path: root/arch
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authorNick Desaulniers <ndesaulniers@google.com>2022-08-10 15:24:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-08-10 18:30:09 -0700
commitffcf9c5700e49c0aee42dcba9a12ba21338e8136 (patch)
treeee5cde302a8420a8c2af2aeeaed8f4b83d324651 /arch
parent0d362be5b14200b77ecc2127936a5ff82fbffe41 (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>
Diffstat (limited to 'arch')
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 $(call ld-option, --no-dynamic-linker)
LDFLAGS_vmlinux += --orphan-handling=warn
+LDFLAGS_vmlinux += -z noexecstack
+ifeq ($(CONFIG_LD_IS_BFD),y)
+LDFLAGS_vmlinux += $(call ld-option,--no-warn-rwx-segments)
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
quiet_cmd_vdso_and_check = VDSO $@

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