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Subject[tip: core/build] arm64/build: Remove .eh_frame* sections due to unwind tables
The following commit has been merged into the core/build branch of tip:

Commit-ID: 6e0a66d10c5b629369afa47b753d0ec46fa812dd
Gitweb: https://git.kernel.org/tip/6e0a66d10c5b629369afa47b753d0ec46fa812dd
Author: Kees Cook <keescook@chromium.org>
AuthorDate: Fri, 21 Aug 2020 12:42:51 -07:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 01 Sep 2020 09:50:36 +02:00

arm64/build: Remove .eh_frame* sections due to unwind tables

Avoid .eh_frame* section generation by making sure both CFLAGS and AFLAGS
contain -fno-asychronous-unwind-tables and -fno-unwind-tables.

With all sources of .eh_frame now removed from the build, drop this
DISCARD so we can be alerted in the future if it returns unexpectedly
once orphan section warnings have been enabled.

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200821194310.3089815-11-keescook@chromium.org
---
arch/arm64/Makefile | 5 ++++-
arch/arm64/kernel/vmlinux.lds.S | 1 -
2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 55bc854..6de7f55 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -47,13 +47,16 @@ endif

KBUILD_CFLAGS += -mgeneral-regs-only \
$(compat_vdso) $(cc_has_k_constraint)
-KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
KBUILD_AFLAGS += $(compat_vdso)

KBUILD_CFLAGS += $(call cc-option,-mabi=lp64)
KBUILD_AFLAGS += $(call cc-option,-mabi=lp64)

+# Avoid generating .eh_frame* sections.
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+
ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
prepare: stack_protector_prepare
stack_protector_prepare: prepare0
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 13fc2ec..c2b8426 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -94,7 +94,6 @@ SECTIONS
*(.discard.*)
*(.interp .dynamic)
*(.dynsym .dynstr .hash .gnu.hash)
- *(.eh_frame)
}

. = KIMAGE_VADDR + TEXT_OFFSET;
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