linux-stable/arch/s390/kernel/runtime_instr.c
Heiko Carstens 9eaba29c79 s390/runtime_instrumentation: fix storage key handling
The key member of the runtime instrumentation control block contains
only the access key, not the complete storage key. Therefore the value
must be shifted by four bits.
Note: this is only relevant for debugging purposes in case somebody
compiles a kernel with a default storage access key set to a value not
equal to zero.

Fixes: e4b8b3f33f ("s390: add support for runtime instrumentation")
Reported-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2020-08-17 13:17:10 +02:00

102 lines
2.2 KiB
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;
}