From mboxrd@z Thu Jan 1 00:00:00 1970 From: Igor Stoppa Subject: [PATCH 12/12] x86_64: __clear_user as case of __memset_user Date: Wed, 19 Dec 2018 23:33:38 +0200 Message-Id: <20181219213338.26619-13-igor.stoppa@huawei.com> In-Reply-To: <20181219213338.26619-1-igor.stoppa@huawei.com> References: <20181219213338.26619-1-igor.stoppa@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To: Andy Lutomirski , Matthew Wilcox , Peter Zijlstra , Dave Hansen , Mimi Zohar Cc: igor.stoppa@huawei.com, Nadav Amit , Kees Cook , linux-integrity@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: 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 CC: Andy Lutomirski CC: Nadav Amit CC: Matthew Wilcox CC: Peter Zijlstra CC: Kees Cook CC: Dave Hansen CC: Mimi Zohar CC: linux-integrity@vger.kernel.org CC: kernel-hardening@lists.openwall.com CC: linux-mm@kvack.org CC: linux-kernel@vger.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