 18  * 02110-1301, USA.
 19  */
 20 
 21 #include <linux/sched.h>
 22 #include <linux/types.h>
 23 #include <linux/module.h>
 24 #include <linux/tick.h>
 25 #include <linux/uaccess.h>
 26 #include <linux/slab.h>
 27 #include <linux/tracehook.h>
 28 
 29 /*
 30  * Program thread launch.  Often defined as a macro in processor.h,
 31  * but we're shooting for a small footprint and it's not an inner-loop
 32  * performance-critical operation.
 33  *
 34  * The Hexagon ABI specifies that R28 is zero'ed before program launch,
 35  * so that gets automatically done here.  If we ever stop doing that here,
 36  * we'll probably want to define the ELF_PLAT_INIT macro.
 37  */
 38 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
 39 {
 40         /* We want to zero all data-containing registers. Is this overkill? */
 41         memset(regs, 0, sizeof(*regs));
 42         /* We might want to also zero all Processor registers here */
 43         pt_set_usermode(regs);
 44         pt_set_elr(regs, pc);
 45         pt_set_rte_sp(regs, sp);
 46 }
 47 
 48 /*
 49  *  Spin, or better still, do a hardware or VM wait instruction
 50  *  If hardware or VM offer wait termination even though interrupts
 51  *  are disabled.
 52  */
 53 void arch_cpu_idle(void)
 54 {
 55         __vmwait();
 56         /*  interrupts wake us up, but irqs are still disabled */
 57         local_irq_enable();
 58 }
 59 
 60 /*
 61  *  Return saved PC of a blocked thread
 62  */
 63 unsigned long thread_saved_pc(struct task_struct *tsk)
 64 {
 65         return 0;
 66 }
 67 
 68 /*
 69  * Copy architecture-specific thread state
 70  */
 71 int copy_thread(unsigned long clone_flags, unsigned long usp,
 72                 unsigned long arg, struct task_struct *p)
 73 {
 74         struct thread_info *ti = task_thread_info(p);
 75         struct hexagon_switch_stack *ss;
 76         struct pt_regs *childregs;
 77         asmlinkage void ret_from_fork(void);
 78 
 79         childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
 80                                         sizeof(*childregs));
 81 
 82         ti->regs = childregs;
 83 
 84         /*
 85          * Establish kernel stack pointer and initial PC for new thread
 86          * Note that unlike the usual situation, we do not copy the
 87          * parent's callee-saved here; those are in pt_regs and whatever
 88          * we leave here will be overridden on return to userland.
 89          */
 90         ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
 91                                                     sizeof(*ss));
 92         ss->lr = (unsigned long)ret_from_fork;
 93         p->thread.switch_sp = ss;
 94         if (unlikely(p->flags & PF_KTHREAD)) {
 95                 memset(childregs, 0, sizeof(struct pt_regs));
 96                 /* r24 <- fn, r25 <- arg */
 97                 ss->r24 = usp;
 98                 ss->r25 = arg;
 99                 pt_set_kmode(childregs);
100                 return 0;
101         }
102         memcpy(childregs, current_pt_regs(), sizeof(*childregs));
103         ss->r2524 = 0;
104 
105         if (usp)
106                 pt_set_rte_sp(childregs, usp);
107 
108         /* Child sees zero return value */
109         childregs->r00 = 0;
110 
111         /*
112          * The clone syscall has the C signature:
113          * int [r0] clone(int flags [r0],
114          *           void *child_frame [r1],
115          *           void *parent_tid [r2],
116          *           void *child_tid [r3],
117          *           void *thread_control_block [r4]);
118          * ugp is used to provide TLS support.
119          */
120         if (clone_flags & CLONE_SETTLS)
121                 childregs->ugp = childregs->r04;
122 
123         /*
124          * Parent sees new pid -- not necessary, not even possible at
125          * this point in the fork process
126          * Might also want to set things like ti->addr_limit
127          */
128 
129         return 0;
130 }
131 
132 /*
133  * Release any architecture-specific resources locked by thread
134  */
135 void release_thread(struct task_struct *dead_task)
136 {
137 }
138 
139 /*
140  * Free any architecture-specific thread data structures, etc.
141  */
142 void exit_thread(void)
143 {
144 }
145 
146 /*
147  * Some archs flush debug and FPU info here
148  */
149 void flush_thread(void)
150 {
151 }
152 
153 /*
154  * The "wait channel" terminology is archaic, but what we want
155  * is an identification of the point at which the scheduler
156  * was invoked by a blocked thread.
157  */
158 unsigned long get_wchan(struct task_struct *p)
159 {
160         unsigned long fp, pc;
161         unsigned long stack_page;
162         int count = 0;
163         if (!p || p == current || p->state == TASK_RUNNING)
164                 return 0;
165 
166         stack_page = (unsigned long)task_stack_page(p);
167         fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
168         do {
169                 if (fp < (stack_page + sizeof(struct thread_info)) ||
170                         fp >= (THREAD_SIZE - 8 + stack_page))
171                         return 0;
172                 pc = ((unsigned long *)fp)[1];
173                 if (!in_sched_functions(pc))
174                         return pc;
175                 fp = *(unsigned long *) fp;
176         } while (count++ < 16);
177 
178         return 0;
179 }
180 
181 /*
182  * Required placeholder.
183  */
184 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
185 {
186         return 0;
187 }
188 
189 
190 /*
191  * Called on the exit path of event entry; see vm_entry.S
192  *
193  * Interrupts will already be disabled.
194  *
195  * Returns 0 if there's no need to re-check for more work.
196  */
197 
198 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
199 {
200         if (!(thread_info_flags & _TIF_WORK_MASK)) {
201                 return 0;
202         }  /* shortcut -- no work to be done */
203 
204         local_irq_enable();
205 
206         if (thread_info_flags & _TIF_NEED_RESCHED) {
207                 schedule();
208                 return 1;
209         }
210 
211         if (thread_info_flags & _TIF_SIGPENDING) {
212                 do_signal(regs);
213                 return 1;
214         }
215 
216         if (thread_info_flags & _TIF_NOTIFY_RESUME) {
217                 clear_thread_flag(TIF_NOTIFY_RESUME);
218                 tracehook_notify_resume(regs);
219                 return 1;
220         }
221 
222         /* Should not even reach here */
223         panic("%s: bad thread_info flags 0x%08x\n", __func__,
224                 thread_info_flags);
225 }
226 

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