/* * Process creation support for Hexagon * * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 and * only version 2 as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301, USA. */ #include <linux/sched.h>#include <linux/types.h>#include <linux/module.h>#include <linux/tick.h>#include <linux/uaccess.h>#include <linux/slab.h> /* * Kernel thread creation.  The desired kernel function is "wrapped" * in the kernel_thread_helper function, which does cleanup * afterwards. */static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *)){	do_exit(fn(arg));} int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags){	struct pt_regs regs; 	memset(&regs, 0, sizeof(regs));	/*	 * Yes, we're exploting illicit knowledge of the ABI here.	 */	regs.r00 = (unsigned long) arg;	regs.r01 = (unsigned long) fn;	pt_set_elr(&regs, (unsigned long)kernel_thread_helper);	pt_set_kmode(&regs); 	return do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);}EXPORT_SYMBOL(kernel_thread); /* * 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){	/* Set to run with user-mode data segmentation */	set_fs(USER_DS);	/* 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. */static void default_idle(void){	__vmwait();} void (*idle_sleep)(void) = default_idle; void cpu_idle(void){	while (1) {		tick_nohz_stop_sched_tick(1);		local_irq_disable();		while (!need_resched()) {			idle_sleep();			/*  interrupts wake us up, but aren't serviced  */			local_irq_enable();	/* service interrupt   */			local_irq_disable();		}		local_irq_enable();		tick_nohz_restart_sched_tick();		schedule();	}} /* *  Return saved PC of a blocked thread */unsigned long thread_saved_pc(struct task_struct *tsk){	return 0;} /* * Copy architecture-specific thread state */int copy_thread(unsigned long clone_flags, unsigned long usp,		unsigned long unused, struct task_struct *p,		struct pt_regs *regs){	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)); 	memcpy(childregs, regs, sizeof(*childregs));	ti->regs = childregs; 	/*	 * Establish kernel stack pointer and initial PC for new thread	 */	ss = (struct hexagon_switch_stack *) ((unsigned long) childregs -						    sizeof(*ss));	ss->lr = (unsigned long)ret_from_fork;	p->thread.switch_sp = ss; 	/* If User mode thread, set pt_reg stack pointer as per parameter */	if (user_mode(childregs)) {		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 = childregs->r04; 		/*		 * 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		 */	} else {		/*		 * If kernel thread, resume stack is kernel stack base.		 * Note that this is pointer arithmetic on pt_regs *		 */		pt_set_rte_sp(childregs, (unsigned long)(childregs + 1));		/*		 * We need the current thread_info fast path pointer		 * set up in pt_regs.  The register to be used is		 * parametric for assembler code, but the mechanism		 * doesn't drop neatly into C.  Needs to be fixed.		 */		childregs->THREADINFO_REG = (unsigned long) ti;	} 	/*	 * thread_info pointer is pulled out of task_struct "stack"	 * field on switch_to.	 */	p->stack = (void *)ti; 	return 0;} /* * Release any architecture-specific resources locked by thread */void release_thread(struct task_struct *dead_task){} /* * Free any architecture-specific thread data structures, etc. */void exit_thread(void){} /* * 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;} /* * Borrowed from PowerPC -- basically allow smaller kernel stacks if we * go crazy with the page sizes. */#if THREAD_SHIFT < PAGE_SHIFT static struct kmem_cache *thread_info_cache; struct thread_info *alloc_thread_info_node(struct task_struct *tsk, int node){	struct thread_info *ti; 	ti = kmem_cache_alloc_node(thread_info_cache, GFP_KERNEL, node);	if (unlikely(ti == NULL))		return NULL;#ifdef CONFIG_DEBUG_STACK_USAGE	memset(ti, 0, THREAD_SIZE);#endif	return ti;} void free_thread_info(struct thread_info *ti){	kmem_cache_free(thread_info_cache, ti);} /*  Weak symbol; called by init/main.c  */ void thread_info_cache_init(void){	thread_info_cache = kmem_cache_create("thread_info", THREAD_SIZE,					      THREAD_SIZE, 0, NULL);	BUG_ON(thread_info_cache == NULL);} #endif /* THREAD_SHIFT < PAGE_SHIFT */ /* * Required placeholder. */int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu){	return 0;}