[RFC PATCH -next V2 4/7] arm64: add copy_from_user to machine check safe

From: Tong Tiangen <tongtiangen@huawei.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>, <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>
Cc: <linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	Tong Tiangen <tongtiangen@huawei.com>
Subject: [RFC PATCH -next V2 4/7] arm64: add copy_from_user to machine check safe
Date: Wed, 6 Apr 2022 09:13:08 +0000	[thread overview]
Message-ID: <20220406091311.3354723-5-tongtiangen@huawei.com> (raw)
In-Reply-To: <20220406091311.3354723-1-tongtiangen@huawei.com>

Add scenarios copy_from_user to machine check safe.

The data copied is user data and is machine check safe, so just kill
the user process and isolate the error page, not necessary panic.

Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
---
 arch/arm64/include/asm/asm-uaccess.h | 16 ++++++++++++++++
 arch/arm64/lib/copy_from_user.S      | 11 ++++++-----
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index 0557af834e03..f31c8978e1af 100644
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -92,4 +92,20 @@ alternative_else_nop_endif
 
 		_asm_extable	8888b,\l;
 	.endm
+
+	.macro user_ldp_mc l, reg1, reg2, addr, post_inc
+8888:		ldtr	\reg1, [\addr];
+8889:		ldtr	\reg2, [\addr, #8];
+		add	\addr, \addr, \post_inc;
+
+		_asm_extable_mc	8888b, \l;
+		_asm_extable_mc	8889b, \l;
+	.endm
+
+	.macro user_ldst_mc l, inst, reg, addr, post_inc
+8888:		\inst		\reg, [\addr];
+		add		\addr, \addr, \post_inc;
+
+		_asm_extable_mc	8888b, \l;
+	.endm
 #endif
diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S
index 34e317907524..d9d7c5291871 100644
--- a/arch/arm64/lib/copy_from_user.S
+++ b/arch/arm64/lib/copy_from_user.S
@@ -21,7 +21,7 @@
  */
 
 	.macro ldrb1 reg, ptr, val
-	user_ldst 9998f, ldtrb, \reg, \ptr, \val
+	user_ldst_mc 9998f, ldtrb, \reg, \ptr, \val
 	.endm
 
 	.macro strb1 reg, ptr, val
@@ -29,7 +29,7 @@
 	.endm
 
 	.macro ldrh1 reg, ptr, val
-	user_ldst 9997f, ldtrh, \reg, \ptr, \val
+	user_ldst_mc 9997f, ldtrh, \reg, \ptr, \val
 	.endm
 
 	.macro strh1 reg, ptr, val
@@ -37,7 +37,7 @@
 	.endm
 
 	.macro ldr1 reg, ptr, val
-	user_ldst 9997f, ldtr, \reg, \ptr, \val
+	user_ldst_mc 9997f, ldtr, \reg, \ptr, \val
 	.endm
 
 	.macro str1 reg, ptr, val
@@ -45,7 +45,7 @@
 	.endm
 
 	.macro ldp1 reg1, reg2, ptr, val
-	user_ldp 9997f, \reg1, \reg2, \ptr, \val
+	user_ldp_mc 9997f, \reg1, \reg2, \ptr, \val
 	.endm
 
 	.macro stp1 reg1, reg2, ptr, val
@@ -62,7 +62,8 @@ SYM_FUNC_START(__arch_copy_from_user)
 	ret
 
 	// Exception fixups
-9997:	cmp	dst, dstin
+9997:	cbz	x0, 9998f			// Check machine check exception
+	cmp	dst, dstin
 	b.ne	9998f
 	// Before being absolutely sure we couldn't copy anything, try harder
 USER(9998f, ldtrb tmp1w, [srcin])
-- 
2.18.0.huawei.25

