robin.thoni/ipxe - git rthoni.com

Michael Brown 36817ea260 [mromprefix] Report a dummy size at offset 0x02 of .mrom payload The size of the .mrom payload (the second PCI ROM image) is defined in its PCI header. The code type for the .mrom payload image is deliberately set to an invalid value (0xff) to ensure that no BIOS tries to parse anything in the image other than the PCI header. Since the code type is not set to 0x00 ("Intel x86, PC-AT compatible"), bytes 0x02-0x17 should not be interpreted by the BIOS as being in the standard ISA expansion ROM format. In particular, the byte at offset 0x02 does not represent the length of the ROM image (in 512-byte blocks). However, some Dell BIOSes seem to erroneously use the byte at offset 0x02 to determine the length of the .mrom payload when walking the list of PCI ROM images. Since this byte is currently set to zero, this can lead to the BIOS getting stuck in an infinite loop during POST. (This problem may not arise if the .mrom payload is the final image in the ROM, since the BIOS will then have no reason to attempt to locate the next image.) One possible workaround would be to put the real payload size in this byte, but doing so would constrain the .mrom payload size to 128kB (see commit 8049a52 ("[mromprefix] Allow for .mrom images larger than 128kB") for more details). Another possible workaround would be to put the real payload size as a word in bytes 0x02-0x03 (as is done for EFI ROMs). This would not constrain the .mrom payload size, but a payload size which happened to be exactly 128kB would result in a zero value in the byte at offset 0x02 and so could still result in infinite loops on BIOSes with this bug. We choose to place a fixed value of 0x01 in the byte at offset 0x02. This should at least prevent the BIOS from getting stuck in an infinite loop. (The BIOS may walk into the middle of the .mrom payload, where it will almost certainly not find a valid {0x55,0xaa} signature or a valid PCIR header, and will therefore hopefully abort processing.) Reported-by: Wissam Shoukair <wissams@mellanox.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>		9 år sedan
contrib	[errdb] Strip platform error code for non-platform-generated errors	11 år sedan
src	[mromprefix] Report a dummy size at offset 0x02 of .mrom payload	9 år sedan
COPYING	[legal] Update GPLv2 licence text	10 år sedan
COPYING.GPLv2	[legal] Update GPLv2 licence text	10 år sedan
COPYING.UBDL	[legal] Add support for the Unmodified Binary Distribution Licence	10 år sedan
README	[doc] Re-add README file	14 år sedan

iPXE README File

Quick start guide:

   cd src
   make

For any more detailed instructions, see http://ipxe.org