| Message ID | 20220823010830.2675419-1-davidgow@google.com |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | arch: um: Mark the stack non-executable to fix a binutils warning | expand |
Looks good to me: Reviewed-by: Lukas Straub <lukasstraub2@web.de> Tested-by: Lukas Straub <lukasstraub2@web.de> Regards, Lukas Straub --
On 8/22/22 18:08, David Gow wrote: > 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 <davidgow@google.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Thanks. > --- > arch/um/Makefile | 9 ++++++++- > arch/x86/um/vdso/Makefile | 2 +- > 2 files changed, 9 insertions(+), 2 deletions(-)
----- Ursprüngliche Mail ----- > Von: "Randy Dunlap" <rdunlap@infradead.org> >> 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 <davidgow@google.com> > > Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested This patch causes a build error on one of my systems: /usr/lib64/gcc/x86_64-suse-linux/7/../../../../x86_64-suse-linux/bin/ld: unrecognized option '--no-warn-rwx-segments' /usr/lib64/gcc/x86_64-suse-linux/7/../../../../x86_64-suse-linux/bin/ld: use the --help option for usage information collect2: error: ld returned 1 exit status Just like in commit ffcf9c5700e4 ("x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments") you need to test for it. Thanks, //richard
diff --git a/arch/um/Makefile b/arch/um/Makefile index f2fe63bfd819..75d5c704b3a8 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -132,10 +132,17 @@ export LDS_ELF_FORMAT := $(ELF_FORMAT) # The wrappers will select whether using "malloc" or the kernel allocator. LINK_WRAPS = -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc +# Avoid binutils 2.39+ warnings by marking the stack non-executable and +# ignorning warnings for the kallsyms sections. +LINK_RWXSECTION = -Wl,-z,noexecstack +ifeq ($(CONFIG_LD_IS_BFD),y) +LINK_RWXSECTION += -Wl,--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 CFLAGS_vmlinux := $(LINK-y) $(LINK_WRAPS) $(LINK_RWXSECTION) $(LD_FLAGS_CMDLINE) # 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 #
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 <davidgow@google.com> --- arch/um/Makefile | 9 ++++++++- arch/x86/um/vdso/Makefile | 2 +- 2 files changed, 9 insertions(+), 2 deletions(-)