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Commit c7fb93ec authored by Michael Brown's avatar Michael Brown Committed by Matt Fleming
Browse files

x86/efi: Include a .bss section within the PE/COFF headers 



The PE/COFF headers currently describe only the initialised-data
portions of the image, and result in no space being allocated for the
uninitialised-data portions.  Consequently, the EFI boot stub will end
up overwriting unexpected areas of memory, with unpredictable results.

Fix by including a .bss section in the PE/COFF headers (functionally
equivalent to the init_size field in the bzImage header).

Signed-off-by: default avatarMichael Brown <mbrown@fensystems.co.uk>
Cc: Thomas Bächler <thomas@archlinux.org>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
parent 29e2435f

arch/x86/boot/header.S

+22 −4
Original line number Diff line number Diff line
@@ -91,8 +91,7 @@ bs_die: 


	.section ".bsdata", "a"

bugger_off_msg:

	.ascii	"Direct floppy boot is not supported. "

	.ascii	"Use a boot loader program instead.\r\n"

	.ascii	"Use a boot loader.\r\n"

	.ascii	"\n"

	.ascii	"Remove disk and press any key to reboot...\r\n"

	.byte	0
@@ -108,7 +107,7 @@ coff_header: 
#else

	.word	0x8664				# x86-64

#endif

	.word	3				# nr_sections

	.word	4				# nr_sections

	.long	0 				# TimeDateStamp

	.long	0				# PointerToSymbolTable

	.long	1				# NumberOfSymbols
@@ -250,6 +249,25 @@ section_table: 
	.word	0				# NumberOfLineNumbers

	.long	0x60500020			# Characteristics (section flags)



	#

	# The offset & size fields are filled in by build.c.

	#

	.ascii	".bss"

	.byte	0

	.byte	0

	.byte	0

	.byte	0

	.long	0

	.long	0x0

	.long	0				# Size of initialized data

						# on disk

	.long	0x0

	.long	0				# PointerToRelocations

	.long	0				# PointerToLineNumbers

	.word	0				# NumberOfRelocations

	.word	0				# NumberOfLineNumbers

	.long	0xc8000080			# Characteristics (section flags)



#endif /* CONFIG_EFI_STUB */



	# Kernel attributes; used by setup.  This is part 1 of the

arch/x86/boot/tools/build.c

+30 −8
Original line number Diff line number Diff line
@@ -143,7 +143,7 @@ static void usage(void) 


#ifdef CONFIG_EFI_STUB



static void update_pecoff_section_header(char *section_name, u32 offset, u32 size)

static void update_pecoff_section_header_fields(char *section_name, u32 vma, u32 size, u32 datasz, u32 offset)

{

	unsigned int pe_header;

	unsigned short num_sections;
@@ -164,10 +164,10 @@ static void update_pecoff_section_header(char *section_name, u32 offset, u32 siz 
			put_unaligned_le32(size, section + 0x8);



			/* section header vma field */

			put_unaligned_le32(offset, section + 0xc);

			put_unaligned_le32(vma, section + 0xc);



			/* section header 'size of initialised data' field */

			put_unaligned_le32(size, section + 0x10);

			put_unaligned_le32(datasz, section + 0x10);



			/* section header 'file offset' field */

			put_unaligned_le32(offset, section + 0x14);
@@ -179,6 +179,11 @@ static void update_pecoff_section_header(char *section_name, u32 offset, u32 siz 
	}

}



static void update_pecoff_section_header(char *section_name, u32 offset, u32 size)

{

	update_pecoff_section_header_fields(section_name, offset, size, size, offset);

}



static void update_pecoff_setup_and_reloc(unsigned int size)

{

	u32 setup_offset = 0x200;
@@ -203,9 +208,6 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz) 


	pe_header = get_unaligned_le32(&buf[0x3c]);



	/* Size of image */

	put_unaligned_le32(file_sz, &buf[pe_header + 0x50]);



	/*

	 * Size of code: Subtract the size of the first sector (512 bytes)

	 * which includes the header.
@@ -220,6 +222,22 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz) 
	update_pecoff_section_header(".text", text_start, text_sz);

}



static void update_pecoff_bss(unsigned int file_sz, unsigned int init_sz)

{

	unsigned int pe_header;

	unsigned int bss_sz = init_sz - file_sz;



	pe_header = get_unaligned_le32(&buf[0x3c]);



	/* Size of uninitialized data */

	put_unaligned_le32(bss_sz, &buf[pe_header + 0x24]);



	/* Size of image */

	put_unaligned_le32(init_sz, &buf[pe_header + 0x50]);



	update_pecoff_section_header_fields(".bss", file_sz, bss_sz, 0, 0);

}



static int reserve_pecoff_reloc_section(int c)

{

	/* Reserve 0x20 bytes for .reloc section */
@@ -259,6 +277,8 @@ static void efi_stub_entry_update(void) 
static inline void update_pecoff_setup_and_reloc(unsigned int size) {}

static inline void update_pecoff_text(unsigned int text_start,

				      unsigned int file_sz) {}

static inline void update_pecoff_bss(unsigned int file_sz,

				     unsigned int init_sz) {}

static inline void efi_stub_defaults(void) {}

static inline void efi_stub_entry_update(void) {}
@@ -310,7 +330,7 @@ static void parse_zoffset(char *fname) 


int main(int argc, char ** argv)

{

	unsigned int i, sz, setup_sectors;

	unsigned int i, sz, setup_sectors, init_sz;

	int c;

	u32 sys_size;

	struct stat sb;
@@ -376,7 +396,9 @@ int main(int argc, char ** argv) 
	buf[0x1f1] = setup_sectors-1;

	put_unaligned_le32(sys_size, &buf[0x1f4]);



	update_pecoff_text(setup_sectors * 512, sz + i + ((sys_size * 16) - sz));

	update_pecoff_text(setup_sectors * 512, i + (sys_size * 16));

	init_sz = get_unaligned_le32(&buf[0x260]);

	update_pecoff_bss(i + (sys_size * 16), init_sz);



	efi_stub_entry_update();