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Maciej W. Rozycki
f3d1b0c224
[ Upstream commit8e0780d30b] Fix an issue in call_o32() where the upper 32-bit half of incoming n64 stack arguments is fetched and used for outgoing o32 stack arguments on big-endian platforms. This code was adapted from arch/mips/dec/prom/call_o32.S which was meant for a little-endian platform only and therefore using 32-bit loads from 64-bit stack slot locations holding incoming stack arguments resulted in correct values being retrieved for data that is expected to be 32-bit. This works on little-endian platforms where the lower 32-bit half of the 64-bit value is located at every 64-bit stack slot location. However on big-endian platforms the lower 32-bit half is instead located at offset 4 from every 64-bit stack slot location. So to fix the issue the offset of 4 would have to be used on big-endian platforms only, or alternatively a 64-bit load from the 64-bit stack slot location can be used across the board, as the subsequent 32-bit store to the corresponding outgoing stack argument slot will correctly truncate the value and cause no unpredictable result. We already take advantage of this architectural feature for the incoming arguments held in $a6 and $a7 registers, since the o32 wrapper does not know how many incoming arguments there are and consequently propagates incoming data which may not be 32-bit. Since this code is generally supposed to be used with the stack located in cached memory there is no extra overhead expected for 64-bit loads as opposed to 32-bit ones, so pick this variant for code simplicity. Fixes:231a35d372("[MIPS] RM: Collected changes") Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.