[PATCH] x86/copy_user: Remove 64-bit asm _copy_*_user variants

* [PATCH] x86/copy_user: Remove 64-bit asm _copy_*_user variants
@ 2016-10-31 15:10 Borislav Petkov
  2016-11-01  7:13 ` [tip:x86/asm] x86/copy_user: Unify the code by removing the 64-bit asm _copy_*_user() variants tip-bot for Borislav Petkov
  2016-11-01 23:02 ` [PATCH] x86/copy_user: Remove 64-bit asm _copy_*_user variants Linus Torvalds
  0 siblings, 2 replies; 3+ messages in thread
From: Borislav Petkov @ 2016-10-31 15:10 UTC (permalink / raw)
  To: X86 ML; +Cc: Andy Lutomirski, Linus Torvalds, LKML

From: Borislav Petkov <bp@suse.de>

We already have the same functionality in usercopy_32.c. Share it with
64-bit and get rid of some more asm glue which is not needed anymore.

Signed-off-by: Borislav Petkov <bp@suse.de>
---

Guys, please double-check me on this but I think the asm and the
access_ok() macros are equivalent so we can get rid of the asm gunk and
redirect to the __copy_*_user variants after checking...

 arch/x86/lib/copy_user_64.S | 47 -------------------------------------------
 arch/x86/lib/usercopy.c     | 49 +++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/lib/usercopy_32.c  | 49 ---------------------------------------------
 3 files changed, 49 insertions(+), 96 deletions(-)

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index d376e4b48f88..c5959576c315 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -16,53 +16,6 @@
 #include <asm/smap.h>
 #include <asm/export.h>
 
-/* Standard copy_to_user with segment limit checking */
-ENTRY(_copy_to_user)
-	mov PER_CPU_VAR(current_task), %rax
-	movq %rdi,%rcx
-	addq %rdx,%rcx
-	jc bad_to_user
-	cmpq TASK_addr_limit(%rax),%rcx
-	ja bad_to_user
-	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
-		      "jmp copy_user_generic_string",		\
-		      X86_FEATURE_REP_GOOD,			\
-		      "jmp copy_user_enhanced_fast_string",	\
-		      X86_FEATURE_ERMS
-ENDPROC(_copy_to_user)
-EXPORT_SYMBOL(_copy_to_user)
-
-/* Standard copy_from_user with segment limit checking */
-ENTRY(_copy_from_user)
-	mov PER_CPU_VAR(current_task), %rax
-	movq %rsi,%rcx
-	addq %rdx,%rcx
-	jc bad_from_user
-	cmpq TASK_addr_limit(%rax),%rcx
-	ja bad_from_user
-	ALTERNATIVE_2 "jmp copy_user_generic_unrolled",		\
-		      "jmp copy_user_generic_string",		\
-		      X86_FEATURE_REP_GOOD,			\
-		      "jmp copy_user_enhanced_fast_string",	\
-		      X86_FEATURE_ERMS
-ENDPROC(_copy_from_user)
-EXPORT_SYMBOL(_copy_from_user)
-
-
-	.section .fixup,"ax"
-	/* must zero dest */
-ENTRY(bad_from_user)
-bad_from_user:
-	movl %edx,%ecx
-	xorl %eax,%eax
-	rep
-	stosb
-bad_to_user:
-	movl %edx,%eax
-	ret
-ENDPROC(bad_from_user)
-	.previous
-
 /*
  * copy_user_generic_unrolled - memory copy with exception handling.
  * This version is for CPUs like P4 that don't have efficient micro
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index b4908789484e..c074799bddae 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -34,3 +34,52 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(copy_from_user_nmi);
+
+/**
+ * copy_to_user: - Copy a block of data into user space.
+ * @to:   Destination address, in user space.
+ * @from: Source address, in kernel space.
+ * @n:    Number of bytes to copy.
+ *
+ * Context: User context only. This function may sleep if pagefaults are
+ *          enabled.
+ *
+ * Copy data from kernel space to user space.
+ *
+ * Returns number of bytes that could not be copied.
+ * On success, this will be zero.
+ */
+unsigned long _copy_to_user(void __user *to, const void *from, unsigned n)
+{
+	if (access_ok(VERIFY_WRITE, to, n))
+		n = __copy_to_user(to, from, n);
+	return n;
+}
+EXPORT_SYMBOL(_copy_to_user);
+
+/**
+ * copy_from_user: - Copy a block of data from user space.
+ * @to:   Destination address, in kernel space.
+ * @from: Source address, in user space.
+ * @n:    Number of bytes to copy.
+ *
+ * Context: User context only. This function may sleep if pagefaults are
+ *          enabled.
+ *
+ * Copy data from user space to kernel space.
+ *
+ * Returns number of bytes that could not be copied.
+ * On success, this will be zero.
+ *
+ * If some data could not be copied, this function will pad the copied
+ * data to the requested size using zero bytes.
+ */
+unsigned long _copy_from_user(void *to, const void __user *from, unsigned n)
+{
+	if (access_ok(VERIFY_READ, from, n))
+		n = __copy_from_user(to, from, n);
+	else
+		memset(to, 0, n);
+	return n;
+}
+EXPORT_SYMBOL(_copy_from_user);
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 3bc7baf2a711..0b281217c890 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -640,52 +640,3 @@ unsigned long __copy_from_user_ll_nocache_nozero(void *to, const void __user *fr
 	return n;
 }
 EXPORT_SYMBOL(__copy_from_user_ll_nocache_nozero);
-
-/**
- * copy_to_user: - Copy a block of data into user space.
- * @to:   Destination address, in user space.
- * @from: Source address, in kernel space.
- * @n:    Number of bytes to copy.
- *
- * Context: User context only. This function may sleep if pagefaults are
- *          enabled.
- *
- * Copy data from kernel space to user space.
- *
- * Returns number of bytes that could not be copied.
- * On success, this will be zero.
- */
-unsigned long _copy_to_user(void __user *to, const void *from, unsigned n)
-{
-	if (access_ok(VERIFY_WRITE, to, n))
-		n = __copy_to_user(to, from, n);
-	return n;
-}
-EXPORT_SYMBOL(_copy_to_user);
-
-/**
- * copy_from_user: - Copy a block of data from user space.
- * @to:   Destination address, in kernel space.
- * @from: Source address, in user space.
- * @n:    Number of bytes to copy.
- *
- * Context: User context only. This function may sleep if pagefaults are
- *          enabled.
- *
- * Copy data from user space to kernel space.
- *
- * Returns number of bytes that could not be copied.
- * On success, this will be zero.
- *
- * If some data could not be copied, this function will pad the copied
- * data to the requested size using zero bytes.
- */
-unsigned long _copy_from_user(void *to, const void __user *from, unsigned n)
-{
-	if (access_ok(VERIFY_READ, from, n))
-		n = __copy_from_user(to, from, n);
-	else
-		memset(to, 0, n);
-	return n;
-}
-EXPORT_SYMBOL(_copy_from_user);
-- 
2.10.0

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