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Date: Fri, 21 Dec 2018 20:14:23 +0200
From: Igor Stoppa <igor.stoppa@...il.com>
To: Andy Lutomirski <luto@...capital.net>,
Matthew Wilcox <willy@...radead.org>,
Peter Zijlstra <peterz@...radead.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>,
Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc: igor.stoppa@...wei.com,
Nadav Amit <nadav.amit@...il.com>,
Kees Cook <keescook@...omium.org>,
Ahmed Soliman <ahmedsoliman@...a.vt.edu>,
linux-integrity@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH 12/12] x86_64: __clear_user as case of __memset_user
To avoid code duplication, re-use __memset_user(), when clearing
user-space memory.
The overhead should be minimal (2 extra register assignments) and
outside of the writing loop.
Signed-off-by: Igor Stoppa <igor.stoppa@...wei.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Nadav Amit <nadav.amit@...il.com>
CC: Matthew Wilcox <willy@...radead.org>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Kees Cook <keescook@...omium.org>
CC: Dave Hansen <dave.hansen@...ux.intel.com>
CC: Mimi Zohar <zohar@...ux.vnet.ibm.com>
CC: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
CC: Ahmed Soliman <ahmedsoliman@...a.vt.edu>
CC: linux-integrity@...r.kernel.org
CC: kernel-hardening@...ts.openwall.com
CC: linux-mm@...ck.org
CC: linux-kernel@...r.kernel.org
---
arch/x86/lib/usercopy_64.c | 29 +----------------------------
1 file changed, 1 insertion(+), 28 deletions(-)
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 84f8f8a20b30..ab6aabb62055 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -69,34 +69,7 @@ EXPORT_SYMBOL(memset_user);
unsigned long __clear_user(void __user *addr, unsigned long size)
{
- long __d0;
- might_fault();
- /* no memory constraint because it doesn't change any memory gcc knows
- about */
- stac();
- asm volatile(
- " testq %[size8],%[size8]\n"
- " jz 4f\n"
- "0: movq $0,(%[dst])\n"
- " addq $8,%[dst]\n"
- " decl %%ecx ; jnz 0b\n"
- "4: movq %[size1],%%rcx\n"
- " testl %%ecx,%%ecx\n"
- " jz 2f\n"
- "1: movb $0,(%[dst])\n"
- " incq %[dst]\n"
- " decl %%ecx ; jnz 1b\n"
- "2:\n"
- ".section .fixup,\"ax\"\n"
- "3: lea 0(%[size1],%[size8],8),%[size8]\n"
- " jmp 2b\n"
- ".previous\n"
- _ASM_EXTABLE_UA(0b, 3b)
- _ASM_EXTABLE_UA(1b, 2b)
- : [size8] "=&c"(size), [dst] "=&D" (__d0)
- : [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr));
- clac();
- return size;
+ return __memset_user(addr, 0, size);
}
EXPORT_SYMBOL(__clear_user);
--
2.19.1
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