From patchwork Wed Mar 31 21:27:11 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 12176437 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 01940C001B3 for ; Wed, 31 Mar 2021 21:28:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DFD1E61041 for ; Wed, 31 Mar 2021 21:28:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232661AbhCaV2Q (ORCPT ); Wed, 31 Mar 2021 17:28:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232672AbhCaV1i (ORCPT ); Wed, 31 Mar 2021 17:27:38 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D3B6C061765 for ; Wed, 31 Mar 2021 14:27:38 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id a19so3691908ybg.10 for ; Wed, 31 Mar 2021 14:27:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=i1PxfqvHNAZaUSY0Wt2J9hLbKLkB/NragVXsh/CJXkk=; b=CgrLOqIhy6I4HPpgcvaJ2Kf5auntmv+ua+he8hCf1xZOx39XpJXZZQKDjnLwMtvYdc Coi9ppbfXIt+chJQ+QAqS+uMcGf3PwWgeivSHwdv4kpzv+rr2THIbfrCVVg6whJabjHV 2SJxgs1puZMWys7KvUR5E+GbWAG2gwUT/GVAk45+lS65j4BBiznnMwegCCuQHsgryS2u QzL22ZL9lFhVWUNp8q+UhG8SLH8hbhdY0GCTNzBAfacJ68xebK4pOQ0ZV2n5FHyUqPaj SKhOoLjlOqVTxE7XxST/QkBjkfCEkkv080ZLYXfJXOwteQgLmCab9Xy/VvS1MHxuU5DN Wx1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=i1PxfqvHNAZaUSY0Wt2J9hLbKLkB/NragVXsh/CJXkk=; b=A2SzXLo9sc4LN/HGdfD/v+Wwgr/tDQm/Lp4hHgHT65M1jg9fC4ysSNwiZjP54Tt5k/ kOmB47QAsUqWEs3W/QZ8VDS9lzGXUHh0iImTdjJbyWOCa0L+UXZukMVNbp1iaDCv6xH5 1/fd7QBpilqW1Tx78ipq8nAZRhtybQhSFKkDYOIx/JdVDSAkwUmQTdgNpG8/XmszZ6OO hK/eiWIRcmq/U3Y1Qr9LhpddUcjwGIucW5CLyBlozwoEWpXHA3MsuWEIRYKxkgcgl+CF XzzXN2fI0rTCUUifpA0WIAX7Em1VC5T7MxoBx1tCZN1QWYhpdihX2qU5QoS2QvR/lAZV L2Iw== X-Gm-Message-State: AOAM533fzR/7yXKsdsv+C6/xuAIfygOQANoGCIuNJw7Mwy28nQQa8Y42 wv+tia1hb9Xcki+O3jBhNBUEa/uF7AB9/uOqiyo= X-Google-Smtp-Source: ABdhPJwLdAoVrfnuDHDuevSolHBmZu5plw9zwt9KPh0wtZT3FBVDe5eapKH2T6ID9dt0hQP3DBYLyas9XQhdZJ5fFFM= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:7933:7015:a5d5:3835]) (user=samitolvanen job=sendgmr) by 2002:a5b:5c7:: with SMTP id w7mr7418520ybp.164.1617226057459; Wed, 31 Mar 2021 14:27:37 -0700 (PDT) Date: Wed, 31 Mar 2021 14:27:11 -0700 In-Reply-To: <20210331212722.2746212-1-samitolvanen@google.com> Message-Id: <20210331212722.2746212-8-samitolvanen@google.com> Mime-Version: 1.0 References: <20210331212722.2746212-1-samitolvanen@google.com> X-Mailer: git-send-email 2.31.0.291.g576ba9dcdaf-goog Subject: [PATCH v4 07/17] kallsyms: strip ThinLTO hashes from static functions From: Sami Tolvanen To: Kees Cook Cc: Nathan Chancellor , Nick Desaulniers , Masahiro Yamada , Will Deacon , Jessica Yu , Arnd Bergmann , Tejun Heo , "Paul E. McKenney" , Christoph Hellwig , Peter Zijlstra , Sedat Dilek , bpf@vger.kernel.org, linux-hardening@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org With CONFIG_CFI_CLANG and ThinLTO, Clang appends a hash to the names of all static functions not marked __used. This can break userspace tools that don't expect the function name to change, so strip out the hash from the output. Suggested-by: Jack Pham Signed-off-by: Sami Tolvanen Reviewed-by: Kees Cook --- kernel/kallsyms.c | 55 ++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 50 insertions(+), 5 deletions(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 8043a90aa50e..c851ca0ed357 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -161,6 +161,27 @@ static unsigned long kallsyms_sym_address(int idx) return kallsyms_relative_base - 1 - kallsyms_offsets[idx]; } +#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_LTO_CLANG_THIN) +/* + * LLVM appends a hash to static function names when ThinLTO and CFI are + * both enabled, i.e. foo() becomes foo$707af9a22804d33c81801f27dcfe489b. + * This causes confusion and potentially breaks user space tools, so we + * strip the suffix from expanded symbol names. + */ +static inline bool cleanup_symbol_name(char *s) +{ + char *res; + + res = strrchr(s, '$'); + if (res) + *res = '\0'; + + return res != NULL; +} +#else +static inline bool cleanup_symbol_name(char *s) { return false; } +#endif + /* Lookup the address for this symbol. Returns 0 if not found. */ unsigned long kallsyms_lookup_name(const char *name) { @@ -173,6 +194,9 @@ unsigned long kallsyms_lookup_name(const char *name) if (strcmp(namebuf, name) == 0) return kallsyms_sym_address(i); + + if (cleanup_symbol_name(namebuf) && strcmp(namebuf, name) == 0) + return kallsyms_sym_address(i); } return module_kallsyms_lookup_name(name); } @@ -303,7 +327,9 @@ const char *kallsyms_lookup(unsigned long addr, namebuf, KSYM_NAME_LEN); if (modname) *modname = NULL; - return namebuf; + + ret = namebuf; + goto found; } /* See if it's in a module or a BPF JITed image. */ @@ -316,11 +342,16 @@ const char *kallsyms_lookup(unsigned long addr, if (!ret) ret = ftrace_mod_address_lookup(addr, symbolsize, offset, modname, namebuf); + +found: + cleanup_symbol_name(namebuf); return ret; } int lookup_symbol_name(unsigned long addr, char *symname) { + int res; + symname[0] = '\0'; symname[KSYM_NAME_LEN - 1] = '\0'; @@ -331,15 +362,23 @@ int lookup_symbol_name(unsigned long addr, char *symname) /* Grab name */ kallsyms_expand_symbol(get_symbol_offset(pos), symname, KSYM_NAME_LEN); - return 0; + goto found; } /* See if it's in a module. */ - return lookup_module_symbol_name(addr, symname); + res = lookup_module_symbol_name(addr, symname); + if (res) + return res; + +found: + cleanup_symbol_name(symname); + return 0; } int lookup_symbol_attrs(unsigned long addr, unsigned long *size, unsigned long *offset, char *modname, char *name) { + int res; + name[0] = '\0'; name[KSYM_NAME_LEN - 1] = '\0'; @@ -351,10 +390,16 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size, kallsyms_expand_symbol(get_symbol_offset(pos), name, KSYM_NAME_LEN); modname[0] = '\0'; - return 0; + goto found; } /* See if it's in a module. */ - return lookup_module_symbol_attrs(addr, size, offset, modname, name); + res = lookup_module_symbol_attrs(addr, size, offset, modname, name); + if (res) + return res; + +found: + cleanup_symbol_name(name); + return 0; } /* Look up a kernel symbol and return it in a text buffer. */