x86/ibt: Dont generate ENDBR in .discard.text

Having ENDBR in discarded sections can easily lead to relocations into
discarded sections which the linkers aren't really fond of. Objtool
also shouldn't generate them, but why tempt fate.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.054842742@infradead.org

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index a12458a7a8d4af15b9380a0d4cc336a6d1c80723..896e48d45828cba79d15d5d9a98ea55fc62f9bbe 100644 (file)
--- a/arch/x86/include/asm/setup.h
+++ b/arch/x86/include/asm/setup.h
@@ -8,6 +8,7 @@
 
 #include <linux/linkage.h>
 #include <asm/page_types.h>
+#include <asm/ibt.h>
 
 #ifdef __i386__
 
@@ -119,7 +120,7 @@ void *extend_brk(size_t size, size_t align);
  * executable.)
  */
 #define RESERVE_BRK(name,sz)                                           \
-       static void __section(".discard.text") __used notrace           \
+       static void __section(".discard.text") __noendbr __used notrace \
        __brk_reservation_fn_##name##__(void) {                         \
                asm volatile (                                          \
                        ".pushsection .brk_reservation,\"aw\",@nobits;" \