// SPDX-License-Identifier: GPL-2.0
/*
 * This file handles the architecture-dependent parts of process handling.
 */

#include <linux/sched/debug.h>
#include <linux/ptrace.h>
#include <linux/elfcore.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/random.h>

#include <asm/fpu.h>

#include "proto.h"

/*
 * Power off function, if any
 */
void (*pm_power_off)(void) = machine_power_off;
EXPORT_SYMBOL(pm_power_off);

struct halt_info {
	int mode;
	char *restart_cmd;
};

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

void arch_cpu_idle(void)
{
	int i;

	local_irq_enable();
	cpu_relax();

	if (is_in_guest())
		hcall(HCALL_HALT, 0, 0, 0);
	else {
		for (i = 0; i < 16; i++)
			asm("nop");
		asm("halt");
	}
}

static void common_shutdown_1(void *generic_ptr)
{
	struct halt_info *how = (struct halt_info *)generic_ptr;
	int cpuid = smp_processor_id();

	/* No point in taking interrupts anymore. */
	local_irq_disable();

#ifdef CONFIG_SMP
	/* Secondaries halt here. */
	if (cpuid != 0) {
		set_cpu_present(cpuid, false);
		set_cpu_possible(cpuid, false);

		if (is_in_guest()) {
			hcall(HCALL_SET_CLOCKEVENT, 0, 0, 0);
			while (1)
				asm("nop");
		} else
			asm("halt");
	}
#endif
	if (sw64_platform->kill_arch)
		sw64_platform->kill_arch(how->mode);
}

static void common_shutdown(int mode, char *restart_cmd)
{
	struct halt_info args;

	args.mode = mode;
	args.restart_cmd = restart_cmd;
	on_each_cpu(common_shutdown_1, &args, 0);
}

void machine_restart(char *restart_cmd)
{
	common_shutdown(LINUX_REBOOT_CMD_RESTART, restart_cmd);
}


void machine_halt(void)
{
	common_shutdown(LINUX_REBOOT_CMD_HALT, NULL);
}


void machine_power_off(void)
{
	common_shutdown(LINUX_REBOOT_CMD_POWER_OFF, NULL);
}


/* Used by sysrq-p, among others.  I don't believe r9-r15 are ever
 * saved in the context it's used.
 */

void
show_regs(struct pt_regs *regs)
{
	show_regs_print_info(KERN_DEFAULT);
	dik_show_regs(regs, NULL);
}

/*
 * Re-start a thread when doing execve()
 */
void
start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
	regs->pc = pc;
	regs->ps = 8;
	wrusp(sp);
}
EXPORT_SYMBOL(start_thread);


void
flush_thread(void)
{
	/* Arrange for each exec'ed process to start off with a clean slate
	 * with respect to the FPU.  This is all exceptions disabled.
	 */
	current_thread_info()->ieee_state = 0;
	wrfpcr(FPCR_DYN_NORMAL | ieee_swcr_to_fpcr(0));

	/* Clean slate for TLS.  */
	current_thread_info()->pcb.unique = 0;
}

void
release_thread(struct task_struct *dead_task)
{
}

/*
 * Copy architecture-specific thread state
 */

int
copy_thread(unsigned long clone_flags, unsigned long usp,
	   unsigned long kthread_arg, struct task_struct *p,
	   unsigned long tls)
{
	extern void ret_from_fork(void);
	extern void ret_from_kernel_thread(void);

	struct thread_info *childti = task_thread_info(p);
	struct pt_regs *childregs = task_pt_regs(p);
	struct pt_regs *regs = current_pt_regs();
	struct switch_stack *childstack, *stack;

	childstack = ((struct switch_stack *) childregs) - 1;
	childti->pcb.ksp = (unsigned long) childstack;
	childti->pcb.flags = 7;	/* set FEN, clear everything else */

	if (unlikely(p->flags & PF_KTHREAD)) {
		/* kernel thread */
		memset(childstack, 0,
			sizeof(struct switch_stack) + sizeof(struct pt_regs));
		childstack->r26 = (unsigned long) ret_from_kernel_thread;
		childstack->r9 = usp;	/* function */
		childstack->r10 = kthread_arg;
		childti->pcb.usp = 0;
		return 0;
	}
	/*
	 * Note: if CLONE_SETTLS is not set, then we must inherit the
	 * value from the parent, which will have been set by the block
	 * copy in dup_task_struct.  This is non-intuitive, but is
	 * required for proper operation in the case of a threaded
	 * application calling fork.
	 */
	if (clone_flags & CLONE_SETTLS)
		childti->pcb.unique = tls;
	else
		regs->r20 = 0;
	childti->pcb.usp = usp ?: rdusp();
	*childregs = *regs;
	childregs->r0 = 0;
	childregs->r19 = 0;
	stack = ((struct switch_stack *) regs) - 1;
	*childstack = *stack;
	p->thread = current->thread;
	childstack->r26 = (unsigned long) ret_from_fork;
	return 0;
}

/*
 * Fill in the user structure for a ELF core dump.
 */
void
dump_elf_thread(elf_greg_t *dest, struct pt_regs *pt, struct thread_info *ti)
{
	/* switch stack follows right below pt_regs: */
	struct switch_stack *sw = ((struct switch_stack *) pt) - 1;

	dest[0] = pt->r0;
	dest[1] = pt->r1;
	dest[2] = pt->r2;
	dest[3] = pt->r3;
	dest[4] = pt->r4;
	dest[5] = pt->r5;
	dest[6] = pt->r6;
	dest[7] = pt->r7;
	dest[8] = pt->r8;
	dest[9] = sw->r9;
	dest[10] = sw->r10;
	dest[11] = sw->r11;
	dest[12] = sw->r12;
	dest[13] = sw->r13;
	dest[14] = sw->r14;
	dest[15] = sw->r15;
	dest[16] = pt->r16;
	dest[17] = pt->r17;
	dest[18] = pt->r18;
	dest[19] = pt->r19;
	dest[20] = pt->r20;
	dest[21] = pt->r21;
	dest[22] = pt->r22;
	dest[23] = pt->r23;
	dest[24] = pt->r24;
	dest[25] = pt->r25;
	dest[26] = pt->r26;
	dest[27] = pt->r27;
	dest[28] = pt->r28;
	dest[29] = pt->gp;
	dest[30] = ti == current_thread_info() ? rdusp() : ti->pcb.usp;
	dest[31] = pt->pc;

	/* Once upon a time this was the PS value.  Which is stupid
	 * since that is always 8 for usermode.  Usurped for the more
	 * useful value of the thread's UNIQUE field.
	 */
	dest[32] = ti->pcb.unique;
}
EXPORT_SYMBOL(dump_elf_thread);

int
dump_elf_task(elf_greg_t *dest, struct task_struct *task)
{
	dump_elf_thread(dest, task_pt_regs(task), task_thread_info(task));
	return 1;
}
EXPORT_SYMBOL(dump_elf_task);

int
dump_elf_task_fp(elf_fpreg_t *dest, struct task_struct *task)
{
	memcpy(dest, &task->thread.ctx_fp, 32 * 8);
	return 1;
}
EXPORT_SYMBOL(dump_elf_task_fp);

/*
 * Return saved PC of a blocked thread.  This assumes the frame
 * pointer is the 6th saved long on the kernel stack and that the
 * saved return address is the first long in the frame.  This all
 * holds provided the thread blocked through a call to schedule() ($15
 * is the frame pointer in schedule() and $15 is saved at offset 48 by
 * entry.S:do_switch_stack).
 *
 * Under heavy swap load I've seen this lose in an ugly way.  So do
 * some extra sanity checking on the ranges we expect these pointers
 * to be in so that we can fail gracefully.  This is just for ps after
 * all.  -- r~
 */

unsigned long
thread_saved_pc(struct task_struct *t)
{
	unsigned long base = (unsigned long)task_stack_page(t);
	unsigned long fp, sp = task_thread_info(t)->pcb.ksp;

	if (sp > base && sp+6*8 < base + 16*1024) {
		fp = ((unsigned long *)sp)[6];
		if (fp > sp && fp < base + 16*1024)
			return *(unsigned long *)fp;
	}

	return 0;
}

unsigned long
get_wchan(struct task_struct *p)
{
	unsigned long schedule_frame;
	unsigned long pc, base, sp;

	if (!p || p == current || p->state == TASK_RUNNING)
		return 0;
	/*
	 * This one depends on the frame size of schedule().  Do a
	 * "disass schedule" in gdb to find the frame size.  Also, the
	 * code assumes that sleep_on() follows immediately after
	 * interruptible_sleep_on() and that add_timer() follows
	 * immediately after interruptible_sleep().  Ugly, isn't it?
	 * Maybe adding a wchan field to task_struct would be better,
	 * after all...
	 */

	pc = thread_saved_pc(p);
	if (in_sched_functions(pc)) {
		base = (unsigned long)task_stack_page(p);
		sp = task_thread_info(p)->pcb.ksp;
		schedule_frame = ((unsigned long *)sp)[6];
		if (schedule_frame > sp && schedule_frame < base + 16*1024)
			return ((unsigned long *)schedule_frame)[12];
	}
	return pc;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
	return randomize_page(mm->brk, 0x02000000);
}