linux-kernel - [tip: core/rseq] rseq: Use static branch for syscall exit debug when GENERIC_IRQ

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Message-ID: <176173341760.2601451.1484495948667542485.tip-bot2@tip-bot2>
Date: Wed, 29 Oct 2025 10:23:37 -0000
From: "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: core/rseq] rseq: Use static branch for syscall exit debug when
 GENERIC_IRQ_ENTRY=y

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     785637e834310e88ce00cb9eed2ba7ba03ea561d
Gitweb:        https://git.kernel.org/tip/785637e834310e88ce00cb9eed2ba7ba03ea561d
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:45:05 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:17 +01:00

rseq: Use static branch for syscall exit debug when GENERIC_IRQ_ENTRY=y

Make the syscall exit debug mechanism available via the static branch on
architectures which utilize the generic entry code.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Link: https://patch.msgid.link/20251027084307.333440475@linutronix.de
---
 include/linux/entry-common.h |  2 +-
 include/linux/rseq_entry.h   |  9 +++++++++
 kernel/rseq.c                | 10 ++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 75b194c..d967184 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -146,7 +146,7 @@ static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
 			local_irq_enable();
 	}
 
-	rseq_syscall(regs);
+	rseq_debug_syscall_return(regs);
 
 	/*
 	 * Do one-time syscall specific work. If these work items are
diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h
index 5bdcf5b..fb53a6f 100644
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -296,9 +296,18 @@ static __always_inline void rseq_exit_to_user_mode(void)
 	ev->events = 0;
 }
 
+void __rseq_debug_syscall_return(struct pt_regs *regs);
+
+static 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 void rseq_exit_to_user_mode(void) { }
+static inline void rseq_debug_syscall_return(struct pt_regs *regs) { }
 #endif /* !CONFIG_RSEQ */
 
 #endif /* _LINUX_RSEQ_ENTRY_H */
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 07d9fa7..5f21270 100644
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -473,12 +473,11 @@ error:
 	force_sigsegv(sig);
 }
 
-#ifdef CONFIG_DEBUG_RSEQ
 /*
  * Terminate the process if a syscall is issued within a restartable
  * sequence.
  */
-void rseq_syscall(struct pt_regs *regs)
+void __rseq_debug_syscall_return(struct pt_regs *regs)
 {
 	struct task_struct *t = current;
 	u64 csaddr;
@@ -496,6 +495,13 @@ void rseq_syscall(struct pt_regs *regs)
 fail:
 	force_sig(SIGSEGV);
 }
+
+#ifdef CONFIG_DEBUG_RSEQ
+/* Kept around to keep GENERIC_ENTRY=n architectures supported. */
+void rseq_syscall(struct pt_regs *regs)
+{
+	__rseq_debug_syscall_return(regs);
+}
 #endif
 
 /*