A couple of instructions of grub's stage1 get modified when copied to the MBR (replaced by NOOPs). Check for this condition, and skip these bytes while compare stage1 and MBR. Signed-off-by: Cleber Rosa <crosa@xxxxxxxxxx> --- grubby.c | 19 ++++++++++++++++--- 1 files changed, 16 insertions(+), 3 deletions(-) diff --git a/grubby.c b/grubby.c index f21a7f8..7c98978 100644 --- a/grubby.c +++ b/grubby.c @@ -51,6 +51,9 @@ #define MAX_EXTRA_INITRDS 16 /* code segment checked by --bootloader-probe */ #define CODE_SEG_SIZE 128 /* code segment checked by --bootloader-probe */ +#define NOOP_OPCODE 0x90 +#define JMP_SHORT_OPCODE 0xeb + /* comments get lumped in with indention */ struct lineElement { char * item; @@ -2467,12 +2470,22 @@ int checkDeviceBootloader(const char * device, const unsigned char * boot) { if (memcmp(boot, bootSect, 3)) return 0; - if (boot[1] == 0xeb) { + if (boot[1] == JMP_SHORT_OPCODE) { offset = boot[2] + 2; } else if (boot[1] == 0xe8 || boot[1] == 0xe9) { offset = (boot[3] << 8) + boot[2] + 2; - } else if (boot[0] == 0xeb) { - offset = boot[1] + 2; + } else if (boot[0] == JMP_SHORT_OPCODE) { + offset = boot[1] + 2; + /* + * it looks like grub, when copying stage1 into the mbr, patches stage1 + * right after the JMP location, replacing other instructions such as + * JMPs for NOOPs. So, relax the check a little bit by skipping those + * different bytes. + */ + if ((bootSect[offset + 1] == NOOP_OPCODE) + && (bootSect[offset + 2] == NOOP_OPCODE)) { + offset = offset + 3; + } } else if (boot[0] == 0xe8 || boot[0] == 0xe9) { offset = (boot[2] << 8) + boot[1] + 2; } else { -- 1.7.6.4 _______________________________________________ Anaconda-devel-list mailing list Anaconda-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/anaconda-devel-list