Merge tag 'core-build-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull orphan section checking from Ingo Molnar:
 "Orphan link sections were a long-standing source of obscure bugs,
  because the heuristics that various linkers & compilers use to handle
  them (include these bits into the output image vs discarding them
  silently) are both highly idiosyncratic and also version dependent.

  Instead of this historically problematic mess, this tree by Kees Cook
  (et al) adds build time asserts and build time warnings if there's any
  orphan section in the kernel or if a section is not sized as expected.

  And because we relied on so many silent assumptions in this area, fix
  a metric ton of dependencies and some outright bugs related to this,
  before we can finally enable the checks on the x86, ARM and ARM64
  platforms"

* tag 'core-build-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits)
  x86/boot/compressed: Warn on orphan section placement
  x86/build: Warn on orphan section placement
  arm/boot: Warn on orphan section placement
  arm/build: Warn on orphan section placement
  arm64/build: Warn on orphan section placement
  x86/boot/compressed: Add missing debugging sections to output
  x86/boot/compressed: Remove, discard, or assert for unwanted sections
  x86/boot/compressed: Reorganize zero-size section asserts
  x86/build: Add asserts for unwanted sections
  x86/build: Enforce an empty .got.plt section
  x86/asm: Avoid generating unused kprobe sections
  arm/boot: Handle all sections explicitly
  arm/build: Assert for unwanted sections
  arm/build: Add missing sections
  arm/build: Explicitly keep .ARM.attributes sections
  arm/build: Refactor linker script headers
  arm64/build: Assert for unwanted sections
  arm64/build: Add missing DWARF sections
  arm64/build: Use common DISCARDS in linker script
  arm64/build: Remove .eh_frame* sections due to unwind tables
  ...

6 files changed, 51 insertions, 21 deletions

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 4e877354515f..e589da3c8949 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -16,6 +16,10 @@ LDFLAGS_vmlinux	+= --be8
 KBUILD_LDFLAGS_MODULE	+= --be8
 endif
 
+# We never want expected sections to be placed heuristically by the
+# linker. All sections should be explicitly named in the linker script.
+LDFLAGS_vmlinux += $(call ld-option, --orphan-handling=warn)
+
 ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
 KBUILD_LDS_MODULE	+= $(srctree)/arch/arm/kernel/module.lds
 endif
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index b1147b7f2c8d..58028abd05d9 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -123,6 +123,8 @@ endif
 LDFLAGS_vmlinux += --no-undefined
 # Delete all temporary local symbols
 LDFLAGS_vmlinux += -X
+# Report orphan sections
+LDFLAGS_vmlinux += $(call ld-option, --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 09ac33f52814..b914be3a207b 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/ : {
+    COMMON_DISCARDS
     *(.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
@@ -36,9 +40,7 @@ SECTIONS
     *(.start)
     *(.text)
     *(.text.*)
-    *(.gnu.warning)
-    *(.glue_7t)
-    *(.glue_7)
+    ARM_STUBS_TEXT
   }
   .table : ALIGN(4) {
     _table_start = .;
@@ -128,12 +130,10 @@ 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
+  ARM_DETAILS
+
+  ARM_ASSERTS
 }
 ASSERT(_edata_real == _edata, "error: zImage file size is incorrect");
diff --git a/arch/arm/kernel/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h
index 381a8e105fa5..4a91428c324d 100644
--- a/arch/arm/kernel/vmlinux.lds.h
+++ b/arch/arm/include/asm/vmlinux.lds.h
@@ -1,4 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#include <asm-generic/vmlinux.lds.h>
 
 #ifdef CONFIG_HOTPLUG_CPU
 #define ARM_CPU_DISCARD(x)
@@ -49,8 +50,29 @@
 		EXIT_CALL						\
 		ARM_MMU_DISCARD(*(.text.fixup))				\
 		ARM_MMU_DISCARD(*(__ex_table))				\
-		*(.discard)						\
-		*(.discard.*)
+		COMMON_DISCARDS
+
+/*
+ * Sections that should stay zero sized, which is safer to explicitly
+ * check instead of blindly discarding.
+ */
+#define ARM_ASSERTS							\
+	.plt : {							\
+		*(.iplt) *(.rel.iplt) *(.iplt) *(.igot.plt)		\
+	}								\
+	ASSERT(SIZEOF(.plt) == 0,					\
+	       "Unexpected run-time procedure linkages detected!")
+
+#define ARM_DETAILS							\
+		ELF_DETAILS						\
+		.ARM.attributes 0 : { *(.ARM.attributes) }
+
+#define ARM_STUBS_TEXT							\
+		*(.gnu.warning)						\
+		*(.glue_7)						\
+		*(.glue_7t)						\
+		*(.vfp11_veneer)                                        \
+		*(.v4_bx)
 
 #define ARM_TEXT							\
 		IDMAP_TEXT						\
@@ -64,9 +86,7 @@
 		CPUIDLE_TEXT						\
 		LOCK_TEXT						\
 		KPROBES_TEXT						\
-		*(.gnu.warning)						\
-		*(.glue_7)						\
-		*(.glue_7t)						\
+		ARM_STUBS_TEXT						\
 		. = ALIGN(4);						\
 		*(.got)			/* Global offset table */	\
 		ARM_CPU_KEEP(PROC_INFO)
diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
index 6d2be994ae58..50136828f5b5 100644
--- a/arch/arm/kernel/vmlinux-xip.lds.S
+++ b/arch/arm/kernel/vmlinux-xip.lds.S
@@ -9,15 +9,13 @@
 
 #include <linux/sizes.h>
 
-#include <asm-generic/vmlinux.lds.h>
+#include <asm/vmlinux.lds.h>
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 #include <asm/memory.h>
 #include <asm/mpu.h>
 #include <asm/page.h>
 
-#include "vmlinux.lds.h"
-
 OUTPUT_ARCH(arm)
 ENTRY(stext)
 
@@ -152,6 +150,10 @@ SECTIONS
 	_end = .;
 
 	STABS_DEBUG
+	DWARF_DEBUG
+	ARM_DETAILS
+
+	ARM_ASSERTS
 }
 
 /*
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 7f24bc08403e..5f4922e858d0 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -9,15 +9,13 @@
 #else
 
 #include <linux/pgtable.h>
-#include <asm-generic/vmlinux.lds.h>
+#include <asm/vmlinux.lds.h>
 #include <asm/cache.h>
 #include <asm/thread_info.h>
 #include <asm/memory.h>
 #include <asm/mpu.h>
 #include <asm/page.h>
 
-#include "vmlinux.lds.h"
-
 OUTPUT_ARCH(arm)
 ENTRY(stext)
 
@@ -151,6 +149,10 @@ SECTIONS
 	_end = .;
 
 	STABS_DEBUG
+	DWARF_DEBUG
+	ARM_DETAILS
+
+	ARM_ASSERTS
 }
 
 #ifdef CONFIG_STRICT_KERNEL_RWX