From 57f0f512b273f60d52568b8c6b77e17f5636edc0 Mon Sep 17 00:00:00 2001
From: André Fabian Silva Delgado <emulatorman@parabola.nu>
Date: Wed, 5 Aug 2015 17:04:01 -0300
Subject: Initial import

---
 arch/x86/lib/cmpxchg16b_emu.S | 59 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)
 create mode 100644 arch/x86/lib/cmpxchg16b_emu.S

(limited to 'arch/x86/lib/cmpxchg16b_emu.S')

diff --git a/arch/x86/lib/cmpxchg16b_emu.S b/arch/x86/lib/cmpxchg16b_emu.S
new file mode 100644
index 000000000..40a172541
--- /dev/null
+++ b/arch/x86/lib/cmpxchg16b_emu.S
@@ -0,0 +1,59 @@
+/*
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; version 2
+ *	of the License.
+ *
+ */
+#include <linux/linkage.h>
+#include <asm/dwarf2.h>
+#include <asm/percpu.h>
+
+.text
+
+/*
+ * Inputs:
+ * %rsi : memory location to compare
+ * %rax : low 64 bits of old value
+ * %rdx : high 64 bits of old value
+ * %rbx : low 64 bits of new value
+ * %rcx : high 64 bits of new value
+ * %al  : Operation successful
+ */
+ENTRY(this_cpu_cmpxchg16b_emu)
+CFI_STARTPROC
+
+#
+# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not
+# via the ZF.  Caller will access %al to get result.
+#
+# Note that this is only useful for a cpuops operation.  Meaning that we
+# do *not* have a fully atomic operation but just an operation that is
+# *atomic* on a single cpu (as provided by the this_cpu_xx class of
+# macros).
+#
+	pushfq_cfi
+	cli
+
+	cmpq PER_CPU_VAR((%rsi)), %rax
+	jne .Lnot_same
+	cmpq PER_CPU_VAR(8(%rsi)), %rdx
+	jne .Lnot_same
+
+	movq %rbx, PER_CPU_VAR((%rsi))
+	movq %rcx, PER_CPU_VAR(8(%rsi))
+
+	CFI_REMEMBER_STATE
+	popfq_cfi
+	mov $1, %al
+	ret
+
+	CFI_RESTORE_STATE
+.Lnot_same:
+	popfq_cfi
+	xor %al,%al
+	ret
+
+CFI_ENDPROC
+
+ENDPROC(this_cpu_cmpxchg16b_emu)
-- 
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