Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753418AbcDRKud (ORCPT ); Mon, 18 Apr 2016 06:50:33 -0400 Received: from mail.kernel.org ([198.145.29.136]:35130 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751335AbcDRKua (ORCPT ); Mon, 18 Apr 2016 06:50:30 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Andreas Schwab , Geert Uytterhoeven , Zefan Li Subject: [PATCH 3.4 63/92] m68k: Define asmlinkage_protect Date: Mon, 18 Apr 2016 18:46:08 +0800 Message-Id: <1460976397-5688-63-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1460976338-5631-1-git-send-email-lizf@kernel.org> References: <1460976338-5631-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2755 Lines: 73 From: Andreas Schwab 3.4.112-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 8474ba74193d302e8340dddd1e16c85cc4b98caf upstream. Make sure the compiler does not modify arguments of syscall functions. This can happen if the compiler generates a tailcall to another function. For example, without asmlinkage_protect sys_openat is compiled into this function: sys_openat: clr.l %d0 move.w 18(%sp),%d0 move.l %d0,16(%sp) jbra do_sys_open Note how the fourth argument is modified in place, modifying the register %d4 that gets restored from this stack slot when the function returns to user-space. The caller may expect the register to be unmodified across system calls. Signed-off-by: Andreas Schwab Signed-off-by: Geert Uytterhoeven Signed-off-by: Zefan Li --- arch/m68k/include/asm/linkage.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/arch/m68k/include/asm/linkage.h b/arch/m68k/include/asm/linkage.h index 5a822bb..066e74f 100644 --- a/arch/m68k/include/asm/linkage.h +++ b/arch/m68k/include/asm/linkage.h @@ -4,4 +4,34 @@ #define __ALIGN .align 4 #define __ALIGN_STR ".align 4" +/* + * Make sure the compiler doesn't do anything stupid with the + * arguments on the stack - they are owned by the *caller*, not + * the callee. This just fools gcc into not spilling into them, + * and keeps it from doing tailcall recursion and/or using the + * stack slots for temporaries, since they are live and "used" + * all the way to the end of the function. + */ +#define asmlinkage_protect(n, ret, args...) \ + __asmlinkage_protect##n(ret, ##args) +#define __asmlinkage_protect_n(ret, args...) \ + __asm__ __volatile__ ("" : "=r" (ret) : "0" (ret), ##args) +#define __asmlinkage_protect0(ret) \ + __asmlinkage_protect_n(ret) +#define __asmlinkage_protect1(ret, arg1) \ + __asmlinkage_protect_n(ret, "m" (arg1)) +#define __asmlinkage_protect2(ret, arg1, arg2) \ + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2)) +#define __asmlinkage_protect3(ret, arg1, arg2, arg3) \ + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3)) +#define __asmlinkage_protect4(ret, arg1, arg2, arg3, arg4) \ + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4)) +#define __asmlinkage_protect5(ret, arg1, arg2, arg3, arg4, arg5) \ + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4), "m" (arg5)) +#define __asmlinkage_protect6(ret, arg1, arg2, arg3, arg4, arg5, arg6) \ + __asmlinkage_protect_n(ret, "m" (arg1), "m" (arg2), "m" (arg3), \ + "m" (arg4), "m" (arg5), "m" (arg6)) + #endif -- 1.9.1