cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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runtime_instr.c (2268B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Copyright IBM Corp. 2012
      4 * Author(s): Jan Glauber <jang@linux.vnet.ibm.com>
      5 */
      6
      7#include <linux/kernel.h>
      8#include <linux/syscalls.h>
      9#include <linux/signal.h>
     10#include <linux/mm.h>
     11#include <linux/slab.h>
     12#include <linux/init.h>
     13#include <linux/errno.h>
     14#include <linux/kernel_stat.h>
     15#include <linux/sched/task_stack.h>
     16
     17#include <asm/runtime_instr.h>
     18#include <asm/cpu_mf.h>
     19#include <asm/irq.h>
     20
     21#include "entry.h"
     22
     23/* empty control block to disable RI by loading it */
     24struct runtime_instr_cb runtime_instr_empty_cb;
     25
     26void runtime_instr_release(struct task_struct *tsk)
     27{
     28	kfree(tsk->thread.ri_cb);
     29}
     30
     31static void disable_runtime_instr(void)
     32{
     33	struct task_struct *task = current;
     34	struct pt_regs *regs;
     35
     36	if (!task->thread.ri_cb)
     37		return;
     38	regs = task_pt_regs(task);
     39	preempt_disable();
     40	load_runtime_instr_cb(&runtime_instr_empty_cb);
     41	kfree(task->thread.ri_cb);
     42	task->thread.ri_cb = NULL;
     43	preempt_enable();
     44
     45	/*
     46	 * Make sure the RI bit is deleted from the PSW. If the user did not
     47	 * switch off RI before the system call the process will get a
     48	 * specification exception otherwise.
     49	 */
     50	regs->psw.mask &= ~PSW_MASK_RI;
     51}
     52
     53static void init_runtime_instr_cb(struct runtime_instr_cb *cb)
     54{
     55	cb->rla = 0xfff;
     56	cb->s = 1;
     57	cb->k = 1;
     58	cb->ps = 1;
     59	cb->pc = 1;
     60	cb->key = PAGE_DEFAULT_KEY >> 4;
     61	cb->v = 1;
     62}
     63
     64/*
     65 * The signum argument is unused. In older kernels it was used to
     66 * specify a real-time signal. For backwards compatibility user space
     67 * should pass a valid real-time signal number (the signum argument
     68 * was checked in older kernels).
     69 */
     70SYSCALL_DEFINE2(s390_runtime_instr, int, command, int, signum)
     71{
     72	struct runtime_instr_cb *cb;
     73
     74	if (!test_facility(64))
     75		return -EOPNOTSUPP;
     76
     77	if (command == S390_RUNTIME_INSTR_STOP) {
     78		disable_runtime_instr();
     79		return 0;
     80	}
     81
     82	if (command != S390_RUNTIME_INSTR_START)
     83		return -EINVAL;
     84
     85	if (!current->thread.ri_cb) {
     86		cb = kzalloc(sizeof(*cb), GFP_KERNEL);
     87		if (!cb)
     88			return -ENOMEM;
     89	} else {
     90		cb = current->thread.ri_cb;
     91		memset(cb, 0, sizeof(*cb));
     92	}
     93
     94	init_runtime_instr_cb(cb);
     95
     96	/* now load the control block to make it available */
     97	preempt_disable();
     98	current->thread.ri_cb = cb;
     99	load_runtime_instr_cb(cb);
    100	preempt_enable();
    101	return 0;
    102}