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

…ux/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
  ...

arch/alpha/kernel/vmlinux.lds.S

@@ -72,6 +72,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 }

arch/arc/kernel/vmlinux.lds.S

@@ -122,6 +122,7 @@ SECTIONS
 	_end = . ;
 
 	STABS_DEBUG
+	ELF_DETAILS
 	DISCARDS
 
 	.arcextmap 0 : {

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

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
 

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");

arch/arm/kernel/vmlinux.lds.h → 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)

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
 }
 
 /*

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

arch/arm64/Makefile

@@ -28,6 +28,10 @@ LDFLAGS_vmlinux	+= --fix-cortex-a53-843419
   endif
 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_ARM64_USE_LSE_ATOMICS), y)
   ifneq ($(CONFIG_ARM64_LSE_ATOMICS), y)
 $(warning LSE atomics not supported by binutils)
@@ -46,13 +50,16 @@ 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

arch/arm64/kernel/smccc-call.S

@@ -9,7 +9,6 @@
 #include <asm/assembler.h>
 
 	.macro SMCCC instr
-	.cfi_startproc
 	\instr	#0
 	ldr	x4, [sp]
 	stp	x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
@@ -21,7 +20,6 @@
 	b.ne	1f
 	str	x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS]
 1:	ret
-	.cfi_endproc
 	.endm
 
 /*

arch/arm64/kernel/vmlinux.lds.S

@@ -6,6 +6,7 @@
  */
 
 #define RO_EXCEPTION_TABLE_ALIGN	8
+#define RUNTIME_DISCARD_EXIT
 
 #include <asm-generic/vmlinux.lds.h>
 #include <asm/cache.h>
@@ -96,13 +97,10 @@ SECTIONS
 	 * matching the same input section name.  There is no documented
 	 * order of matching.
 	 */
+	DISCARDS
 	/DISCARD/ : {
-		EXIT_CALL
-		*(.discard)
-		*(.discard.*)
 		*(.interp .dynamic)
 		*(.dynsym .dynstr .hash .gnu.hash)
-		*(.eh_frame)
 	}
 
 	. = KIMAGE_VADDR;
@@ -131,6 +129,14 @@ SECTIONS
 		*(.got)			/* Global offset table		*/
 	}
 
+	/*
+	 * Make sure that the .got.plt is either completely empty or it
+	 * contains only the lazy dispatch entries.
+	 */
+	.got.plt : { *(.got.plt) }
+	ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18,
+	       "Unexpected GOT/PLT entries detected!")
+
 	. = ALIGN(SEGMENT_ALIGN);
 	_etext = .;			/* End of text section */
 
@@ -249,8 +255,22 @@ SECTIONS
 	_end = .;
 
 	STABS_DEBUG
+	DWARF_DEBUG
+	ELF_DETAILS
 
 	HEAD_SYMBOLS
+
+	/*
+	 * Sections that should stay zero sized, which is safer to
+	 * explicitly check instead of blindly discarding.
+	 */
+	.plt : {
+		*(.plt) *(.plt.*) *(.iplt) *(.igot)
+	}
+	ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
+
+	.data.rel.ro : { *(.data.rel.ro) }
+	ASSERT(SIZEOF(.data.rel.ro) == 0, "Unexpected RELRO detected!")
 }
 
 #include "image-vars.h"

arch/arm64/mm/mmu.c

@@ -43,7 +43,7 @@
 u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
 u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
 
-u64 __section(".mmuoff.data.write") vabits_actual;
+u64 __section(.mmuoff.data.write) vabits_actual;
 EXPORT_SYMBOL(vabits_actual);
 
 u64 kimage_voffset __ro_after_init;

arch/csky/kernel/vmlinux.lds.S

@@ -109,6 +109,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 }

arch/hexagon/kernel/vmlinux.lds.S

@@ -67,5 +67,6 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 }

arch/ia64/kernel/vmlinux.lds.S

@@ -218,6 +218,7 @@ SECTIONS {
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	/* Default discards */
 	DISCARDS

arch/mips/kernel/vmlinux.lds.S

@@ -202,6 +202,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	/* These must appear regardless of  .  */
 	.gptab.sdata : {

arch/nds32/kernel/vmlinux.lds.S

@@ -64,6 +64,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 }

arch/nios2/kernel/vmlinux.lds.S

@@ -58,6 +58,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 }

arch/openrisc/kernel/vmlinux.lds.S

@@ -103,6 +103,7 @@ SECTIONS
 	/* Throw in the debugging sections */
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
         /* Sections to be discarded -- must be last */
 	DISCARDS

arch/parisc/boot/compressed/vmlinux.lds.S

@@ -84,6 +84,7 @@ SECTIONS
 	}
 
 	STABS_DEBUG
+	ELF_DETAILS
 	.note 0 : { *(.note) }
 
 	/* Sections to be discarded */

arch/parisc/kernel/vmlinux.lds.S

@@ -164,6 +164,7 @@ SECTIONS
 	_end = . ;
 
 	STABS_DEBUG
+	ELF_DETAILS
 	.note 0 : { *(.note) }
 
 	/* Sections to be discarded */

arch/powerpc/kernel/vmlinux.lds.S

@@ -360,8 +360,8 @@ SECTIONS
 	PROVIDE32 (end = .);
 
 	STABS_DEBUG
-
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 	/DISCARD/ : {

arch/riscv/kernel/vmlinux.lds.S

@@ -98,6 +98,7 @@ SECTIONS
 
 	STABS_DEBUG
 	DWARF_DEBUG
+	ELF_DETAILS
 
 	DISCARDS
 }