vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO_DATA

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

Signed-off-by: Kees Cook <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Will Deacon <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Michael Ellerman <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: Rick Edgecombe <[email protected]>
Cc: Segher Boessenkool <[email protected]>
Cc: x86-ml <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

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_EXCEPTION_TABLE_ALIGN
+#define RO_EXCEPTION_TABLE	EXCEPTION_TABLE(RO_EXCEPTION_TABLE_ALIGN)
+#else
+#define RO_EXCEPTION_TABLE
+#endif
+
 /* Align . to a 8 byte boundary equals to maximum function alignment. */
 #define ALIGN_FUNCTION()  . = ALIGN(8)
 
@@ -513,6 +524,7 @@
 		__stop___modver = .;					\
 	}								\
 									\
+	RO_EXCEPTION_TABLE						\
 	NOTES								\
 									\
 	. = ALIGN((align));						\