Luke Nelson bfabff3cb0 bpf, riscv: Modify JIT ctx to support compressed instructions
This patch makes the necessary changes to struct rv_jit_context and to
bpf_int_jit_compile to support compressed riscv (RVC) instructions in
the BPF JIT.

It changes the JIT image to be u16 instead of u32, since RVC instructions
are 2 bytes as opposed to 4.

It also changes ctx->offset and ctx->ninsns to refer to 2-byte
instructions rather than 4-byte ones. The riscv PC is required to be
16-bit aligned with or without RVC, so this is sufficient to refer to
any valid riscv offset.

The code for computing jump offsets in bytes is updated accordingly,
and factored into a new "ninsns_rvoff" function to simplify the code.

Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200721025241.8077-2-luke.r.nels@gmail.com
2020-07-21 13:26:25 -07:00

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.
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