From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yb1-xb49.google.com ([2607:f8b0:4864:20::b49]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oatXk-009NH9-Q7 for linux-um@lists.infradead.org; Wed, 21 Sep 2022 06:49:17 +0000 Received: by mail-yb1-xb49.google.com with SMTP id d8-20020a25bc48000000b00680651cf051so4349350ybk.23 for ; Tue, 20 Sep 2022 23:49:03 -0700 (PDT) Date: Wed, 21 Sep 2022 14:48:55 +0800 Mime-Version: 1.0 Message-ID: <20220921064855.2841607-1-davidgow@google.com> Subject: [PATCH v2] arch: um: Mark the stack non-executable to fix a binutils warning From: David Gow List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: Richard Weinberger , Anton Ivanov , Johannes Berg , Nick Desaulniers Cc: David Gow , Thomas Gleixner , Ingo Molnar , Dave Hansen , Linus Torvalds , Brendan Higgins , Daniel Latypov , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, kunit-dev@googlegroups.com, x86@kernel.org, Lukas Straub , Randy Dunlap Since binutils 2.39, ld will print a warning if any stack section is executable, which is the default for stack sections on files without a .note.GNU-stack section. This was fixed for x86 in commit ffcf9c5700e4 ("x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments"), but remained broken for UML, resulting in several warnings: /usr/bin/ld: warning: arch/x86/um/vdso/vdso.o: missing .note.GNU-stack section implies executable stack /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker /usr/bin/ld: warning: .tmp_vmlinux.kallsyms1 has a LOAD segment with RWX permissions /usr/bin/ld: warning: .tmp_vmlinux.kallsyms1.o: missing .note.GNU-stack section implies executable stack /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker /usr/bin/ld: warning: .tmp_vmlinux.kallsyms2 has a LOAD segment with RWX permissions /usr/bin/ld: warning: .tmp_vmlinux.kallsyms2.o: missing .note.GNU-stack section implies executable stack /usr/bin/ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker /usr/bin/ld: warning: vmlinux has a LOAD segment with RWX permissions Link both the VDSO and vmlinux with -z noexecstack, fixing the warnings about .note.GNU-stack sections. In addition, pass --no-warn-rwx-segments to dodge the remaining warnings about LOAD segments with RWX permissions in the kallsyms objects. (Note that this flag is apparently not available on lld, so hide it behind a test for BFD, which is what the x86 patch does.) Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ffcf9c5700e49c0aee42dcba9a12ba21338e8136 Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107 Signed-off-by: David Gow Reviewed-by: Lukas Straub Tested-by: Lukas Straub Acked-by: Randy Dunlap # build-tested --- Note that this still doesn't seem to be working properly with make LLVM=1. It doesn't appear to break anything, and still is an improvement for gcc, so seems worthwhile anyway... Changes since v1: http://lists.infradead.org/pipermail/linux-um/2022-August/004234.html - Pass the -z noexecstack and --no-warn-rwx-segments flags as LDFLAGS, rather than as CFLAGS via -Wl - Check that --no-warn-rwx-segments exists with the ld-option function (Thanks Richard) - Add Lukas and Randy's tags. arch/um/Makefile | 8 ++++++++ arch/x86/um/vdso/Makefile | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/um/Makefile b/arch/um/Makefile index f2fe63bfd819..f1d4d67157be 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -132,10 +132,18 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT) # The wrappers will select whether using "malloc" or the kernel allocator. LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc +# Avoid binutils 2.39+ warnings by marking the stack non-executable and +# ignorning warnings for the kallsyms sections. +LDFLAGS_EXECSTACK = -z noexecstack +ifeq ($(CONFIG_LD_IS_BFD),y) +LDFLAGS_EXECSTACK += $(call ld-option,--no-warn-rwx-segments) +endif + LD_FLAGS_CMDLINE = $(foreach opt,$(KBUILD_LDFLAGS),-Wl,$(opt)) # Used by link-vmlinux.sh which has special support for um link export CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LD_FLAGS_CMDLINE) +export LDFLAGS_vmlinux := $(LDFLAGS_EXECSTACK) # When cleaning we don't include .config, so we don't include # TT or skas makefiles and don't clean skas_ptregs.h. diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile index 8c0396fd0e6f..6fbe97c52c99 100644 --- a/arch/x86/um/vdso/Makefile +++ b/arch/x86/um/vdso/Makefile @@ -65,7 +65,7 @@ quiet_cmd_vdso = VDSO $@ -Wl,-T,$(filter %.lds,$^) $(filter %.o,$^) && \ sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@' -VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv +VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv -z noexecstack GCOV_PROFILE := n # -- 2.37.3.968.ga6b4b080e4-goog _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um