Merge branch 'nfsd-5.8' of git://linux-nfs.org/~cel/cel-2.6 into for-5.8-incoming

consideration the effect of compiler optimisations which may occur

when tail-calls are used and marked with the noreturn GCC attribute.

Probed Pointers from BPF / tracing

----------------------------------

::

	%pks	kernel string

	%pus	user string

The ``k`` and ``u`` specifiers are used for printing prior probed memory from

either kernel memory (k) or user memory (u). The subsequent ``s`` specifier

results in printing a string. For direct use in regular vsnprintf() the (k)

and (u) annotation is ignored, however, when used out of BPF's bpf_trace_printk(),

for example, it reads the memory it is pointing to without faulting.

Kernel Pointers

---------------

- compatible :

	- "fsl,vf610-edma" for eDMA used similar to that on Vybrid vf610 SoC

	- "fsl,imx7ulp-edma" for eDMA2 used similar to that on i.mx7ulp

	- "fsl,fsl,ls1028a-edma" for eDMA used similar to that on Vybrid vf610 SoC

	- "fsl,ls1028a-edma" followed by "fsl,vf610-edma" for eDMA used on the

	  LS1028A SoC.

- reg : Specifies base physical address(s) and size of the eDMA registers.

	The 1st region is eDMA control register's address and size.

	The 2nd and the 3rd regions are programmable channel multiplexing

      - running

      - ICE OS Default Package

      - The name of the DDP package that is active in the device. The DDP

        package is loaded by the driver during initialization. Each varation

        of DDP package shall have a unique name.

        package is loaded by the driver during initialization. Each

        variation of the DDP package has a unique name.

    * - ``fw.app``

      - running

      - 1.3.1.0

3. Raw Gadget provides a way to select a UDC device/driver to bind to,

   while GadgetFS currently binds to the first available UDC.

4. Raw Gadget uses predictable endpoint names (handles) across different

   UDCs (as long as UDCs have enough endpoints of each required transfer

   type).

4. Raw Gadget explicitly exposes information about endpoints addresses and

   capabilities allowing a user to write UDC-agnostic gadgets.

5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.

   Raw Gadget and react to those depending on what kind of USB device

   needs to be emulated.

Note, that some UDC drivers have fixed addresses assigned to endpoints, and

therefore arbitrary endpoint addresses can't be used in the descriptors.

Nevertheles, Raw Gadget provides a UDC-agnostic way to write USB gadgets.

Once a USB_RAW_EVENT_CONNECT event is received via USB_RAW_IOCTL_EVENT_FETCH,

the USB_RAW_IOCTL_EPS_INFO ioctl can be used to find out information about

endpoints that the UDC driver has. Based on that information, the user must

chose UDC endpoints that will be used for the gadget being emulated, and

properly assign addresses in endpoint descriptors.

You can find usage examples (along with a test suite) here:

https://github.com/xairy/raw-gadget

Internal details

~~~~~~~~~~~~~~~~

Currently every endpoint read/write ioctl submits a USB request and waits until

its completion. This is the desired mode for coverage-guided fuzzing (as we'd

like all USB request processing happen during the lifetime of a syscall),

and must be kept in the implementation. (This might be slow for real world

applications, thus the O_NONBLOCK improvement suggestion below.)

Potential future improvements

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

- Implement ioctl's for setting/clearing halt status on endpoints.

- Reporting more events (suspend, resume, etc.) through

  USB_RAW_IOCTL_EVENT_FETCH.

- Report more events (suspend, resume, etc.) through USB_RAW_IOCTL_EVENT_FETCH.

- Support O_NONBLOCK I/O.

- Support USB 3 features (accept SS endpoint companion descriptor when

  enabling endpoints; allow providing stream_id for bulk transfers).

- Support ISO transfer features (expose frame_number for completed requests).

   arm/index

   devices/index

   running-nested-guests