[PATCH 14/17] x86/boot: Drop PE/COFF .reloc section

Ard Biesheuvel
2023-08-18T13:46:25Z

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>
---
arch/x86/boot/header.S | 20 -----------
arch/x86/boot/tools/build.c | 35 +++-----------------
2 files changed, 5 insertions(+), 50 deletions(-)

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index c23c5feef37e55ed..ccfb7a7d8c29275e 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -159,26 +159,6 @@ 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.
diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index 6b6282a96c6ab24d..08065c333b482174 100644
--- a/arch/x86/boot/tools/build.c
+++ b/arch/x86/boot/tools/build.c
@@ -45,8 +45,6 @@ typedef unsigned int u32;
/* This must be large enough to hold the entire setup */
u8 buf[(SETUP_SECT_NUM+1)*512];

-#define PECOFF_RELOC_RESERVE 0x20
-
#ifdef CONFIG_EFI_MIXED
#define PECOFF_COMPAT_RESERVE 0x20
#else
@@ -183,24 +181,13 @@ 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);
@@ -217,21 +204,10 @@ 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)
@@ -310,7 +286,6 @@ 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;
@@ -320,7 +295,7 @@ 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);
--
2.39.2