From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753483AbcAZVMu (ORCPT ); Tue, 26 Jan 2016 16:12:50 -0500 Received: from mail.skyhub.de ([78.46.96.112]:56888 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751663AbcAZVMS (ORCPT ); Tue, 26 Jan 2016 16:12:18 -0500 From: Borislav Petkov To: Ingo Molnar Cc: LKML Subject: [PATCH 08/10] x86/alternatives: Discard dynamic check after init Date: Tue, 26 Jan 2016 22:12:08 +0100 Message-Id: <1453842730-28463-9-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.3.5 In-Reply-To: <1453842730-28463-1-git-send-email-bp@alien8.de> References: <1453842730-28463-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Brian Gerst Move the code to do the dynamic check to the altinstr_aux section so that it is discarded after alternatives have run and a static branch has been chosen. This way we're changing the dynamic branch from C code to assembly, which makes it *substantially* smaller while avoiding a completely unnecessary call to an out of line function. Boris: change it to do TESTB, as hpa suggests. Signed-off-by: Brian Gerst Cc: Andrew Morton Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Dave Young Cc: Denys Vlasenko Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kristen Carlson Accardi Cc: Laura Abbott Cc: Linus Torvalds Cc: "Peter Zijlstra (Intel)" Cc: Prarit Bhargava Cc: Ross Zwisler Cc: Thomas Gleixner Cc: x86-ml Link: http://lkml.kernel.org/r/1452972124-7380-1-git-send-email-brgerst@gmail.com Signed-off-by: Borislav Petkov --- arch/x86/include/asm/cpufeature.h | 19 ++++++++++++------- arch/x86/kernel/cpu/common.c | 6 ------ 2 files changed, 12 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index d48bf024f335..cab88ff86caf 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -130,8 +130,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; */ #if CC_HAVE_ASM_GOTO && defined(CONFIG_X86_FAST_FEATURE_TESTS) -extern bool __static_cpu_has(u16 bit); - /* * Static testing of CPU features. Used the same as boot_cpu_has(). * These will statically patch the target code for additional @@ -139,7 +137,7 @@ extern bool __static_cpu_has(u16 bit); */ static __always_inline __pure bool _static_cpu_has(u16 bit) { - asm_volatile_goto("1: jmp %l[t_dynamic]\n" + asm_volatile_goto("1: jmp 6f\n" "2:\n" ".skip -(((5f-4f) - (2b-1b)) > 0) * " "((5f-4f) - (2b-1b)),0x90\n" @@ -164,13 +162,20 @@ static __always_inline __pure bool _static_cpu_has(u16 bit) " .byte 0\n" /* repl len */ " .byte 0\n" /* pad len */ ".previous\n" - : : "i" (bit), "i" (X86_FEATURE_ALWAYS) - : : t_dynamic, t_no); + ".section .altinstr_aux,\"ax\"\n" + "6:\n" + " testb %[bitnum],%[cap_byte]\n" + " jnz %l[t_yes]\n" + " jmp %l[t_no]\n" + ".previous\n" + : : "i" (bit), "i" (X86_FEATURE_ALWAYS), + [bitnum] "i" (1 << (bit & 7)), + [cap_byte] "m" (((const char *)boot_cpu_data.x86_capability)[bit >> 3]) + : : t_yes, t_no); + t_yes: return true; t_no: return false; - t_dynamic: - return __static_cpu_has(bit); } #define static_cpu_has(bit) \ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index ee499817f3f5..079d83fc6488 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1475,12 +1475,6 @@ void cpu_init(void) } #endif -inline bool __static_cpu_has(u16 bit) -{ - return boot_cpu_has(bit); -} -EXPORT_SYMBOL_GPL(__static_cpu_has); - static void bsp_resume(void) { if (this_cpu->c_bsp_resume) -- 2.3.5