objtool: Move noreturn function list to separate file

This makes it a little cleaner and easier to maintain.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/cecacf07a69a244c74474c18b7652627de67a528.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

objtool: Detect missing __noreturn annotations

Most "unreachable instruction" warnings these days seem to actually be
the result of a missing __noreturn annotation. Add an explicit check
for that.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/6e2b93d8c65eaed6c4166a358269dc0ef01f890c.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

objtool: Include backtrace in verbose mode

Include backtrace in verbose mode. This makes it easy to gather all the
information needed for diagnosing objtool warnings.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/c255224fabcf7e64bac232fec1c77c9fc2d7d7ab.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

objtool: Add verbose option for disassembling affected functions

When a warning is associated with a function, add an option to
disassemble that function.

This makes it easier for reporters to submit the information needed to
diagnose objtool warnings.

Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/dd0fe13428ede186f09c74059a8001f4adcea5fc.1681853186.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

docs: move x86 documentation into Documentation/arch/

Move the x86 documentation under Documentation/arch/ as a way of cleaning
up the top-level directory and making the structure of our docs more
closely match the structure of the source directories it describes.

All in-kernel references to the old paths have been updated.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/lkml/20230315211523.108836-1-corbet@lwn.net/
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

objtool: Check that module init/exit function is an indirect call target

Some out-of-tree modules still do not use module_init() / module_exit()
macros and simply create functions with magic names init_module() and
cleanup_module() instead. As a result, these functions are not recognized
as indirect call targets by objtool and such module fails to load into an
IBT enabled kernel.

This old way is not even documented any more but it is cleaner to issue
a warning than to let the module fail on load without obvious reason.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230118105215.B9DA960514@lion.mk-sys.cz

objtool: Update documentation

The objtool documentation is very stack validation centric. Broaden the
documentation and describe all the features objtool supports.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/b6a84d301d9f73ec6725752654097f4e31fa1b69.1650300597.git.jpoimboe@redhat.com