Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756453AbZFLNse (ORCPT ); Fri, 12 Jun 2009 09:48:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933254AbZFLNkr (ORCPT ); Fri, 12 Jun 2009 09:40:47 -0400 Received: from cantor.suse.de ([195.135.220.2]:42309 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933216AbZFLNkk (ORCPT ); Fri, 12 Jun 2009 09:40:40 -0400 From: Petr Tesarik To: LKML Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Roland McGrath , Petr Tesarik Subject: [PATCH v2 7/8] x86: check the size of GOT in vDSO Date: Fri, 12 Jun 2009 15:40:39 +0200 Message-Id: <1244814040-5810-8-git-send-email-ptesarik@suse.cz> X-Mailer: git-send-email 1.6.0.2 In-Reply-To: <1244814040-5810-1-git-send-email-ptesarik@suse.cz> References: <1244814040-5810-1-git-send-email-ptesarik@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3245 Lines: 95 There should be no real entries in the GOT, because they are basically pointers to dynamic symbols, and that will not work correctly without a real dynamic linker for the vDSO. However, the ABI pre-defines three entries in the GOT which are always present, so the GOT section is never completely empty. We can check that there are no extra entries beyond these three. To make it work: - move the GOT into a separate section - check the size of that section - pass -m32 or -m64 to the pre-processor to get the correct definition of __SIZEOF_POINTER__ Signed-off-by: Petr Tesarik --- arch/x86/vdso/Makefile | 5 +++-- arch/x86/vdso/vdso-layout.lds.S | 20 +++++++++++++++++++- 2 files changed, 22 insertions(+), 3 deletions(-) diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile index 16a9020..8c7f06a 100644 --- a/arch/x86/vdso/Makefile +++ b/arch/x86/vdso/Makefile @@ -23,7 +23,8 @@ $(obj)/vdso.o: $(obj)/vdso.so targets += vdso.so vdso.so.dbg vdso.lds $(vobjs-y) -export CPPFLAGS_vdso.lds += -P -C +vdso-cppflags = -P -C +export CPPFLAGS_vdso.lds += -m64 $(vdso-cppflags) VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -Wl,-soname=linux-vdso.so.1 \ -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 @@ -68,7 +69,7 @@ vdso32.so-$(VDSO32-y) += sysenter vdso32-images = $(vdso32.so-y:%=vdso32-%.so) -CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds) +CPPFLAGS_vdso32.lds = -m32 $(vdso-cppflags) VDSO_LDFLAGS_vdso32.lds = -m elf_i386 -Wl,-soname=linux-gate.so.1 # This makes sure the $(obj) subdirectory exists even though vdso32/ diff --git a/arch/x86/vdso/vdso-layout.lds.S b/arch/x86/vdso/vdso-layout.lds.S index ffd17e8..3b56e2f 100644 --- a/arch/x86/vdso/vdso-layout.lds.S +++ b/arch/x86/vdso/vdso-layout.lds.S @@ -44,13 +44,15 @@ SECTIONS .dynamic : { *(.dynamic) } :text :dynamic + .got : { + *(.got.plt) *(.got) + } :text .rodata : { *(.rodata*) } :text .data : { *(.data*) - *(.got.plt) *(.got) *(.gnu.linkonce.d.*) *(.bss*) *(.gnu.linkonce.b.*) @@ -113,6 +115,22 @@ SECTIONS */ ASSERT(!SIZEOF(.broken), "The vdso linker script found a section that is bad. See vdso-layout.lds.S for details."); +/* This assert is triggered if the resulting GOT is larger than the + * minimum defined by the ABI, i.e. there is some actual use of the + * GOT. + * + * To find the offending symbols you may: + * 1. temporarily disable this check + * 2. examine the dynamic relocations of the resulting vDSO with + * objdump -R + * + * To find the places where the symbols were used, you may: + * 1. add -Wl,--emit-relocs to VDSO_LDFLAGS + * 2. run objdump -r on the resulting vDSO and look for all + * GOT-type relocations. + */ +ASSERT(SIZEOF(.got) == 3*__SIZEOF_POINTER__, "The vdso linker script found a wrong reference to an external object. See vdso-layout.lds.S for details."); + /* * Very old versions of ld do not recognize this name token; use the constant. */ -- 1.6.0.2 -- 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/