[tip: x86/entry] x86/entry: Disable interrupts for native_load_gs_index() in C code

["tip-bot2 for Thomas Gleixner" <tip-bot2@xxxxxxxxxxxxx>]

The following commit has been merged into the x86/entry branch of tip:

Commit-ID:     800c8a1afb8e9d71ffb1ff54d6a2cf5c45dc50b5
Gitweb:        https://git.kernel.org/tip/800c8a1afb8e9d71ffb1ff54d6a2cf5c45dc50b5
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Wed, 04 Mar 2020 23:32:15 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 19 May 2020 16:03:53 +02:00

x86/entry: Disable interrupts for native_load_gs_index() in C code

There is absolutely no point in doing this in ASM code. Move it to C.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200505134903.531534675@xxxxxxxxxxxxx


---
 arch/x86/entry/entry_64.S            | 11 +++--------
 arch/x86/include/asm/special_insns.h | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9866b54..be8ed3a 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1041,22 +1041,17 @@ idtentry simd_coprocessor_error		do_simd_coprocessor_error	has_error_code=0
  *
  * Is in entry.text as it shouldn't be instrumented.
  */
-SYM_FUNC_START(native_load_gs_index)
+SYM_FUNC_START(asm_load_gs_index)
 	FRAME_BEGIN
-	pushfq
-	DISABLE_INTERRUPTS(CLBR_ANY & ~CLBR_RDI)
-	TRACE_IRQS_OFF
 	SWAPGS
 .Lgs_change:
 	movl	%edi, %gs
 2:	ALTERNATIVE "", "mfence", X86_BUG_SWAPGS_FENCE
 	SWAPGS
-	TRACE_IRQS_FLAGS (%rsp)
-	popfq
 	FRAME_END
 	ret
-SYM_FUNC_END(native_load_gs_index)
-EXPORT_SYMBOL(native_load_gs_index)
+SYM_FUNC_END(asm_load_gs_index)
+EXPORT_SYMBOL(asm_load_gs_index)
 
 	_ASM_EXTABLE(.Lgs_change, .Lbad_gs)
 	.section .fixup, "ax"
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 6d37b8f..82436cb 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -7,6 +7,7 @@
 
 #include <asm/nops.h>
 #include <asm/processor-flags.h>
+#include <linux/irqflags.h>
 #include <linux/jump_label.h>
 
 /*
@@ -129,7 +130,16 @@ static inline void native_wbinvd(void)
 	asm volatile("wbinvd": : :"memory");
 }
 
-extern asmlinkage void native_load_gs_index(unsigned);
+extern asmlinkage void asm_load_gs_index(unsigned int selector);
+
+static inline void native_load_gs_index(unsigned int selector)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	asm_load_gs_index(selector);
+	local_irq_restore(flags);
+}
 
 static inline unsigned long __read_cr4(void)
 {
@@ -186,7 +196,7 @@ static inline void wbinvd(void)
 
 #ifdef CONFIG_X86_64
 
-static inline void load_gs_index(unsigned selector)
+static inline void load_gs_index(unsigned int selector)
 {
 	native_load_gs_index(selector);
 }