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-rw-r--r--docs/system/generic-loader.rst117
-rw-r--r--docs/system/index.rst1
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diff --git a/docs/system/generic-loader.rst b/docs/system/generic-loader.rst
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+..
+ 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.
+
+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.
+
+``<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.
+
+All values are parsed using the standard QemuOps parsing. This allows the user
+to specify any values in any format supported. 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
+
+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.
+
+``<cpu-num>``
+ The number of the CPU whose PC should be set to the specified value.
+
+All values are parsed using the standard QemuOpts parsing. This allows the user
+to specify any values in any format supported. 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 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.
+
+``<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 the
+ memory address where the raw file is loaded or the entry point
+ specified in the executable format header. This option should only
+ be used for the boot image. This will also cause the image to be
+ written to the specified CPU's address space. If not specified, the
+ default is CPU 0. <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.
+
+All values are parsed using the standard QemuOpts parsing. This allows the user
+to specify any values in any format supported. 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
+
+Restrictions and ToDos
+^^^^^^^^^^^^^^^^^^^^^^
+
+At the moment it is just assumed that if you specify a cpu-num then
+you want to set the PC as well. This might not always be the case. In
+future the internal state 'set_pc' (which exists in the generic loader
+now) should be exposed to the user so that they can choose if the PC
+is set or not.
+
+
diff --git a/docs/system/index.rst b/docs/system/index.rst
index 625b494372..cee1c83540 100644
--- a/docs/system/index.rst
+++ b/docs/system/index.rst
@@ -25,6 +25,7 @@ Contents:
usb
ivshmem
linuxboot
+ generic-loader
vnc-security
tls
gdb