path: root/arch/mips/kernel/process.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
 * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
 * Copyright (C) 2004 Thiemo Seufer
 * Copyright (C) 2013  Imagination Technologies Ltd.
 */
#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
#include <linux/kernel.h>
#include <linux/nmi.h>
#include <linux/personality.h>
#include <linux/prctl.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>

#include <asm/abi.h>
#include <asm/asm.h>
#include <asm/dsemul.h>
#include <asm/dsp.h>
#include <asm/exec.h>
#include <asm/fpu.h>
#include <asm/inst.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
#include <asm/isadep.h>
#include <asm/msa.h>
#include <asm/mips-cps.h>
#include <asm/mipsregs.h>
#include <asm/processor.h>
#include <asm/reg.h>
#include <asm/stacktrace.h>

#ifdef CONFIG_HOTPLUG_CPU
void __noreturn arch_cpu_idle_dead(void)
{
	play_dead();
}
#endif

asmlinkage void ret_from_fork(void);
asmlinkage void ret_from_kernel_thread(void);

void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
{
	unsigned long status;

	/* New thread loses kernel privileges. */
	status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_CU2|ST0_FR|KU_MASK);
	status |= KU_USER;
	regs->cp0_status = status;
	lose_fpu(0);
	clear_thread_flag(TIF_MSA_CTX_LIVE);
	clear_used_math();
#ifdef CONFIG_MIPS_FP_SUPPORT
	atomic_set(&current->thread.bd_emu_frame, BD_EMUFRAME_NONE);
#endif
	init_dsp();
	regs->cp0_epc = pc;
	regs->regs[29] = sp;
}

void exit_thread(struct task_struct *tsk)
{
	/*
	 * User threads may have allocated a delay slot emulation frame.
	 * If so, clean up that allocation.
	 */
	if (!(current->flags & PF_KTHREAD))
		dsemul_thread_cleanup(tsk);
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
	/*
	 * Save any process state which is live in hardware registers to the
	 * parent context prior to duplication. This prevents the new child
	 * state becoming stale if the parent is preempted before copy_thread()
	 * gets a chance to save the parent's live hardware registers to the
	 * child context.
	 */
	preempt_disable();

	if (is_msa_enabled())
		save_msa(current);
	else if (is_fpu_owner())
		_save_fp(current);

	save_dsp(current);

	preempt_enable();

	*dst = *src;
	return 0;
}

/*
 * Copy architecture-specific thread state
 */
int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
{
	u64 clone_flags = args->flags;
	unsigned long usp = args->stack;
	unsigned long tls = args->tls;
	struct thread_info *ti = task_thread_info(p);
	struct pt_regs *childregs, *regs = current_pt_regs();
	unsigned long childksp;

	childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;

	/* set up new TSS. */
	childregs = (struct pt_regs *) childksp - 1;
	/*  Put the stack after the struct pt_regs.  */
	childksp = (unsigned long) childregs;
	p->thread.cp0_status = (read_c0_status() & ~(ST0_CU2|ST0_CU1)) | ST0_KERNEL_CUMASK;

	/*
	 * New tasks lose permission to use the fpu. This accelerates context
	 * switching for most programs since they don't use the fpu.
	 */
	clear_tsk_thread_flag(p, TIF_USEDFPU);
	clear_tsk_thread_flag(p, TIF_USEDMSA);
	clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);

#ifdef CONFIG_MIPS_MT_FPAFF
	clear_tsk_thread_flag(p, TIF_FPUBOUND);
#endif /* CONFIG_MIPS_MT_FPAFF */

	if (unlikely(args->fn)) {
		/* kernel thread */
		unsigned long status = p->thread.cp0_status;
		memset(childregs, 0, sizeof(struct pt_regs));
		p->thread.reg16 = (unsigned long)args->fn;
		p->thread.reg17 = (unsigned long)args->fn_arg;
		p->thread.reg29 = childksp;
		p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
#if defined(CONFIG_CPU_R3000)
		status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
			 ((status & (ST0_KUC | ST0_IEC)) << 2);
#else
		status |= ST0_EXL;
#endif
		childregs->cp0_status = status;
		return 0;
	}

	/* user thread */
	*childregs = *regs;
	childregs->regs[7] = 0; /* Clear error flag */
	childregs->regs[2] = 0; /* Child gets zero as return value */
	if (usp)
		childregs->regs[29] = usp;

	p->thread.reg29 = (unsigned long) childregs;
	p->thread.reg31 = (unsigned long