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authorLinus Torvalds <torvalds@linux-foundation.org>2020-04-08 12:50:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-12 16:57:57 -0700
commitea6f043fc9847e670b91dfbf1ef1cdff3451c152 (patch)
treeb91a008b262a787388e8bd72a511a9602ff060f8 /arch/x86/lib
parent53acd350503d56a73aa6c61bced1699e8396c6d0 (diff)
x86: Make __get_user() generate an out-of-line call
Instead of inlining the whole stac/lfence/mov/clac sequence (which also requires individual exception table entries and several asm instruction alternatives entries), just generate "call __get_user_nocheck_X" for the __get_user() cases. We can use all the same infrastructure that we already do for the regular "get_user()", and the end result is simpler source code, and much simpler code generation. It also means that when I introduce asm goto with input for "unsafe_get_user()", there are no nasty interactions with the __get_user() code. Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/lib')
-rw-r--r--arch/x86/lib/getuser.S60
1 files changed, 60 insertions, 0 deletions
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index c8a85b512796..2cd902e06062 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -35,6 +35,8 @@
#include <asm/smap.h>
#include <asm/export.h>
+#define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC
+
.text
SYM_FUNC_START(__get_user_1)
mov PER_CPU_VAR(current_task), %_ASM_DX
@@ -114,6 +116,52 @@ SYM_FUNC_START(__get_user_8)
SYM_FUNC_END(__get_user_8)
EXPORT_SYMBOL(__get_user_8)
+/* .. and the same for __get_user, just without the range checks */
+SYM_FUNC_START(__get_user_nocheck_1)
+ ASM_STAC
+ ASM_BARRIER_NOSPEC
+6: movzbl (%_ASM_AX),%edx
+ xor %eax,%eax
+ ASM_CLAC
+ ret
+SYM_FUNC_END(__get_user_nocheck_1)
+EXPORT_SYMBOL(__get_user_nocheck_1)
+
+SYM_FUNC_START(__get_user_nocheck_2)
+ ASM_STAC
+ ASM_BARRIER_NOSPEC
+7: movzwl (%_ASM_AX),%edx
+ xor %eax,%eax
+ ASM_CLAC
+ ret
+SYM_FUNC_END(__get_user_nocheck_2)
+EXPORT_SYMBOL(__get_user_nocheck_2)
+
+SYM_FUNC_START(__get_user_nocheck_4)
+ ASM_STAC
+ ASM_BARRIER_NOSPEC
+8: movl (%_ASM_AX),%edx
+ xor %eax,%eax
+ ASM_CLAC
+ ret
+SYM_FUNC_END(__get_user_nocheck_4)
+EXPORT_SYMBOL(__get_user_nocheck_4)
+
+SYM_FUNC_START(__get_user_nocheck_8)
+ ASM_STAC
+ ASM_BARRIER_NOSPEC
+#ifdef CONFIG_X86_64
+9: movq (%_ASM_AX),%rdx
+#else
+9: movl (%_ASM_AX),%edx
+10: movl 4(%_ASM_AX),%ecx
+#endif
+ xor %eax,%eax
+ ASM_CLAC
+ ret
+SYM_FUNC_END(__get_user_nocheck_8)
+EXPORT_SYMBOL(__get_user_nocheck_8)
+
SYM_CODE_START_LOCAL(.Lbad_get_user_clac)
ASM_CLAC
@@ -134,6 +182,7 @@ bad_get_user_8:
SYM_CODE_END(.Lbad_get_user_8_clac)
#endif
+/* get_user */
_ASM_EXTABLE_UA(1b, .Lbad_get_user_clac)
_ASM_EXTABLE_UA(2b, .Lbad_get_user_clac)
_ASM_EXTABLE_UA(3b, .Lbad_get_user_clac)
@@ -143,3 +192,14 @@ SYM_CODE_END(.Lbad_get_user_8_clac)
_ASM_EXTABLE_UA(4b, .Lbad_get_user_8_clac)
_ASM_EXTABLE_UA(5b, .Lbad_get_user_8_clac)
#endif
+
+/* __get_user */
+ _ASM_EXTABLE_UA(6b, .Lbad_get_user_clac)
+ _ASM_EXTABLE_UA(7b, .Lbad_get_user_clac)
+ _ASM_EXTABLE_UA(8b, .Lbad_get_user_clac)
+#ifdef CONFIG_X86_64
+ _ASM_EXTABLE_UA(9b, .Lbad_get_user_clac)
+#else
+ _ASM_EXTABLE_UA(9b, .Lbad_get_user_8_clac)
+ _ASM_EXTABLE_UA(10b, .Lbad_get_user_8_clac)
+#endif