[tip: x86/core] x86/linkage: Add ENDBR to SYM_FUNC_START*()

["tip-bot2 for Peter Zijlstra" <tip-bot2@linutronix.de>]

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

Commit-ID:     1d295d6e83f8ce357cafe11a86dab1deecb13963
Gitweb:        https://git.kernel.org/tip/1d295d6e83f8ce357cafe11a86dab1deecb13963
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Tue, 08 Mar 2022 16:30:25 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 08 Mar 2022 23:53:30 +01:00

x86/linkage: Add ENDBR to SYM_FUNC_START*()

Ensure the ASM functions have ENDBR on for IBT builds, this follows
the ARM64 example. Unlike ARM64, we'll likely end up overwriting them
with poison.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154317.992708941@infradead.org
---
 arch/x86/include/asm/linkage.h | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/x86/include/asm/linkage.h b/arch/x86/include/asm/linkage.h
index 0309079..85865f1 100644
--- a/arch/x86/include/asm/linkage.h
+++ b/arch/x86/include/asm/linkage.h
@@ -3,6 +3,7 @@
 #define _ASM_X86_LINKAGE_H
 
 #include <linux/stringify.h>
+#include <asm/ibt.h>
 
 #undef notrace
 #define notrace __attribute__((no_instrument_function))
@@ -34,5 +35,35 @@
 
 #endif /* __ASSEMBLY__ */
 
+/* SYM_FUNC_START -- use for global functions */
+#define SYM_FUNC_START(name)				\
+	SYM_START(name, SYM_L_GLOBAL, SYM_A_ALIGN)	\
+	ENDBR
+
+/* SYM_FUNC_START_NOALIGN -- use for global functions, w/o alignment */
+#define SYM_FUNC_START_NOALIGN(name)			\
+	SYM_START(name, SYM_L_GLOBAL, SYM_A_NONE)	\
+	ENDBR
+
+/* SYM_FUNC_START_LOCAL -- use for local functions */
+#define SYM_FUNC_START_LOCAL(name)			\
+	SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)	\
+	ENDBR
+
+/* SYM_FUNC_START_LOCAL_NOALIGN -- use for local functions, w/o alignment */
+#define SYM_FUNC_START_LOCAL_NOALIGN(name)		\
+	SYM_START(name, SYM_L_LOCAL, SYM_A_NONE)	\
+	ENDBR
+
+/* SYM_FUNC_START_WEAK -- use for weak functions */
+#define SYM_FUNC_START_WEAK(name)			\
+	SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN)	\
+	ENDBR
+
+/* SYM_FUNC_START_WEAK_NOALIGN -- use for weak functions, w/o alignment */
+#define SYM_FUNC_START_WEAK_NOALIGN(name)		\
+	SYM_START(name, SYM_L_WEAK, SYM_A_NONE)		\
+	ENDBR
+
 #endif /* _ASM_X86_LINKAGE_H */