2 * Process creation support for Hexagon
4 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
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.
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.
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
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>
29 * Program thread launch. Often defined as a macro in processor.h,
30 * but we're shooting for a small footprint and it's not an inner-loop
31 * performance-critical operation.
33 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
34 * so that gets automatically done here. If we ever stop doing that here,
35 * we'll probably want to define the ELF_PLAT_INIT macro.
37 void start_thread(struct pt_regs
*regs
, unsigned long pc
, unsigned long sp
)
39 /* Set to run with user-mode data segmentation */
41 /* We want to zero all data-containing registers. Is this overkill? */
42 memset(regs
, 0, sizeof(*regs
));
43 /* We might want to also zero all Processor registers here */
44 pt_set_usermode(regs
);
46 pt_set_rte_sp(regs
, sp
);
50 * Spin, or better still, do a hardware or VM wait instruction
51 * If hardware or VM offer wait termination even though interrupts
54 static void default_idle(void)
59 void (*idle_sleep
)(void) = default_idle
;
64 tick_nohz_idle_enter();
66 while (!need_resched()) {
68 /* interrupts wake us up, but aren't serviced */
69 local_irq_enable(); /* service interrupt */
73 tick_nohz_idle_exit();
79 * Return saved PC of a blocked thread
81 unsigned long thread_saved_pc(struct task_struct
*tsk
)
87 * Copy architecture-specific thread state
89 int copy_thread(unsigned long clone_flags
, unsigned long usp
,
90 unsigned long arg
, struct task_struct
*p
)
92 struct thread_info
*ti
= task_thread_info(p
);
93 struct hexagon_switch_stack
*ss
;
94 struct pt_regs
*childregs
;
95 asmlinkage
void ret_from_fork(void);
97 childregs
= (struct pt_regs
*) (((unsigned long) ti
+ THREAD_SIZE
) -
100 ti
->regs
= childregs
;
103 * Establish kernel stack pointer and initial PC for new thread
104 * Note that unlike the usual situation, we do not copy the
105 * parent's callee-saved here; those are in pt_regs and whatever
106 * we leave here will be overridden on return to userland.
108 ss
= (struct hexagon_switch_stack
*) ((unsigned long) childregs
-
110 ss
->lr
= (unsigned long)ret_from_fork
;
111 p
->thread
.switch_sp
= ss
;
112 if (unlikely(p
->flags
& PF_KTHREAD
)) {
113 memset(childregs
, 0, sizeof(struct pt_regs
));
114 /* r24 <- fn, r25 <- arg */
115 ss
->r2524
= usp
| ((u64
)arg
<< 32);
116 pt_set_kmode(childregs
);
119 memcpy(childregs
, current_pt_regs(), sizeof(*childregs
));
123 pt_set_rte_sp(childregs
, usp
);
125 /* Child sees zero return value */
129 * The clone syscall has the C signature:
130 * int [r0] clone(int flags [r0],
131 * void *child_frame [r1],
132 * void *parent_tid [r2],
133 * void *child_tid [r3],
134 * void *thread_control_block [r4]);
135 * ugp is used to provide TLS support.
137 if (clone_flags
& CLONE_SETTLS
)
138 childregs
->ugp
= childregs
->r04
;
141 * Parent sees new pid -- not necessary, not even possible at
142 * this point in the fork process
143 * Might also want to set things like ti->addr_limit
150 * Release any architecture-specific resources locked by thread
152 void release_thread(struct task_struct
*dead_task
)
157 * Free any architecture-specific thread data structures, etc.
159 void exit_thread(void)
164 * Some archs flush debug and FPU info here
166 void flush_thread(void)
171 * The "wait channel" terminology is archaic, but what we want
172 * is an identification of the point at which the scheduler
173 * was invoked by a blocked thread.
175 unsigned long get_wchan(struct task_struct
*p
)
177 unsigned long fp
, pc
;
178 unsigned long stack_page
;
180 if (!p
|| p
== current
|| p
->state
== TASK_RUNNING
)
183 stack_page
= (unsigned long)task_stack_page(p
);
184 fp
= ((struct hexagon_switch_stack
*)p
->thread
.switch_sp
)->fp
;
186 if (fp
< (stack_page
+ sizeof(struct thread_info
)) ||
187 fp
>= (THREAD_SIZE
- 8 + stack_page
))
189 pc
= ((unsigned long *)fp
)[1];
190 if (!in_sched_functions(pc
))
192 fp
= *(unsigned long *) fp
;
193 } while (count
++ < 16);
199 * Required placeholder.
201 int dump_fpu(struct pt_regs
*regs
, elf_fpregset_t
*fpu
)