[tip: x86/core] x86/ibt: Dont generate ENDBR in .discard.text

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     2b6ff7dea670a4623fae1d2349806fc7f8e305d1
Gitweb:        https://git.kernel.org/tip/2b6ff7dea670a4623fae1d2349806fc7f8e305d1
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Tue, 08 Mar 2022 16:30:43 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 15 Mar 2022 10:32:42 +01:00

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@xxxxxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220308154319.054842742@xxxxxxxxxxxxx
---
 arch/x86/include/asm/setup.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
index a12458a..896e48d 100644
--- 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;" \