linux-kernel - [PATCH v3 4/6] x86/uaccess: Convert 32-bit get

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Message-ID: <088fc8f27c278791f3af29f94e09278b5fa07bea.1730166635.git.jpoimboe@kernel.org>
Date: Mon, 28 Oct 2024 18:56:17 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Waiman Long <longman@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Mark Rutland <mark.rutland@....com>,
	"Kirill A . Shutemov" <kirill@...temov.name>
Subject: [PATCH v3 4/6] x86/uaccess: Convert 32-bit get_user() to unconditional pointer masking

Convert the 32-bit get_user() implementations to use the new
unconditional masking scheme for consistency with 64-bit.

Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/lib/getuser.S | 33 ++++++++++++++-------------------
 1 file changed, 14 insertions(+), 19 deletions(-)

diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index 998d5be6b794..5bce27670baa 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -37,22 +37,19 @@
 
 #define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC
 
-.macro check_range size:req
+.macro mask_user_address size:req
 .if IS_ENABLED(CONFIG_X86_64)
 	movq $0x0123456789abcdef,%rdx
   1:
   .pushsection runtime_ptr_USER_PTR_MAX,"a"
 	.long 1b - 8 - .
   .popsection
-	cmp %rax, %rdx
-	sbb %rdx, %rdx
-	or %rdx, %rax
 .else
-	cmp $TASK_SIZE_MAX-\size+1, %eax
-	jae .Lbad_get_user
-	sbb %edx, %edx		/* array_index_mask_nospec() */
-	and %edx, %eax
+	mov $TASK_SIZE_MAX-\size, %edx
 .endif
+	cmp %_ASM_AX, %_ASM_DX
+	sbb %_ASM_DX, %_ASM_DX
+	or  %_ASM_DX, %_ASM_AX
 .endm
 
 .macro UACCESS op src dst
@@ -63,7 +60,7 @@
 
 	.text
 SYM_FUNC_START(__get_user_1)
-	check_range size=1
+	mask_user_address size=1
 	ASM_STAC
 	UACCESS movzbl (%_ASM_AX),%edx
 	xor %eax,%eax
@@ -73,7 +70,7 @@ SYM_FUNC_END(__get_user_1)
 EXPORT_SYMBOL(__get_user_1)
 
 SYM_FUNC_START(__get_user_2)
-	check_range size=2
+	mask_user_address size=2
 	ASM_STAC
 	UACCESS movzwl (%_ASM_AX),%edx
 	xor %eax,%eax
@@ -83,7 +80,7 @@ SYM_FUNC_END(__get_user_2)
 EXPORT_SYMBOL(__get_user_2)
 
 SYM_FUNC_START(__get_user_4)
-	check_range size=4
+	mask_user_address size=4
 	ASM_STAC
 	UACCESS movl (%_ASM_AX),%edx
 	xor %eax,%eax
@@ -93,14 +90,12 @@ SYM_FUNC_END(__get_user_4)
 EXPORT_SYMBOL(__get_user_4)
 
 SYM_FUNC_START(__get_user_8)
-#ifndef CONFIG_X86_64
-	xor %ecx,%ecx
-#endif
-	check_range size=8
+	mask_user_address size=8
 	ASM_STAC
 #ifdef CONFIG_X86_64
 	UACCESS movq (%_ASM_AX),%rdx
 #else
+	xor %ecx,%ecx
 	UACCESS movl (%_ASM_AX),%edx
 	UACCESS movl 4(%_ASM_AX),%ecx
 #endif
@@ -113,7 +108,7 @@ EXPORT_SYMBOL(__get_user_8)
 /* .. and the same for __get_user, just without the range checks */
 SYM_FUNC_START(__get_user_nocheck_1)
 #ifdef CONFIG_X86_64
-	check_range size=1
+	mask_user_address size=1
 #else
 	ASM_BARRIER_NOSPEC
 #endif
@@ -127,7 +122,7 @@ EXPORT_SYMBOL(__get_user_nocheck_1)
 
 SYM_FUNC_START(__get_user_nocheck_2)
 #ifdef CONFIG_X86_64
-	check_range size=2
+	mask_user_address size=2
 #else
 	ASM_BARRIER_NOSPEC
 #endif
@@ -141,7 +136,7 @@ EXPORT_SYMBOL(__get_user_nocheck_2)
 
 SYM_FUNC_START(__get_user_nocheck_4)
 #ifdef CONFIG_X86_64
-	check_range size=4
+	mask_user_address size=4
 #else
 	ASM_BARRIER_NOSPEC
 #endif
@@ -155,7 +150,7 @@ EXPORT_SYMBOL(__get_user_nocheck_4)
 
 SYM_FUNC_START(__get_user_nocheck_8)
 #ifdef CONFIG_X86_64
-	check_range size=8
+	mask_user_address size=8
 #else
 	ASM_BARRIER_NOSPEC
 #endif
-- 
2.47.0