NAME¶

iucode_tool - Tool to manipulate Intel® IA‐32/X86‐64 microcode bundles

SYNOPSIS¶

iucode_tool [options] [[-ttype] filename|dirname] ...

DESCRIPTION¶

iucode_tool is an utility that can load Intel® processor microcode data from files in both text and binary microcode bundle formats.

It can output a list of the microcodes in these files, merge them, upload them to the kernel (to upgrade the microcode in the system processor cores) or write some of them out to a file in binary format for later use.

iucode_tool will load all microcodes in the specified files and directories to memory, in order to process them. Duplicated and outdated microcodes will be discarded. It can read microcode data from standard input (stdin), by specifying a file name of “-” (minus sign).

Microcode data files are assumed to be in .dat text format if they have a .dat suffix, and to be in binary format otherwise. Standard input (stdin) is assumed to be in .dat text format. The -t option can be used to change the type of the files specified after it, including for stdin.

If a directory is specified, all files whose names do not begin with a dot will be loaded, in unspecified order. Nested directories are skipped.

Empty files and directories are ignored, and will be skipped.

You can select which microcodes should be written out, listed or uploaded to the kernel using the -S, -s, --date-before and --date-after options. Should none of those options be specified, all microcodes will be selected.

You can upload the selected microcodes to the kernel, write them out to a file (in binary format), to a Linux early initramfs archive, to per-processor-signature files in a directory, or to per-microcode files in a directory using the -w, --write-earlyfw, -k, -K, and -W options.

iucode_tool will identify microcodes in its output and error messages using a “n/k” notation, where “n” is the bundle number, and “k” is the microcode number within that bundle. The output of the --list-all option when processing multiple input files is the best example of how it works.

For more information about Intel processor microcodes, please read the included documentation and the Intel manuals listed in the SEE ALSO section.

OPTIONS¶

iucode_tool accepts the following options:

-q, --quiet

Inhibit usual output.

-v, --verbose

Print more information. Use more than once for added verbosity.

-h, -?, --help

List all available options and their meanings.

--usage

Show summary of options.

-V, --version

Show version of program.

-t type

Sets the file type of the following files. type can be:

--downgrade

When multiple versions of the microcode for a specific processor are available from different files, keep the one from the file loaded last, regardless of revision levels. Files are always loaded in the order they were specified in the command line. This option has no effect when just one file has been loaded.

--no-downgrade

When multiple versions of the microcode for a specific processor are available from different files, keep the one with the highest revision level. This is the default mode of operation.

--strict-checks

Perform strict checks on the microcode data. It will refuse to load microcodes and microcode data files with unexpected size and metadata. It will also refuse to load microcode entries that have the same metadata, but different payload. This is the default mode of operation.

--no-strict-checks

Perform less strict checks on the microcode data. Use only if you happen to come across a microcode data file that has microcodes with weird sizes or incorrect non-critical metadata (such as invalid dates), which you want to retain. If you just want to skip those, use the --ignore-broken option.

--ignore-broken

Skip broken microcode entries when loading a microcode data file, instead of aborting program execution. If the microcode entry has an unsupported format or had its header severely corrupted, all remaining data in the file will have to be ignored. In that case, using a file type of recover microcode in binary format (-tr option) is recommended, as it can skip over badly mangled microcode data.

--no-ignore-broken

Abort program execution if a broken microcode is found while loading a microcode data file. This is the default mode of operation.

-s ! | [!]signature[,[pf_mask][,[lt:|eq:|gt:]revision]]

Select microcodes by the specified signature, processor flags mask (pf_mask), and revision.

If the processor flags mask is specified, it will select only microcodes that are suitable for at least one of the processor flag combinations present in the mask.

If the revision is specified, optionally prefixed by one of the “eq:”, “lt:” or “gt:” operators, it will select only microcodes that have that same revision (if no operator, or if the “eq:” operator is used), or microcodes that have a revision that is less than (“lt:” operator), or greater than (“gt:” operator), the one specified.

Specify more than once to select more microcodes. This option can be combined with the --scan-system option to select more microcodes. If signature is prefixed with a “!” (exclamation mark), it will deselect microcodes instead. Ordering matters, with later -s options overriding earlier ones, including --scan-system.

When specifying signature and pf_mask, hexadecimal numbers must be prefixed with “0x”, and octal numbers with “0”. Decimal numbers must not have leading zeros, otherwise they would be interpreted as octal numbers.

The special notation -s! (with no signature parameter) instructs iucode_tool to require explicit inclusion of microcode signatures (using the non-negated form of -s, or using --scan-system).

-S, --scan-system[=mode]

Select microcodes by scanning online processors on this system for their signatures.

This option can be used only once, and it can be combined with the -s option to select more microcodes. The microcodes selected by --scan-system can also be deselected by a later -s !signature option.

The optional mode argument (accepted only by the long version of the option) selects the strategy used to scan processors:

--date-before=YYYY-MM-DD and --date-after=YYYY-MM-DD

Limit the selected microcodes by a date range. The date must be given in ISO format, with four digits for the year and two digits for the month and day and “-” (minus sign) for the separator. Dates are not range-checked, so you can use --date-after=2000-00-00 to select all microcodes dated since January 1st, 2000.

--loose-date-filtering

When a date range is specified, all revisions of the microcode will be considered for selection (ignoring just the date range, all other filters still apply) should any of the microcode's revisions be within the date range.

--strict-date-filtering

When a date range is specified, select only microcodes which are within the date range. This is the default mode of operation.

-l, --list

List selected microcode signatures to standard output (stdout).

-L, --list-all

List all microcode signatures while they're being processed to standard output (stdout).

-k[device], --kernel[=device]

Upload selected microcodes to the kernel. Optionally, the device path can be specified (default: /dev/cpu/microcode). This update method is deprecated: it will be removed eventually from the kernel and from iucode_tool.

-K[directory], --write-firmware[=directory]

Write selected microcodes with the file names expected by the Linux kernel firmware loader. Optionally, the destination directory can be specified (default: /lib/firmware/intel‐ucode).

-wfile, --write-to=file

Write selected microcodes to a file in binary format.

--write-earlyfw=file

Write selected microcodes to an early initramfs archive, which should be prepended to the regular initramfs to allow the kernel to update processor microcode very early during system boot.

-Wdirectory, --write-named-to=directory

Write selected microcodes to the specified directory, one microcode per file, in binary format. The file names reflect the microcode signature, processor flags mask and revision.

--write-all-named-to=directory

Write every microcode to the specified directory, one microcode per file, in binary format. The file names reflect the microcode signature, processor flags mask and revision. This is the only way to write out every revision of the same microcode.

--overwrite

Remove the destination file before writing, if it exists and is not a directory. The destination file is not overwritten in-place. Hardlinks will be severed, and any existing access permissions, ACLs and other extended attributes of the old destination file will be lost.

--no-overwrite

Abort if the destination file already exists. This is the default mode of operation. Do note that iucode_tool does not follow non-directory symlinks when writing files.

--mini-earlyfw

Optimize the early initramfs cpio container for minimal size. It will change the cpio block size to 16 bytes, and remove header entries for the parent directories of the microcode data file. As a result, the microcode data file will not be available to the regular initramfs, and tools might complain about the non-standard cpio block size.

This will typically reduce the early initramfs size by 736 bytes.

--normal-earlyfw

Optimize the early initramfs size for tool compatibility. This is the default mode of operation. The microcode data file will be available inside the regular initramfs as well.

NOTES¶

iucode_tool reads all data to memory before doing any processing. It enforces a sanity limit of a maximum of 1GiB worth of binary microcode data per microcode data file.

All informational and error messages are sent to standard error (stderr), while user-requested output (such as output generated by the list options) is sent to standard output (stdout).

iucode_tool creates files with permissions 0644 (rw-r--r--), modified by the current umask.

iucode_tool's selected microcode listing and microcode output files are sorted first by processor signature (in ascending order), and then by processor flags mask (in descending order).

When multiple revisions of a microcode are selected, the older ones will be skipped. Only the newest selected revision of a microcode (or the last one in load order when the --downgrade option is active) will be written to a file or uploaded to the kernel.

Intel microcode data files, both in binary and text formats, can be concatenated to generate a bigger and still valid microcode data file.

iucode_tool does not follow symlinks when writing microcode data files. It will either refuse to write the file and abort (default mode of operation), or (when the --overwrite option is active) it will remove the target symlink or file (and therefore breaking hardlinks) before writing the new file.

iucode_tool does follow directory symlinks to locate the directory to write files into.

EXAMPLES¶

BUGS¶

Microcode with negative revision numbers is not special-cased, and will not be preferred over regular microcode.

The downgrade mode should be used only for microcodes with the same processor flags mask. It cannot handle the corner cases where modifying a processor flags mask would be required to force the kernel to load a lower revision of a microcode, and iucode_tool will issue an warning when that happens. So far, this has not proved to be a relevant limitation as changes to the processor flags mask of post-launch, production microcode updates are very rare.

The loader version microcode metadata field is ignored by iucode_tool. This shouldn't cause problems as long as the same signature never needs more than a single type of loader.

Files are not replaced atomically: if iucode_tool is interrupted while writing to a file, that file will be corrupted.

SEE ALSO¶

The Intel 64 and IA‐32 Architectures Software Developer's Manual, Volume 3A: System Programming Guide, Part 1 (order number 253668), section 9.11.

AUTHOR¶

Henrique de Moraes Holschuh <hmh@hmh.eng.br>