riscv: mm: stub extable related functions/macros for !MMU

extable relies on the MMU to work properly, so it's useless to
include __ex_table sections and build extable related functions for
!MMU case.

Signed-off-by: Jisheng Zhang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: xhackerustc

arch/riscv/include/asm/asm-extable.h

@@ -7,6 +7,8 @@
 #define EX_TYPE_BPF			2
 #define EX_TYPE_UACCESS_ERR_ZERO	3
 
+#ifdef CONFIG_MMU
+
 #ifdef __ASSEMBLY__
 
 #define __ASM_EXTABLE_RAW(insn, fixup, type, data)	\
@@ -62,4 +64,8 @@
 
 #endif /* __ASSEMBLY__ */
 
+#else /* CONFIG_MMU */
+	#define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err)
+#endif /* CONFIG_MMU */
+
 #endif /* __ASM_ASM_EXTABLE_H */

arch/riscv/include/asm/extable.h

@@ -32,7 +32,11 @@ do {							\
 	(b)->data = (tmp).data;				\
 } while (0)
 
+#ifdef CONFIG_MMU
 bool fixup_exception(struct pt_regs *regs);
+#else
+static inline bool fixup_exception(struct pt_regs *regs) { return false; }
+#endif
 
 #if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
 bool ex_handler_bpf(const struct exception_table_entry *ex, struct pt_regs *regs);

arch/riscv/mm/Makefile

@@ -13,8 +13,7 @@ endif
 KCOV_INSTRUMENT_init.o := n
 
 obj-y += init.o
-obj-y += extable.o
-obj-$(CONFIG_MMU) += fault.o pageattr.o
+obj-$(CONFIG_MMU) += extable.o fault.o pageattr.o
 obj-y += cacheflush.o
 obj-y += context.o
 obj-y += pgtable.o