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
  ...

1 files changed, 34 insertions, 65 deletions

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 03557f2174bf..659fad53ca82 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -33,32 +33,13 @@
 #include <asm/bootparam.h>
 
 /*
- * The 32-bit x86 assembler in binutils 2.26 will generate R_386_GOT32X
- * relocation to get the symbol address in PIC.  When the compressed x86
- * kernel isn't built as PIC, the linker optimizes R_386_GOT32X
- * relocations to their fixed symbol addresses.  However, when the
- * compressed x86 kernel is loaded at a different address, it leads
- * to the following load failure:
- *
- *   Failed to allocate space for phdrs
- *
- * during the decompression stage.
- *
- * If the compressed x86 kernel is relocatable at run-time, it should be
- * compiled with -fPIE, instead of -fPIC, if possible and should be built as
- * Position Independent Executable (PIE) so that linker won't optimize
- * R_386_GOT32X relocation to its fixed symbol address.  Older
- * linkers generate R_386_32 relocations against locally defined symbols,
- * _bss, _ebss, _got, _egot and _end, in PIE.  It isn't wrong, just less
- * optimal than R_386_RELATIVE.  But the x86 kernel fails to properly handle
- * R_386_32 relocations when relocating the kernel.  To generate
- * R_386_RELATIVE relocations, we mark _bss, _ebss, _got, _egot and _end as
- * hidden:
+ * These symbols needed to be marked as .hidden to prevent the BFD linker from
+ * generating R_386_32 (rather than R_386_RELATIVE) relocations for them when
+ * the 32-bit compressed kernel is linked as PIE. This is no longer necessary,
+ * but it doesn't hurt to keep them .hidden.
  */
 	.hidden _bss
 	.hidden _ebss
-	.hidden _got
-	.hidden _egot
 	.hidden _end
 
 	__HEAD
@@ -77,10 +58,10 @@ SYM_FUNC_START(startup_32)
 	leal	(BP_scratch+4)(%esi), %esp
 	call	1f
 1:	popl	%edx
-	subl	$1b, %edx
+	addl	$_GLOBAL_OFFSET_TABLE_+(.-1b), %edx
 
 	/* Load new GDT */
-	leal	gdt(%edx), %eax
+	leal	gdt@GOTOFF(%edx), %eax
 	movl	%eax, 2(%eax)
 	lgdt	(%eax)
 
@@ -93,14 +74,16 @@ SYM_FUNC_START(startup_32)
 	movl	%eax, %ss
 
 /*
- * %edx contains the address we are loaded at by the boot loader and %ebx
- * contains the address where we should move the kernel image temporarily
- * for safe in-place decompression. %ebp contains the address that the kernel
- * will be decompressed to.
+ * %edx contains the address we are loaded at by the boot loader (plus the
+ * offset to the GOT).  The below code calculates %ebx to be the address where
+ * we should move the kernel image temporarily for safe in-place decompression
+ * (again, plus the offset to the GOT).
+ *
+ * %ebp is calculated to be the address that the kernel will be decompressed to.
  */
 
 #ifdef CONFIG_RELOCATABLE
-	movl	%edx, %ebx
+	leal	startup_32@GOTOFF(%edx), %ebx
 
 #ifdef CONFIG_EFI_STUB
 /*
@@ -111,7 +94,7 @@ SYM_FUNC_START(startup_32)
  *	image_offset = startup_32 - image_base
  * Otherwise image_offset will be zero and has no effect on the calculations.
  */
-	subl    image_offset(%edx), %ebx
+	subl    image_offset@GOTOFF(%edx), %ebx
 #endif
 
 	movl	BP_kernel_alignment(%esi), %eax
@@ -128,10 +111,10 @@ SYM_FUNC_START(startup_32)
 	movl	%ebx, %ebp	// Save the output address for later
 	/* Target address to relocate to for decompression */
 	addl    BP_init_size(%esi), %ebx
-	subl    $_end, %ebx
+	subl    $_end@GOTOFF, %ebx
 
 	/* Set up the stack */
-	leal	boot_stack_end(%ebx), %esp
+	leal	boot_stack_end@GOTOFF(%ebx), %esp
 
 	/* Zero EFLAGS */
 	pushl	$0
@@ -142,8 +125,8 @@ SYM_FUNC_START(startup_32)
  * where decompression in place becomes safe.
  */
 	pushl	%esi
-	leal	(_bss-4)(%edx), %esi
-	leal	(_bss-4)(%ebx), %edi
+	leal	(_bss@GOTOFF-4)(%edx), %esi
+	leal	(_bss@GOTOFF-4)(%ebx), %edi
 	movl	$(_bss - startup_32), %ecx
 	shrl	$2, %ecx
 	std
@@ -156,14 +139,14 @@ SYM_FUNC_START(startup_32)
 	 * during extract_kernel below. To avoid any issues, repoint the GDTR
 	 * to the new copy of the GDT.
 	 */
-	leal	gdt(%ebx), %eax
+	leal	gdt@GOTOFF(%ebx), %eax
 	movl	%eax, 2(%eax)
 	lgdt	(%eax)
 
 /*
  * Jump to the relocated address.
  */
-	leal	.Lrelocated(%ebx), %eax
+	leal	.Lrelocated@GOTOFF(%ebx), %eax
 	jmp	*%eax
 SYM_FUNC_END(startup_32)
 
@@ -173,7 +156,7 @@ SYM_FUNC_START_ALIAS(efi_stub_entry)
 	add	$0x4, %esp
 	movl	8(%esp), %esi	/* save boot_params pointer */
 	call	efi_main
-	leal	startup_32(%eax), %eax
+	/* efi_main returns the possibly relocated address of startup_32 */
 	jmp	*%eax
 SYM_FUNC_END(efi32_stub_entry)
 SYM_FUNC_END_ALIAS(efi_stub_entry)
@@ -186,40 +169,26 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
  * Clear BSS (stack is currently empty)
  */
 	xorl	%eax, %eax
-	leal	_bss(%ebx), %edi
-	leal	_ebss(%ebx), %ecx
+	leal	_bss@GOTOFF(%ebx), %edi
+	leal	_ebss@GOTOFF(%ebx), %ecx
 	subl	%edi, %ecx
 	shrl	$2, %ecx
 	rep	stosl
 
 /*
- * Adjust our own GOT
- */
-	leal	_got(%ebx), %edx
-	leal	_egot(%ebx), %ecx
-1:
-	cmpl	%ecx, %edx
-	jae	2f
-	addl	%ebx, (%edx)
-	addl	$4, %edx
-	jmp	1b
-2:
-
-/*
  * Do the extraction, and jump to the new kernel..
  */
-				/* push arguments for extract_kernel: */
-	pushl	$z_output_len	/* decompressed length, end of relocs */
-
-	pushl	%ebp		/* output address */
-
-	pushl	$z_input_len	/* input_len */
-	leal	input_data(%ebx), %eax
-	pushl	%eax		/* input_data */
-	leal	boot_heap(%ebx), %eax
-	pushl	%eax		/* heap area */
-	pushl	%esi		/* real mode pointer */
-	call	extract_kernel	/* returns kernel location in %eax */
+	/* push arguments for extract_kernel: */
+
+	pushl	output_len@GOTOFF(%ebx)	/* decompressed length, end of relocs */
+	pushl	%ebp			/* output address */
+	pushl	input_len@GOTOFF(%ebx)	/* input_len */
+	leal	input_data@GOTOFF(%ebx), %eax
+	pushl	%eax			/* input_data */
+	leal	boot_heap@GOTOFF(%ebx), %eax
+	pushl	%eax			/* heap area */
+	pushl	%esi			/* real mode pointer */
+	call	extract_kernel		/* returns kernel location in %eax */
 	addl	$24, %esp
 
 /*