From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751133AbWD3OSe (ORCPT ); Sun, 30 Apr 2006 10:18:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751132AbWD3OSZ (ORCPT ); Sun, 30 Apr 2006 10:18:25 -0400 Received: from host199-105.pool8255.interbusiness.it ([82.55.105.199]:23960 "EHLO zion.home.lan") by vger.kernel.org with ESMTP id S1751130AbWD3OSA (ORCPT ); Sun, 30 Apr 2006 10:18:00 -0400 From: "Paolo 'Blaisorblade' Giarrusso" Subject: [PATCH 5/7] uml: fix compilation and execution with hardened GCC Date: Sun, 30 Apr 2006 16:16:19 +0200 To: Andrew Morton Cc: Jeff Dike , linux-kernel@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net Message-Id: <20060430141619.9060.68951.stgit@zion.home.lan> In-Reply-To: <20060430141512.9060.39338.stgit@zion.home.lan> References: <20060430141512.9060.39338.stgit@zion.home.lan> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo 'Blaisorblade' Giarrusso To make some half-assembly stubs compile, disable various "hardened" GCC features: *) we can't make it build PIC code as we need %ebx to do syscalls and GCC wants it free for PIC *) we can't leave stack protection as the stub is moved (not relocated!) in memory so the RIP-relative access to the canary tries reading from an unmapped address and causes a segfault, since we move the stub of various megabytes (the exact amount will be decided at runtime) away from the link-time address. Signed-off-by: Paolo 'Blaisorblade' Giarrusso --- arch/um/Makefile | 6 +++++- arch/um/kernel/skas/Makefile | 9 ++++++++- arch/um/sys-i386/Makefile | 2 ++ arch/um/sys-x86_64/Makefile | 2 ++ 4 files changed, 17 insertions(+), 2 deletions(-) diff --git a/arch/um/Makefile b/arch/um/Makefile index 930e006..bed604a 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -118,6 +118,10 @@ prepare: $(ARCH_DIR)/include/kern_consta LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib +CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,) \ + $(call cc-option, -fno-stack-protector,) \ + $(call cc-option, -fno-stack-protector-all,) + CPP_MODE-$(CONFIG_MODE_TT) := -DMODE_TT CONFIG_KERNEL_STACK_ORDER ?= 2 STACK_SIZE := $(shell echo $$[ 4096 * (1 << $(CONFIG_KERNEL_STACK_ORDER)) ] ) @@ -227,4 +231,4 @@ $(ARCH_DIR)/include/kern_constants.h: $( @echo ' SYMLINK $@' $(Q)ln -sf ../../../include/asm-um/asm-offsets.h $@ -export SUBARCH USER_CFLAGS OS +export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS diff --git a/arch/um/kernel/skas/Makefile b/arch/um/kernel/skas/Makefile index 57181a9..ad84296 100644 --- a/arch/um/kernel/skas/Makefile +++ b/arch/um/kernel/skas/Makefile @@ -11,4 +11,11 @@ USER_OBJS := clone.o include arch/um/scripts/Makefile.rules # clone.o is in the stub, so it can't be built with profiling -$(obj)/clone.o : c_flags = -Wp,-MD,$(depfile) $(call unprofile,$(USER_CFLAGS)) +# GCC hardened also auto-enables -fpic, but we need %ebx so it can't work -> +# disable it + +CFLAGS_clone.o := $(CFLAGS_NO_HARDENING) + +# since we're setting c_flags we _must_ add $(CFLAGS_$(*F).o). + +$(obj)/clone.o : c_flags = -Wp,-MD,$(depfile) $(call unprofile,$(USER_CFLAGS)) $(CFLAGS_$(*F).o) diff --git a/arch/um/sys-i386/Makefile b/arch/um/sys-i386/Makefile index 82121ab..3734c3e 100644 --- a/arch/um/sys-i386/Makefile +++ b/arch/um/sys-i386/Makefile @@ -13,6 +13,8 @@ USER_OBJS := bugs.o ptrace_user.o sigcon USER_OBJS += user-offsets.s extra-y += user-offsets.s +CFLAGS_stub_segv.o := $(CFLAGS_NO_HARDENING) + extra-$(CONFIG_MODE_TT) += unmap.o include arch/um/scripts/Makefile.rules diff --git a/arch/um/sys-x86_64/Makefile b/arch/um/sys-x86_64/Makefile index f739bea..6d3b29c 100644 --- a/arch/um/sys-x86_64/Makefile +++ b/arch/um/sys-x86_64/Makefile @@ -21,6 +21,8 @@ USER_OBJS := ptrace_user.o sigcontext.o USER_OBJS += user-offsets.s extra-y += user-offsets.s +CFLAGS_stub_segv.o := $(CFLAGS_NO_HARDENING) + extra-$(CONFIG_MODE_TT) += unmap.o include arch/um/scripts/Makefile.rules