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/sched/debug.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/task_stack.h>
25 #include <linux/types.h>
26 #include <linux/module.h>
27 #include <linux/tick.h>
28 #include <linux/uaccess.h>
29 #include <linux/slab.h>
30 #include <linux/tracehook.h>
33 * Program thread launch. Often defined as a macro in processor.h,
34 * but we're shooting for a small footprint and it's not an inner-loop
35 * performance-critical operation.
37 * The Hexagon ABI specifies that R28 is zero'ed before program launch,
38 * so that gets automatically done here. If we ever stop doing that here,
39 * we'll probably want to define the ELF_PLAT_INIT macro.
41 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
43 /* We want to zero all data-containing registers. Is this overkill? */
44 memset(regs, 0, sizeof(*regs));
45 /* We might want to also zero all Processor registers here */
46 pt_set_usermode(regs);
48 pt_set_rte_sp(regs, sp);
52 * Spin, or better still, do a hardware or VM wait instruction
53 * If hardware or VM offer wait termination even though interrupts
56 void arch_cpu_idle(void)
59 /* interrupts wake us up, but irqs are still disabled */
64 * Return saved PC of a blocked thread
66 unsigned long thread_saved_pc(struct task_struct *tsk)
72 * Copy architecture-specific thread state
74 int copy_thread(unsigned long clone_flags, unsigned long usp,
75 unsigned long arg, struct task_struct *p)
77 struct thread_info *ti = task_thread_info(p);
78 struct hexagon_switch_stack *ss;
79 struct pt_regs *childregs;
80 asmlinkage void ret_from_fork(void);
82 childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -
88 * Establish kernel stack pointer and initial PC for new thread
89 * Note that unlike the usual situation, we do not copy the
90 * parent's callee-saved here; those are in pt_regs and whatever
91 * we leave here will be overridden on return to userland.
93 ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -
95 ss->lr = (unsigned long)ret_from_fork;
96 p->thread.switch_sp = ss;
97 if (unlikely(p->flags & PF_KTHREAD)) {
98 memset(childregs, 0, sizeof(struct pt_regs));
99 /* r24 <- fn, r25 <- arg */
102 pt_set_kmode(childregs);
105 memcpy(childregs, current_pt_regs(), sizeof(*childregs));
109 pt_set_rte_sp(childregs, usp);
111 /* Child sees zero return value */
115 * The clone syscall has the C signature:
116 * int [r0] clone(int flags [r0],
117 * void *child_frame [r1],
118 * void *parent_tid [r2],
119 * void *child_tid [r3],
120 * void *thread_control_block [r4]);
121 * ugp is used to provide TLS support.
123 if (clone_flags & CLONE_SETTLS)
124 childregs->ugp = childregs->r04;
127 * Parent sees new pid -- not necessary, not even possible at
128 * this point in the fork process
129 * Might also want to set things like ti->addr_limit
136 * Release any architecture-specific resources locked by thread
138 void release_thread(struct task_struct *dead_task)
143 * Some archs flush debug and FPU info here
145 void flush_thread(void)
150 * The "wait channel" terminology is archaic, but what we want
151 * is an identification of the point at which the scheduler
152 * was invoked by a blocked thread.
154 unsigned long get_wchan(struct task_struct *p)
156 unsigned long fp, pc;
157 unsigned long stack_page;
159 if (!p || p == current || p->state == TASK_RUNNING)
162 stack_page = (unsigned long)task_stack_page(p);
163 fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;
165 if (fp < (stack_page + sizeof(struct thread_info)) ||
166 fp >= (THREAD_SIZE - 8 + stack_page))
168 pc = ((unsigned long *)fp)[1];
169 if (!in_sched_functions(pc))
171 fp = *(unsigned long *) fp;
172 } while (count++ < 16);
178 * Required placeholder.
180 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
187 * Called on the exit path of event entry; see vm_entry.S
189 * Interrupts will already be disabled.
191 * Returns 0 if there's no need to re-check for more work.
194 int do_work_pending(struct pt_regs *regs, u32 thread_info_flags)
196 if (!(thread_info_flags & _TIF_WORK_MASK)) {
198 } /* shortcut -- no work to be done */
202 if (thread_info_flags & _TIF_NEED_RESCHED) {
207 if (thread_info_flags & _TIF_SIGPENDING) {
212 if (thread_info_flags & _TIF_NOTIFY_RESUME) {
213 clear_thread_flag(TIF_NOTIFY_RESUME);
214 tracehook_notify_resume(regs);
218 /* Should not even reach here */
219 panic("%s: bad thread_info flags 0x%08x\n", __func__,