[tip: core/build] arm64/build: Remove .eh_frame* sections due to unwind tables

[tip-bot2 for Kees Cook]

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@xxxxxxxxxxxx>
AuthorDate:    Fri, 21 Aug 2020 12:42:51 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Acked-by: Will Deacon <will@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200821194310.3089815-11-keescook@xxxxxxxxxxxx
---
 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;