linux-kernel - [PATCH 9/9] arm/boot: Warn on orphan section placement

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Message-Id: <20200228002244.15240-10-keescook@chromium.org>
Date:   Thu, 27 Feb 2020 16:22:44 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Borislav Petkov <bp@...e.de>
Cc:     Kees Cook <keescook@...omium.org>, "H.J. Lu" <hjl.tools@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <masahiroy@...nel.org>, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH 9/9] arm/boot: 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.

Use common macros for debug sections, discards, and text stubs. Add
discards for unwanted .note, and .rel sections. Finally, enable orphan
section warning.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/arm/boot/compressed/Makefile      |  2 ++
 arch/arm/boot/compressed/vmlinux.lds.S | 17 +++++++----------
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index da599c3a1193..7faa2b5e7e16 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -136,6 +136,8 @@ endif
 LDFLAGS_vmlinux += --no-undefined
 # Delete all temporary local symbols
 LDFLAGS_vmlinux += -X
+# Report orphan sections
+LDFLAGS_vmlinux += --orphan-handling=warn
 # Next argument is a linker script
 LDFLAGS_vmlinux += -T
 
diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S
index fc7ed03d8b93..a6a51b5d2328 100644
--- a/arch/arm/boot/compressed/vmlinux.lds.S
+++ b/arch/arm/boot/compressed/vmlinux.lds.S
@@ -2,6 +2,7 @@
 /*
  *  Copyright (C) 2000 Russell King
  */
+#include <asm/vmlinux.lds.h>
 
 #ifdef CONFIG_CPU_ENDIAN_BE8
 #define ZIMAGE_MAGIC(x) ( (((x) >> 24) & 0x000000ff) | \
@@ -17,8 +18,11 @@ ENTRY(_start)
 SECTIONS
 {
   /DISCARD/ : {
+    ARM_COMMON_DISCARD
     *(.ARM.exidx*)
     *(.ARM.extab*)
+    *(.note.*)
+    *(.rel.*)
     /*
      * Discard any r/w data - this produces a link error if we have any,
      * which is required for PIC decompression.  Local data generates
@@ -37,9 +41,7 @@ SECTIONS
     *(.text)
     *(.text.*)
     *(.fixup)
-    *(.gnu.warning)
-    *(.glue_7t)
-    *(.glue_7)
+    ARM_STUBS_TEXT
   }
   .table : ALIGN(4) {
     _table_start = .;
@@ -124,12 +126,7 @@ SECTIONS
   PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data));
   PROVIDE(__pecoff_end = ALIGN(512));
 
-  .stab 0		: { *(.stab) }
-  .stabstr 0		: { *(.stabstr) }
-  .stab.excl 0		: { *(.stab.excl) }
-  .stab.exclstr 0	: { *(.stab.exclstr) }
-  .stab.index 0		: { *(.stab.index) }
-  .stab.indexstr 0	: { *(.stab.indexstr) }
-  .comment 0		: { *(.comment) }
+  STABS_DEBUG
+  DWARF_DEBUG
 }
 ASSERT(_edata_real == _edata, "error: zImage file size is incorrect");
-- 
2.20.1