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1d17e808cf
1) Protect the event mask modification against the membarrier() IPI as
otherwise the RmW operation is unprotected and events might be lost.
2) Fix the weak symbol reference in rseq selftests
The current weak RSEQ symbols definitions which were added to allow
static linkage are not working correctly as the effectively re-define
the glibc symbols leading to multiple versions of the symbols when
compiled with -fno-common. Mark them as 'extern' to convert them from
weak symbol definitions to weak symbol references. That works with
static and dynamic linkage independent of -fcommon and -fno-common.
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Merge tag 'core-rseq-2025-09-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull rseq updates from Thomas Gleixner:
"Two fixes for RSEQ:
- Protect the event mask modification against the membarrier() IPI as
otherwise the RmW operation is unprotected and events might be lost
- Fix the weak symbol reference in rseq selftests
The current weak RSEQ symbols definitions which were added to allow
static linkage are not working correctly as they effectively
re-define the glibc symbols leading to multiple versions of the
symbols when compiled with -fno-common.
Mark them as 'extern' to convert them from weak symbol definitions
to weak symbol references. That works with static and dynamic
linkage independent of -fcommon and -fno-common"
* tag 'core-rseq-2025-09-29' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rseq/selftests: Use weak symbol reference, not definition, to link with glibc
rseq: Protect event mask against membarrier IPI
137 lines
3.1 KiB
C
137 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
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#ifndef _LINUX_RSEQ_H
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#define _LINUX_RSEQ_H
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#ifdef CONFIG_RSEQ
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#include <linux/preempt.h>
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#include <linux/sched.h>
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#ifdef CONFIG_MEMBARRIER
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# define RSEQ_EVENT_GUARD irq
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#else
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# define RSEQ_EVENT_GUARD preempt
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#endif
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/*
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* Map the event mask on the user-space ABI enum rseq_cs_flags
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* for direct mask checks.
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*/
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enum rseq_event_mask_bits {
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RSEQ_EVENT_PREEMPT_BIT = RSEQ_CS_FLAG_NO_RESTART_ON_PREEMPT_BIT,
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RSEQ_EVENT_SIGNAL_BIT = RSEQ_CS_FLAG_NO_RESTART_ON_SIGNAL_BIT,
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RSEQ_EVENT_MIGRATE_BIT = RSEQ_CS_FLAG_NO_RESTART_ON_MIGRATE_BIT,
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};
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enum rseq_event_mask {
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RSEQ_EVENT_PREEMPT = (1U << RSEQ_EVENT_PREEMPT_BIT),
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RSEQ_EVENT_SIGNAL = (1U << RSEQ_EVENT_SIGNAL_BIT),
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RSEQ_EVENT_MIGRATE = (1U << RSEQ_EVENT_MIGRATE_BIT),
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};
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static inline void rseq_set_notify_resume(struct task_struct *t)
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{
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if (t->rseq)
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set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
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}
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void __rseq_handle_notify_resume(struct ksignal *sig, struct pt_regs *regs);
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static inline void rseq_handle_notify_resume(struct ksignal *ksig,
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struct pt_regs *regs)
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{
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if (current->rseq)
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__rseq_handle_notify_resume(ksig, regs);
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}
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static inline void rseq_signal_deliver(struct ksignal *ksig,
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struct pt_regs *regs)
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{
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scoped_guard(RSEQ_EVENT_GUARD)
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__set_bit(RSEQ_EVENT_SIGNAL_BIT, ¤t->rseq_event_mask);
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rseq_handle_notify_resume(ksig, regs);
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}
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/* rseq_preempt() requires preemption to be disabled. */
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static inline void rseq_preempt(struct task_struct *t)
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{
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__set_bit(RSEQ_EVENT_PREEMPT_BIT, &t->rseq_event_mask);
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rseq_set_notify_resume(t);
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}
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/* rseq_migrate() requires preemption to be disabled. */
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static inline void rseq_migrate(struct task_struct *t)
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{
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__set_bit(RSEQ_EVENT_MIGRATE_BIT, &t->rseq_event_mask);
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rseq_set_notify_resume(t);
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}
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/*
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* If parent process has a registered restartable sequences area, the
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* child inherits. Unregister rseq for a clone with CLONE_VM set.
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*/
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static inline void rseq_fork(struct task_struct *t, u64 clone_flags)
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{
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if (clone_flags & CLONE_VM) {
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t->rseq = NULL;
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t->rseq_len = 0;
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t->rseq_sig = 0;
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t->rseq_event_mask = 0;
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} else {
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t->rseq = current->rseq;
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t->rseq_len = current->rseq_len;
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t->rseq_sig = current->rseq_sig;
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t->rseq_event_mask = current->rseq_event_mask;
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}
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}
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static inline void rseq_execve(struct task_struct *t)
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{
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t->rseq = NULL;
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t->rseq_len = 0;
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t->rseq_sig = 0;
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t->rseq_event_mask = 0;
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}
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#else
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static inline void rseq_set_notify_resume(struct task_struct *t)
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{
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}
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static inline void rseq_handle_notify_resume(struct ksignal *ksig,
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struct pt_regs *regs)
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{
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}
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static inline void rseq_signal_deliver(struct ksignal *ksig,
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struct pt_regs *regs)
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{
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}
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static inline void rseq_preempt(struct task_struct *t)
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{
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}
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static inline void rseq_migrate(struct task_struct *t)
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{
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}
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static inline void rseq_fork(struct task_struct *t, u64 clone_flags)
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{
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}
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static inline void rseq_execve(struct task_struct *t)
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{
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}
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#endif
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#ifdef CONFIG_DEBUG_RSEQ
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void rseq_syscall(struct pt_regs *regs);
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#else
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static inline void rseq_syscall(struct pt_regs *regs)
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{
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}
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#endif
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#endif /* _LINUX_RSEQ_H */
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