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Both uprobes and alternatives have insn_is_nop() variants, unify them and make sure insn_is_nop() works for both x86_64 and i386. Specifically, uprobe must not compare userspace instructions to kernel nops as that does not work right in the compat case. For the uprobe case we therefore must recognise common 32bit and 64bit nops. Because uprobe will consume the instruction as a nop, it must not mistakenly claim a non-nop instruction to be a nop. Eg. 'REX.b3 NOP' is 'xchg %r8,%rax' - not a nop. For the kernel case similar constraints apply, is it used to optimize NOPs by replacing strings of short(er) nops with longer nops. Must not claim an instruction is a nop if it really isn't. Not recognising a nop is non-fatal. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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 reStructuredText 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.