377 lines
12 KiB
Plaintext
377 lines
12 KiB
Plaintext
/*
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* Copyright (c) 2014 The Chromium OS Authors.
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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Native Execution of U-Boot
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==========================
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The 'sandbox' architecture is designed to allow U-Boot to run under Linux on
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almost any hardware. To achieve this it builds U-Boot (so far as possible)
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as a normal C application with a main() and normal C libraries.
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All of U-Boot's architecture-specific code therefore cannot be built as part
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of the sandbox U-Boot. The purpose of running U-Boot under Linux is to test
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all the generic code, not specific to any one architecture. The idea is to
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create unit tests which we can run to test this upper level code.
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CONFIG_SANDBOX is defined when building a native board.
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The board name is 'sandbox' but the vendor name is unset, so there is a
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single board in board/sandbox.
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CONFIG_SANDBOX_BIG_ENDIAN should be defined when running on big-endian
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machines.
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Note that standalone/API support is not available at present.
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Basic Operation
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---------------
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To run sandbox U-Boot use something like:
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make sandbox_defconfig all
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./u-boot
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Note:
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If you get errors about 'sdl-config: Command not found' you may need to
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install libsdl1.2-dev or similar to get SDL support. Alternatively you can
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build sandbox without SDL (i.e. no display/keyboard support) by removing
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the CONFIG_SANDBOX_SDL line in include/configs/sandbox.h or using:
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make sandbox_defconfig all NO_SDL=1
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./u-boot
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If you are building on a 32-bit machine you may get errors from __ffs.h
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about shifting more than the machine word size. Edit the config file
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include/configs/sandbox.h and change CONFIG_SANDBOX_BITS_PER_LONG to 32.
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U-Boot will start on your computer, showing a sandbox emulation of the serial
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console:
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U-Boot 2014.04 (Mar 20 2014 - 19:06:00)
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DRAM: 128 MiB
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Using default environment
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In: serial
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Out: lcd
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Err: lcd
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=>
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You can issue commands as your would normally. If the command you want is
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not supported you can add it to include/configs/sandbox.h.
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To exit, type 'reset' or press Ctrl-C.
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Console / LCD support
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---------------------
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Assuming that CONFIG_SANDBOX_SDL is defined when building, you can run the
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sandbox with LCD and keyboard emulation, using something like:
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./u-boot -d u-boot.dtb -l
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This will start U-Boot with a window showing the contents of the LCD. If
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that window has the focus then you will be able to type commands as you
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would on the console. You can adjust the display settings in the device
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tree file - see arch/sandbox/dts/sandbox.dts.
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Command-line Options
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--------------------
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Various options are available, mostly for test purposes. Use -h to see
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available options. Some of these are described below.
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The terminal is normally in what is called 'raw-with-sigs' mode. This means
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that you can use arrow keys for command editing and history, but if you
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press Ctrl-C, U-Boot will exit instead of handling this as a keypress.
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Other options are 'raw' (so Ctrl-C is handled within U-Boot) and 'cooked'
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(where the terminal is in cooked mode and cursor keys will not work, Ctrl-C
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will exit).
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As mentioned above, -l causes the LCD emulation window to be shown.
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A device tree binary file can be provided with -d. If you edit the source
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(it is stored at arch/sandbox/dts/sandbox.dts) you must rebuild U-Boot to
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recreate the binary file.
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To execute commands directly, use the -c option. You can specify a single
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command, or multiple commands separated by a semicolon, as is normal in
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U-Boot. Be careful with quoting as the shall will normally process and
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swallow quotes. When -c is used, U-Boot exists after the command is complete,
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but you can force it to go to interactive mode instead with -i.
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Memory Emulation
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----------------
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Memory emulation is supported, with the size set by CONFIG_SYS_SDRAM_SIZE.
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The -m option can be used to read memory from a file on start-up and write
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it when shutting down. This allows preserving of memory contents across
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test runs. You can tell U-Boot to remove the memory file after it is read
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(on start-up) with the --rm_memory option.
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To access U-Boot's emulated memory within the code, use map_sysmem(). This
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function is used throughout U-Boot to ensure that emulated memory is used
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rather than the U-Boot application memory. This provides memory starting
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at 0 and extending to the size of the emulation.
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Storing State
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-------------
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With sandbox you can write drivers which emulate the operation of drivers on
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real devices. Some of these drivers may want to record state which is
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preserved across U-Boot runs. This is particularly useful for testing. For
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example, the contents of a SPI flash chip should not disappear just because
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U-Boot exits.
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State is stored in a device tree file in a simple format which is driver-
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specific. You then use the -s option to specify the state file. Use -r to
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make U-Boot read the state on start-up (otherwise it starts empty) and -w
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to write it on exit (otherwise the stored state is left unchanged and any
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changes U-Boot made will be lost). You can also use -n to tell U-Boot to
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ignore any problems with missing state. This is useful when first running
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since the state file will be empty.
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The device tree file has one node for each driver - the driver can store
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whatever properties it likes in there. See 'Writing Sandbox Drivers' below
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for more details on how to get drivers to read and write their state.
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Running and Booting
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-------------------
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Since there is no machine architecture, sandbox U-Boot cannot actually boot
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a kernel, but it does support the bootm command. Filesystems, memory
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commands, hashing, FIT images, verified boot and many other features are
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supported.
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When 'bootm' runs a kernel, sandbox will exit, as U-Boot does on a real
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machine. Of course in this case, no kernel is run.
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It is also possible to tell U-Boot that it has jumped from a temporary
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previous U-Boot binary, with the -j option. That binary is automatically
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removed by the U-Boot that gets the -j option. This allows you to write
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tests which emulate the action of chain-loading U-Boot, typically used in
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a situation where a second 'updatable' U-Boot is stored on your board. It
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is very risky to overwrite or upgrade the only U-Boot on a board, since a
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power or other failure will brick the board and require return to the
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manufacturer in the case of a consumer device.
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Supported Drivers
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-----------------
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U-Boot sandbox supports these emulations:
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- Block devices
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- Chrome OS EC
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- GPIO
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- Host filesystem (access files on the host from within U-Boot)
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- I2C
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- Keyboard (Chrome OS)
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- LCD
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- Network
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- Serial (for console only)
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- Sound (incomplete - see sandbox_sdl_sound_init() for details)
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- SPI
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- SPI flash
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- TPM (Trusted Platform Module)
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A wide range of commands is implemented. Filesystems which use a block
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device are supported.
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Also sandbox supports driver model (CONFIG_DM) and associated commands.
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Linux RAW Networking Bridge
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---------------------------
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The sandbox_eth_raw driver bridges traffic between the bottom of the network
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stack and the RAW sockets API in Linux. This allows much of the U-Boot network
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functionality to be tested in sandbox against real network traffic.
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For Ethernet network adapters, the bridge utilizes the RAW AF_PACKET API. This
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is needed to get access to the lowest level of the network stack in Linux. This
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means that all of the Ethernet frame is included. This allows the U-Boot network
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stack to be fully used. In other words, nothing about the Linux network stack is
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involved in forming the packets that end up on the wire. To receive the
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responses to packets sent from U-Boot the network interface has to be set to
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promiscuous mode so that the network card won't filter out packets not destined
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for its configured (on Linux) MAC address.
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The RAW sockets Ethernet API requires elevated privileges in Linux. You can
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either run as root, or you can add the capability needed like so:
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sudo /sbin/setcap "CAP_NET_RAW+ep" /path/to/u-boot
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The default device tree for sandbox includes an entry for eth0 on the sandbox
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host machine whose alias is "eth1". The following are a few examples of network
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operations being tested on the eth0 interface.
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sudo /path/to/u-boot -D
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DHCP
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....
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set autoload no
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set ethact eth1
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dhcp
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PING
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....
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set autoload no
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set ethact eth1
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dhcp
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ping $gatewayip
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TFTP
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....
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set autoload no
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set ethact eth1
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dhcp
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set serverip WWW.XXX.YYY.ZZZ
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tftpboot u-boot.bin
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The bridge also support (to a lesser extent) the localhost inderface, 'lo'.
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The 'lo' interface cannot use the RAW AF_PACKET API because the lo interface
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doesn't support Ethernet-level traffic. It is a higher-level interface that is
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expected only to be used at the AF_INET level of the API. As such, the most raw
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we can get on that interface is the RAW AF_INET API on UDP. This allows us to
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set the IP_HDRINCL option to include everything except the Ethernet header in
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the packets we send and receive.
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Because only UDP is supported, ICMP traffic will not work, so expect that ping
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commands will time out.
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The default device tree for sandbox includes an entry for lo on the sandbox
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host machine whose alias is "eth5". The following is an example of a network
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operation being tested on the lo interface.
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TFTP
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....
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set ethact eth5
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tftpboot u-boot.bin
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SPI Emulation
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-------------
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Sandbox supports SPI and SPI flash emulation.
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This is controlled by the spi_sf argument, the format of which is:
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bus:cs:device:file
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bus - SPI bus number
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cs - SPI chip select number
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device - SPI device emulation name
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file - File on disk containing the data
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For example:
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dd if=/dev/zero of=spi.bin bs=1M count=4
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./u-boot --spi_sf 0:0:M25P16:spi.bin
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With this setup you can issue SPI flash commands as normal:
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=>sf probe
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SF: Detected M25P16 with page size 64 KiB, total 2 MiB
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=>sf read 0 0 10000
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SF: 65536 bytes @ 0x0 Read: OK
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=>
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Since this is a full SPI emulation (rather than just flash), you can
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also use low-level SPI commands:
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=>sspi 0:0 32 9f
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FF202015
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This is issuing a READ_ID command and getting back 20 (ST Micro) part
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0x2015 (the M25P16).
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Drivers are connected to a particular bus/cs using sandbox's state
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structure (see the 'spi' member). A set of operations must be provided
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for each driver.
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Configuration settings for the curious are:
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CONFIG_SANDBOX_SPI_MAX_BUS
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The maximum number of SPI buses supported by the driver (default 1).
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CONFIG_SANDBOX_SPI_MAX_CS
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The maximum number of chip selects supported by the driver
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(default 10).
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CONFIG_SPI_IDLE_VAL
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The idle value on the SPI bus
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Writing Sandbox Drivers
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-----------------------
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Generally you should put your driver in a file containing the word 'sandbox'
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and put it in the same directory as other drivers of its type. You can then
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implement the same hooks as the other drivers.
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To access U-Boot's emulated memory, use map_sysmem() as mentioned above.
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If your driver needs to store configuration or state (such as SPI flash
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contents or emulated chip registers), you can use the device tree as
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described above. Define handlers for this with the SANDBOX_STATE_IO macro.
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See arch/sandbox/include/asm/state.h for documentation. In short you provide
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a node name, compatible string and functions to read and write the state.
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Since writing the state can expand the device tree, you may need to use
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state_setprop() which does this automatically and avoids running out of
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space. See existing code for examples.
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Testing
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-------
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U-Boot sandbox can be used to run various tests, mostly in the test/
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directory. These include:
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command_ut
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- Unit tests for command parsing and handling
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compression
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- Unit tests for U-Boot's compression algorithms, useful for
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security checking. It supports gzip, bzip2, lzma and lzo.
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driver model
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- Run this pytest
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./test/py/test.py --bd sandbox --build -k ut_dm -v
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image
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- Unit tests for images:
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test/image/test-imagetools.sh - multi-file images
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test/image/test-fit.py - FIT images
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tracing
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- test/trace/test-trace.sh tests the tracing system (see README.trace)
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verified boot
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- See test/vboot/vboot_test.sh for this
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If you change or enhance any of the above subsystems, you shold write or
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expand a test and include it with your patch series submission. Test
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coverage in U-Boot is limited, as we need to work to improve it.
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Note that many of these tests are implemented as commands which you can
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run natively on your board if desired (and enabled).
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It would be useful to have a central script to run all of these.
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--
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Simon Glass <sjg@chromium.org>
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Updated 22-Mar-14
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