From patchwork Mon Aug 12 03:31:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Chancellor X-Patchwork-Id: 11089263 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2B39314DB for ; Mon, 12 Aug 2019 03:31:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1D53127DCD for ; Mon, 12 Aug 2019 03:31:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 10F8D27F86; Mon, 12 Aug 2019 03:31:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8FD1027DCD for ; Mon, 12 Aug 2019 03:31:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726573AbfHLDbf (ORCPT ); Sun, 11 Aug 2019 23:31:35 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:39533 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726144AbfHLDbe (ORCPT ); Sun, 11 Aug 2019 23:31:34 -0400 Received: by mail-wr1-f65.google.com with SMTP id t16so13199976wra.6; Sun, 11 Aug 2019 20:31:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=vWEzzku9YP0pC2dVc45a5odEYQH6f9+aCPyBPp3kmxo=; b=SE46LZAyzH6U02vpi2RK3qP0aLUW1s+/BySNKx1Vx4S8RXZICkMsI/eJv+OqXAwPP3 zvcL+q8quy9DClR6kQeC2lScNnSM+ejjox7aOtH5YfkUQwBYBgn/2tfaqVFaY5PaboST lkmwAEWyFKNvfXTrltJpGO+rWBYvxYpWbEhUVcR0Y8ftxIA+BwLfv2xdTsS1ywqc8Nwq DjDFHd0hqOILYBuv+Hdku+V8EeM67hr3aueaUlu9dmvJXUjVs75WpAeguDfsiSjI9PNp Y8QYv175125TSd/rQ63ui22KWJSxRI+34UAgeSBdM1PVSGCTDQZBjm8Vy6trqLCHRipJ mEDw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=vWEzzku9YP0pC2dVc45a5odEYQH6f9+aCPyBPp3kmxo=; b=KdMnbGsrAuHssIOgZBC79FZbMuA5XtI3xzqd2kmCt9wxaHlrpzceS5dto4b+TSOfcn ZDDwbYcqBCflYaerKpwJetTS16J8q1uCi+ai6A1B3uEVTrVqs/blxfagjuVU/f7hacHB PSQMB1FGANv7YmY/kb4bCAwiEx+dPAPWgzrpMPT/u2LquIbhB5LWPl2OFSW3N67+FR9T mvUuRi/WUokUaV3VQbMMRbrVFL4ChlMd+o7Cyi9XePa2p527rJzc0fgEldlA42ZOP3v5 zODYvLPr1SYrAtv8uRCLrI3Oex6NvHsVoFy5G3lAqYSsJ7GUM6ZXEBDMIYo5U/JUxzzW Y/2A== X-Gm-Message-State: APjAAAUo3qYi/zEVIIzkGL5viLdHWD3FJkQlLPuAvlMY8Kg86RcKAtkk x5Efcqhw8NuHyfk+IXMxisQ= X-Google-Smtp-Source: APXvYqxmGrFmRa688YKY6KKrrvbIKQnMYH/dlZ8HtOC/RsQAE59TS2Ihfg/5QMeiJhniZfHANkVALg== X-Received: by 2002:adf:f04d:: with SMTP id t13mr37798273wro.133.1565580691538; Sun, 11 Aug 2019 20:31:31 -0700 (PDT) Received: from localhost.localdomain ([2a01:4f8:222:2f1b::2]) by smtp.gmail.com with ESMTPSA id f12sm117299330wrg.5.2019.08.11.20.31.30 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sun, 11 Aug 2019 20:31:31 -0700 (PDT) From: Nathan Chancellor To: Ralf Baechle , Paul Burton , James Hogan Cc: Nick Desaulniers , linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nathan Chancellor Subject: [PATCH 1/5] MIPS: Don't use bc_false uninitialized in __mm_isBranchInstr Date: Sun, 11 Aug 2019 20:31:16 -0700 Message-Id: <20190812033120.43013-2-natechancellor@gmail.com> X-Mailer: git-send-email 2.23.0.rc2 In-Reply-To: <20190812033120.43013-1-natechancellor@gmail.com> References: <20190812033120.43013-1-natechancellor@gmail.com> MIME-Version: 1.0 Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP clang warns: arch/mips/kernel/branch.c:148:8: error: variable 'bc_false' is used uninitialized whenever switch case is taken [-Werror,-Wsometimes-uninitialized] case mm_bc2t_op: ^~~~~~~~~~ arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here if (bc_false) ^~~~~~~~ arch/mips/kernel/branch.c:149:8: error: variable 'bc_false' is used uninitialized whenever switch case is taken [-Werror,-Wsometimes-uninitialized] case mm_bc1t_op: ^~~~~~~~~~ arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here if (bc_false) ^~~~~~~~ arch/mips/kernel/branch.c:142:4: note: variable 'bc_false' is declared here int bc_false = 0; ^ 2 errors generated. When mm_bc1t_op and mm_bc2t_op are taken, the bc_false initialization does not happen, which leads to a garbage value upon use, as illustrated below with a small sample program. $ mipsel-linux-gnu-gcc --version | head -n1 mipsel-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0 $ clang --version | head -n1 ClangBuiltLinux clang version 9.0.0 (git://github.com/llvm/llvm-project 544315b4197034a3be8acd12cba56a75fb1f08dc) (based on LLVM 9.0.0svn) $ cat test.c #include static void switch_scoped(int opcode) { switch (opcode) { case 1: case 2: { int bc_false = 0; bc_false = 4; case 3: case 4: printf("\t* switch scoped bc_false = %d\n", bc_false); } } } static void function_scoped(int opcode) { int bc_false = 0; switch (opcode) { case 1: case 2: { bc_false = 4; case 3: case 4: printf("\t* function scoped bc_false = %d\n", bc_false); } } } int main(void) { int opcode; for (opcode = 1; opcode < 5; opcode++) { printf("opcode = %d:\n", opcode); switch_scoped(opcode); function_scoped(opcode); printf("\n"); } return 0; } $ mipsel-linux-gnu-gcc -std=gnu89 -static test.c && \ qemu-mipsel a.out opcode = 1: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 2: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 3: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 opcode = 4: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 $ clang -std=gnu89 --target=mipsel-linux-gnu -m32 -static test.c && \ qemu-mipsel a.out opcode = 1: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 2: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 3: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 opcode = 4: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 Move the definition up so that we get the right behavior and mark it __maybe_unused as it will not be used when CONFIG_MIPS_FP_SUPPORT isn't enabled. Fixes: 6a1cc218b9cc ("MIPS: branch: Remove FP branch handling when CONFIG_MIPS_FP_SUPPORT=n") Link: https://github.com/ClangBuiltLinux/linux/issues/603 Signed-off-by: Nathan Chancellor --- arch/mips/kernel/branch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c index 1db29957a931..2c38f75d87ff 100644 --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -58,6 +58,7 @@ int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, unsigned long *contpc) { union mips_instruction insn = (union mips_instruction)dec_insn.insn; + int __maybe_unused bc_false = 0; if (!cpu_has_mmips) return 0; @@ -139,7 +140,6 @@ int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, #ifdef CONFIG_MIPS_FP_SUPPORT case mm_bc2f_op: case mm_bc1f_op: { - int bc_false = 0; unsigned int fcr31; unsigned int bit;