Messages in this thread | | | Date | Wed, 10 Aug 2022 19:06:00 -0600 | Subject | Re: [PATCH v2 0/2] link with -z noexecstack --no-warn-rwx-segments | From | Jens Axboe <> |
| |
On 8/10/22 4:24 PM, Nick Desaulniers wrote: > 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: vmlinux: 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: 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. > > Broken up into 2 patches; one for the top level vmlinux, one x86 > specific since a few places in the x86 build reset KBUILD_LDFLAGS.
For x86-64:
Tested-by: Jens Axboe <axboe@kernel.dk>
-- Jens Axboe
| |