x86/mm: Fix -Wmissing-prototypes warnings for arch/x86/mm/init.c

Fix -Wmissing-prototypes warnings:

  arch/x86/mm/init.c:81:6:
  warning: no previous prototype for ‘x86_has_pat_wp’ [-Wmissing-prototypes]
  bool x86_has_pat_wp(void)

  arch/x86/mm/init.c:86:22:
  warning: no previous prototype for ‘pgprot2cachemode’ [-Wmissing-prototypes]
  enum page_cache_mode pgprot2cachemode(pgprot_t pgprot)

by including the respective header containing prototypes. Also fix:

  arch/x86/mm/init.c:893:13:
  warning: no previous prototype for ‘mem_encrypt_free_decrypted_mem’ [-Wmissing-prototypes]
  void __weak mem_encrypt_free_decrypted_mem(void) { }

by making it static inline for the !CONFIG_AMD_MEM_ENCRYPT case. This
warning happens when CONFIG_AMD_MEM_ENCRYPT is not enabled (defconfig
for example):

  ./arch/x86/include/asm/mem_encrypt.h:80:27:
  warning: inline function ‘mem_encrypt_free_decrypted_mem’ declared weak [-Wattributes]
  static inline void __weak mem_encrypt_free_decrypted_mem(void) { }
                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

It's ok to convert to static inline because the function is used only in
x86. Is not shared with other architectures so drop the __weak too.

 [ bp: Massage and adjust __weak comments while at it. ]
Signed-off-by: Benjamin Thiel <b.thiel@posteo.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200606122629.2720-1-b.thiel@posteo.de

arch/x86/include/asm/mem_encrypt.h

@@ -43,9 +43,10 @@ void __init sme_enable(struct boot_params *bp);
 int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
 int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
 
+void __init mem_encrypt_free_decrypted_mem(void);
+
 /* Architecture __weak replacement functions */
 void __init mem_encrypt_init(void);
-void __init mem_encrypt_free_decrypted_mem(void);
 
 bool sme_active(void);
 bool sev_active(void);
@@ -77,6 +78,8 @@ early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0;
 static inline int __init
 early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
 
+static inline void mem_encrypt_free_decrypted_mem(void) { }
+
 #define __bss_decrypted
 
 #endif	/* CONFIG_AMD_MEM_ENCRYPT */

arch/x86/mm/init.c

@@ -25,6 +25,7 @@
 #include <asm/cpufeature.h>
 #include <asm/pti.h>
 #include <asm/text-patching.h>
+#include <asm/memtype.h>
 
 /*
  * We need to define the tracepoints somewhere, and tlb.c
@@ -912,8 +913,6 @@ void free_kernel_image_pages(const char *what, void *begin, void *end)
 		set_memory_np_noalias(begin_ul, len_pages);
 }
 
-void __weak mem_encrypt_free_decrypted_mem(void) { }
-
 void __ref free_initmem(void)
 {
 	e820__reallocate_tables();

arch/x86/mm/mem_encrypt.c

@@ -376,7 +376,6 @@ bool force_dma_unencrypted(struct device *dev)
 	return false;
 }
 
-/* Architecture __weak replacement functions */
 void __init mem_encrypt_free_decrypted_mem(void)
 {
 	unsigned long vaddr, vaddr_end, npages;
@@ -401,6 +400,7 @@ void __init mem_encrypt_free_decrypted_mem(void)
 	free_init_pages("unused decrypted", vaddr, vaddr_end);
 }
 
+/* Architecture __weak replacement functions */
 void __init mem_encrypt_init(void)
 {
 	if (!sme_me_mask)