linux-kernel - [RFC][PATCH 0/6] x86: Kernel IBT beginnings

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Date:   Mon, 22 Nov 2021 18:03:01 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        ndesaulniers@...gle.com, keescook@...omium.org,
        samitolvanen@...gle.com
Subject: [RFC][PATCH 0/6] x86: Kernel IBT beginnings

Hi,

So I hacked this up on Friday night / Saturday morning and spend all of today
cleaning it up.

It is the very bare beginnings of kernel IBT support. Since I'm lacking any
sort of actual hardware it even lacks fun things like code to write to the MSRs
to enable the IBT tracker etc..

However, it should have most of the ENDBR instructions in the right place -- I
hope :-) That said; I would *really* like compiler support for this stuff to be
improved, the amount of fixups done by objtool is obscene.

The end result still boots on ancient x86-64 hardware, for whatever that's
worth (when built with the below turd included that is).

Enjoy!

---

diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 5cdd9bc5c385..1d180bbe7b28 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -142,6 +142,11 @@ objtool_link()
 		info OBJTOOL ${1}
 		tools/objtool/objtool ${objtoolcmd} ${objtoolopt} ${1}
 	fi
+
+	if [ "${CONFIG_X86_IBT}" = "y" ]; then
+		# XXX less ugleh
+		tools/objtool/objtool check --no-fp --retpoline --uaccess --vmlinux --duplicate --ibt --ibt-fix-direct --ibt-seal ${1}
+	fi
 }

 # Link of vmlinux