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From:   David Woodhouse <dwmw@amazon.co.uk>
To:     tglx@linutronix.de, karahmed@amazon.de, x86@kernel.org,
        linux-kernel@vger.kernel.org, bp@alien8.de, peterz@infradead.org
Subject: [PATCH 1/2] x86/retpoline: No retpolines for built-in __init functions
Date:   Thu,  1 Feb 2018 11:27:20 +0000
Message-Id: <1517484441-1420-2-git-send-email-dwmw@amazon.co.uk>
In-Reply-To: <1517484441-1420-1-git-send-email-dwmw@amazon.co.uk>
References: <1517484441-1420-1-git-send-email-dwmw@amazon.co.uk>
Sender: linux-kernel-owner@vger.kernel.org
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There's no point in building init code with retpolines, since it runs before
any potentially hostile userspace does. And before the retpoline is actually
ALTERNATIVEd into place, for much of it.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
 include/linux/init.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/init.h b/include/linux/init.h
index ea1b311..506a981 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -5,6 +5,13 @@
 #include <linux/compiler.h>
 #include <linux/types.h>
 
+/* Built-in __init functions needn't be compiled with retpoline */
+#if defined(RETPOLINE) && !defined(MODULE)
+#define __noretpoline __attribute__((indirect_branch("keep")))
+#else
+#define __noretpoline
+#endif
+
 /* These macros are used to mark some functions or 
  * initialized data (doesn't apply to uninitialized data)
  * as `initialization' functions. The kernel can take this
@@ -40,7 +47,7 @@
 
 /* These are for everybody (although not all archs will actually
    discard it in modules) */
-#define __init		__section(.init.text) __cold  __latent_entropy
+#define __init		__section(.init.text) __cold  __latent_entropy __noretpoline
 #define __initdata	__section(.init.data)
 #define __initconst	__section(.init.rodata)
 #define __exitdata	__section(.exit.data)
-- 
2.7.4