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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: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1330436245-24875-6-git-send-email-matt@console-pimps.org
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Matt Fleming 2012-02-28 13:37:24 +00:00 committed by H. Peter Anvin
parent d40f833630
commit 92f42c50f2
1 changed files with 15 additions and 16 deletions
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31
arch/x86/boot/tools/build.c
View File

@ -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 */