linux-kernel - [PATCH 14/29] vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO

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Message-Id: <20190926175602.33098-15-keescook@chromium.org>
Date:   Thu, 26 Sep 2019 10:55:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-alpha@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 14/29] vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO_DATA

Many architectures have an EXCEPTION_TABLE that needs only to be
read-only. As such, it should live in RO_DATA. This creates a macro to
identify this case for the architectures that can move EXCEPTION_TABLE
into RO_DATA.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/asm-generic/vmlinux.lds.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d57a28786bb8..35a6cba39d9f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -69,6 +69,17 @@
 #define NOTES_HEADERS_RESTORE
 #endif
 
+/*
+ * Some architectures have non-executable read-only exception tables.
+ * They can be added to the RO_DATA segment by specifying their desired
+ * alignment.
+ */
+#ifdef RO_DATA_EXCEPTION_TABLE_ALIGN
+#define RO_DATA_EXCEPTION_TABLE	EXCEPTION_TABLE(RO_DATA_EXCEPTION_TABLE_ALIGN)
+#else
+#define RO_DATA_EXCEPTION_TABLE
+#endif
+
 /* Align . to a 8 byte boundary equals to maximum function alignment. */
 #define ALIGN_FUNCTION()  . = ALIGN(8)
 
@@ -508,6 +519,7 @@
 		__stop___modver = .;					\
 	}								\
 									\
+	RO_DATA_EXCEPTION_TABLE						\
 	NOTES								\
 									\
 	. = ALIGN((align));						\
-- 
2.17.1