On Thu, Dec 08, 2022 at 05:31:06PM -0600, Tom Saeger wrote:
On Thu, Dec 08, 2022 at 09:34:40PM +0100, Greg Kroah-Hartman wrote:
On Tue, Dec 06, 2022 at 01:43:08PM -0700, Tom Saeger wrote:
Backport of: 0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments") breaks arm64 Build ID when CONFIG_MODVERSIONS=y.
CONFIG_MODVERSIONS adds extra tooling to calculate symbol versions. This kernel's KBUILD tooling uses both relocatable (-r) and (-z noexecstack) to link head.o which results in ld adding a .note.GNU-stack section. Final linking of vmlinux should add a .NOTES segment containing the Build ID, but does NOT if head.o has a .note.GNU-stack section.
Selectively remove -z noexecstack from head.o's KBUILD_LDFLAGS to prevent .note.GNU-stack from being added to head.o. Final link of vmlinux then properly adds .NOTES segment containing Build ID that can be read using tools like 'readelf -n'.
Cc: stable@vger.kernel.org # 5.15, 5.10, 5.4 Signed-off-by: Tom Saeger tom.saeger@oracle.com
arch/arm64/kernel/Makefile | 5 +++++ 1 file changed, 5 insertions(+)
Why isn't this needed in Linus's tree?
0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments")
was merged after 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS")
Linus's tree never had -z noexecstack with these same KBUILD rules.
Then it needs to say that, in detail, in this changelog please.
And why not cc: everyone involved in this, I would need acks from maintainers to be able to accept this...
Fair request.
Between ~5.3 and 5.19-rc1 cherry-picking 0d362be5b142 ("Makefile: link with -z noexecstack --no-warn-rwx-segments") and building arm64 with CONFIG_MODVERSIONS=y results in vmlinux missing Build ID
head.S is compiled to head.o head.o is linked (ld) with -r and -z noexecstack which adds .note.GNU-stack section in head.o head.o is then linked again with vmlinux (resulting vmlinux is missing .NOTE segment)
Can folks confirm/deny ld behavior is expected (arm64)? And whether the above patch would be an acceptable fix for these kernel versions?
repro test in cover letter: https://lore.kernel.org/all/cover.1670358255.git.tom.saeger@oracle.com/#r
Please resend, no need for a cover letter for just one patch, and include all of the needed info in the changelog itself.
thanks,
greg k-h