Generic Loader
The ‘loader’ device allows the user to load multiple images or values into QEMU at startup.
Loading Data into Memory Values
The loader device allows memory values to be set from the command line. This can be done by following the syntax below:
-device loader,addr=<addr>,data=<data>,data-len=<data-len> \
[,data-be=<data-be>][,cpu-num=<cpu-num>]
<addr>The address to store the data in.
Note that as usual with QEMU numeric option values, the default is to treat the argument as decimal. To specify a value in hex, prefix it with ‘0x’.
<data>The value to be written to the address. The maximum size of the data is 8 bytes.
<data-len>The length of the data in bytes. This argument must be included if the data argument is.
<data-be>Set to true if the data to be stored on the guest should be written as big endian data. The default is to write little endian data.
<cpu-num>The number of the CPU’s address space where the data should be loaded. If not specified the address space of the first CPU is used.
An example of loading value 0x8000000e to address 0xfd1a0104 is:
-device loader,addr=0xfd1a0104,data=0x8000000e,data-len=4
Setting a CPU’s Program Counter
The loader device allows the CPU’s PC to be set from the command line. This can be done by following the syntax below:
-device loader,addr=<addr>,cpu-num=<cpu-num>
<addr>The value to use as the CPU’s PC.
Note that as usual with QEMU numeric option values, the default is to treat the argument as decimal. To specify a value in hex, prefix it with ‘0x’.
<cpu-num>The number of the CPU whose PC should be set to the specified value.
An example of setting CPU 0’s PC to 0x8000 is:
-device loader,addr=0x8000,cpu-num=0
Loading Files
The loader device also allows files to be loaded into memory. It can load ELF, U-Boot, and Intel HEX executable formats as well as raw images. The syntax is shown below:
-device loader,file=<file>[,addr=<addr>][,cpu-num=<cpu-num>][,force-raw=<raw>]
<file>A file to be loaded into memory
<addr>The memory address where the file should be loaded. This is required for raw images and ignored for non-raw files.
Note that as usual with QEMU numeric option values, the default is to treat the argument as decimal. To specify a value in hex, prefix it with ‘0x’.
<cpu-num>This specifies the CPU that should be used. This is an optional argument with two effects:
this CPU’s address space is used to load the data
this CPU’s PC will be set to the address where the raw file is loaded or the entry point specified in the executable format header
If this option is not specified, then the data will be loaded via the address space of the first CPU, and no CPU will have its PC set.
Note that there is currently no way to specify the address space to load the data without also causing that CPU’s PC to be set.
Since it sets the starting PC, this option should only be used for the boot image.
<force-raw>Setting ‘force-raw=on’ forces the file to be treated as a raw image. This can be used to load supported executable formats as if they were raw.
An example of loading an ELF file which CPU0 will boot is shown below:
-device loader,file=./images/boot.elf,cpu-num=0