From: "tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
"Borislav Petkov (AMD)" <bp@alien8.de>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: x86/alternatives] x86/alternatives: Add longer 64-bit NOPs
Date: Wed, 31 May 2023 11:57:16 -0000 [thread overview]
Message-ID: <168553423659.404.5660759235465936351.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20230515093020.661756940@infradead.org>
The following commit has been merged into the x86/alternatives branch of tip:
Commit-ID: df25edbac31ea87b488789d44a362063542b5967
Gitweb: https://git.kernel.org/tip/df25edbac31ea87b488789d44a362063542b5967
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 15 May 2023 11:28:05 +02:00
Committer: Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Wed, 31 May 2023 10:21:21 +02:00
x86/alternatives: Add longer 64-bit NOPs
By adding support for longer NOPs there are a few more alternatives
that can turn into a single instruction.
Add up to NOP11, the same limit where GNU as .nops also stops
generating longer nops. This is because a number of uarchs have severe
decode penalties for more than 3 prefixes.
[ bp: Sync up with the version in tools/ while at it. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230515093020.661756940@infradead.org
---
arch/x86/include/asm/nops.h | 16 ++++++++++++++--
arch/x86/kernel/alternative.c | 10 ++++++++++
tools/arch/x86/include/asm/nops.h | 16 ++++++++++++++--
3 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/nops.h b/arch/x86/include/asm/nops.h
index c5573ea..1c1b755 100644
--- a/arch/x86/include/asm/nops.h
+++ b/arch/x86/include/asm/nops.h
@@ -34,6 +34,8 @@
#define BYTES_NOP7 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00
#define BYTES_NOP8 0x3e,BYTES_NOP7
+#define ASM_NOP_MAX 8
+
#else
/*
@@ -47,6 +49,9 @@
* 6: osp nopl 0x00(%eax,%eax,1)
* 7: nopl 0x00000000(%eax)
* 8: nopl 0x00000000(%eax,%eax,1)
+ * 9: cs nopl 0x00000000(%eax,%eax,1)
+ * 10: osp cs nopl 0x00000000(%eax,%eax,1)
+ * 11: osp osp cs nopl 0x00000000(%eax,%eax,1)
*/
#define BYTES_NOP1 0x90
#define BYTES_NOP2 0x66,BYTES_NOP1
@@ -56,6 +61,15 @@
#define BYTES_NOP6 0x66,BYTES_NOP5
#define BYTES_NOP7 0x0f,0x1f,0x80,0x00,0x00,0x00,0x00
#define BYTES_NOP8 0x0f,0x1f,0x84,0x00,0x00,0x00,0x00,0x00
+#define BYTES_NOP9 0x2e,BYTES_NOP8
+#define BYTES_NOP10 0x66,BYTES_NOP9
+#define BYTES_NOP11 0x66,BYTES_NOP10
+
+#define ASM_NOP9 _ASM_BYTES(BYTES_NOP9)
+#define ASM_NOP10 _ASM_BYTES(BYTES_NOP10)
+#define ASM_NOP11 _ASM_BYTES(BYTES_NOP11)
+
+#define ASM_NOP_MAX 11
#endif /* CONFIG_64BIT */
@@ -68,8 +82,6 @@
#define ASM_NOP7 _ASM_BYTES(BYTES_NOP7)
#define ASM_NOP8 _ASM_BYTES(BYTES_NOP8)
-#define ASM_NOP_MAX 8
-
#ifndef __ASSEMBLY__
extern const unsigned char * const x86_nops[];
#endif
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 93aa95a..0747d29 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -98,6 +98,11 @@ static const unsigned char x86nops[] =
BYTES_NOP6,
BYTES_NOP7,
BYTES_NOP8,
+#ifdef CONFIG_64BIT
+ BYTES_NOP9,
+ BYTES_NOP10,
+ BYTES_NOP11,
+#endif
};
const unsigned char * const x86_nops[ASM_NOP_MAX+1] =
@@ -111,6 +116,11 @@ const unsigned char * const x86_nops[ASM_NOP_MAX+1] =
x86nops + 1 + 2 + 3 + 4 + 5,
x86nops + 1 + 2 + 3 + 4 + 5 + 6,
x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
+#ifdef CONFIG_64BIT
+ x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8,
+ x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9,
+ x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10,
+#endif
};
/*
diff --git a/tools/arch/x86/include/asm/nops.h b/tools/arch/x86/include/asm/nops.h
index c5573ea..1c1b755 100644
--- a/tools/arch/x86/include/asm/nops.h
+++ b/tools/arch/x86/include/asm/nops.h
@@ -34,6 +34,8 @@
#define BYTES_NOP7 0x8d,0xb4,0x26,0x00,0x00,0x00,0x00
#define BYTES_NOP8 0x3e,BYTES_NOP7
+#define ASM_NOP_MAX 8
+
#else
/*
@@ -47,6 +49,9 @@
* 6: osp nopl 0x00(%eax,%eax,1)
* 7: nopl 0x00000000(%eax)
* 8: nopl 0x00000000(%eax,%eax,1)
+ * 9: cs nopl 0x00000000(%eax,%eax,1)
+ * 10: osp cs nopl 0x00000000(%eax,%eax,1)
+ * 11: osp osp cs nopl 0x00000000(%eax,%eax,1)
*/
#define BYTES_NOP1 0x90
#define BYTES_NOP2 0x66,BYTES_NOP1
@@ -56,6 +61,15 @@
#define BYTES_NOP6 0x66,BYTES_NOP5
#define BYTES_NOP7 0x0f,0x1f,0x80,0x00,0x00,0x00,0x00
#define BYTES_NOP8 0x0f,0x1f,0x84,0x00,0x00,0x00,0x00,0x00
+#define BYTES_NOP9 0x2e,BYTES_NOP8
+#define BYTES_NOP10 0x66,BYTES_NOP9
+#define BYTES_NOP11 0x66,BYTES_NOP10
+
+#define ASM_NOP9 _ASM_BYTES(BYTES_NOP9)
+#define ASM_NOP10 _ASM_BYTES(BYTES_NOP10)
+#define ASM_NOP11 _ASM_BYTES(BYTES_NOP11)
+
+#define ASM_NOP_MAX 11
#endif /* CONFIG_64BIT */
@@ -68,8 +82,6 @@
#define ASM_NOP7 _ASM_BYTES(BYTES_NOP7)
#define ASM_NOP8 _ASM_BYTES(BYTES_NOP8)
-#define ASM_NOP_MAX 8
-
#ifndef __ASSEMBLY__
extern const unsigned char * const x86_nops[];
#endif
next prev parent reply other threads:[~2023-05-31 11:57 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-15 9:28 [PATCH 0/2] x86/alternatives: More nops and some shrinkage Peter Zijlstra
2023-05-15 9:28 ` [PATCH 1/2] x86_64: Longer NOPs Peter Zijlstra
2023-05-31 11:57 ` tip-bot2 for Peter Zijlstra [this message]
[not found] ` <20230515093020.729622326@infradead.org>
2023-05-15 9:47 ` [PATCH 2/2] x86: Shorten RESET_CALL_DEPTH Andrew.Cooper3
2023-05-15 10:26 ` Peter Zijlstra
2023-05-31 11:57 ` [tip: x86/alternatives] x86/nospec: " tip-bot2 for Peter Zijlstra
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