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=-25.6 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 2FEDFC433DF for ; Sat, 15 Aug 2020 00:24:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBCDC2074D for ; Sat, 15 Aug 2020 00:24:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="L3cjo58S" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726868AbgHOAY3 (ORCPT ); Fri, 14 Aug 2020 20:24:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726596AbgHOAY3 (ORCPT ); Fri, 14 Aug 2020 20:24:29 -0400 Received: from mail-qv1-xf49.google.com (mail-qv1-xf49.google.com [IPv6:2607:f8b0:4864:20::f49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB4F9C061385 for ; Fri, 14 Aug 2020 17:24:28 -0700 (PDT) Received: by mail-qv1-xf49.google.com with SMTP id l18so7056848qvq.16 for ; Fri, 14 Aug 2020 17:24:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=XRzGQ7xGX/sFN7c8Gj9tV2IiOtNpdC4f2YfZedk7h2c=; b=L3cjo58SrUy7KFXgcMpEtxPUkK6nFHCdECr6hz0JngvEIo+tQDBMqL7MIhJnheK6WB AYUI/ErQO7CMh7M2c+tzkGPUFHxiXuo+wU/dfQI/hnB2B7Wu7jj8nyUIf8kRRbJ7urbi E+9mHB88xM7jGW4skoOw3m3Ea1irBY8nrIJLDup0O78Z+ghnbXrsONYSHWFyTzR8Ghdn LjYyimThv+zFEub528avQ46xO58t4kv7EuxHC8wrCWc8k/V/o6EMFHj/9gUVas/QLGw+ Wp18MnI4qGrU1oHVOwOlhPYhqLSWNQ1r+OsEgAgNEydNtq7RJZl8Qpq1eLFzZgkMaIFy sMZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=XRzGQ7xGX/sFN7c8Gj9tV2IiOtNpdC4f2YfZedk7h2c=; b=ieVup7Nfa0sDa3z2j4ClTS80IcDxcJOmItZ0jfIVfvR7Wmlc9FQY3gpqyABQH7C5Xf W651cidYcMnpx38q/PGUtjWsdkqUuC1eGLSPSwba9t18bltaKQ9ipg1FEg5C+U1VXgXe NjlhKSncYm+Ryf0Dvxvv8e5CYuzUITm4lPuX4tWsI+p55Bx9zhIU6RIwYoO/kwqrVx+6 vnoC8l0iXVtFM5rzlgKp3NQxBUfkqDm6gWIgAB+0wHbwKAQS+e47tBm5m5uzYjsd97f+ Tn4mmTDYh+gBFMhCcZkMZF1pPyXixerYJHshy10mPn7qmlM3ePyQeZq1YArrs5UeB0hN mOaA== X-Gm-Message-State: AOAM531/P+POLySxcP+RmwbnzOzJDnLLLFqDunEXQ8uEHIza5DQP/XiR OuRAPTfF8oe3q7Id6zCMb3Aii4/7qPD8X2rupss= X-Google-Smtp-Source: ABdhPJzOm3IFfI3nNhI3u/ndph4cDdUq8GGSmKQkiNXTpMrnurkQJwXTZk9v15oscx27u9xKAQRQqDeTuk2/zjHzMEw= X-Received: by 2002:a0c:fbd1:: with SMTP id n17mr5138941qvp.4.1597451067876; Fri, 14 Aug 2020 17:24:27 -0700 (PDT) Date: Fri, 14 Aug 2020 17:24:15 -0700 Message-Id: <20200815002417.1512973-1-ndesaulniers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.220.ged08abb693-goog Subject: [PATCH] lib/string.c: implement stpcpy From: Nick Desaulniers To: Andrew Morton Cc: "=?UTF-8?q?D=C3=A1vid=20Bolvansk=C3=BD?=" , Eli Friedman , Nick Desaulniers , stable@vger.kernel.org, Sami Tolvanen , Joe Perches , Tony Luck , Yury Norov , Daniel Axtens , Arvind Sankar , Dan Williams , "Joel Fernandes (Google)" , Andy Shevchenko , Kees Cook , Alexandru Ardelean , linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com Content-Type: text/plain; charset="UTF-8" Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org LLVM implemented a recent "libcall optimization" that lowers calls to `sprintf(dest, "%s", str)` where the return value is used to `stpcpy(dest, str) - dest`. This generally avoids the machinery involved in parsing format strings. `stpcpy` is just like `strcpy` except: 1. it returns the pointer to the new tail of `dest`. This allows you to chain multiple calls to `stpcpy` in one statement. 2. it requires the parameters not to overlap. Calling `sprintf` with overlapping arguments was clarified in ISO C99 and POSIX.1-2001 to be undefined behavior. `stpcpy` was first standardized in POSIX.1-2008. Implement this so that we don't observe linkage failures due to missing symbol definitions for `stpcpy`. Similar to last year's fire drill with: commit 5f074f3e192f ("lib/string.c: implement a basic bcmp") This optimization was introduced into clang-12. Cc: stable@vger.kernel.org Link: https://bugs.llvm.org/show_bug.cgi?id=47162 Link: https://github.com/ClangBuiltLinux/linux/issues/1126 Link: https://man7.org/linux/man-pages/man3/stpcpy.3.html Link: https://pubs.opengroup.org/onlinepubs/9699919799/functions/stpcpy.html Link: https://reviews.llvm.org/D85963 Reported-by: Sami Tolvanen Signed-off-by: Nick Desaulniers --- include/linux/string.h | 3 +++ lib/string.c | 23 +++++++++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/include/linux/string.h b/include/linux/string.h index b1f3894a0a3e..e570b9b10f50 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -31,6 +31,9 @@ size_t strlcpy(char *, const char *, size_t); #ifndef __HAVE_ARCH_STRSCPY ssize_t strscpy(char *, const char *, size_t); #endif +#ifndef __HAVE_ARCH_STPCPY +extern char *stpcpy(char *__restrict, const char *__restrict__); +#endif /* Wraps calls to strscpy()/memset(), no arch specific code required */ ssize_t strscpy_pad(char *dest, const char *src, size_t count); diff --git a/lib/string.c b/lib/string.c index 6012c385fb31..81bc4d62c256 100644 --- a/lib/string.c +++ b/lib/string.c @@ -272,6 +272,29 @@ ssize_t strscpy_pad(char *dest, const char *src, size_t count) } EXPORT_SYMBOL(strscpy_pad); +#ifndef __HAVE_ARCH_STPCPY +/** + * stpcpy - copy a string from src to dest returning a pointer to the new end + * of dest, including src's NULL terminator. May overrun dest. + * @dest: pointer to end of string being copied into. Must be large enough + * to receive copy. + * @src: pointer to the beginning of string being copied from. Must not overlap + * dest. + * + * stpcpy differs from strcpy in two key ways: + * 1. inputs must not overlap. + * 2. return value is the new NULL terminated character. (for strcpy, the + * return value is a pointer to src. + */ +#undef stpcpy +char *stpcpy(char *__restrict__ dest, const char *__restrict__ src) +{ + while ((*dest++ = *src++) != '\0') + /* nothing */; + return dest; +} +#endif + #ifndef __HAVE_ARCH_STRCAT /** * strcat - Append one %NUL-terminated string to another -- 2.28.0.220.ged08abb693-goog