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Date: Wed, 13 May 2015 11:52:48 +0200
From: Borislav Petkov <bp@...en8.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...capital.net>,
Denys Vlasenko <dvlasenk@...hat.com>,
lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] Drop some asm from copy_user_64.S
On Tue, May 12, 2015 at 11:53:20PM +0200, Borislav Petkov wrote:
> > That said, I think you should uninline those things, and move them
> > from a header file to a C file (arch/x86/lib/uaccess.c?).
It is starting to look better wrt size:
x86_64_defconfig:
text data bss dec hex filename
before: 12375798 1812800 1085440 15274038 e91036 vmlinux
after: 12269658 1812800 1085440 15167898 e7719a vmlinux
Now we CALL _copy_*_user which does CALL the optimal alternative
version. Advantage is that we're saving some space and alternatives
application for copy_user* is being done in less places, i.e.
arch/x86/lib/uaccess_64.c. If I move all copy_user_generic() callers
there, it would be the only compilation unit where the alternatives will
be done.
The disadvantage is that we have CALL after CALL and I wanted to have a
single CALL directly to the optimal copy_user function. That'll cost us
space, though, and more alternatives sites to patch during boot...
Thoughts?
Here's the first step only:
---
arch/x86/include/asm/uaccess.h | 7 ++-----
arch/x86/include/asm/uaccess_64.h | 44 ++++-----------------------------------
arch/x86/lib/Makefile | 2 +-
arch/x86/lib/uaccess_64.c | 42 +++++++++++++++++++++++++++++++++++++
4 files changed, 49 insertions(+), 46 deletions(-)
create mode 100644 arch/x86/lib/uaccess_64.c
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 098f3fd5cc75..bdd5234fe9a3 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -642,11 +642,8 @@ extern struct movsl_mask {
# include <asm/uaccess_64.h>
#endif
-extern __always_inline __must_check
-int _copy_from_user(void *dst, const void __user *src, unsigned size);
-
-extern __always_inline __must_check
-int _copy_to_user(void __user *dst, const void *src, unsigned size);
+extern __must_check int _copy_from_user(void *dst, const void __user *src, unsigned size);
+extern __must_check int _copy_to_user(void __user *dst, const void *src, unsigned size);
#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
# define copy_user_diag __compiletime_error
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 1aebc658acf9..440ba6b91c86 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -23,31 +23,11 @@ copy_user_generic_string(void *to, const void *from, unsigned len);
__must_check unsigned long
copy_user_generic_unrolled(void *to, const void *from, unsigned len);
-static __always_inline __must_check unsigned long
-copy_user_generic(void *to, const void *from, unsigned len)
-{
- unsigned ret;
-
- /*
- * If CPU has ERMS feature, use copy_user_enhanced_fast_string.
- * Otherwise, if CPU has rep_good feature, use copy_user_generic_string.
- * Otherwise, use copy_user_generic_unrolled.
- */
- alternative_call_2(copy_user_generic_unrolled,
- copy_user_generic_string,
- X86_FEATURE_REP_GOOD,
- copy_user_enhanced_fast_string,
- X86_FEATURE_ERMS,
- ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from),
- "=d" (len)),
- "1" (to), "2" (from), "3" (len)
- : "memory", "rcx", "r8", "r9", "r10", "r11");
- return ret;
-}
-
__must_check unsigned long
copy_in_user(void __user *to, const void __user *from, unsigned len);
+extern __must_check unsigned long copy_user_generic(void *to, const void *from, unsigned len);
+
static __always_inline __must_check
int __copy_from_user_nocheck(void *dst, const void __user *src, unsigned size)
{
@@ -98,16 +78,7 @@ int __copy_from_user(void *dst, const void __user *src, unsigned size)
return __copy_from_user_nocheck(dst, src, size);
}
-static __always_inline __must_check
-int _copy_from_user(void *dst, const void __user *src, unsigned size)
-{
- if (!access_ok(VERIFY_READ, src, size)) {
- memset(dst, 0, size);
- return 0;
- }
-
- return copy_user_generic(dst, src, size);
-}
+extern __must_check int _copy_from_user(void *dst, const void __user *src, unsigned size);
static __always_inline __must_check
int __copy_to_user_nocheck(void __user *dst, const void *src, unsigned size)
@@ -159,14 +130,7 @@ int __copy_to_user(void __user *dst, const void *src, unsigned size)
return __copy_to_user_nocheck(dst, src, size);
}
-static __always_inline __must_check
-int _copy_to_user(void __user *dst, const void *src, unsigned size)
-{
- if (!access_ok(VERIFY_WRITE, dst, size))
- return size;
-
- return copy_user_generic(dst, src, size);
-}
+__must_check int _copy_to_user(void __user *dst, const void *src, unsigned size);
static __always_inline __must_check
int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 982989d282ff..1885cc5eee32 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -40,6 +40,6 @@ else
lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
lib-y += clear_page_64.o copy_page_64.o
lib-y += memmove_64.o memset_64.o
- lib-y += copy_user_64.o
+ lib-y += copy_user_64.o uaccess_64.o
lib-y += cmpxchg16b_emu.o
endif
diff --git a/arch/x86/lib/uaccess_64.c b/arch/x86/lib/uaccess_64.c
new file mode 100644
index 000000000000..6cd15d874ab4
--- /dev/null
+++ b/arch/x86/lib/uaccess_64.c
@@ -0,0 +1,42 @@
+#include <asm/uaccess.h>
+
+__always_inline __must_check unsigned long
+copy_user_generic(void *to, const void *from, unsigned len)
+{
+ unsigned ret;
+
+ /*
+ * If CPU has ERMS feature, use copy_user_enhanced_fast_string.
+ * Otherwise, if CPU has rep_good feature, use copy_user_generic_string.
+ * Otherwise, use copy_user_generic_unrolled.
+ */
+ alternative_call_2(copy_user_generic_unrolled,
+ copy_user_generic_string,
+ X86_FEATURE_REP_GOOD,
+ copy_user_enhanced_fast_string,
+ X86_FEATURE_ERMS,
+ ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from),
+ "=d" (len)),
+ "1" (to), "2" (from), "3" (len)
+ : "memory", "rcx", "r8", "r9", "r10", "r11");
+ return ret;
+}
+EXPORT_SYMBOL_GPL(copy_user_generic);
+
+__must_check int _copy_from_user(void *dst, const void __user *src, unsigned size)
+{
+ if (!access_ok(VERIFY_READ, src, size)) {
+ memset(dst, 0, size);
+ return 0;
+ }
+
+ return copy_user_generic(dst, src, size);
+}
+
+__must_check int _copy_to_user(void __user *dst, const void *src, unsigned size)
+{
+ if (!access_ok(VERIFY_WRITE, dst, size))
+ return size;
+
+ return copy_user_generic(dst, src, size);
+}
--
2.3.5
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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