// SPDX-License-Identifier: GPL-2.0-only/* * Process creation support for Hexagon * * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved. */ #include <linux/sched.h>#include <linux/sched/debug.h>#include <linux/sched/task.h>#include <linux/sched/task_stack.h>#include <linux/types.h>#include <linux/module.h>#include <linux/tick.h>#include <linux/uaccess.h>#include <linux/slab.h>#include <linux/tracehook.h> /* * Program thread launch.  Often defined as a macro in processor.h, * but we're shooting for a small footprint and it's not an inner-loop * performance-critical operation. * * The Hexagon ABI specifies that R28 is zero'ed before program launch, * so that gets automatically done here.  If we ever stop doing that here, * we'll probably want to define the ELF_PLAT_INIT macro. */void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp){	/* We want to zero all data-containing registers. Is this overkill? */	memset(regs, 0, sizeof(*regs));	/* We might want to also zero all Processor registers here */	pt_set_usermode(regs);	pt_set_elr(regs, pc);	pt_set_rte_sp(regs, sp);} /* *  Spin, or better still, do a hardware or VM wait instruction *  If hardware or VM offer wait termination even though interrupts *  are disabled. */void arch_cpu_idle(void){	__vmwait();	/*  interrupts wake us up, but irqs are still disabled */	local_irq_enable();} /* * Copy architecture-specific thread state */int copy_thread(unsigned long clone_flags, unsigned long usp, unsigned long arg,		struct task_struct *p, unsigned long tls){	struct thread_info *ti = task_thread_info(p);	struct hexagon_switch_stack *ss;	struct pt_regs *childregs;	asmlinkage void ret_from_fork(void); 	childregs = (struct pt_regs *) (((unsigned long) ti + THREAD_SIZE) -					sizeof(*childregs)); 	ti->regs = childregs; 	/*	 * Establish kernel stack pointer and initial PC for new thread	 * Note that unlike the usual situation, we do not copy the	 * parent's callee-saved here; those are in pt_regs and whatever	 * we leave here will be overridden on return to userland.	 */	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -						    sizeof(*ss));	ss->lr = (unsigned long)ret_from_fork;	p->thread.switch_sp = ss;	if (unlikely(p->flags & PF_KTHREAD)) {		memset(childregs, 0, sizeof(struct pt_regs));		/* r24 <- fn, r25 <- arg */		ss->r24 = usp;		ss->r25 = arg;		pt_set_kmode(childregs);		return 0;	}	memcpy(childregs, current_pt_regs(), sizeof(*childregs));	ss->r2524 = 0; 	if (usp)		pt_set_rte_sp(childregs, usp); 	/* Child sees zero return value */	childregs->r00 = 0; 	/*	 * The clone syscall has the C signature:	 * int [r0] clone(int flags [r0],	 *           void *child_frame [r1],	 *           void *parent_tid [r2],	 *           void *child_tid [r3],	 *           void *thread_control_block [r4]);	 * ugp is used to provide TLS support.	 */	if (clone_flags & CLONE_SETTLS)		childregs->ugp = tls; 	/*	 * Parent sees new pid -- not necessary, not even possible at	 * this point in the fork process	 * Might also want to set things like ti->addr_limit	 */ 	return 0;} /* * Release any architecture-specific resources locked by thread */void release_thread(struct task_struct *dead_task){} /* * Some archs flush debug and FPU info here */void flush_thread(void){} /* * The "wait channel" terminology is archaic, but what we want * is an identification of the point at which the scheduler * was invoked by a blocked thread. */unsigned long get_wchan(struct task_struct *p){	unsigned long fp, pc;	unsigned long stack_page;	int count = 0;	if (!p || p == current || p->state == TASK_RUNNING)		return 0; 	stack_page = (unsigned long)task_stack_page(p);	fp = ((struct hexagon_switch_stack *)p->thread.switch_sp)->fp;	do {		if (fp < (stack_page + sizeof(struct thread_info)) ||			fp >= (THREAD_SIZE - 8 + stack_page))			return 0;		pc = ((unsigned long *)fp)[1];		if (!in_sched_functions(pc))			return pc;		fp = *(unsigned long *) fp;	} while (count++ < 16); 	return 0;} /* * Called on the exit path of event entry; see vm_entry.S * * Interrupts will already be disabled. * * Returns 0 if there's no need to re-check for more work. */ int do_work_pending(struct pt_regs *regs, u32 thread_info_flags){	if (!(thread_info_flags & _TIF_WORK_MASK)) {		return 0;	}  /* shortcut -- no work to be done */ 	local_irq_enable(); 	if (thread_info_flags & _TIF_NEED_RESCHED) {		schedule();		return 1;	} 	if (thread_info_flags & _TIF_SIGPENDING) {		do_signal(regs);		return 1;	} 	if (thread_info_flags & _TIF_NOTIFY_RESUME) {		clear_thread_flag(TIF_NOTIFY_RESUME);		tracehook_notify_resume(regs);		return 1;	} 	/* Should not even reach here */	panic("%s: bad thread_info flags 0x%08x\n", __func__,		thread_info_flags);}