Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932091AbbKLXSs (ORCPT ); Thu, 12 Nov 2015 18:18:48 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44850 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754481AbbKLXSo (ORCPT ); Thu, 12 Nov 2015 18:18:44 -0500 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Andreas Schwab , Geert Uytterhoeven , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 007/155] m68k: Define asmlinkage_protect Date: Thu, 12 Nov 2015 15:16:01 -0800 Message-Id: <1447370309-357-8-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1447370309-357-1-git-send-email-kamal@canonical.com> References: <1447370309-357-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3015 Lines: 78 3.19.8-ckt10 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Andreas Schwab 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: Kamal Mostafa --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/