96dc89d526
Current we store the userspace r1 to PACATMSCRATCH before finally saving it to the thread struct. In theory an exception could be taken here (like a machine check or SLB miss) that could write PACATMSCRATCH and hence corrupt the userspace r1. The SLB fault currently doesn't touch PACATMSCRATCH, but others do. We've never actually seen this happen but it's theoretically possible. Either way, the code is fragile as it is. This patch saves r1 to the kernel stack (which can't fault) before we turn MSR[RI] back on. PACATMSCRATCH is still used but only with MSR[RI] off. We then copy r1 from the kernel stack to the thread struct once we have MSR[RI] back on. Suggested-by: Breno Leitao <leitao@debian.org> Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.