linux-kernel - [patch 13/16] x86/entry: Move irqflags and context tracking to C for simple idtentries

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Message-Id: <20200225224145.444611199@linutronix.de>
Date:   Tue, 25 Feb 2020 23:33:34 +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 13/16] x86/entry: Move irqflags and context tracking to C for simple idtentries

Now that everything is converted to the new IDTENTRY mechansim, move the
irq tracing and the invocation of enter_to_user_mode() to C code, i.e. into
the idtentry_enter() inline which is invoked through the IDTENTRY magic.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/entry/entry_32.S       |    1 -
 arch/x86/entry/entry_64.S       |    9 ---------
 arch/x86/include/asm/idtentry.h |   19 ++++++++++++++++++-
 3 files changed, 18 insertions(+), 11 deletions(-)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -1452,7 +1452,6 @@ SYM_CODE_START_LOCAL_NOALIGN(common_exce
 	movl	PT_ORIG_EAX(%esp), %edx		# get the error code
 	movl	$-1, PT_ORIG_EAX(%esp)		# no syscall to restart
 
-	TRACE_IRQS_OFF
 	movl	%esp, %eax			# pt_regs pointer
 	CALL_NOSPEC %edi
 	jmp	ret_from_exception
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -511,15 +511,6 @@ SYM_CODE_END(spurious_entries_start)
 		GET_CR2_INTO(%r12);
 	.endif
 
-	TRACE_IRQS_OFF
-
-#ifdef CONFIG_CONTEXT_TRACKING
-	testb	$3, CS(%rsp)
-	jz	.Lfrom_kernel_no_ctxt_tracking_\@
-	CALL_enter_from_user_mode
-.Lfrom_kernel_no_ctxt_tracking_\@:
-#endif
-
 	movq	%rsp, %rdi			/* pt_regs pointer into 1st argument*/
 
 	.if \has_error_code == 1
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -7,14 +7,31 @@
 
 #ifndef __ASSEMBLY__
 
+#ifdef CONFIG_CONTEXT_TRACKING
+static __always_inline void enter_from_user_context(void)
+{
+	CT_WARN_ON(ct_state() != CONTEXT_USER);
+	user_exit_irqoff();
+}
+#else
+static __always_inline void enter_from_user_context(void) { }
+#endif
+
 /**
  * idtentry_enter - Handle state tracking on idtentry
  * @regs:	Pointer to pt_regs of interrupted context
  *
- * Place holder for now.
+ * Invokes:
+ *  - The hardirq tracer to keep the state consistent as low level ASM
+ *    entry disabled interrupts.
+ *
+ *  - Context tracking if the exception hit user mode
  */
 static __always_inline void idtentry_enter(struct pt_regs *regs)
 {
+	trace_hardirqs_off();
+	if (user_mode(regs))
+		enter_from_user_context();
 }
 
 /**