From 40ce500b7f41916ab432eedd939dc54c61e7e49d Mon Sep 17 00:00:00 2001
From: guenther <guenther@openbsd.org>
Date: Fri, 28 Jul 2023 06:18:35 +0000
Subject: [PATCH] Add CODEPATCH_CODE() macro to simplify defining a symbol for
 a chunk of code to use in codepatching.  Use that for all the existing
 codepatching snippets.

Similarly, add CODEPATCH_CODE_LEN() which is CODEPATCH_CODE() but also
provides a short variable holding the length of the codepatch snippet.
Use that for some snippets that will be used for retpoline replacement.

ok kettenis@ deraadt@
---
 sys/arch/amd64/amd64/copy.S        | 12 +++-------
 sys/arch/amd64/amd64/locore.S      | 36 +++++++++---------------------
 sys/arch/amd64/include/codepatch.h | 18 ++++++++++++++-
 3 files changed, 31 insertions(+), 35 deletions(-)

diff --git a/sys/arch/amd64/amd64/copy.S b/sys/arch/amd64/amd64/copy.S
index ae254bf1587..f09ebf929b2 100644
--- a/sys/arch/amd64/amd64/copy.S
+++ b/sys/arch/amd64/amd64/copy.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: copy.S,v 1.18 2023/01/31 15:18:54 deraadt Exp $	*/
+/*	$OpenBSD: copy.S,v 1.19 2023/07/28 06:18:35 guenther Exp $	*/
 /*	$NetBSD: copy.S,v 1.1 2003/04/26 18:39:26 fvdl Exp $	*/
 
 /*
@@ -299,11 +299,5 @@ copystr_return:
 	ret
 	lfence
 
-	.section .rodata
-	.globl	_stac
-_stac:
-	stac
-
-	.globl	_clac
-_clac:
-	clac
+CODEPATCH_CODE(_stac,	stac)
+CODEPATCH_CODE(_clac,	clac)
diff --git a/sys/arch/amd64/amd64/locore.S b/sys/arch/amd64/amd64/locore.S
index 2046f0997c8..9024948b899 100644
--- a/sys/arch/amd64/amd64/locore.S
+++ b/sys/arch/amd64/amd64/locore.S
@@ -1,4 +1,4 @@
-/*	$OpenBSD: locore.S,v 1.138 2023/07/27 00:28:24 guenther Exp $	*/
+/*	$OpenBSD: locore.S,v 1.139 2023/07/28 06:18:35 guenther Exp $	*/
 /*	$NetBSD: locore.S,v 1.13 2004/03/25 18:33:17 drochner Exp $	*/
 
 /*
@@ -1084,30 +1084,16 @@ NENTRY(xsetbv_resume)
 	lfence
 END(xsetbv_user)
 
-	.section .rodata
-	.globl	_xrstor
-_xrstor:
-	xrstor64	(%rdi)
-
-	.globl	_xrstors
-_xrstors:
-	xrstors64	(%rdi)
-
-	.globl	_xsave
-_xsave:
-	xsave64		(%rdi)
-
-	.globl	_xsaves
-_xsaves:
-	xsaves64	(%rdi)
-
-	.globl	_xsaveopt
-_xsaveopt:
-	xsaveopt64	(%rdi)
-
-	.globl	_pcid_set_reuse
-_pcid_set_reuse:
-	orl	$(CR3_REUSE_PCID >> 32),CPUVAR(USER_CR3 + 4)
+CODEPATCH_CODE(_xrstor,		xrstor64 (%rdi))
+CODEPATCH_CODE(_xrstors,	xrstors64 (%rdi))
+CODEPATCH_CODE(_xsave,		xsave64 (%rdi))
+CODEPATCH_CODE(_xsaves,		xsaves64 (%rdi))
+CODEPATCH_CODE(_xsaveopt,	xsaveopt64 (%rdi))
+CODEPATCH_CODE(_pcid_set_reuse,
+		orl	$(CR3_REUSE_PCID >> 32),CPUVAR(USER_CR3 + 4))
+CODEPATCH_CODE_LEN(_jmprax,	jmp *%rax; int3)
+CODEPATCH_CODE_LEN(_jmpr11,	jmp *%r11; int3)
+CODEPATCH_CODE_LEN(_jmpr13,	jmp *%r13; int3)
 
 ENTRY(pagezero)
 	RETGUARD_SETUP(pagezero, r11)
diff --git a/sys/arch/amd64/include/codepatch.h b/sys/arch/amd64/include/codepatch.h
index 50618bddad0..71fe9475710 100644
--- a/sys/arch/amd64/include/codepatch.h
+++ b/sys/arch/amd64/include/codepatch.h
@@ -1,4 +1,4 @@
-/*      $OpenBSD: codepatch.h,v 1.15 2023/07/10 03:32:10 guenther Exp $    */
+/*      $OpenBSD: codepatch.h,v 1.16 2023/07/28 06:18:35 guenther Exp $    */
 /*
  * Copyright (c) 2014-2015 Stefan Fritsch <sf@sfritsch.de>
  *
@@ -97,4 +97,20 @@ void codepatch_disable(void);
 	.byte	0x0f, 0x1f, 0x40, 0x00				;\
 	CODEPATCH_END2(997, CPTAG_PCID_SET_REUSE)
 
+/* Would be neat if these could be in something like .cptext */
+#define CODEPATCH_CODE(symbol, instructions...)		\
+	.section .rodata;				\
+	.globl	symbol;					\
+symbol:	instructions;					\
+	.size	symbol, . - symbol
+
+/* provide a (short) variable with the length of the patch */
+#define CODEPATCH_CODE_LEN(symbol, instructions...)	\
+	CODEPATCH_CODE(symbol, instructions);		\
+996:	.globl	symbol##_len;				\
+	.align	2;					\
+symbol##_len:						\
+	.short	996b - symbol;				\
+	.size	symbol##_len, 2
+
 #endif /* _MACHINE_CODEPATCH_H_ */
-- 
2.20.1