linux-kernel - [PATCH 1/1] x86/speculation, objtool: Annotate indirect calls/jumps for objtool on 32bit

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Date:   Wed, 14 Mar 2018 11:24:27 +0000
From:   Andy Whitcroft <apw@...onical.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Andy Whitcroft <apw@...onical.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] x86/speculation, objtool: Annotate indirect calls/jumps for objtool on 32bit

In 9e0e3c5130e9 ("x86/speculation, objtool: Annotate indirect calls/jumps
for objtool") we added annotations for CALL_NOSPEC/JMP_NOSPEC on x86 64bit.
We did not annotate the 32bit path.  Annotate it similarly.

Signed-off-by: Andy Whitcroft <apw@...onical.com>
---
 arch/x86/include/asm/nospec-branch.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

    While reviewing indirect calls in our builds I noted that the
    i386 retpoline CALL_NOSPEC is not annotated safe even though
    its amd64 equivalent is.  I cannot see any reason this is not
    also inherantly safe.  Peter was there a reason that you did
    not annotate this one too?  Anyhow, on the assumption this was
    just missed, this patch annotates it.

    -apw

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index d0dabeae0505..07886162bdf8 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -183,7 +183,10 @@
  * otherwise we'll run out of registers. We don't care about CET
  * here, anyway.
  */
-# define CALL_NOSPEC ALTERNATIVE("call *%[thunk_target]\n",	\
+# define CALL_NOSPEC 						\
+	ALTERNATIVE(						\
+	ANNOTATE_RETPOLINE_SAFE					\
+	"call *%[thunk_target]\n",				\
 	"       jmp    904f;\n"					\
 	"       .align 16\n"					\
 	"901:	call   903f;\n"					\
-- 
2.15.1