d1a997ba4c
When checking for libc rseq support in the library constructor, don't only depend on the symbols presence, check that the registration was completed. This targets a scenario where the libc has rseq support but it is not wired for the current architecture in 'bits/rseq.h', we want to fallback to our internal registration mechanism. Signed-off-by: Michael Jeanson <mjeanson@efficios.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Link: https://lore.kernel.org/r/20220614154830.1367382-4-mjeanson@efficios.com
151 lines
3.3 KiB
C
151 lines
3.3 KiB
C
// SPDX-License-Identifier: LGPL-2.1
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/*
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* rseq.c
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*
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* Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; only
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* version 2.1 of the License.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*/
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#define _GNU_SOURCE
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#include <errno.h>
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#include <sched.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <syscall.h>
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#include <assert.h>
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#include <signal.h>
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#include <limits.h>
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#include <dlfcn.h>
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#include <stddef.h>
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#include "../kselftest.h"
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#include "rseq.h"
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static const ptrdiff_t *libc_rseq_offset_p;
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static const unsigned int *libc_rseq_size_p;
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static const unsigned int *libc_rseq_flags_p;
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/* Offset from the thread pointer to the rseq area. */
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ptrdiff_t rseq_offset;
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/* Size of the registered rseq area. 0 if the registration was
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unsuccessful. */
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unsigned int rseq_size = -1U;
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/* Flags used during rseq registration. */
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unsigned int rseq_flags;
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static int rseq_ownership;
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static
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__thread struct rseq_abi __rseq_abi __attribute__((tls_model("initial-exec"))) = {
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.cpu_id = RSEQ_ABI_CPU_ID_UNINITIALIZED,
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};
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static int sys_rseq(struct rseq_abi *rseq_abi, uint32_t rseq_len,
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int flags, uint32_t sig)
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{
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return syscall(__NR_rseq, rseq_abi, rseq_len, flags, sig);
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}
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int rseq_available(void)
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{
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int rc;
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rc = sys_rseq(NULL, 0, 0, 0);
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if (rc != -1)
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abort();
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switch (errno) {
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case ENOSYS:
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return 0;
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case EINVAL:
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return 1;
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default:
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abort();
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}
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}
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int rseq_register_current_thread(void)
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{
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int rc;
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if (!rseq_ownership) {
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/* Treat libc's ownership as a successful registration. */
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return 0;
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}
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rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), 0, RSEQ_SIG);
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if (rc)
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return -1;
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assert(rseq_current_cpu_raw() >= 0);
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return 0;
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}
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int rseq_unregister_current_thread(void)
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{
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int rc;
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if (!rseq_ownership) {
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/* Treat libc's ownership as a successful unregistration. */
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return 0;
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}
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rc = sys_rseq(&__rseq_abi, sizeof(struct rseq_abi), RSEQ_ABI_FLAG_UNREGISTER, RSEQ_SIG);
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if (rc)
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return -1;
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return 0;
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}
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static __attribute__((constructor))
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void rseq_init(void)
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{
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libc_rseq_offset_p = dlsym(RTLD_NEXT, "__rseq_offset");
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libc_rseq_size_p = dlsym(RTLD_NEXT, "__rseq_size");
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libc_rseq_flags_p = dlsym(RTLD_NEXT, "__rseq_flags");
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if (libc_rseq_size_p && libc_rseq_offset_p && libc_rseq_flags_p &&
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*libc_rseq_size_p != 0) {
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/* rseq registration owned by glibc */
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rseq_offset = *libc_rseq_offset_p;
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rseq_size = *libc_rseq_size_p;
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rseq_flags = *libc_rseq_flags_p;
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return;
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}
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if (!rseq_available())
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return;
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rseq_ownership = 1;
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rseq_offset = (void *)&__rseq_abi - rseq_thread_pointer();
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rseq_size = sizeof(struct rseq_abi);
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rseq_flags = 0;
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}
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static __attribute__((destructor))
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void rseq_exit(void)
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{
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if (!rseq_ownership)
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return;
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rseq_offset = 0;
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rseq_size = -1U;
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rseq_ownership = 0;
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}
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int32_t rseq_fallback_current_cpu(void)
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{
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int32_t cpu;
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cpu = sched_getcpu();
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if (cpu < 0) {
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perror("sched_getcpu()");
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abort();
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}
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return cpu;
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}
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