linux-kernel - [PATCH v4 14/17] arm/build: Warn on orphan section placement

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Message-Id: <20200629061840.4065483-15-keescook@chromium.org>
Date:   Sun, 28 Jun 2020 23:18:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Will Deacon <will@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>, x86@...nel.org,
        clang-built-linux@...glegroups.com, linux-arch@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 14/17] arm/build: Warn on orphan section placement

We don't want to depend on the linker's orphan section placement
heuristics as these can vary between linkers, and may change between
versions. All sections need to be explicitly named in the linker
script.

Specifically, this would have made a recently fixed bug very obvious:

ld: warning: orphan section `.fixup' from `arch/arm/lib/copy_from_user.o' being placed in section `.fixup'

Discard unneeded sections .iplt, .rel.iplt, .igot.plt, and .modinfo.

Add missing text stub sections .vfp11_veneer and .v4_bx.

Add debug sections explicitly.

Finally enable orphan section warning.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/include/asm/vmlinux.lds.h | 6 +++++-
 arch/arm/kernel/vmlinux-xip.lds.S  | 1 +
 arch/arm/kernel/vmlinux.lds.S      | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h
index c66b16cd8837..d44fae722e7a 100644
--- a/arch/arm/include/asm/vmlinux.lds.h
+++ b/arch/arm/include/asm/vmlinux.lds.h
@@ -39,6 +39,8 @@
 		__idmap_text_end = .;					\
 
 #define ARM_COMMON_DISCARD						\
+		*(.iplt) *(.rel.iplt) *(.igot.plt)                      \
+		*(.modinfo)                                             \
 		*(.discard)						\
 		*(.discard.*)
 
@@ -63,7 +65,9 @@
 #define ARM_STUBS_TEXT							\
 		*(.gnu.warning)						\
 		*(.glue_7)						\
-		*(.glue_7t)
+		*(.glue_7t)						\
+		*(.vfp11_veneer)                                        \
+		*(.v4_bx)
 
 #define ARM_TEXT							\
 		IDMAP_TEXT						\
diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
index 57fcbf55f913..11ffa79751da 100644
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@@ -150,6 +150,7 @@ SECTIONS
 	_end = .;
 
 	STABS_DEBUG
+	DWARF_DEBUG
 	ARM_DETAILS
 }
 
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 1d3d3b599635..dc672fe35de3 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -149,6 +149,7 @@ SECTIONS
 	_end = .;
 
 	STABS_DEBUG
+	DWARF_DEBUG
 	ARM_DETAILS
 }
 
-- 
2.25.1