69e168ebdc
NFP shift instruction has something special. If shift direction is left
then shift amount of 1 to 31 is specified as 32 minus the amount to shift.
But no need to do this for indirect shift which has shift amount be 0. Even
after we do this subtraction, shift amount 0 will be turned into 32 which
will eventually be encoded the same as 0 because only low 5 bits are
encoded, but shift amount be 32 will fail the FIELD_PREP check done later
on shift mask (0x1f), due to 32 is out of mask range. Such error has been
observed when compiling nfp/bpf/jit.c using gcc 8.3 + O3.
This issue has started when indirect shift support added after which the
incoming shift amount to __emit_shf could be 0, therefore it is at that
time shift amount adjustment inside __emit_shf should have been tightened.
Fixes: 991f5b3651f6 ("nfp: bpf: support logic indirect shifts (BPF_[L|R]SH | BPF_X)")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Reported-by: Pablo Cascón <pablo.cascon@netronome.com
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@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.