[Xen-devel] [PATCH 1/3] x86: Add definitions for NOP operation

[Feng Wu <feng.wu@xxxxxxxxx>]

This patch adds definitions for different length of NOP operation.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
 xen/include/asm-x86/nops.h | 71 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 xen/include/asm-x86/nops.h

diff --git a/xen/include/asm-x86/nops.h b/xen/include/asm-x86/nops.h
new file mode 100644
index 0000000..f38df58
--- /dev/null
+++ b/xen/include/asm-x86/nops.h
@@ -0,0 +1,71 @@
+#ifndef __X86_ASM_NOPS_H__
+#define __X86_ASM_NOPS_H__
+
+#include <xen/stringify.h>
+
+/*
+ * Define nops for use with alternative().
+ */
+
+/*
+ * Opteron 64bit nops
+ * 1: nop
+ * 2: osp nop
+ * 3: osp osp nop
+ * 4: osp osp osp nop
+ */
+#define K8_NOP1 0x90
+#define K8_NOP2 0x66,K8_NOP1
+#define K8_NOP3 0x66,K8_NOP2
+#define K8_NOP4 0x66,K8_NOP3
+#define K8_NOP5 K8_NOP3,K8_NOP2
+#define K8_NOP6 K8_NOP3,K8_NOP3
+#define K8_NOP7 K8_NOP4,K8_NOP3
+#define K8_NOP8 K8_NOP4,K8_NOP4
+
+/*
+ * P6 nops
+ * uses eax dependencies (Intel-recommended choice)
+ * 1: nop
+ * 2: osp nop
+ * 3: nopl (%eax)
+ * 4: nopl 0x00(%eax)
+ * 5: nopl 0x00(%eax,%eax,1)
+ * 6: osp nopl 0x00(%eax,%eax,1)
+ * 7: nopl 0x00000000(%eax)
+ * 8: nopl 0x00000000(%eax,%eax,1)
+ *    Note: All the above are assumed to be a single instruction.
+ *          There is kernel code that depends on this.
+ */
+#define P6_NOP1 0x90
+#define P6_NOP2 0x66,0x90
+#define P6_NOP3 0x0f,0x1f,0x00
+#define P6_NOP4 0x0f,0x1f,0x40,0
+#define P6_NOP5 0x0f,0x1f,0x44,0x00,0
+#define P6_NOP6 0x66,0x0f,0x1f,0x44,0x00,0
+#define P6_NOP7 0x0f,0x1f,0x80,0,0,0,0
+#define P6_NOP8 0x0f,0x1f,0x84,0x00,0,0,0,0
+
+#ifdef __ASSEMBLY__
+#define _ASM_MK_NOP(x) .byte x
+#else
+#define _ASM_MK_NOP(x) ".byte " __stringify(x) "\n"
+#endif
+
+#define ASM_NOP1 _ASM_MK_NOP(K8_NOP1)
+#define ASM_NOP2 _ASM_MK_NOP(K8_NOP2)
+#define ASM_NOP3 _ASM_MK_NOP(K8_NOP3)
+#define ASM_NOP4 _ASM_MK_NOP(K8_NOP4)
+#define ASM_NOP5 _ASM_MK_NOP(K8_NOP5)
+#define ASM_NOP6 _ASM_MK_NOP(K8_NOP6)
+#define ASM_NOP7 _ASM_MK_NOP(K8_NOP7)
+#define ASM_NOP8 _ASM_MK_NOP(K8_NOP8)
+
+#define ASM_NOP_MAX 8
+
+#ifndef __ASSEMBLY__
+extern const unsigned char * const *ideal_nops;
+extern void arch_init_ideal_nops(void);
+#endif
+
+#endif /* __X86_ASM_NOPS_H__ */
-- 
1.8.3.1


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