Merge tag 'core-entry-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core entry code updates from Thomas Gleixner:
 "Updates for the generic and architecture entry code:

   - Move LoongArch and RISC-V ret_from_fork() implementations to C code
     so that syscall_exit_user_mode() can be inlined

   - Split the RISC-V ret_from_fork() implementation into return to user
     and return to kernel, which gives a measurable performance
     improvement

   - Inline syscall_exit_user_mode() which benefits all architectures by
     avoiding a function call and letting the compiler do better
     optimizations"

* tag 'core-entry-2025-05-25' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  LoongArch: entry: Fix include order
  entry: Inline syscall_exit_to_user_mode()
  LoongArch: entry: Migrate ret_from_fork() to C
  riscv: entry: Split ret_from_fork() into user and kernel
  riscv: entry: Convert ret_from_fork() to C

1 files changed, 41 insertions, 2 deletions

diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index fc61d0205c97..f94f3fdf15fc 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -14,6 +14,7 @@
 #include <linux/kmsan.h>
 
 #include <asm/entry-common.h>
+#include <asm/syscall.h>
 
 /*
  * Define dummy _TIF work flags if not defined by the architecture or for
@@ -367,6 +368,15 @@ static __always_inline void exit_to_user_mode(void)
 }
 
 /**
+ * syscall_exit_work - Handle work before returning to user mode
+ * @regs:	Pointer to current pt_regs
+ * @work:	Current thread syscall work
+ *
+ * Do one-time syscall specific work.
+ */
+void syscall_exit_work(struct pt_regs *regs, unsigned long work);
+
+/**
  * syscall_exit_to_user_mode_work - Handle work before returning to user mode
  * @regs:	Pointer to currents pt_regs
  *
@@ -379,7 +389,30 @@ static __always_inline void exit_to_user_mode(void)
  * make the final state transitions. Interrupts must stay disabled between
  * return from this function and the invocation of exit_to_user_mode().
  */
-void syscall_exit_to_user_mode_work(struct pt_regs *regs);
+static __always_inline void syscall_exit_to_user_mode_work(struct pt_regs *regs)
+{
+	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
+	unsigned long nr = syscall_get_nr(current, regs);
+
+	CT_WARN_ON(ct_state() != CT_STATE_KERNEL);
+
+	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
+		if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
+			local_irq_enable();
+	}
+
+	rseq_syscall(regs);
+
+	/*
+	 * Do one-time syscall specific work. If these work items are
+	 * enabled, we want to run them exactly once per syscall exit with
+	 * interrupts enabled.
+	 */
+	if (unlikely(work & SYSCALL_WORK_EXIT))
+		syscall_exit_work(regs, work);
+	local_irq_disable_exit_to_user();
+	exit_to_user_mode_prepare(regs);
+}
 
 /**
  * syscall_exit_to_user_mode - Handle work before returning to user mode
@@ -410,7 +443,13 @@ void syscall_exit_to_user_mode_work(struct pt_regs *regs);
  * exit_to_user_mode(). This function is preferred unless there is a
  * compelling architectural reason to use the separate functions.
  */
-void syscall_exit_to_user_mode(struct pt_regs *regs);
+static __always_inline void syscall_exit_to_user_mode(struct pt_regs *regs)
+{
+	instrumentation_begin();
+	syscall_exit_to_user_mode_work(regs);
+	instrumentation_end();
+	exit_to_user_mode();
+}
 
 /**
  * irqentry_enter_from_user_mode - Establish state before invoking the irq handler