Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754355AbdGLV2A (ORCPT ); Wed, 12 Jul 2017 17:28:00 -0400 Received: from mail-pf0-f179.google.com ([209.85.192.179]:33622 "EHLO mail-pf0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753637AbdGLV17 (ORCPT ); Wed, 12 Jul 2017 17:27:59 -0400 From: Matthias Kaehlcke To: Chris J Arges , Josh Poimboeuf , Borislav Petkov , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Douglas Anderson , Michael Davidson , Greg Hackmann , Nick Desaulniers , Stephen Hines , Kees Cook , Arnd Bergmann , Bernhard.Rosenkranzer@linaro.org, Matthias Kaehlcke Subject: [PATCH] Revert "x86/uaccess: Add stack frame output operand in get_user() inline asm" Date: Wed, 12 Jul 2017 14:27:44 -0700 Message-Id: <20170712212744.23660-1-mka@chromium.org> X-Mailer: git-send-email 2.13.2.932.g7449e964c-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1457 Lines: 33 Commit f05058c4d652 supposedly "forces a stack frame to be created before the inline asm code if CONFIG_FRAME_POINTER is enabled by listing the stack pointer as an output operand for the get_user() inline assembly statement.". This doesn't work as intended, at least with gcc v4.9.2 and x86-64 the generated code is exactly the same with and without the patch. However clang adds an extra instruction that adjusts %rsp, which ends up causing double faults all over the place. Signed-off-by: Matthias Kaehlcke --- arch/x86/include/asm/uaccess.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h index 476ea27f490b..9ec2beab73df 100644 --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -161,11 +161,10 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) ({ \ int __ret_gu; \ register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX); \ - register void *__sp asm(_ASM_SP); \ __chk_user_ptr(ptr); \ might_fault(); \ - asm volatile("call __get_user_%P4" \ - : "=a" (__ret_gu), "=r" (__val_gu), "+r" (__sp) \ + asm volatile("call __get_user_%P3" \ + : "=a" (__ret_gu), "=r" (__val_gu) \ : "0" (ptr), "i" (sizeof(*(ptr)))); \ (x) = (__force __typeof__(*(ptr))) __val_gu; \ __builtin_expect(__ret_gu, 0); \ -- 2.13.2.932.g7449e964c-goog