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// SPDX-License-Identifier: LGPL-2.1
/*
* rseq.c
*
* Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; only
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
#define _GNU_SOURCE
#include <errno.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <syscall.h>
#include <assert.h>
#include <signal.h>
#include <limits.h>
#include "rseq.h"
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
__thread volatile struct rseq __rseq_abi = {
.cpu_id = RSEQ_CPU_ID_UNINITIALIZED,
};
/*
* Shared with other libraries. This library may take rseq ownership if it is
* still 0 when executing the library constructor. Set to 1 by library
* constructor when handling rseq. Set to 0 in destructor if handling rseq.
*/
int __rseq_handled;
/* Whether this library have ownership of rseq registration. */
static int rseq_ownership;
static __thread volatile uint32_t __rseq_refcount;
static void signal_off_save(sigset_t *oldset)
{
sigset_t set;
int ret;
sigfillset(&set);
ret = pthread_sigmask(SIG_BLOCK, &set, oldset);
if (ret)
abort();
}
static void signal_restore(sigset_t oldset)
{
int ret;
ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
if (ret)
abort();
}
static int sys_rseq(volatile struct rseq *rseq_abi, uint32_t rseq_len,
int flags, uint32_t sig)
{
return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
}
int rseq_register_current_thread(void)
{
int rc, ret = 0;
sigset_t oldset;
if (!rseq_ownership)
return 0;
signal_off_save(&oldset);
if (__rseq_refcount == UINT_MAX) {
ret = -1;
goto end;
}
if (__rseq_refcount++)
goto end;
rc = sys_rseq(&__rseq_abi, sizeof(struct rseq), 0, RSEQ_SIG);
if (!rc) {
assert(rseq_current_cpu_raw() >= 0);
goto end;
}
if (errno != EBUSY)
__rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
ret = -1;
__rseq_refcount--;
end:
signal_restore(oldset);
return ret;
}
int rseq_unregister_current_thread(void)
{
int rc, ret = 0;
sigset_t oldset;
if (!rseq_ownership)
return 0;
signal_off_save(&oldset);
if (!__rseq_refcount) {
ret = -1;
goto end;
}
if (--__rseq_refcount)
goto end;
rc = sys_rseq(&__rseq_abi, sizeof(struct rseq),
RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
if (!rc)
goto end;
__rseq_refcount = 1;
ret = -1;
end:
signal_restore(oldset);
return ret;
}
int32_t rseq_fallback_current_cpu(void)
{
int32_t cpu;
cpu = sched_getcpu();
if (cpu < 0) {
perror("sched_getcpu()");
abort();
}
return cpu;
}
void __attribute__((constructor)) rseq_init(void)
{
/* Check whether rseq is handled by another library. */
if (__rseq_handled)
return;
__rseq_handled = 1;
rseq_ownership = 1;
}
void __attribute__((destructor)) rseq_fini(void)
{
if (!rseq_ownership)
return;
__rseq_handled = 0;
rseq_ownership = 0;
}
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