arch/s390/kernel/runtime_instr.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright IBM Corp. 2012
 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/sched/task_stack.h>

#include <asm/runtime_instr.h>
#include <asm/cpu_mf.h>
#include <asm/irq.h>

#include "entry.h"

/* empty control block to disable RI by loading it */
struct runtime_instr_cb runtime_instr_empty_cb;

void runtime_instr_release(struct task_struct *tsk)
{
	kfree(tsk->thread.ri_cb);
}

static void disable_runtime_instr(void)
{
	struct task_struct *task = current;
	struct pt_regs *regs;

	if (!task->thread.ri_cb)
		return;
	regs = task_pt_regs(task);
	preempt_disable();
	load_runtime_instr_cb(&runtime_instr_empty_cb);
	kfree(task->thread.ri_cb);
	task->thread.ri_cb = NULL;
	preempt_enable();

	/*
	 * Make sure the RI bit is deleted from the PSW. If the user did not
	 * switch off RI before the system call the process will get a
	 * specification exception otherwise.
	 */
	regs->psw.mask &= ~PSW_MASK_RI;
}

static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
{
	cb->rla = 0xfff;
	cb->s = 1;
	cb->k = 1;
	cb->ps = 1;
	cb->pc = 1;
	cb->key = PAGE_DEFAULT_KEY >> 4;
	cb->v = 1;
}

/*
 * The signum argument is unused. In older kernels it was used to
 * specify a real-time signal. For backwards compatibility user space
 * should pass a valid real-time signal number (the signum argument
 * was checked in older kernels).
 */
SYSCALL_DEFINE2(s390_runtime_instr, int, command, int, signum)
{
	struct runtime_instr_cb *cb;

	if (!test_facility(64))
		return -EOPNOTSUPP;

	if (command == S390_RUNTIME_INSTR_STOP) {
		disable_runtime_instr();
		return 0;
	}

	if (command != S390_RUNTIME_INSTR_START)
		return -EINVAL;

	if (!current->thread.ri_cb) {
		cb = kzalloc(sizeof(*cb), GFP_KERNEL);
		if (!cb)
			return -ENOMEM;
	} else {
		cb = current->thread.ri_cb;
		memset(cb, 0, sizeof(*cb));
	}

	init_runtime_instr_cb(cb);

	/* now load the control block to make it available */
	preempt_disable();
	current->thread.ri_cb = cb;
	load_runtime_instr_cb(cb);
	preempt_enable();
	return 0;
}