diff options
| author | Nick Desaulniers <ndesaulniers@google.com> | 2022-08-10 15:24:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-08-10 18:30:09 -0700 |
| commit | ffcf9c5700e49c0aee42dcba9a12ba21338e8136 (patch) | |
| tree | ee5cde302a8420a8c2af2aeeaed8f4b83d324651 | |
| parent | 0d362be5b14200b77ecc2127936a5ff82fbffe41 (diff) | |
x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments
Users of GNU ld (BFD) from binutils 2.39+ will observe multiple
instances of a new warning when linking kernels in the form:
ld: warning: arch/x86/boot/pmjump.o: missing .note.GNU-stack section implies executable stack
ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
ld: warning: arch/x86/boot/compressed/vmlinux has a LOAD segment with RWX permissions
Generally, we would like to avoid the stack being executable. Because
there could be a need for the stack to be executable, assembler sources
have to opt-in to this security feature via explicit creation of the
.note.GNU-stack feature (which compilers create by default) or command
line flag --noexecstack. Or we can simply tell the linker the
production of such sections is irrelevant and to link the stack as
--noexecstack.
LLVM's LLD linker defaults to -z noexecstack, so this flag isn't
strictly necessary when linking with LLD, only BFD, but it doesn't hurt
to be explicit here for all linkers IMO. --no-warn-rwx-segments is
currently BFD specific and only available in the current latest release,
so it's wrapped in an ld-option check.
While the kernel makes extensive usage of ELF sections, it doesn't use
permissions from ELF segments.
Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
Link: https://github.com/llvm/llvm-project/issues/57009
Reported-and-tested-by: Jens Axboe <axboe@kernel.dk>
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/x86/boot/Makefile | 2 | ||||
| -rw-r--r-- | arch/x86/boot/compressed/Makefile | 4 | ||||
| -rw-r--r-- | arch/x86/entry/vdso/Makefile | 2 |
3 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile index b5aecb524a8a..ffec8bb01ba8 100644 --- a/arch/x86/boot/Makefile +++ b/arch/x86/boot/Makefile @@ -103,7 +103,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE AFLAGS_header.o += -I$(objtree)/$(obj) $(obj)/header.o: $(obj)/zoffset.h -LDFLAGS_setup.elf := -m elf_i386 -T +LDFLAGS_setup.elf := -m elf_i386 -z noexecstack -T $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE $(call if_changed,ld) diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index 19e1905dcbf6..35ce1a64068b 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -69,6 +69,10 @@ LDFLAGS_vmlinux := -pie $(call ld-option, --no-dynamic-linker) ifdef CONFIG_LD_ORPHAN_WARN LDFLAGS_vmlinux += --orphan-handling=warn endif +LDFLAGS_vmlinux += -z noexecstack +ifeq ($(CONFIG_LD_IS_BFD),y) +LDFLAGS_vmlinux += $(call ld-option,--no-warn-rwx-segments) +endif LDFLAGS_vmlinux += -T hostprogs := mkpiggy diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index 76cd790ed0bd..12f6c4d714cd 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -180,7 +180,7 @@ quiet_cmd_vdso = VDSO $@ sh $(srctree)/$(src)/checkundef.sh '$(NM)' '$@' VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 \ - $(call ld-option, --eh-frame-hdr) -Bsymbolic + $(call ld-option, --eh-frame-hdr) -Bsymbolic -z noexecstack GCOV_PROFILE := n quiet_cmd_vdso_and_check = VDSO $@ |