d804db3daf
[ Upstream commit 9d1f0ec9f71780e69ceb9d91697600c747d6e02e ] Rewrote the RISC-V memmove() assembly implementation. The previous implementation did not check memory alignment and it compared 2 pointers with a signed comparison. The misaligned memory access would cause the kernel to crash on systems that did not emulate it in firmware and did not support it in hardware. Firmware emulation is slow and may not exist. The RISC-V spec does not guarantee that support for misaligned memory accesses will exist. It should not be depended on. This patch now checks for XLEN granularity of co-alignment between the pointers. Failing that, copying is done by loading from the 2 contiguous and naturally aligned XLEN memory locations containing the overlapping XLEN sized data to be copied. The data is shifted into the correct place and binary or'ed together on each iteration. The result is then stored into the corresponding naturally aligned XLEN sized location in the destination. For unaligned data at the terminations of the regions to be copied or for copies less than (2 * XLEN) in size, byte copy is used. This patch also now uses unsigned comparison for the pointers and migrates to the newer assembler annotations from the now deprecated ones. Signed-off-by: Michael T. Kloos <michael@michaelkloos.com> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> 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.