From 92f42c50f227ad228f815a8f4eec872524dae3a5 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Tue, 28 Feb 2012 13:37:24 +0000 Subject: [PATCH] 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 Cc: Nick Bowler Tested-by: Stephen Rothwell Reported-by: Stephen Rothwell Signed-off-by: Matt Fleming Link: http://lkml.kernel.org/r/1330436245-24875-6-git-send-email-matt@console-pimps.org Signed-off-by: H. Peter Anvin --- arch/x86/boot/tools/build.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c index 4e9bd6bcafa6..f2ac95ece0cc 100644 --- a/arch/x86/boot/tools/build.c +++ b/arch/x86/boot/tools/build.c @@ -34,6 +34,7 @@ #include #include #include +#include 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 */ -- 2.39.5