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| author | H. Peter Anvin <hpa@zytor.com> | 2008-02-19 08:24:33 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-02-26 12:55:51 +0100 |
| commit | 4cd20952d74323df06e438c0c3273b5be89d6bfd (patch) | |
| tree | dc9891edf781808943d5eb16da9a9c23f65ba0a2 /include/asm-x86 | |
| parent | x86: don't use P6_NOPs if compiling with CONFIG_X86_GENERIC (diff) | |
| download | linux-4cd20952d74323df06e438c0c3273b5be89d6bfd.tar.xz linux-4cd20952d74323df06e438c0c3273b5be89d6bfd.zip | |
x86: add comments for NOPs
Add comments describing the various NOP sequences.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/asm-x86')
| -rw-r--r-- | include/asm-x86/nops.h | 62 |
1 files changed, 45 insertions, 17 deletions
diff --git a/include/asm-x86/nops.h b/include/asm-x86/nops.h index c52b334b8166..e3b2bce0aff8 100644 --- a/include/asm-x86/nops.h +++ b/include/asm-x86/nops.h @@ -3,17 +3,29 @@ /* Define nops for use with alternative() */ -/* generic versions from gas */ -#define GENERIC_NOP1 ".byte 0x90\n" -#define GENERIC_NOP2 ".byte 0x89,0xf6\n" -#define GENERIC_NOP3 ".byte 0x8d,0x76,0x00\n" -#define GENERIC_NOP4 ".byte 0x8d,0x74,0x26,0x00\n" -#define GENERIC_NOP5 GENERIC_NOP1 GENERIC_NOP4 -#define GENERIC_NOP6 ".byte 0x8d,0xb6,0x00,0x00,0x00,0x00\n" -#define GENERIC_NOP7 ".byte 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00\n" -#define GENERIC_NOP8 GENERIC_NOP1 GENERIC_NOP7 +/* 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_NOP2 ".byte 0x89,0xf6\n" +#define GENERIC_NOP3 ".byte 0x8d,0x76,0x00\n" +#define GENERIC_NOP4 ".byte 0x8d,0x74,0x26,0x00\n" +#define GENERIC_NOP5 GENERIC_NOP1 GENERIC_NOP4 +#define GENERIC_NOP6 ".byte 0x8d,0xb6,0x00,0x00,0x00,0x00\n" +#define GENERIC_NOP7 ".byte 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00\n" +#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_NOP2 ".byte 0x66,0x90\n" #define K8_NOP3 ".byte 0x66,0x66,0x90\n" @@ -23,19 +35,35 @@ #define K8_NOP7 K8_NOP4 K8_NOP3 #define K8_NOP8 K8_NOP4 K8_NOP4 -/* K7 nops */ -/* uses eax dependencies (arbitary choice) */ -#define K7_NOP1 GENERIC_NOP1 +/* K7 nops + 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_NOP2 ".byte 0x8b,0xc0\n" #define K7_NOP3 ".byte 0x8d,0x04,0x20\n" #define K7_NOP4 ".byte 0x8d,0x44,0x20,0x00\n" #define K7_NOP5 K7_NOP4 ASM_NOP1 #define K7_NOP6 ".byte 0x8d,0x80,0,0,0,0\n" -#define K7_NOP7 ".byte 0x8D,0x04,0x05,0,0,0,0\n" -#define K7_NOP8 K7_NOP7 ASM_NOP1 +#define K7_NOP7 ".byte 0x8D,0x04,0x05,0,0,0,0\n" +#define K7_NOP8 K7_NOP7 ASM_NOP1 -/* P6 nops */ -/* uses eax dependencies (Intel-recommended choice) */ +/* 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) +*/ #define P6_NOP1 GENERIC_NOP1 #define P6_NOP2 ".byte 0x66,0x90\n" #define P6_NOP3 ".byte 0x0f,0x1f,0x00\n" |