Xu Kuohai 042152c27c bpf, arm64: Sign return address for JITed code
Sign return address for JITed code when the kernel is built with pointer
authentication enabled:

1. Sign LR with paciasp instruction before LR is pushed to stack. Since
   paciasp acts like landing pads for function entry, no need to insert
   bti instruction before paciasp.

2. Authenticate LR with autiasp instruction after LR is popped from stack.

For BPF tail call, the stack frame constructed by the caller is reused by
the callee. That is, the stack frame is constructed by the caller and
destructed by the callee. Thus LR is signed and pushed to the stack in the
caller's prologue, and poped from the stack and authenticated in the
callee's epilogue.

For BPF2BPF call, the caller and callee construct their own stack frames,
and sign and authenticate their own LRs.

Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://events.static.linuxfound.org/sites/events/files/slides/slides_23.pdf
Link: https://lore.kernel.org/bpf/20220402073942.3782529-1-xukuohai@huawei.com
2022-04-06 00:04:22 +02:00

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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