Subject: [PATCH 3/4] arm64/head: avoid symbol names pointing into first 64 KB of kernel image

From: Ard Biesheuvel <[email-masked]>
Date: Tue, 27 Oct 2020 08:32:08 +0100

We no longer map the first 64 KB of the kernel image, as there is nothing
there that we ever need to refer back to once the kernel has booted. Even
though facilities like kallsyms are very careful to only refer to the
region that starts at _stext when mapping virtual addresses to symbol
names, let's avoid any confusion by switching to local .L prefixed symbol
names for the EFI header, as none of them have any significance to the
rest of the kernel.

Signed-off-by: Ard Biesheuvel <[email-masked]>
---
 arch/arm64/kernel/efi-header.S | 46 ++++++++++----------
 1 file changed, 22 insertions(+), 24 deletions(-)

diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S
index 3ad4aecff033..ddaf57d825b5 100644
--- a/arch/arm64/kernel/efi-header.S
+++ b/arch/arm64/kernel/efi-header.S
@@ -9,28 +9,26 @@
 
 	.macro	__EFI_PE_HEADER
 	.long	PE_MAGIC
-coff_header:
 	.short	IMAGE_FILE_MACHINE_ARM64		// Machine
-	.short	section_count				// NumberOfSections
+	.short	.Lsection_count				// NumberOfSections
 	.long	0 					// TimeDateStamp
 	.long	0					// PointerToSymbolTable
 	.long	0					// NumberOfSymbols
-	.short	section_table - optional_header		// SizeOfOptionalHeader
+	.short	.Lsection_table - .Loptional_header	// SizeOfOptionalHeader
 	.short	IMAGE_FILE_DEBUG_STRIPPED | \
 		IMAGE_FILE_EXECUTABLE_IMAGE | \
 		IMAGE_FILE_LINE_NUMS_STRIPPED		// Characteristics
 
-optional_header:
+.Loptional_header:
 	.short	PE_OPT_MAGIC_PE32PLUS			// PE32+ format
 	.byte	0x02					// MajorLinkerVersion
 	.byte	0x14					// MinorLinkerVersion
-	.long	__initdata_begin - efi_header_end	// SizeOfCode
+	.long	__initdata_begin - .Lefi_header_end	// SizeOfCode
 	.long	__pecoff_data_size			// SizeOfInitializedData
 	.long	0					// SizeOfUninitializedData
 	.long	__efistub_efi_pe_entry - _head		// AddressOfEntryPoint
-	.long	efi_header_end - _head			// BaseOfCode
+	.long	.Lefi_header_end - _head		// BaseOfCode
 
-extra_header_fields:
 	.quad	0					// ImageBase
 	.long	SEGMENT_ALIGN				// SectionAlignment
 	.long	PECOFF_FILE_ALIGNMENT			// FileAlignment
@@ -45,7 +43,7 @@ extra_header_fields:
 	.long	_end - _head				// SizeOfImage
 
 	// Everything before the kernel image is considered part of the header
-	.long	efi_header_end - _head			// SizeOfHeaders
+	.long	.Lefi_header_end - _head		// SizeOfHeaders
 	.long	0					// CheckSum
 	.short	IMAGE_SUBSYSTEM_EFI_APPLICATION		// Subsystem
 	.short	0					// DllCharacteristics
@@ -54,7 +52,7 @@ extra_header_fields:
 	.quad	0					// SizeOfHeapReserve
 	.quad	0					// SizeOfHeapCommit
 	.long	0					// LoaderFlags
-	.long	(section_table - .) / 8			// NumberOfRvaAndSizes
+	.long	(.Lsection_table - .) / 8		// NumberOfRvaAndSizes
 
 	.quad	0					// ExportTable
 	.quad	0					// ImportTable
@@ -64,17 +62,17 @@ extra_header_fields:
 	.quad	0					// BaseRelocationTable
 
 #ifdef CONFIG_DEBUG_EFI
-	.long	efi_debug_table - _head			// DebugTable
-	.long	efi_debug_table_size
+	.long	.Lefi_debug_table - _head		// DebugTable
+	.long	.Lefi_debug_table_size
 #endif
 
 	// Section table
-section_table:
+.Lsection_table:
 	.ascii	".text\0\0\0"
-	.long	__initdata_begin - efi_header_end	// VirtualSize
-	.long	efi_header_end - _head			// VirtualAddress
-	.long	__initdata_begin - efi_header_end	// SizeOfRawData
-	.long	efi_header_end - _head			// PointerToRawData
+	.long	__initdata_begin - .Lefi_header_end	// VirtualSize
+	.long	.Lefi_header_end - _head		// VirtualAddress
+	.long	__initdata_begin - .Lefi_header_end	// SizeOfRawData
+	.long	.Lefi_header_end - _head		// PointerToRawData
 
 	.long	0					// PointerToRelocations
 	.long	0					// PointerToLineNumbers
@@ -98,7 +96,7 @@ section_table:
 		IMAGE_SCN_MEM_READ | \
 		IMAGE_SCN_MEM_WRITE			// Characteristics
 
-	.set	section_count, (. - section_table) / 40
+	.set	.Lsection_count, (. - .Lsection_table) / 40
 
 #ifdef CONFIG_DEBUG_EFI
 	/*
@@ -114,21 +112,21 @@ section_table:
 	__INITRODATA
 
 	.align	2
-efi_debug_table:
+.Lefi_debug_table:
 	// EFI_IMAGE_DEBUG_DIRECTORY_ENTRY
 	.long	0					// Characteristics
 	.long	0					// TimeDateStamp
 	.short	0					// MajorVersion
 	.short	0					// MinorVersion
 	.long	IMAGE_DEBUG_TYPE_CODEVIEW		// Type
-	.long	efi_debug_entry_size			// SizeOfData
+	.long	.Lefi_debug_entry_size			// SizeOfData
 	.long	0					// RVA
-	.long	efi_debug_entry - _head			// FileOffset
+	.long	.Lefi_debug_entry - _head		// FileOffset
 
-	.set	efi_debug_table_size, . - efi_debug_table
+	.set	.Lefi_debug_table_size, . - .Lefi_debug_table
 	.previous
 
-efi_debug_entry:
+.Lefi_debug_entry:
 	// EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY
 	.ascii	"NB10"					// Signature
 	.long	0					// Unknown
@@ -137,9 +135,9 @@ efi_debug_entry:
 
 	.asciz	VMLINUX_PATH
 
-	.set	efi_debug_entry_size, . - efi_debug_entry
+	.set	.Lefi_debug_entry_size, . - .Lefi_debug_entry
 #endif
 
 	.balign	SEGMENT_ALIGN
-efi_header_end:
+.Lefi_header_end:
 	.endm
-- 
2.17.1

_______________________________________________
linux-arm-kernel mailing list
[email-masked]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel