Hexagon: Add init_task and process functions

/*

 * Init task definition

 *

 * 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/mm.h>

#include <linux/module.h>

#include <linux/sched.h>

#include <linux/init_task.h>

#include <linux/fs.h>

#include <linux/mqueue.h>

#include <asm/thread_info.h>

#include <asm/uaccess.h>

#include <asm/pgtable.h>

static struct signal_struct init_signals = INIT_SIGNALS(init_signals);

static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);

/*

 * Initial thread structure.

 *

 * We need to make sure that this is 8192-byte aligned due to the

 * way process stacks are handled. This is done by making sure

 * the linker maps this in the .text segment right after head.S,

 * and making head.S ensure the proper alignment.

 */

union thread_union init_thread_union

	__attribute__((__section__(".data.init_task"),

		__aligned__(THREAD_SIZE))) = {

			INIT_THREAD_INFO(init_task)

		};

/*

 * Initial task structure.

 *

 * All other task structs will be allocated on slabs in fork.c

 */

struct task_struct init_task = INIT_TASK(init_task);

EXPORT_SYMBOL(init_task);

/*

 * 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;

}