[PATCH v3 4/6] x86/uaccess: Convert 32-bit get_user() to unconditional pointer masking

[Josh Poimboeuf]

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

Signed-off-by: Josh Poimboeuf <jpoim...@kernel.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