linux-stable/arch/x86/entry
Nick Desaulniers ffcf9c5700 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>
2022-08-10 18:30:09 -07:00
..
syscalls Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
vdso x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments 2022-08-10 18:30:09 -07:00
vsyscall x86/vsyscall_emu/64: Don't use RET in vsyscall emulation 2022-06-27 10:33:58 +02:00
calling.h x86/retbleed: Add fine grained Kconfig knobs 2022-06-29 17:43:41 +02:00
common.c X86 entry code related updates: 2021-06-29 12:44:51 -07:00
entry.S x86/bugs: Add retbleed=ibpb 2022-06-27 10:34:00 +02:00
entry_32.S x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n 2022-06-27 10:34:00 +02:00
entry_64.S x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt 2022-07-14 09:45:12 +02:00
entry_64_compat.S objtool: Add entry UNRET validation 2022-06-27 10:34:00 +02:00
Makefile x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y 2022-08-04 12:23:50 +02:00
syscall_32.c x86/syscalls: Stop filling syscall arrays with *_sys_ni_syscall 2021-05-20 15:03:59 +02:00
syscall_64.c x86/syscalls: Stop filling syscall arrays with *_sys_ni_syscall 2021-05-20 15:03:59 +02:00
syscall_x32.c x86/syscalls: Stop filling syscall arrays with *_sys_ni_syscall 2021-05-20 15:03:59 +02:00
thunk_32.S x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y 2022-08-04 12:23:50 +02:00
thunk_64.S x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y 2022-08-04 12:23:50 +02:00