Commit-ID: 3693ca81151eacd498675baae56abede577e8b31
Gitweb: https://git.kernel.org/tip/3693ca81151eacd498675baae56abede577e8b31
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 1 Mar 2019 15:24:33 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 3 Apr 2019 09:36:29 +0200
x86/uaccess: Move copy_user_handle_tail() into asm
By writing the function in asm we avoid cross object code flow and
objtool no longer gets confused about a 'stray' CLAC.
Also; the asm version is actually _simpler_.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/asm.h | 24 --------------------
arch/x86/include/asm/uaccess_64.h | 3 ---
arch/x86/lib/copy_user_64.S | 48 +++++++++++++++++++++++++++++++++++++++
arch/x86/lib/usercopy_64.c | 20 ----------------
4 files changed, 48 insertions(+), 47 deletions(-)
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h
index 6467757bb39f..3ff577c0b102 100644
--- a/arch/x86/include/asm/asm.h
+++ b/arch/x86/include/asm/asm.h
@@ -148,30 +148,6 @@
_ASM_PTR (entry); \
.popsection
-.macro ALIGN_DESTINATION
- /* check for bad alignment of destination */
- movl %edi,%ecx
- andl $7,%ecx
- jz 102f /* already aligned */
- subl $8,%ecx
- negl %ecx
- subl %ecx,%edx
-100: movb (%rsi),%al
-101: movb %al,(%rdi)
- incq %rsi
- incq %rdi
- decl %ecx
- jnz 100b
-102:
- .section .fixup,"ax"
-103: addl %ecx,%edx /* ecx is zerorest also */
- jmp copy_user_handle_tail
- .previous
-
- _ASM_EXTABLE_UA(100b, 103b)
- _ASM_EXTABLE_UA(101b, 103b)
- .endm
-
#else
# define _EXPAND_EXTABLE_HANDLE(x) #x
# define _ASM_EXTABLE_HANDLE(from, to, handler) \
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index a9d637bc301d..5cd1caa8bc65 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -207,9 +207,6 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
return __copy_user_flushcache(dst, src, size);
}
-unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len);
-
unsigned long
mcsafe_handle_tail(char *to, char *from, unsigned len);
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index db4e5aa0858b..b2f1822084ae 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -16,6 +16,30 @@
#include <asm/smap.h>
#include <asm/export.h>
+.macro ALIGN_DESTINATION
+ /* check for bad alignment of destination */
+ movl %edi,%ecx
+ andl $7,%ecx
+ jz 102f /* already aligned */
+ subl $8,%ecx
+ negl %ecx
+ subl %ecx,%edx
+100: movb (%rsi),%al
+101: movb %al,(%rdi)
+ incq %rsi
+ incq %rdi
+ decl %ecx
+ jnz 100b
+102:
+ .section .fixup,"ax"
+103: addl %ecx,%edx /* ecx is zerorest also */
+ jmp copy_user_handle_tail
+ .previous
+
+ _ASM_EXTABLE_UA(100b, 103b)
+ _ASM_EXTABLE_UA(101b, 103b)
+ .endm
+
/*
* copy_user_generic_unrolled - memory copy with exception handling.
* This version is for CPUs like P4 that don't have efficient micro
@@ -193,6 +217,30 @@ ENTRY(copy_user_enhanced_fast_string)
ENDPROC(copy_user_enhanced_fast_string)
EXPORT_SYMBOL(copy_user_enhanced_fast_string)
+/*
+ * Try to copy last bytes and clear the rest if needed.
+ * Since protection fault in copy_from/to_user is not a normal situation,
+ * it is not necessary to optimize tail handling.
+ *
+ * Input:
+ * rdi destination
+ * rsi source
+ * rdx count
+ *
+ * Output:
+ * eax uncopied bytes or 0 if successful.
+ */
+ALIGN;
+copy_user_handle_tail:
+ movl %edx,%ecx
+1: rep movsb
+2: mov %ecx,%eax
+ ASM_CLAC
+ ret
+
+ _ASM_EXTABLE_UA(1b, 2b)
+ENDPROC(copy_user_handle_tail)
+
/*
* copy_user_nocache - Uncached memory copy with exception handling
* This will force destination out of cache for more performance.
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index ee42bb0cbeb3..9952a01cad24 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -54,26 +54,6 @@ unsigned long clear_user(void __user *to, unsigned long n)
}
EXPORT_SYMBOL(clear_user);
-/*
- * Try to copy last bytes and clear the rest if needed.
- * Since protection fault in copy_from/to_user is not a normal situation,
- * it is not necessary to optimize tail handling.
- */
-__visible unsigned long
-copy_user_handle_tail(char *to, char *from, unsigned len)
-{
- for (; len; --len, to++) {
- char c;
-
- if (__get_user_nocheck(c, from++, sizeof(char)))
- break;
- if (__put_user_nocheck(c, to, sizeof(char)))
- break;
- }
- clac();
- return len;
-}
-
/*
* Similar to copy_user_handle_tail, probe for the write fault point,
* but reuse __memcpy_mcsafe in case a new read error is encountered.
|