82caf7aba1
Calling kdump kernel is a two-step process that involves invocation of the purgatory code: first time - to verify the new kernel checksum and second time - to call the new kernel itself. The purgatory code operates on real addresses and does not expect any memory protection. Therefore, before the purgatory code is entered the DAT mode is always turned off. However, it is only restored upon return from the new kernel checksum verification. In case the purgatory was called to start the new kernel and failed the control is returned to the old kernel, but the DAT mode continues staying off. The new kernel start failure is unlikely and leads to the disabled wait state anyway. Still that poses a risk, since the kernel code in general is not DAT-off safe and even calling the disabled_wait() function might crash. Introduce call_nodat() macro that allows entering DAT-off mode, calling an arbitrary function and restoring DAT mode back on. Switch all invocations of DAT-off code to that macro and avoid the above described scenario altogether. Name the call_nodat() macro in small letters after the already existing call_on_stack() and put it to the same header file. Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com> Reviewed-by: Heiko Carstens <hca@linux.ibm.com> [hca@linux.ibm.com: some small modifications to call_nodat() macro] Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.