include/linux/rseq.h

Source file repositories/reference/linux-study-clean/include/linux/rseq.h

File Facts

System
Linux kernel
Corpus path
include/linux/rseq.h
Extension
.h
Size
6499 bytes
Lines
205
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if (raise) {
			ev->sched_switch = true;
			rseq_raise_notify_resume(t);
		}
	} else {
		if (ev->has_rseq) {
			t->rseq.event.ids_changed = true;
			t->rseq.event.sched_switch = true;
			rseq_raise_notify_resume(t);
		}
	}
}

/*
 * Invoked from __set_task_cpu() when a task migrates or from
 * mm_cid_schedin() when the CID changes to enforce an IDs update.
 *
 * This does not raise TIF_NOTIFY_RESUME as that happens in
 * rseq_sched_switch_event().
 */
static __always_inline void rseq_sched_set_ids_changed(struct task_struct *t)
{
	t->rseq.event.ids_changed = true;
}

/* Enforce a full update after RSEQ registration and when execve() failed */
static inline void rseq_force_update(void)
{
	if (current->rseq.event.has_rseq) {
		current->rseq.event.ids_changed = true;
		current->rseq.event.sched_switch = true;
		rseq_raise_notify_resume(current);
	}
}

/*
 * KVM/HYPERV invoke resume_user_mode_work() before entering guest mode,
 * which clears TIF_NOTIFY_RESUME on architectures that don't use the
 * generic TIF bits and therefore can't provide a separate TIF_RSEQ flag.
 *
 * To avoid updating user space RSEQ in that case just to do it eventually
 * again before returning to user space, because __rseq_handle_slowpath()
 * does nothing when invoked with NULL register state.
 *
 * After returning from guest mode, before exiting to userspace, hypervisors
 * must invoke this function to re-raise TIF_NOTIFY_RESUME if necessary.
 */
static inline void rseq_virt_userspace_exit(void)
{
	/*
	 * The generic optimization for deferring RSEQ updates until the next
	 * exit relies on having a dedicated TIF_RSEQ.
	 */
	if (!IS_ENABLED(CONFIG_HAVE_GENERIC_TIF_BITS) &&
	    current->rseq.event.sched_switch)
		rseq_raise_notify_resume(current);
}

static inline void rseq_reset(struct task_struct *t)
{
	/* Protect against preemption and membarrier IPI */
	guard(irqsave)();
	memset(&t->rseq, 0, sizeof(t->rseq));
	t->rseq.ids.cpu_id = RSEQ_CPU_ID_UNINITIALIZED;
}

static inline void rseq_execve(struct task_struct *t)
{
	rseq_reset(t);
}

/*
 * If parent process has a registered restartable sequences area, the
 * child inherits. Unregister rseq for a clone with CLONE_VM set.
 *
 * On fork, keep the IDs (CPU, MMCID) of the parent, which avoids a fault
 * on the COW page on exit to user space, when the child stays on the same
 * CPU as the parent. That's obviously not guaranteed, but in overcommit
 * scenarios it is more likely and optimizes for the fork/exec case without
 * taking the fault.
 */
static inline void rseq_fork(struct task_struct *t, u64 clone_flags)
{
	if (clone_flags & CLONE_VM)
		rseq_reset(t);
	else
		t->rseq = current->rseq;
}

/*

Annotation

Implementation Notes