riscv: Consistify protect_kernel_linear_mapping_text_rodata() use

The various uses of protect_kernel_linear_mapping_text_rodata() are
not consistent:
  - Its definition depends on "64BIT && !XIP_KERNEL",
  - Its forward declaration depends on MMU,
  - Its single caller depends on "STRICT_KERNEL_RWX && 64BIT && MMU &&
    !XIP_KERNEL".

Fix this by settling on the dependencies of the caller, which can be
simplified as STRICT_KERNEL_RWX depends on "MMU && !XIP_KERNEL".
Provide a dummy definition, as the caller is protected by
"IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)" instead of "#ifdef
CONFIG_STRICT_KERNEL_RWX".
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/include/asm/set_memory.h

@@ -17,7 +17,6 @@ int set_memory_x(unsigned long addr, int numpages);
 int set_memory_nx(unsigned long addr, int numpages);
 int set_memory_rw_nx(unsigned long addr, int numpages);
 void protect_kernel_text_data(void);
-void protect_kernel_linear_mapping_text_rodata(void);
 #else
 static inline int set_memory_ro(unsigned long addr, int numpages) { return 0; }
 static inline int set_memory_rw(unsigned long addr, int numpages) { return 0; }
@@ -27,6 +26,12 @@ static inline void protect_kernel_text_data(void) {}
 static inline int set_memory_rw_nx(unsigned long addr, int numpages) { return 0; }
 #endif
 
+#if defined(CONFIG_64BIT) && defined(CONFIG_STRICT_KERNEL_RWX)
+void protect_kernel_linear_mapping_text_rodata(void);
+#else
+static inline void protect_kernel_linear_mapping_text_rodata(void) {}
+#endif
+
 int set_direct_map_invalid_noflush(struct page *page);
 int set_direct_map_default_noflush(struct page *page);
 bool kernel_page_present(struct page *page);

arch/riscv/kernel/setup.c

@@ -293,9 +293,7 @@ void __init setup_arch(char **cmdline_p)
 
 	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
 		protect_kernel_text_data();
-#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
 		protect_kernel_linear_mapping_text_rodata();
-#endif
 	}
 
 #ifdef CONFIG_SWIOTLB

arch/riscv/mm/init.c

@@ -645,7 +645,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 #endif
 }
 
-#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
+#if defined(CONFIG_64BIT) && defined(CONFIG_STRICT_KERNEL_RWX)
 void protect_kernel_linear_mapping_text_rodata(void)
 {
 	unsigned long text_start = (unsigned long)lm_alias(_start);