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=-3.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 7C18BC433DF for ; Wed, 24 Jun 2020 15:52:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4AC29206F7 for ; Wed, 24 Jun 2020 15:52:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Y2X+D5Mk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404724AbgFXPwp (ORCPT ); Wed, 24 Jun 2020 11:52:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35188 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404166AbgFXPv4 (ORCPT ); Wed, 24 Jun 2020 11:51:56 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C98C1C061573 for ; Wed, 24 Jun 2020 08:51:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=bWebdPWO2kZ+aSt51nW30p9g5yFg2ky94+FiGxSEiuw=; b=Y2X+D5MksEJyPVKfWcXXt6m2IV iNFTJSHsVTYz/BbjS12IAJr9GQ3mmBKOJ3iLdrkf7a1EXfup4shB+KtPcimtEWE7ak9U3IsZu07NP KImHVXYgh9SDn71egRN7iL5CdL0C9n9ZNje9s9h+06LV7UYZGDVfe37f341Tguoxms57eYKSWJH5U pQUmzfwxjBd657Qs12ues2/2+eb8/4Y3z0EcnH7uNI8DmOdxp++DLsxPBOGgK18NvNYJj0ES5Yu+B MBKi1q7jxdfMZpphdTJnDvOZ0CZUOx2IDVwUrq+qwfUw+SoLL6MCMpn3wQBicQ4nN4pu5G4vzlAaj Lgl0KzLw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo7gD-0001eC-V6; Wed, 24 Jun 2020 15:51:18 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id BE00E3079D4; Wed, 24 Jun 2020 17:51:14 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 0778D236E7765; Wed, 24 Jun 2020 17:51:14 +0200 (CEST) Message-ID: <20200624154157.590995873@infradead.org> User-Agent: quilt/0.66 Date: Wed, 24 Jun 2020 17:30:38 +0200 From: Peter Zijlstra To: x86@kernel.org Cc: peterz@infradead.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, pbonzini@redhat.com, mathieu.desnoyers@efficios.com, linux@rasmusvillemoes.dk Subject: [PATCH v5 14/17] static_call: Handle tail-calls References: <20200624153024.794671356@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org GCC can turn our static_call(name)(args...) into a tail call, in which case we get a JMP.d32 into the trampoline (which then does a further tail-call). Teach objtool to recognise and mark these in .static_call_sites and adjust the code patching to deal with this. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/kernel/static_call.c | 21 ++++++++++++++++++--- include/linux/static_call.h | 4 ++-- include/linux/static_call_types.h | 7 +++++++ kernel/static_call.c | 21 +++++++++++++-------- tools/include/linux/static_call_types.h | 7 +++++++ tools/objtool/check.c | 18 +++++++++++++----- 6 files changed, 60 insertions(+), 18 deletions(-) --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -41,15 +41,30 @@ static void __static_call_transform(void text_poke_bp(insn, code, size, NULL); } -void arch_static_call_transform(void *site, void *tramp, void *func) +static inline enum insn_type __sc_insn(bool null, bool tail) +{ + /* + * Encode the following table without branches: + * + * tail null insn + * -----+-------+------ + * 0 | 0 | CALL + * 0 | 1 | NOP + * 1 | 0 | JMP + * 1 | 1 | RET + */ + return 2*tail + null; +} + +void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) { mutex_lock(&text_mutex); if (tramp) - __static_call_transform(tramp, func ? JMP : RET, func); + __static_call_transform(tramp, __sc_insn(!func, true), func); if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) - __static_call_transform(site, func ? CALL : NOP, func); + __static_call_transform(site, __sc_insn(!func, tail), func); mutex_unlock(&text_mutex); } --- a/include/linux/static_call.h +++ b/include/linux/static_call.h @@ -103,7 +103,7 @@ /* * Either @site or @tramp can be NULL. */ -extern void arch_static_call_transform(void *site, void *tramp, void *func); +extern void arch_static_call_transform(void *site, void *tramp, void *func, bool tail); #define STATIC_CALL_TRAMP_ADDR(name) &STATIC_CALL_TRAMP(name) @@ -206,7 +206,7 @@ void __static_call_update(struct static_ { cpus_read_lock(); WRITE_ONCE(key->func, func); - arch_static_call_transform(NULL, tramp, func); + arch_static_call_transform(NULL, tramp, func, false); cpus_read_unlock(); } --- a/include/linux/static_call_types.h +++ b/include/linux/static_call_types.h @@ -17,6 +17,13 @@ #define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name)) /* + * Flags in the low bits of static_call_site::key. + */ +#define STATIC_CALL_SITE_TAIL 1UL /* tail call */ +#define STATIC_CALL_SITE_INIT 2UL /* init section */ +#define STATIC_CALL_SITE_FLAGS 3UL + +/* * The static call site table needs to be created by external tooling (objtool * or a compiler plugin). */ --- a/kernel/static_call.c +++ b/kernel/static_call.c @@ -15,8 +15,6 @@ extern struct static_call_site __start_s static bool static_call_initialized; -#define STATIC_CALL_INIT 1UL - /* mutex to protect key modules/sites */ static DEFINE_MUTEX(static_call_mutex); @@ -39,18 +37,23 @@ static inline void *static_call_addr(str static inline struct static_call_key *static_call_key(const struct static_call_site *site) { return (struct static_call_key *) - (((long)site->key + (long)&site->key) & ~STATIC_CALL_INIT); + (((long)site->key + (long)&site->key) & ~STATIC_CALL_SITE_FLAGS); } /* These assume the key is word-aligned. */ static inline bool static_call_is_init(struct static_call_site *site) { - return ((long)site->key + (long)&site->key) & STATIC_CALL_INIT; + return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_INIT; +} + +static inline bool static_call_is_tail(struct static_call_site *site) +{ + return ((long)site->key + (long)&site->key) & STATIC_CALL_SITE_TAIL; } static inline void static_call_set_init(struct static_call_site *site) { - site->key = ((long)static_call_key(site) | STATIC_CALL_INIT) - + site->key = ((long)static_call_key(site) | STATIC_CALL_SITE_INIT) - (long)&site->key; } @@ -104,7 +107,7 @@ void __static_call_update(struct static_ key->func = func; - arch_static_call_transform(NULL, tramp, func); + arch_static_call_transform(NULL, tramp, func, false); /* * If uninitialized, we'll not update the callsites, but they still @@ -154,7 +157,8 @@ void __static_call_update(struct static_ continue; } - arch_static_call_transform(site_addr, NULL, func); + arch_static_call_transform(site_addr, NULL, func, + static_call_is_tail(site)); } } @@ -198,7 +202,8 @@ static int __static_call_init(struct mod key->mods = site_mod; } - arch_static_call_transform(site_addr, NULL, key->func); + arch_static_call_transform(site_addr, NULL, key->func, + static_call_is_tail(site)); } return 0; --- a/tools/include/linux/static_call_types.h +++ b/tools/include/linux/static_call_types.h @@ -17,6 +17,13 @@ #define STATIC_CALL_TRAMP_STR(name) __stringify(STATIC_CALL_TRAMP(name)) /* + * Flags in the low bits of static_call_site::key. + */ +#define STATIC_CALL_SITE_TAIL 1UL /* tail call */ +#define STATIC_CALL_SITE_INIT 2UL /* init section */ +#define STATIC_CALL_SITE_FLAGS 3UL + +/* * The static call site table needs to be created by external tooling (objtool * or a compiler plugin). */ --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -511,7 +511,7 @@ static int create_static_call_sections(s } memset(reloc, 0, sizeof(*reloc)); reloc->sym = key_sym; - reloc->addend = 0; + reloc->addend = is_sibling_call(insn) ? STATIC_CALL_SITE_TAIL : 0; reloc->type = R_X86_64_PC32; reloc->offset = idx * sizeof(struct static_call_site) + 4; reloc->sec = reloc_sec; @@ -720,6 +720,10 @@ static int add_jump_destinations(struct } else { /* external sibling call */ insn->call_dest = reloc->sym; + if (insn->call_dest->static_call_tramp) { + list_add_tail(&insn->static_call_node, + &file->static_call_list); + } continue; } @@ -771,6 +775,10 @@ static int add_jump_destinations(struct /* internal sibling call */ insn->call_dest = insn->jump_dest->func; + if (insn->call_dest->static_call_tramp) { + list_add_tail(&insn->static_call_node, + &file->static_call_list); + } } } } @@ -1639,6 +1647,10 @@ static int decode_sections(struct objtoo if (ret) return ret; + ret = read_static_call_tramps(file); + if (ret) + return ret; + ret = add_jump_destinations(file); if (ret) return ret; @@ -1671,10 +1683,6 @@ static int decode_sections(struct objtoo if (ret) return ret; - ret = read_static_call_tramps(file); - if (ret) - return ret; - return 0; }