Commit 92f42c50 authored by Matt Fleming's avatar Matt Fleming Committed by H. Peter Anvin
Browse files

x86, efi: Fix endian issues and unaligned accesses 



We may need to convert the endianness of the data we read from/write
to 'buf', so let's use {get,put}_unaligned_le32() to do that. Failure
to do so can result in accessing invalid memory, leading to a
segfault.  Stephen Rothwell noticed this bug while cross-building an
x86_64 allmodconfig kernel on PowerPC.

We need to read from and write to 'buf' a byte at a time otherwise
it's possible we'll perform an unaligned access, which can lead to bus
errors when cross-building an x86 kernel on risc architectures.

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Nick Bowler <nbowler@elliptictech.com>
Tested-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Reported-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarMatt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1330436245-24875-6-git-send-email-matt@console-pimps.org


Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent d40f8336

arch/x86/boot/tools/build.c

+15 −16
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <fcntl.h>

#include <sys/mman.h>

#include <asm/boot.h>

#include <tools/le_byteshift.h>



typedef unsigned char  u8;

typedef unsigned short u16;
@@ -41,6 +42,7 @@ typedef unsigned long u32; 


#define DEFAULT_MAJOR_ROOT 0

#define DEFAULT_MINOR_ROOT 0

#define DEFAULT_ROOT_DEV (DEFAULT_MAJOR_ROOT << 8 | DEFAULT_MINOR_ROOT)



/* Minimal number of setup sectors */

#define SETUP_SECT_MIN 5
@@ -159,7 +161,7 @@ int main(int argc, char ** argv) 
		die("read-error on `setup'");

	if (c < 1024)

		die("The setup must be at least 1024 bytes");

	if (buf[510] != 0x55 || buf[511] != 0xaa)

	if (get_unaligned_le16(&buf[510]) != 0xAA55)

		die("Boot block hasn't got boot flag (0xAA55)");

	fclose(file);
@@ -171,8 +173,7 @@ int main(int argc, char ** argv) 
	memset(buf+c, 0, i-c);



	/* Set the default root device */

	buf[508] = DEFAULT_MINOR_ROOT;

	buf[509] = DEFAULT_MAJOR_ROOT;

	put_unaligned_le16(DEFAULT_ROOT_DEV, &buf[508]);



	fprintf(stderr, "Setup is %d bytes (padded to %d bytes).\n", c, i);
@@ -192,44 +193,42 @@ int main(int argc, char ** argv) 


	/* Patch the setup code with the appropriate size parameters */

	buf[0x1f1] = setup_sectors-1;

	buf[0x1f4] = sys_size;

	buf[0x1f5] = sys_size >> 8;

	buf[0x1f6] = sys_size >> 16;

	buf[0x1f7] = sys_size >> 24;

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



#ifdef CONFIG_EFI_STUB

	file_sz = sz + i + ((sys_size * 16) - sz);



	pe_header = *(unsigned int *)&buf[0x3c];

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



	/* Size of code */

	*(unsigned int *)&buf[pe_header + 0x1c] = file_sz;

	put_unaligned_le32(file_sz, &buf[pe_header + 0x1c]);



	/* Size of image */

	*(unsigned int *)&buf[pe_header + 0x50] = file_sz;

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



#ifdef CONFIG_X86_32

	/* Address of entry point */

	*(unsigned int *)&buf[pe_header + 0x28] = i;

	put_unaligned_le32(i, &buf[pe_header + 0x28]);



	/* .text size */

	*(unsigned int *)&buf[pe_header + 0xb0] = file_sz;

	put_unaligned_le32(file_sz, &buf[pe_header + 0xb0]);



	/* .text size of initialised data */

	*(unsigned int *)&buf[pe_header + 0xb8] = file_sz;

	put_unaligned_le32(file_sz, &buf[pe_header + 0xb8]);

#else

	/*

	 * Address of entry point. startup_32 is at the beginning and

	 * the 64-bit entry point (startup_64) is always 512 bytes

	 * after.

	 */

	*(unsigned int *)&buf[pe_header + 0x28] = i + 512;

	put_unaligned_le32(i + 512, &buf[pe_header + 0x28]);



	/* .text size */

	*(unsigned int *)&buf[pe_header + 0xc0] = file_sz;

	put_unaligned_le32(file_sz, &buf[pe_header + 0xc0]);



	/* .text size of initialised data */

	*(unsigned int *)&buf[pe_header + 0xc8] = file_sz;

	put_unaligned_le32(file_sz, &buf[pe_header + 0xc8]);



#endif /* CONFIG_X86_32 */

#endif /* CONFIG_EFI_STUB */

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