@@ -95,6 +95,7 @@ $(vobjs): KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO) $(GCC_PLUGINS_CFLAGS) $(
ifdef CONFIG_X86_IBT
$(vobjs) $(vobjs32): KBUILD_CFLAGS += -fcf-protection=branch
+$(vobjs) $(vobjs32): KBUILD_AFLAGS += -fcf-protection=branch
endif
#
@@ -52,6 +52,23 @@ extern int map_vdso_once(const struct vdso_image *image, unsigned long addr);
extern bool fixup_vdso_exception(struct pt_regs *regs, int trapnr,
unsigned long error_code,
unsigned long fault_addr);
-#endif /* __ASSEMBLER__ */
+#else /* __ASSEMBLER__ */
+
+/*
+ * ENDBR is an instruction for the Indirect Branch Tracking (IBT) component
+ * of CET. IBT prevents attacks by ensuring that (most) indirect branches
+ * function calls may only land at ENDBR instructions. Branches that don't
+ * follow the rules will result in control flow (#CF) exceptions.
+ * ENDBR is a noop when IBT is unsupported or disabled. Most ENDBR
+ * instructions are inserted automatically by the compiler, but branch
+ * targets written in assembly must have ENDBR added manually.
+ */
+#ifdef __CET__
+#include <cet.h>
+#define ENDBR _CET_ENDBR
+#else
+#define ENDBR
+#endif
+#endif /* __ASSEMBLER__ */
#endif /* _ASM_X86_VDSO_H */
ENDBR is a special new instruction for the Indirect Branch Tracking (IBT) component of CET. IBT prevents attacks by ensuring that (most) indirect branches and function calls may only land at ENDBR instructions. Branches that don't follow the rules will result in control flow (#CF) exceptions. ENDBR is a noop when IBT is unsupported or disabled. Most ENDBR instructions are inserted automatically by the compiler, but branch targets written in assembly must have ENDBR added manually. There are two ENDBR versions: endbr64 and endbr32. The compilers (gcc and clang) have _CET_ENDBR defined for the proper one. Introduce ENDBR macro, which equals the compiler macro when enabled, otherwise nothing. Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Jarkko Sakkinen <jarkko@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> --- arch/x86/entry/vdso/Makefile | 1 + arch/x86/include/asm/vdso.h | 19 ++++++++++++++++++- 2 files changed, 19 insertions(+), 1 deletion(-)