Re: [Qemu-devel] [PATCH v8 5/5] docs: Add a generic loader explanation document

[Peter Maydell]

On 2 July 2016 at 02:07, Alistair Francis <address@hidden> wrote:
> Signed-off-by: Alistair Francis <address@hidden>
> ---
> V8:
>  - Improve documentation
> V6:
>  - Fixup documentation
> V4:
>  - Re-write to be more comprehensive
>
>  docs/generic-loader.txt | 60 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 60 insertions(+)
>  create mode 100644 docs/generic-loader.txt

> diff --git a/docs/generic-loader.txt b/docs/generic-loader.txt
> new file mode 100644
> index 0000000..34684fc
> --- /dev/null
> +++ b/docs/generic-loader.txt
> @@ -0,0 +1,60 @@
> +Copyright (c) 2016 Xilinx Inc.
> +
> +This work is licensed under the terms of the GNU GPL, version 2 or later.  
> See
> +the COPYING file in the top-level directory.
> +
> +
> +The 'loader' device allows the user to load multiple images or values into
> +QEMU at startup.
> +
> +Loading 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=<len>
> +    -device loader,addr=<addr>,cpu-num=<cpu-num>
> +
> +    <addr>      - The address to store the data or the value to use as the
> +                  CPU's PC.
> +    <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>   - This will cause the CPU to be reset and the PC to be set to
> +                  the value of addr.
> +
> +For all values both hex and decimal values are allowed. By default the values
> +will be parsed as decimal. To use hex values the user should prefix the 
> number
> +with a '0x'.
> +
> +An example of loading value 0x8000000e to address 0xfd1a0104 is:
> +    -device loader,addr=0xfd1a0104,data=0x8000000e,data-len=4
> +
> +Loading Files
> +-------------
> +The loader device also allows files to be loaded into memory. This can be 
> done
> +similarly to setting memory values. 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 addr in memory that the file should be loaded. This is
> +                  ignored if you are using an ELF (unless force-raw is true).
> +                  This is required if you aren't loading an ELF.
> +    <cpu-num>   - This specifies the CPU that should be used. This is an
> +                  optional argument and will cause the CPU's PC to be set to
> +                  where the image is stored. This option should only be used
> +                  for the boot image.

For an ELF file we use the start address specified in the ELF header, right?

We also end up writing to that CPU's address space, but only for ELF files.

> +    <force-raw> - Forces the file to be treated as a raw image. This can be
> +                  used to specify the load address of ELF files.

Presumably it results in the ELF file being dumped into memory as a raw
image without any regard to what the segment headers say about loading,
offsets, etc?

> +
> +For all values both hex and decimal values are allowed. By default the values
> +will be parsed as decimal. To use hex values the user should prefix the 
> number
> +with a '0x'.
> +
> +An example of loading an ELF file which CPU0 will boot is shown below:
> +    -device loader,file=./images/boot.elf,cpu-num=0

thanks
-- PMM