linux-kernel - [patch V5 22/31] rseq: Use static branch for syscall exit debug when GENERIC_IRQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251022121942.786322453@linutronix.de>
Date: Wed, 22 Oct 2025 14:52:28 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Michael Jeanson <mjeanson@...icios.com>,
 Jens Axboe <axboe@...nel.dk>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Peter Zijlstra <peterz@...radead.org>,
 "Paul E. McKenney" <paulmck@...nel.org>,
 x86@...nel.org,
 Sean Christopherson <seanjc@...gle.com>,
 Wei Liu <wei.liu@...nel.org>
Subject: [patch V5 22/31] 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>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>

---
 include/linux/entry-common.h |    2 +-
 include/linux/rseq_entry.h   |    9 +++++++++
 kernel/rseq.c                |   10 ++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -146,7 +146,7 @@ static __always_inline void syscall_exit
 			local_irq_enable();
 	}
 
-	rseq_syscall(regs);
+	rseq_debug_syscall_return(regs);
 
 	/*
 	 * Do one-time syscall specific work. If these work items are
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -296,9 +296,18 @@ static __always_inline void rseq_exit_to
 	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 */
--- a/kernel/rseq.c
+++ b/kernel/rseq.c
@@ -473,12 +473,11 @@ void __rseq_handle_notify_resume(struct
 	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
 
 /*