restore lost packages from 0.2.3 + fix overwritten 0.2.4 files

- Restore 29 recipe symlinks (libdrm, qtbase, dbus, sddm, pipewire, etc.) - Restore 33 patches (KDE, libdrm, mesa, pipewire, sddm, wireplumber) - Restore 20+ local/scripts (audit, lint, test, build helpers) - Restore src/cook/scheduler.rs, status.rs, gnu-config/ - Restore scripts/patch-inclusion-gate.sh, run_mini1.sh, validate-collision-log.sh - Recover TLC source from HEAD (was overwritten by 0.2.3 checkout) - Recover 11 local/docs plans from HEAD (were overwritten) - Recover qt6-wayland-smoke symlink from HEAD - Fix MOTD: remove garbled ASCII art, use clean text - Update version: 0.2.0 -> 0.2.4 in os-release, motd, config - Reduce filesystem_size: 1536 -> 512 MiB - Add ABSOLUTE RULE to AGENTS.md: never delete/ignore packages - Reduce pcid scheme log verbosity: info -> debug
2026-06-19 12:39:14 +03:00
parent ffbe098ef8
commit dc68054305
6418 changed files with 7066233 additions and 8670 deletions
@@ -0,0 +1,771 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_RSEQ_ENTRY_H
+#define _LINUX_RSEQ_ENTRY_H
+
+/* Must be outside the CONFIG_RSEQ guard to resolve the stubs */
+#ifdef CONFIG_RSEQ_STATS
+#include <linux/percpu.h>
+
+struct rseq_stats {
+	unsigned long	exit;
+	unsigned long	signal;
+	unsigned long	slowpath;
+	unsigned long	fastpath;
+	unsigned long	ids;
+	unsigned long	cs;
+	unsigned long	clear;
+	unsigned long	fixup;
+	unsigned long	s_granted;
+	unsigned long	s_expired;
+	unsigned long	s_revoked;
+	unsigned long	s_yielded;
+	unsigned long	s_aborted;
+};
+
+DECLARE_PER_CPU(struct rseq_stats, rseq_stats);
+
+/*
+ * Slow path has interrupts and preemption enabled, but the fast path
+ * runs with interrupts disabled so there is no point in having the
+ * preemption checks implied in __this_cpu_inc() for every operation.
+ */
+#ifdef RSEQ_BUILD_SLOW_PATH
+#define rseq_stat_inc(which)	this_cpu_inc((which))
+#else
+#define rseq_stat_inc(which)	raw_cpu_inc((which))
+#endif
+
+#else /* CONFIG_RSEQ_STATS */
+#define rseq_stat_inc(x)	do { } while (0)
+#endif /* !CONFIG_RSEQ_STATS */
+
+#ifdef CONFIG_RSEQ
+#include <linux/hrtimer_rearm.h>
+#include <linux/jump_label.h>
+#include <linux/rseq.h>
+#include <linux/sched/signal.h>
+#include <linux/uaccess.h>
+
+#include <linux/tracepoint-defs.h>
+
+#ifdef CONFIG_TRACEPOINTS
+DECLARE_TRACEPOINT(rseq_update);
+DECLARE_TRACEPOINT(rseq_ip_fixup);
+void __rseq_trace_update(struct task_struct *t);
+void __rseq_trace_ip_fixup(unsigned long ip, unsigned long start_ip,
+			   unsigned long offset, unsigned long abort_ip);
+
+static inline void rseq_trace_update(struct task_struct *t, struct rseq_ids *ids)
+{
+	if (tracepoint_enabled(rseq_update) && ids)
+		__rseq_trace_update(t);
+}
+
+static inline void rseq_trace_ip_fixup(unsigned long ip, unsigned long start_ip,
+				       unsigned long offset, unsigned long abort_ip)
+{
+	if (tracepoint_enabled(rseq_ip_fixup))
+		__rseq_trace_ip_fixup(ip, start_ip, offset, abort_ip);
+}
+
+#else /* CONFIG_TRACEPOINT */
+static inline void rseq_trace_update(struct task_struct *t, struct rseq_ids *ids) { }
+static inline void rseq_trace_ip_fixup(unsigned long ip, unsigned long start_ip,
+				       unsigned long offset, unsigned long abort_ip) { }
+#endif /* !CONFIG_TRACEPOINT */
+
+DECLARE_STATIC_KEY_MAYBE(CONFIG_RSEQ_DEBUG_DEFAULT_ENABLE, rseq_debug_enabled);
+
+#ifdef RSEQ_BUILD_SLOW_PATH
+#define rseq_inline
+#else
+#define rseq_inline __always_inline
+#endif
+
+#ifdef CONFIG_RSEQ_SLICE_EXTENSION
+DECLARE_STATIC_KEY_TRUE(rseq_slice_extension_key);
+
+static __always_inline bool rseq_slice_extension_enabled(void)
+{
+	return static_branch_likely(&rseq_slice_extension_key);
+}
+
+extern unsigned int rseq_slice_ext_nsecs;
+bool __rseq_arm_slice_extension_timer(void);
+
+static __always_inline bool rseq_arm_slice_extension_timer(void)
+{
+	if (!rseq_slice_extension_enabled())
+		return false;
+
+	if (likely(!current->rseq.slice.state.granted))
+		return false;
+
+	return __rseq_arm_slice_extension_timer();
+}
+
+static __always_inline void rseq_slice_clear_grant(struct task_struct *t)
+{
+	if (IS_ENABLED(CONFIG_RSEQ_STATS) && t->rseq.slice.state.granted)
+		rseq_stat_inc(rseq_stats.s_revoked);
+	t->rseq.slice.state.granted = false;
+}
+
+/*
+ * Open coded, so it can be invoked within a user access region.
+ *
+ * This clears the user space state of the time slice extensions field only when
+ * the task has registered the optimized RSEQ_ABI V2. Some legacy registrations,
+ * e.g. TCMalloc, have conflicting non-ABI fields in struct RSEQ, which would be
+ * overwritten by an unconditional write.
+ */
+#define rseq_slice_clear_user(rseq, efault)				\
+do {									\
+	if (rseq_slice_extension_enabled())				\
+		unsafe_put_user(0U, &rseq->slice_ctrl.all, efault);	\
+} while (0)
+
+static __always_inline bool __rseq_grant_slice_extension(bool work_pending)
+{
+	struct task_struct *curr = current;
+	struct rseq_slice_ctrl usr_ctrl;
+	union rseq_slice_state state;
+	struct rseq __user *rseq;
+
+	if (!rseq_slice_extension_enabled())
+		return false;
+
+	/* If not enabled or not a return from interrupt, nothing to do. */
+	state = curr->rseq.slice.state;
+	state.enabled &= curr->rseq.event.user_irq;
+	if (likely(!state.state))
+		return false;
+
+	rseq = curr->rseq.usrptr;
+	scoped_user_rw_access(rseq, efault) {
+
+		/*
+		 * Quick check conditions where a grant is not possible or
+		 * needs to be revoked.
+		 *
+		 *  1) Any TIF bit which needs to do extra work aside of
+		 *     rescheduling prevents a grant.
+		 *
+		 *  2) A previous rescheduling request resulted in a slice
+		 *     extension grant.
+		 */
+		if (unlikely(work_pending || state.granted)) {
+			/* Clear user control unconditionally. No point for checking */
+			unsafe_put_user(0U, &rseq->slice_ctrl.all, efault);
+			rseq_slice_clear_grant(curr);
+			return false;
+		}
+
+		unsafe_get_user(usr_ctrl.all, &rseq->slice_ctrl.all, efault);
+		if (likely(!(usr_ctrl.request)))
+			return false;
+
+		/* Grant the slice extention */
+		usr_ctrl.request = 0;
+		usr_ctrl.granted = 1;
+		unsafe_put_user(usr_ctrl.all, &rseq->slice_ctrl.all, efault);
+	}
+
+	rseq_stat_inc(rseq_stats.s_granted);
+
+	curr->rseq.slice.state.granted = true;
+	/* Store expiry time for arming the timer on the way out */
+	curr->rseq.slice.expires = data_race(rseq_slice_ext_nsecs) + ktime_get_mono_fast_ns();
+	/*
+	 * This is racy against a remote CPU setting TIF_NEED_RESCHED in
+	 * several ways:
+	 *
+	 * 1)
+	 *	CPU0			CPU1
+	 *	clear_tsk()
+	 *				set_tsk()
+	 *	clear_preempt()
+	 *				Raise scheduler IPI on CPU0
+	 *	--> IPI
+	 *	    fold_need_resched() -> Folds correctly
+	 * 2)
+	 *	CPU0			CPU1
+	 *				set_tsk()
+	 *	clear_tsk()
+	 *	clear_preempt()
+	 *				Raise scheduler IPI on CPU0
+	 *	--> IPI
+	 *	    fold_need_resched() <- NOOP as TIF_NEED_RESCHED is false
+	 *
+	 * #1 is not any different from a regular remote reschedule as it
+	 *    sets the previously not set bit and then raises the IPI which
+	 *    folds it into the preempt counter
+	 *
+	 * #2 is obviously incorrect from a scheduler POV, but it's not
+	 *    differently incorrect than the code below clearing the
+	 *    reschedule request with the safety net of the timer.
+	 *
+	 * The important part is that the clearing is protected against the
+	 * scheduler IPI and also against any other interrupt which might
+	 * end up waking up a task and setting the bits in the middle of
+	 * the operation:
+	 *
+	 *	clear_tsk()
+	 *	---> Interrupt
+	 *		wakeup_on_this_cpu()
+	 *		set_tsk()
+	 *		set_preempt()
+	 *	clear_preempt()
+	 *
+	 * which would be inconsistent state.
+	 */
+	scoped_guard(irq) {
+		clear_tsk_need_resched(curr);
+		clear_preempt_need_resched();
+	}
+	return true;
+
+efault:
+	force_sig(SIGSEGV);
+	return false;
+}
+
+static __always_inline bool rseq_grant_slice_extension(unsigned long ti_work, unsigned long mask)
+{
+	if (unlikely(__rseq_grant_slice_extension(ti_work & mask))) {
+		hrtimer_rearm_deferred_tif(ti_work);
+		return true;
+	}
+	return false;
+}
+
+#else /* CONFIG_RSEQ_SLICE_EXTENSION */
+static __always_inline bool rseq_slice_extension_enabled(void) { return false; }
+static __always_inline bool rseq_arm_slice_extension_timer(void) { return false; }
+static __always_inline void rseq_slice_clear_grant(struct task_struct *t) { }
+static __always_inline bool rseq_grant_slice_extension(unsigned long ti_work, unsigned long mask) { return false; }
+#define rseq_slice_clear_user(rseq, efault) do { } while (0)
+#endif /* !CONFIG_RSEQ_SLICE_EXTENSION */
+
+bool rseq_debug_update_user_cs(struct task_struct *t, struct pt_regs *regs, unsigned long csaddr);
+
+static __always_inline void rseq_note_user_irq_entry(void)
+{
+	if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY))
+		current->rseq.event.user_irq = true;
+}
+
+/*
+ * Check whether there is a valid critical section and whether the
+ * instruction pointer in @regs is inside the critical section.
+ *
+ *  - If the critical section is invalid, terminate the task.
+ *
+ *  - If valid and the instruction pointer is inside, set it to the abort IP.
+ *
+ *  - If valid and the instruction pointer is outside, clear the critical
+ *    section address.
+ *
+ * Returns true, if the section was valid and either fixup or clear was
+ * done, false otherwise.
+ *
+ * In the failure case task::rseq_event::fatal is set when a invalid
+ * section was found. It's clear when the failure was an unresolved page
+ * fault.
+ *
+ * If inlined into the exit to user path with interrupts disabled, the
+ * caller has to protect against page faults with pagefault_disable().
+ *
+ * In preemptible task context this would be counterproductive as the page
+ * faults could not be fully resolved. As a consequence unresolved page
+ * faults in task context are fatal too.
+ */
+
+#ifdef RSEQ_BUILD_SLOW_PATH
+/*
+ * The debug version is put out of line, but kept here so the code stays
+ * together.
+ *
+ * @csaddr has already been checked by the caller to be in user space
+ */
+bool rseq_debug_update_user_cs(struct task_struct *t, struct pt_regs *regs,
+			       unsigned long csaddr)
+{
+	struct rseq_cs __user *ucs = (struct rseq_cs __user *)(unsigned long)csaddr;
+	u64 start_ip, abort_ip, offset, cs_end, head, tasksize = TASK_SIZE;
+	unsigned long ip = instruction_pointer(regs);
+	u64 __user *uc_head = (u64 __user *) ucs;
+	u32 usig, __user *uc_sig;
+
+	scoped_user_rw_access(ucs, efault) {
+		/*
+		 * Evaluate the user pile and exit if one of the conditions
+		 * is not fulfilled.
+		 */
+		unsafe_get_user(start_ip, &ucs->start_ip, efault);
+		if (unlikely(start_ip >= tasksize))
+			goto die;
+		/* If outside, just clear the critical section. */
+		if (ip < start_ip)
+			goto clear;
+
+		unsafe_get_user(offset, &ucs->post_commit_offset, efault);
+		cs_end = start_ip + offset;
+		/* Check for overflow and wraparound */
+		if (unlikely(cs_end >= tasksize || cs_end < start_ip))
+			goto die;
+
+		/* If not inside, clear it. */
+		if (ip >= cs_end)
+			goto clear;
+
+		unsafe_get_user(abort_ip, &ucs->abort_ip, efault);
+		/* Ensure it's "valid" */
+		if (unlikely(abort_ip >= tasksize || abort_ip < sizeof(*uc_sig)))
+			goto die;
+		/* Validate that the abort IP is not in the critical section */
+		if (unlikely(abort_ip - start_ip < offset))
+			goto die;
+
+		/*
+		 * Check version and flags for 0. No point in emitting
+		 * deprecated warnings before dying. That could be done in
+		 * the slow path eventually, but *shrug*.
+		 */
+		unsafe_get_user(head, uc_head, efault);
+		if (unlikely(head))
+			goto die;
+
+		/* abort_ip - 4 is >= 0. See abort_ip check above */
+		uc_sig = (u32 __user *)(unsigned long)(abort_ip - sizeof(*uc_sig));
+		unsafe_get_user(usig, uc_sig, efault);
+		if (unlikely(usig != t->rseq.sig))
+			goto die;
+
+		/* rseq_event.user_irq is only valid if CONFIG_GENERIC_IRQ_ENTRY=y */
+		if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY)) {
+			/* If not in interrupt from user context, let it die */
+			if (unlikely(!t->rseq.event.user_irq))
+				goto die;
+		}
+		unsafe_put_user(0ULL, &t->rseq.usrptr->rseq_cs, efault);
+		instruction_pointer_set(regs, (unsigned long)abort_ip);
+		rseq_stat_inc(rseq_stats.fixup);
+		break;
+	clear:
+		unsafe_put_user(0ULL, &t->rseq.usrptr->rseq_cs, efault);
+		rseq_stat_inc(rseq_stats.clear);
+		abort_ip = 0ULL;
+	}
+
+	if (unlikely(abort_ip))
+		rseq_trace_ip_fixup(ip, start_ip, offset, abort_ip);
+	return true;
+die:
+	t->rseq.event.fatal = true;
+efault:
+	return false;
+}
+
+#endif /* RSEQ_BUILD_SLOW_PATH */
+
+/*
+ * This only ensures that abort_ip is in the user address space and
+ * validates that it is preceded by the signature.
+ *
+ * No other sanity checks are done here, that's what the debug code is for.
+ */
+static rseq_inline bool
+rseq_update_user_cs(struct task_struct *t, struct pt_regs *regs, unsigned long csaddr)
+{
+	struct rseq_cs __user *ucs = (struct rseq_cs __user *)(unsigned long)csaddr;
+	unsigned long ip = instruction_pointer(regs);
+	unsigned long tasksize = TASK_SIZE;
+	u64 start_ip, abort_ip, offset;
+	u32 usig, __user *uc_sig;
+
+	rseq_stat_inc(rseq_stats.cs);
+
+	if (unlikely(csaddr >= tasksize)) {
+		t->rseq.event.fatal = true;
+		return false;
+	}
+
+	if (static_branch_unlikely(&rseq_debug_enabled))
+		return rseq_debug_update_user_cs(t, regs, csaddr);
+
+	scoped_user_rw_access(ucs, efault) {
+		unsafe_get_user(start_ip, &ucs->start_ip, efault);
+		unsafe_get_user(offset, &ucs->post_commit_offset, efault);
+		unsafe_get_user(abort_ip, &ucs->abort_ip, efault);
+
+		/*
+		 * No sanity checks. If user space screwed it up, it can
+		 * keep the pieces. That's what debug code is for.
+		 *
+		 * If outside, just clear the critical section.
+		 */
+		if (ip - start_ip >= offset)
+			goto clear;
+
+		/*
+		 * Two requirements for @abort_ip:
+		 *   - Must be in user space as x86 IRET would happily return to
+		 *     the kernel.
+		 *   - The four bytes preceding the instruction at @abort_ip must
+		 *     contain the signature.
+		 *
+		 * The latter protects against the following attack vector:
+		 *
+		 * An attacker with limited abilities to write, creates a critical
+		 * section descriptor, sets the abort IP to a library function or
+		 * some other ROP gadget and stores the address of the descriptor
+		 * in TLS::rseq::rseq_cs. An RSEQ abort would then evade ROP
+		 * protection.
+		 */
+		if (unlikely(abort_ip >= tasksize || abort_ip < sizeof(*uc_sig)))
+			goto die;
+
+		/* The address is guaranteed to be >= 0 and < TASK_SIZE */
+		uc_sig = (u32 __user *)(unsigned long)(abort_ip - sizeof(*uc_sig));
+		unsafe_get_user(usig, uc_sig, efault);
+		if (unlikely(usig != t->rseq.sig))
+			goto die;
+
+		/* Invalidate the critical section */
+		unsafe_put_user(0ULL, &t->rseq.usrptr->rseq_cs, efault);
+		/* Update the instruction pointer */
+		instruction_pointer_set(regs, (unsigned long)abort_ip);
+		rseq_stat_inc(rseq_stats.fixup);
+		break;
+	clear:
+		unsafe_put_user(0ULL, &t->rseq.usrptr->rseq_cs, efault);
+		rseq_stat_inc(rseq_stats.clear);
+		abort_ip = 0ULL;
+	}
+
+	if (unlikely(abort_ip))
+		rseq_trace_ip_fixup(ip, start_ip, offset, abort_ip);
+	return true;
+die:
+	t->rseq.event.fatal = true;
+efault:
+	return false;
+}
+
+/*
+ * Updates CPU ID, Node ID and MM CID and reads the critical section
+ * address, when @csaddr != NULL. This allows to put the ID update and the
+ * read under the same uaccess region to spare a separate begin/end.
+ *
+ * As this is either invoked from a C wrapper with @csaddr = NULL or from
+ * the fast path code with a valid pointer, a clever compiler should be
+ * able to optimize the read out. Spares a duplicate implementation.
+ *
+ * Returns true, if the operation was successful, false otherwise.
+ *
+ * In the failure case task::rseq_event::fatal is set when invalid data
+ * was found on debug kernels. It's clear when the failure was an unresolved page
+ * fault.
+ *
+ * If inlined into the exit to user path with interrupts disabled, the
+ * caller has to protect against page faults with pagefault_disable().
+ *
+ * In preemptible task context this would be counterproductive as the page
+ * faults could not be fully resolved. As a consequence unresolved page
+ * faults in task context are fatal too.
+ */
+static rseq_inline
+bool rseq_set_ids_get_csaddr(struct task_struct *t, struct rseq_ids *ids, u64 *csaddr)
+{
+	struct rseq __user *rseq = t->rseq.usrptr;
+
+	scoped_user_rw_access(rseq, efault) {
+		/* Validate the R/O fields for debug and optimized mode */
+		if (static_branch_unlikely(&rseq_debug_enabled) || rseq_v2(t)) {
+			u32 cpu_id, uval;
+
+			unsafe_get_user(cpu_id, &rseq->cpu_id_start, efault);
+			if (cpu_id != t->rseq.ids.cpu_id)
+				goto die;
+			unsafe_get_user(uval, &rseq->cpu_id, efault);
+			if (uval != cpu_id)
+				goto die;
+			unsafe_get_user(uval, &rseq->node_id, efault);
+			if (uval != t->rseq.ids.node_id)
+				goto die;
+			unsafe_get_user(uval, &rseq->mm_cid, efault);
+			if (uval != t->rseq.ids.mm_cid)
+				goto die;
+		}
+
+		unsafe_put_user(ids->cpu_id, &rseq->cpu_id_start, efault);
+		unsafe_put_user(ids->cpu_id, &rseq->cpu_id, efault);
+		unsafe_put_user(ids->node_id, &rseq->node_id, efault);
+		unsafe_put_user(ids->mm_cid, &rseq->mm_cid, efault);
+		if (csaddr)
+			unsafe_get_user(*csaddr, &rseq->rseq_cs, efault);
+
+		/* RSEQ ABI V2 only operations */
+		if (rseq_v2(t))
+			rseq_slice_clear_user(rseq, efault);
+	}
+
+	rseq_slice_clear_grant(t);
+	/* Cache the new values */
+	t->rseq.ids = *ids;
+	rseq_stat_inc(rseq_stats.ids);
+	rseq_trace_update(t, ids);
+	return true;
+
+die:
+	t->rseq.event.fatal = true;
+efault:
+	return false;
+}
+
+/*
+ * Update user space with new IDs and conditionally check whether the task
+ * is in a critical section.
+ */
+static rseq_inline bool rseq_update_usr(struct task_struct *t, struct pt_regs *regs,
+					struct rseq_ids *ids)
+{
+	u64 csaddr;
+
+	if (!rseq_set_ids_get_csaddr(t, ids, &csaddr))
+		return false;
+
+	/*
+	 * On architectures which utilize the generic entry code this
+	 * allows to skip the critical section when the entry was not from
+	 * a user space interrupt, unless debug mode is enabled.
+	 */
+	if (IS_ENABLED(CONFIG_GENERIC_IRQ_ENTRY)) {
+		if (!static_branch_unlikely(&rseq_debug_enabled)) {
+			if (likely(!t->rseq.event.user_irq))
+				return true;
+		}
+	}
+	if (likely(!csaddr))
+		return true;
+	/* Sigh, this really needs to do work */
+	return rseq_update_user_cs(t, regs, csaddr);
+}
+
+/*
+ * If you want to use this then convert your architecture to the generic
+ * entry code. I'm tired of building workarounds for people who can't be
+ * bothered to make the maintenance of generic infrastructure less
+ * burdensome. Just sucking everything into the architecture code and
+ * thereby making others chase the horrible hacks and keep them working is
+ * neither acceptable nor sustainable.
+ */
+#ifdef CONFIG_GENERIC_ENTRY
+
+/*
+ * This is inlined into the exit path because:
+ *
+ * 1) It's a one time comparison in the fast path when there is no event to
+ *    handle
+ *
+ * 2) The access to the user space rseq memory (TLS) is unlikely to fault
+ *    so the straight inline operation is:
+ *
+ *	- Four 32-bit stores only if CPU ID/ MM CID need to be updated
+ *	- One 64-bit load to retrieve the critical section address
+ *
+ * 3) In the unlikely case that the critical section address is != NULL:
+ *
+ *     - One 64-bit load to retrieve the start IP
+ *     - One 64-bit load to retrieve the offset for calculating the end
+ *     - One 64-bit load to retrieve the abort IP
+ *     - One 64-bit load to retrieve the signature
+ *     - One store to clear the critical section address
+ *
+ * The non-debug case implements only the minimal required checking. It
+ * provides protection against a rogue abort IP in kernel space, which
+ * would be exploitable at least on x86, and also against a rogue CS
+ * descriptor by checking the signature at the abort IP. Any fallout from
+ * invalid critical section descriptors is a user space problem. The debug
+ * case provides the full set of checks and terminates the task if a
+ * condition is not met.
+ *
+ * In case of a fault or an invalid value, this sets TIF_NOTIFY_RESUME and
+ * tells the caller to loop back into exit_to_user_mode_loop(). The rseq
+ * slow path there will handle the failure.
+ */
+static __always_inline bool rseq_exit_user_update(struct pt_regs *regs, struct task_struct *t)
+{
+	/*
+	 * Page faults need to be disabled as this is called with
+	 * interrupts disabled
+	 */
+	guard(pagefault)();
+	/*
+	 * This optimization is only valid when the task registered for the
+	 * optimized RSEQ_ABI_V2 variant. Some legacy users rely on the original
+	 * RSEQ implementation behaviour which unconditionally updated the IDs.
+	 * rseq_sched_switch_event() ensures that legacy registrations always
+	 * have both sched_switch and ids_changed set, which is compatible with
+	 * the historical TIF_NOTIFY_RESUME behaviour.
+	 */
+	if (likely(!t->rseq.event.ids_changed)) {
+		struct rseq __user *rseq = t->rseq.usrptr;
+		/*
+		 * If IDs have not changed rseq_event::user_irq must be true
+		 * See rseq_sched_switch_event().
+		 */
+		u64 csaddr;
+
+		scoped_user_rw_access(rseq, efault) {
+			unsafe_get_user(csaddr, &rseq->rseq_cs, efault);
+
+			/* RSEQ ABI V2 only operations */
+			if (rseq_v2(t))
+				rseq_slice_clear_user(rseq, efault);
+		}
+
+		rseq_slice_clear_grant(t);
+
+		if (static_branch_unlikely(&rseq_debug_enabled) || unlikely(csaddr)) {
+			if (unlikely(!rseq_update_user_cs(t, regs, csaddr)))
+				return false;
+		}
+		return true;
+	}
+
+	struct rseq_ids ids = {
+		.cpu_id	 = task_cpu(t),
+		.mm_cid	 = task_mm_cid(t),
+		.node_id = cpu_to_node(ids.cpu_id),
+	};
+
+	return rseq_update_usr(t, regs, &ids);
+efault:
+	return false;
+}
+
+static __always_inline bool __rseq_exit_to_user_mode_restart(struct pt_regs *regs)
+{
+	struct task_struct *t = current;
+
+	/*
+	 * If the task did not go through schedule or got the flag enforced
+	 * by the rseq syscall or execve, then nothing to do here.
+	 *
+	 * CPU ID and MM CID can only change when going through a context
+	 * switch.
+	 *
+	 * rseq_sched_switch_event() sets the rseq_event::sched_switch bit
+	 * only when rseq_event::has_rseq is true. That conditional is
+	 * required to avoid setting the TIF bit if RSEQ is not registered
+	 * for a task. rseq_event::sched_switch is cleared when RSEQ is
+	 * unregistered by a task so it's sufficient to check for the
+	 * sched_switch bit alone.
+	 *
+	 * A sane compiler requires three instructions for the nothing to do
+	 * case including clearing the events, but your mileage might vary.
+	 */
+	if (unlikely((t->rseq.event.sched_switch))) {
+		rseq_stat_inc(rseq_stats.fastpath);
+
+		if (unlikely(!rseq_exit_user_update(regs, t)))
+			return true;
+	}
+	/* Clear state so next entry starts from a clean slate */
+	t->rseq.event.events = 0;
+	return false;
+}
+
+/* Required to allow conversion to GENERIC_ENTRY w/o GENERIC_TIF_BITS */
+#ifdef CONFIG_HAVE_GENERIC_TIF_BITS
+static __always_inline bool test_tif_rseq(unsigned long ti_work)
+{
+	return ti_work & _TIF_RSEQ;
+}
+
+static __always_inline void clear_tif_rseq(void)
+{
+	static_assert(TIF_RSEQ != TIF_NOTIFY_RESUME);
+	clear_thread_flag(TIF_RSEQ);
+}
+#else
+static __always_inline bool test_tif_rseq(unsigned long ti_work) { return true; }
+static __always_inline void clear_tif_rseq(void) { }
+#endif
+
+static __always_inline bool
+rseq_exit_to_user_mode_restart(struct pt_regs *regs, unsigned long ti_work)
+{
+	if (unlikely(test_tif_rseq(ti_work))) {
+		if (unlikely(__rseq_exit_to_user_mode_restart(regs))) {
+			current->rseq.event.slowpath = true;
+			set_tsk_thread_flag(current, TIF_NOTIFY_RESUME);
+			return true;
+		}
+		clear_tif_rseq();
+	}
+	/*
+	 * Arm the slice extension timer if nothing to do anymore and the
+	 * task really goes out to user space.
+	 */
+	return rseq_arm_slice_extension_timer();
+}
+
+#else /* CONFIG_GENERIC_ENTRY */
+static inline bool rseq_exit_to_user_mode_restart(struct pt_regs *regs, unsigned long ti_work)
+{
+	return false;
+}
+#endif /* !CONFIG_GENERIC_ENTRY */
+
+static __always_inline void rseq_syscall_exit_to_user_mode(void)
+{
+	struct rseq_event *ev = &current->rseq.event;
+
+	rseq_stat_inc(rseq_stats.exit);
+
+	/* Needed to remove the store for the !lockdep case */
+	if (IS_ENABLED(CONFIG_LOCKDEP)) {
+		WARN_ON_ONCE(ev->sched_switch);
+		ev->events = 0;
+	}
+}
+
+static __always_inline void rseq_irqentry_exit_to_user_mode(void)
+{
+	struct rseq_event *ev = &current->rseq.event;
+
+	rseq_stat_inc(rseq_stats.exit);
+
+	lockdep_assert_once(!ev->sched_switch);
+
+	/*
+	 * Ensure that event (especially user_irq) is cleared when the
+	 * interrupt did not result in a schedule and therefore the
+	 * rseq processing could not clear it.
+	 */
+	ev->events = 0;
+}
+
+void __rseq_debug_syscall_return(struct pt_regs *regs);
+
+static __always_inline void rseq_debug_syscall_return(struct pt_regs *regs)
+{
+	if (static_branch_unlikely(&rseq_debug_enabled))
+		__rseq_debug_syscall_return(regs);
+}
+#else /* CONFIG_RSEQ */
+static inline void rseq_note_user_irq_entry(void) { }
+static inline bool rseq_exit_to_user_mode_restart(struct pt_regs *regs, unsigned long ti_work)
+{
+	return false;
+}
+static inline void rseq_syscall_exit_to_user_mode(void) { }
+static inline void rseq_irqentry_exit_to_user_mode(void) { }
+static inline void rseq_debug_syscall_return(struct pt_regs *regs) { }
+static inline bool rseq_grant_slice_extension(unsigned long ti_work, unsigned long mask) { return false; }
+#endif /* !CONFIG_RSEQ */
+
+#endif /* _LINUX_RSEQ_ENTRY_H */