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-rw-r--r--arch/x86/lib/cmpxchg8b_emu.S85
1 files changed, 85 insertions, 0 deletions
diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S
new file mode 100644
index 0000000000..49805257b1
--- /dev/null
+++ b/arch/x86/lib/cmpxchg8b_emu.S
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <linux/linkage.h>
+#include <asm/export.h>
+#include <asm/percpu.h>
+#include <asm/processor-flags.h>
+
+.text
+
+#ifndef CONFIG_X86_CMPXCHG64
+
+/*
+ * Emulate 'cmpxchg8b (%esi)' on UP
+ *
+ * Inputs:
+ * %esi : memory location to compare
+ * %eax : low 32 bits of old value
+ * %edx : high 32 bits of old value
+ * %ebx : low 32 bits of new value
+ * %ecx : high 32 bits of new value
+ */
+SYM_FUNC_START(cmpxchg8b_emu)
+
+ pushfl
+ cli
+
+ cmpl 0(%esi), %eax
+ jne .Lnot_same
+ cmpl 4(%esi), %edx
+ jne .Lnot_same
+
+ movl %ebx, 0(%esi)
+ movl %ecx, 4(%esi)
+
+ orl $X86_EFLAGS_ZF, (%esp)
+
+ popfl
+ RET
+
+.Lnot_same:
+ movl 0(%esi), %eax
+ movl 4(%esi), %edx
+
+ andl $(~X86_EFLAGS_ZF), (%esp)
+
+ popfl
+ RET
+
+SYM_FUNC_END(cmpxchg8b_emu)
+EXPORT_SYMBOL(cmpxchg8b_emu)
+
+#endif
+
+#ifndef CONFIG_UML
+
+SYM_FUNC_START(this_cpu_cmpxchg8b_emu)
+
+ pushfl
+ cli
+
+ cmpl PER_CPU_VAR(0(%esi)), %eax
+ jne .Lnot_same2
+ cmpl PER_CPU_VAR(4(%esi)), %edx
+ jne .Lnot_same2
+
+ movl %ebx, PER_CPU_VAR(0(%esi))
+ movl %ecx, PER_CPU_VAR(4(%esi))
+
+ orl $X86_EFLAGS_ZF, (%esp)
+
+ popfl
+ RET
+
+.Lnot_same2:
+ movl PER_CPU_VAR(0(%esi)), %eax
+ movl PER_CPU_VAR(4(%esi)), %edx
+
+ andl $(~X86_EFLAGS_ZF), (%esp)
+
+ popfl
+ RET
+
+SYM_FUNC_END(this_cpu_cmpxchg8b_emu)
+
+#endif