x86/boot: Drop PE/COFF .reloc section

Ancient buggy EFI loaders may have required a .reloc section to be
present at some point in time, but this has not been true for a long
time so the .reloc section can just be dropped.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-16-ardb@google.com

Author: ardbiesheuvel

arch/x86/boot/header.S

@@ -155,26 +155,6 @@ section_table:
 		IMAGE_SCN_MEM_READ		| \
 		IMAGE_SCN_MEM_EXECUTE		# Characteristics
 
-	#
-	# The EFI application loader requires a relocation section
-	# because EFI applications must be relocatable. The .reloc
-	# offset & size fields are filled in by build.c.
-	#
-	.ascii	".reloc"
-	.byte	0
-	.byte	0
-	.long	0
-	.long	0
-	.long	0				# SizeOfRawData
-	.long	0				# PointerToRawData
-	.long	0				# PointerToRelocations
-	.long	0				# PointerToLineNumbers
-	.word	0				# NumberOfRelocations
-	.word	0				# NumberOfLineNumbers
-	.long	IMAGE_SCN_CNT_INITIALIZED_DATA	| \
-		IMAGE_SCN_MEM_READ		| \
-		IMAGE_SCN_MEM_DISCARDABLE	# Characteristics
-
 #ifdef CONFIG_EFI_MIXED
 	#
 	# The offset & size fields are filled in by build.c.

arch/x86/boot/setup.ld

@@ -40,8 +40,8 @@ SECTIONS
 		setup_sig = .;
 		LONG(0x5a5aaa55)
 
-		/* Reserve some extra space for the reloc and compat sections */
-		setup_size = ALIGN(ABSOLUTE(.) + 64, 512);
+		/* Reserve some extra space for the compat section */
+		setup_size = ALIGN(ABSOLUTE(.) + 32, 512);
 		setup_sects = ABSOLUTE(setup_size / 512);
 	}
 

arch/x86/boot/tools/build.c

@@ -47,7 +47,6 @@ typedef unsigned int   u32;
 /* This must be large enough to hold the entire setup */
 u8 buf[SETUP_SECT_MAX*512];
 
-#define PECOFF_RELOC_RESERVE 0x20
 #define PECOFF_COMPAT_RESERVE 0x20
 
 static unsigned long efi32_pe_entry;
@@ -180,24 +179,13 @@ static void update_pecoff_section_header(char *section_name, u32 offset, u32 siz
 	update_pecoff_section_header_fields(section_name, offset, size, size, offset);
 }
 
-static void update_pecoff_setup_and_reloc(unsigned int size)
+static void update_pecoff_setup(unsigned int size)
 {
 	u32 setup_offset = 0x200;
-	u32 reloc_offset = size - PECOFF_RELOC_RESERVE - PECOFF_COMPAT_RESERVE;
-#ifdef CONFIG_EFI_MIXED
-	u32 compat_offset = reloc_offset + PECOFF_RELOC_RESERVE;
-#endif
-	u32 setup_size = reloc_offset - setup_offset;
+	u32 compat_offset = size - PECOFF_COMPAT_RESERVE;
+	u32 setup_size = compat_offset - setup_offset;
 
 	update_pecoff_section_header(".setup", setup_offset, setup_size);
-	update_pecoff_section_header(".reloc", reloc_offset, PECOFF_RELOC_RESERVE);
-
-	/*
-	 * Modify .reloc section contents with a single entry. The
-	 * relocation is applied to offset 10 of the relocation section.
-	 */
-	put_unaligned_le32(reloc_offset + 10, &buf[reloc_offset]);
-	put_unaligned_le32(10, &buf[reloc_offset + 4]);
 
 #ifdef CONFIG_EFI_MIXED
 	update_pecoff_section_header(".compat", compat_offset, PECOFF_COMPAT_RESERVE);
@@ -214,21 +202,10 @@ static void update_pecoff_setup_and_reloc(unsigned int size)
 #endif
 }
 
-static int reserve_pecoff_reloc_section(int c)
-{
-	/* Reserve 0x20 bytes for .reloc section */
-	memset(buf+c, 0, PECOFF_RELOC_RESERVE);
-	return PECOFF_RELOC_RESERVE;
-}
-
 #else
 
-static inline void update_pecoff_setup_and_reloc(unsigned int size) {}
+static inline void update_pecoff_setup(unsigned int size) {}
 
-static inline int reserve_pecoff_reloc_section(int c)
-{
-	return 0;
-}
 #endif /* CONFIG_EFI_STUB */
 
 static int reserve_pecoff_compat_section(int c)
@@ -307,7 +284,6 @@ int main(int argc, char ** argv)
 	fclose(file);
 
 	c += reserve_pecoff_compat_section(c);
-	c += reserve_pecoff_reloc_section(c);
 
 	/* Pad unused space with zeros */
 	setup_sectors = (c + 511) / 512;
@@ -316,7 +292,7 @@ int main(int argc, char ** argv)
 	i = setup_sectors*512;
 	memset(buf+c, 0, i-c);
 
-	update_pecoff_setup_and_reloc(i);
+	update_pecoff_setup(i);
 
 	/* Open and stat the kernel file */
 	fd = open(argv[2], O_RDONLY);