Commit 4cd20952 authored by H. Peter Anvin's avatar H. Peter Anvin Committed by Ingo Molnar

x86: add comments for NOPs

Add comments describing the various NOP sequences.
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 959b3be6
...@@ -3,7 +3,14 @@ ...@@ -3,7 +3,14 @@
/* Define nops for use with alternative() */ /* Define nops for use with alternative() */
/* generic versions from gas */ /* generic versions from gas
1: nop
2: movl %esi,%esi
3: leal 0x00(%esi),%esi
4: leal 0x00(,%esi,1),%esi
6: leal 0x00000000(%esi),%esi
7: leal 0x00000000(,%esi,1),%esi
*/
#define GENERIC_NOP1 ".byte 0x90\n" #define GENERIC_NOP1 ".byte 0x90\n"
#define GENERIC_NOP2 ".byte 0x89,0xf6\n" #define GENERIC_NOP2 ".byte 0x89,0xf6\n"
#define GENERIC_NOP3 ".byte 0x8d,0x76,0x00\n" #define GENERIC_NOP3 ".byte 0x8d,0x76,0x00\n"
...@@ -13,7 +20,12 @@ ...@@ -13,7 +20,12 @@
#define GENERIC_NOP7 ".byte 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00\n" #define GENERIC_NOP7 ".byte 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00\n"
#define GENERIC_NOP8 GENERIC_NOP1 GENERIC_NOP7 #define GENERIC_NOP8 GENERIC_NOP1 GENERIC_NOP7
/* Opteron 64bit nops */ /* Opteron 64bit nops
1: nop
2: osp nop
3: osp osp nop
4: osp osp osp nop
*/
#define K8_NOP1 GENERIC_NOP1 #define K8_NOP1 GENERIC_NOP1
#define K8_NOP2 ".byte 0x66,0x90\n" #define K8_NOP2 ".byte 0x66,0x90\n"
#define K8_NOP3 ".byte 0x66,0x66,0x90\n" #define K8_NOP3 ".byte 0x66,0x66,0x90\n"
...@@ -23,8 +35,15 @@ ...@@ -23,8 +35,15 @@
#define K8_NOP7 K8_NOP4 K8_NOP3 #define K8_NOP7 K8_NOP4 K8_NOP3
#define K8_NOP8 K8_NOP4 K8_NOP4 #define K8_NOP8 K8_NOP4 K8_NOP4
/* K7 nops */ /* K7 nops
/* uses eax dependencies (arbitary choice) */ uses eax dependencies (arbitary choice)
1: nop
2: movl %eax,%eax
3: leal (,%eax,1),%eax
4: leal 0x00(,%eax,1),%eax
6: leal 0x00000000(%eax),%eax
7: leal 0x00000000(,%eax,1),%eax
*/
#define K7_NOP1 GENERIC_NOP1 #define K7_NOP1 GENERIC_NOP1
#define K7_NOP2 ".byte 0x8b,0xc0\n" #define K7_NOP2 ".byte 0x8b,0xc0\n"
#define K7_NOP3 ".byte 0x8d,0x04,0x20\n" #define K7_NOP3 ".byte 0x8d,0x04,0x20\n"
...@@ -34,8 +53,17 @@ ...@@ -34,8 +53,17 @@
#define K7_NOP7 ".byte 0x8D,0x04,0x05,0,0,0,0\n" #define K7_NOP7 ".byte 0x8D,0x04,0x05,0,0,0,0\n"
#define K7_NOP8 K7_NOP7 ASM_NOP1 #define K7_NOP8 K7_NOP7 ASM_NOP1
/* P6 nops */ /* P6 nops
/* uses eax dependencies (Intel-recommended choice) */ 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)
*/
#define P6_NOP1 GENERIC_NOP1 #define P6_NOP1 GENERIC_NOP1
#define P6_NOP2 ".byte 0x66,0x90\n" #define P6_NOP2 ".byte 0x66,0x90\n"
#define P6_NOP3 ".byte 0x0f,0x1f,0x00\n" #define P6_NOP3 ".byte 0x0f,0x1f,0x00\n"
......
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