linux-kernel - [patch 2/8] x86/entry/common: Consolidate syscall entry code

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Date:   Tue, 25 Feb 2020 23:08:03 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: [patch 2/8] x86/entry/common: Consolidate syscall entry code

All syscall entry points call enter_from_user_mode() and
local_irq_enable(). Move that into an inline helper so the interrupt
tracing can be moved into that helper later instead of sprinkling
it all over the place.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/entry/common.c |   48 +++++++++++++++++++++++++++++++++---------------
 1 file changed, 33 insertions(+), 15 deletions(-)

--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -49,6 +49,18 @@
 static inline void enter_from_user_mode(void) {}
 #endif
 
+/*
+ * All syscall entry variants call with interrupts disabled.
+ *
+ * Invoke context tracking if enabled and enable interrupts for further
+ * processing.
+ */
+static __always_inline void syscall_entry_fixups(void)
+{
+	enter_from_user_mode();
+	local_irq_enable();
+}
+
 static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
 {
 #ifdef CONFIG_X86_64
@@ -279,13 +291,11 @@ static void syscall_slow_exit_work(struc
 }
 
 #ifdef CONFIG_X86_64
-__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
+static __always_inline
+void do_syscall_64_irqs_on(unsigned long nr, struct pt_regs *regs)
 {
-	struct thread_info *ti;
+	struct thread_info *ti = current_thread_info();
 
-	enter_from_user_mode();
-	local_irq_enable();
-	ti = current_thread_info();
 	if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY)
 		nr = syscall_trace_enter(regs);
 
@@ -303,6 +313,12 @@ static void syscall_slow_exit_work(struc
 
 	syscall_return_slowpath(regs);
 }
+
+__visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
+{
+	syscall_entry_fixups();
+	do_syscall_64_irqs_on(nr, regs);
+}
 #endif
 
 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
@@ -355,19 +371,17 @@ static __always_inline void do_syscall_3
 /* Handles int $0x80 */
 __visible void do_int80_syscall_32(struct pt_regs *regs)
 {
-	enter_from_user_mode();
-	local_irq_enable();
+	syscall_entry_fixups();
 	do_syscall_32_irqs_on(regs);
 }
 
-/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
-__visible long do_fast_syscall_32(struct pt_regs *regs)
+/* Fast syscall 32bit variant */
+static __always_inline long do_fast_syscall_32_irqs_on(struct pt_regs *regs)
 {
 	/*
 	 * Called using the internal vDSO SYSENTER/SYSCALL32 calling
 	 * convention.  Adjust regs so it looks like we entered using int80.
 	 */
-
 	unsigned long landing_pad = (unsigned long)current->mm->context.vdso +
 		vdso_image_32.sym_int80_landing_pad;
 
@@ -378,10 +392,6 @@ static __always_inline void do_syscall_3
 	 */
 	regs->ip = landing_pad;
 
-	enter_from_user_mode();
-
-	local_irq_enable();
-
 	/* Fetch EBP from where the vDSO stashed it. */
 	if (
 #ifdef CONFIG_X86_64
@@ -437,4 +447,12 @@ static __always_inline void do_syscall_3
 		(regs->flags & (X86_EFLAGS_RF | X86_EFLAGS_TF | X86_EFLAGS_VM)) == 0;
 #endif
 }
-#endif
+
+/* Returns 0 to return using IRET or 1 to return using SYSEXIT/SYSRETL. */
+__visible long do_fast_syscall_32(struct pt_regs *regs)
+{
+	syscall_entry_fixups();
+	return do_fast_syscall_32_irqs_on(regs);
+}
+
+#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */