From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZrOiIRkub/Kn8ek3AUFlRbtyJKSHiBhYeNBRGQHGwjwR8uxm9TOJN7I9nAscNhOZfd8zPes ARC-Seal: i=1; a=rsa-sha256; t=1526937891; cv=none; d=google.com; s=arc-20160816; b=UpfUR7pYzLsEFoFF7CNgNIBVVgLiAhnbOVUupgelGQLVZFXBa8VyobpAs+exeXTE+m bu04YhZjwBbiJVs3BlLAUVltHQn2Z+KuHr9B+GRA7kRKusf7ZzXfXdcuEu025R4WsrxS 1WnBtyLTVtt+md4YZ5LbLjnERyp9v5VCySeH5Hw4lQUHP38KQqU9HPaN/O61fdFYESSB sA5k45WepUSkPhLKdwDnCCR92Z/DujeHxRo/mPOMZQFvcAMId81WkKFlORRgvAG2hJBd kvtHRkfi5ZMBVYxYElCr6JmbuYRXG+KVuFTDPnRxYVxtfJd85cCPYfyE/xEQTWXnTaFJ kamA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:dkim-signature:arc-authentication-results; bh=8BusgR7UX/ileAW+5yEe/c1qYnHORHi/kfMJ1sdEfAw=; b=zZLGRIGE4HK02WHNQRFtPjEFDejGTRaqIjFbcje93B08ZL6o+ukH8tj/2MwuKZWQnZ 4MV1BgNFchdYm8GrJitNSVwXeKtmFo7n1Nqe4W7EmgA0zrwOWLzYEcuI1+oq7mg1zffz XnBmNwhG9dkfyFFBOWBSF4khOKpHYMKUFt07L04kNFIrnwPkwA26MFa4uaEOodDvloat CFK6DOSsVmfxBxfJdiOUCOtuOef9BtQb0G7XZ7Y6hLwn0DhUx4JXpSjGt7jl3noV5O+n 1Ec0m9VTRO/llnlpMxNHeAAdLONKld96/q/HWXG8oHBywJ5qSmemFOUDoUwqPDyDlftr RUhQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=rnKTNHpO; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=rnKTNHpO; spf=pass (google.com: domain of srs0=nia/=ii=linuxfoundation.org=gregkh@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=SRS0=nia/=II=linuxfoundation.org=gregkh@kernel.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.16 062/110] x86/nospec: Simplify alternative_msr_write() Date: Mon, 21 May 2018 23:11:59 +0200 Message-Id: <20180521210511.622233431@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180521210503.823249477@linuxfoundation.org> References: <20180521210503.823249477@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1601109821557476654?= X-GMAIL-MSGID: =?utf-8?q?1601110426752074469?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Linus Torvalds commit 1aa7a5735a41418d8e01fa7c9565eb2657e2ea3f upstream The macro is not type safe and I did look for why that "g" constraint for the asm doesn't work: it's because the asm is more fundamentally wrong. It does movl %[val], %%eax but "val" isn't a 32-bit value, so then gcc will pass it in a register, and generate code like movl %rsi, %eax and gas will complain about a nonsensical 'mov' instruction (it's moving a 64-bit register to a 32-bit one). Passing it through memory will just hide the real bug - gcc still thinks the memory location is 64-bit, but the "movl" will only load the first 32 bits and it all happens to work because x86 is little-endian. Convert it to a type safe inline function with a little trick which hands the feature into the ALTERNATIVE macro. Signed-off-by: Linus Torvalds Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/nospec-branch.h | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -241,15 +241,16 @@ static inline void vmexit_fill_RSB(void) #endif } -#define alternative_msr_write(_msr, _val, _feature) \ - asm volatile(ALTERNATIVE("", \ - "movl %[msr], %%ecx\n\t" \ - "movl %[val], %%eax\n\t" \ - "movl $0, %%edx\n\t" \ - "wrmsr", \ - _feature) \ - : : [msr] "i" (_msr), [val] "i" (_val) \ - : "eax", "ecx", "edx", "memory") +static __always_inline +void alternative_msr_write(unsigned int msr, u64 val, unsigned int feature) +{ + asm volatile(ALTERNATIVE("", "wrmsr", %c[feature]) + : : "c" (msr), + "a" (val), + "d" (val >> 32), + [feature] "i" (feature) + : "memory"); +} static inline void indirect_branch_prediction_barrier(void) {