On Wednesday, April 11, 2018 at 12:23:21 PM UTC+2, f1f0 wrote:
>
> I am proposing to add a Documentation/cell-loading.md file.
> Rather than proposing the .md directly, I prefer to propose raw text
> discussion,
> then work on the cosmetics and links from other parts of the
> Documentation.
>
> -FF
>
> Jailhouse loading of images is pretty flexible but can be disconcerting.
>
> The syntax is:
>
> jailhouse cell load \
> { ID | [--name] NAME } \
> { { IMAGE | { -s | --string } "STRING" } [-a | --address ADDRESS] } ...
>
> Valid forms are:
>
> # loads inamte.bin (offset 0 assumed)
inmate.bin
> jailhouse cell load foocell inmate.bin
>
> # same as above with explicit location
> jailhouse cell load foocell inmate.bin -a 0
>
> # load three binary objects (in order)
> jailhouse cell load foocell \
> inmate.bin \
> sharedobject.so -a 0x100 \
> ramfs.bin -a 0x200
>
> The first example assumes "-a 0".
>
> The last example, loads in the order specified, three binary objects,
> the first one at offset 0, the second one at 0x100.
> Should inmate.bin be larger than 0x100, the upper part will be
> overridden
> by sharedobject.so.
>
> Whatever load order, execution starts in the cell at offset 0.
>
>
> This multi-image loading capability can be used to patch images and
> pass parameters to the image. The following explains how parameters are
> passed
> with the inmate library.
>
> The inmate library assumes a command line string to be located at a
> fixed
> location that is processor specific:
> - On x86 this is offset 0x100 (see inmates/lib/x86/inmate.lds)
> - On arm64, this is offset 0x1000 (see inmates/lib/arm64/inmate.lds.S)
>
> The command line string capacity is fixed (256 bytes by defaylt) by
default
But it is not fixed, inmates may expand it. None of the demo inmates
does, though.
> CMDLINE_BUFFER_SIZE
> in inmates/lib/cmdline.c.
>
> Here is an example to pass parameters stored in the file
> commandline.txt to the last example on an x86 system:
>
> OFFSET=0x100
> jailhouse cell load foocell \
> inmate.bin \
> commanline.txt -a $OFFSET \
> sharedobject.so -a 0x100 \
> ramfs.bin -a 0x200
>
> This command patches inmate.bin at offset 0x100 that happens to be char*
> cmdline for
> inmates that uses Jailhouse inmates library.
>
> Note: on an arm64 we would set OFFSET=0x1000
>
> To be more practical and avoid using a text file, there is an
> image-as-string
> option:
>
> OFFSET=0x100
> jailhouse cell load foocell \
> inmate.bin \
> -s "" -a $OFFSET \
> sharedobject.so -a 0x100 \
> ramfs.bin -a 0x200
>
> The string in the -s need to be less than 255 characters long
> (CMDLINE_BUFFER_SIZE - terminatind \0)
> otherwise it will silently overwrite existing code.
You pointed out this limit above already.
Thanks for kicking this off. As I wrote in the other thread, I think
this information is best located in a man page for the jailhouse tool.
Of course, that would imply writing more than "just" about jailhouse
cell load... :D But maybe we can start the man page with "to-be-written"
stubs.
Jan
--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux
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