From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEB7CC433E9 for ; Wed, 17 Feb 2021 13:28:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F64C64EB3 for ; Wed, 17 Feb 2021 13:28:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233042AbhBQN2I (ORCPT ); Wed, 17 Feb 2021 08:28:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232894AbhBQNS4 (ORCPT ); Wed, 17 Feb 2021 08:18:56 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C751C061797; Wed, 17 Feb 2021 05:17:38 -0800 (PST) Date: Wed, 17 Feb 2021 13:17:35 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1613567856; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vOFuCz4fR9zyc3oqbFnResD0AJQp8DdnXViMVvKDK20=; b=I6ro56W8r65kUg+1twtHD1r4oEXjO6+fOH63/huz1pmsreUMZdCtYbHd/0qTsjboBcg93W RVtlYdZ20aibkLKZGxLXIeOcEu7gKxvY7xVsdKJodGF+LgKdIVX4PSfZMnBVgZOlJ4IV/a 7xh0mcXT1Et0E/fR/fN+hExrlOf5Rh2o2Q7vXOs5zJ2+rsNcU96BITvfVm6S3ijTwJwG+0 fG9Pev055JahWuBxqpasil7/pf6HDx35qUODPJX3OId/Er60CeUpvJRY80A5r+SUex0UWx buefghJ7cIMSpf/MVXLgygbknLHCczG2uFJzDpbzb9BSpGmqWBXSuDP9k2c/gw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1613567856; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=vOFuCz4fR9zyc3oqbFnResD0AJQp8DdnXViMVvKDK20=; b=LVHl6JrhOkuCP9T29UAPKpvl18/YLiSjFqiyPWYaNp+Qbp5+TFO+7hsRfu4wdpbWLtWjEU ZC4RYH3ESjTK70BQ== From: "tip-bot2 for Peter Zijlstra" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] static_call/x86: Add __static_call_return0() Cc: "Peter Zijlstra (Intel)" , Frederic Weisbecker , Ingo Molnar , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20210118141223.123667-2-frederic@kernel.org> References: <20210118141223.123667-2-frederic@kernel.org> MIME-Version: 1.0 Message-ID: <161356785556.20312.8835577071462298948.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 3f2a8fc4b15de18644e8a80a09edda168676e22c Gitweb: https://git.kernel.org/tip/3f2a8fc4b15de18644e8a80a09edda168676e22c Author: Peter Zijlstra AuthorDate: Mon, 18 Jan 2021 15:12:16 +01:00 Committer: Ingo Molnar CommitterDate: Wed, 17 Feb 2021 14:08:43 +01:00 static_call/x86: Add __static_call_return0() Provide a stub function that return 0 and wire up the static call site patching to replace the CALL with a single 5 byte instruction that clears %RAX, the return value register. The function can be cast to any function pointer type that has a single %RAX return (including pointers). Also provide a version that returns an int for convenience. We are clearing the entire %RAX register in any case, whether the return value is 32 or 64 bits, since %RAX is always a scratch register anyway. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lkml.kernel.org/r/20210118141223.123667-2-frederic@kernel.org --- arch/x86/kernel/static_call.c | 17 +++++++++++++++-- include/linux/static_call.h | 12 ++++++++++++ kernel/static_call.c | 5 +++++ 3 files changed, 32 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c index ca9a380..9442c41 100644 --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -11,14 +11,26 @@ enum insn_type { RET = 3, /* tramp / site cond-tail-call */ }; +/* + * data16 data16 xorq %rax, %rax - a single 5 byte instruction that clears %rax + * The REX.W cancels the effect of any data16. + */ +static const u8 xor5rax[] = { 0x66, 0x66, 0x48, 0x31, 0xc0 }; + static void __ref __static_call_transform(void *insn, enum insn_type type, void *func) { + const void *emulate = NULL; int size = CALL_INSN_SIZE; const void *code; switch (type) { case CALL: code = text_gen_insn(CALL_INSN_OPCODE, insn, func); + if (func == &__static_call_return0) { + emulate = code; + code = &xor5rax; + } + break; case NOP: @@ -41,7 +53,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void if (unlikely(system_state == SYSTEM_BOOTING)) return text_poke_early(insn, code, size); - text_poke_bp(insn, code, size, NULL); + text_poke_bp(insn, code, size, emulate); } static void __static_call_validate(void *insn, bool tail) @@ -54,7 +66,8 @@ static void __static_call_validate(void *insn, bool tail) return; } else { if (opcode == CALL_INSN_OPCODE || - !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5)) + !memcmp(insn, ideal_nops[NOP_ATOMIC5], 5) || + !memcmp(insn, xor5rax, 5)) return; } diff --git a/include/linux/static_call.h b/include/linux/static_call.h index a2c0645..bd6735d 100644 --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -142,6 +142,8 @@ extern void __static_call_update(struct static_call_key *key, void *tramp, void extern int static_call_mod_init(struct module *mod); extern int static_call_text_reserved(void *start, void *end); +extern long __static_call_return0(void); + #define DEFINE_STATIC_CALL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ @@ -206,6 +208,11 @@ static inline int static_call_text_reserved(void *start, void *end) return 0; } +static inline long __static_call_return0(void) +{ + return 0; +} + #define EXPORT_STATIC_CALL(name) \ EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \ EXPORT_SYMBOL(STATIC_CALL_TRAMP(name)) @@ -222,6 +229,11 @@ struct static_call_key { void *func; }; +static inline long __static_call_return0(void) +{ + return 0; +} + #define DEFINE_STATIC_CALL(name, _func) \ DECLARE_STATIC_CALL(name, _func); \ struct static_call_key STATIC_CALL_KEY(name) = { \ diff --git a/kernel/static_call.c b/kernel/static_call.c index 84565c2..0bc11b5 100644 --- a/kernel/static_call.c +++ b/kernel/static_call.c @@ -438,6 +438,11 @@ int __init static_call_init(void) } early_initcall(static_call_init); +long __static_call_return0(void) +{ + return 0; +} + #ifdef CONFIG_STATIC_CALL_SELFTEST static int func_a(int x)