ARM: mm: Make virt_to_pfn() a static inline

Making virt_to_pfn() a static inline taking a strongly typed
(const void *) makes the contract of a passing a pointer of that
type to the function explicit and exposes any misuse of the
macro virt_to_pfn() acting polymorphic and accepting many types
such as (void *), (unitptr_t) or (unsigned long) as arguments
without warnings.

Doing this is a bit intrusive: virt_to_pfn() requires
PHYS_PFN_OFFSET and PAGE_SHIFT to be defined, and this is defined in
<asm/page.h>, so this must be included *before* <asm/memory.h>.

The use of macros were obscuring the unclear inclusion order here,
as the macros would eventually be resolved, but a static inline
like this cannot be compiled with unresolved macros.

The naive solution to include <asm/page.h> at the top of
<asm/memory.h> does not work, because <asm/memory.h> sometimes
includes <asm/page.h> at the end of itself, which would create a
confusing inclusion loop. So instead, take the approach to always
unconditionally include <asm/page.h> at the end of <asm/memory.h>

arch/arm uses <asm/memory.h> explicitly in a lot of places,
however it turns out that if we just unconditionally include
<asm/memory.h> into <asm/page.h> and switch all inclusions of
<asm/memory.h> to <asm/page.h> instead, we enforce the right
order and <asm/memory.h> will always have access to the
definitions.

Put an inclusion guard in place making it impossible to include
<asm/memory.h> explicitly.

Link: https://lore.kernel.org/linux-mm/20220701160004.2ffff4e5ab59a55499f4c736@linux-foundation.org/
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: Linus Walleij

arch/arm/common/sharpsl_param.c

@@ -11,7 +11,7 @@
 #include <linux/module.h>
 #include <linux/string.h>
 #include <asm/mach/sharpsl_param.h>
-#include <asm/memory.h>
+#include <asm/page.h>
 
 /*
  * Certain hardware parameters determined at the time of device manufacture,

arch/arm/include/asm/delay.h

@@ -7,7 +7,7 @@
 #ifndef __ASM_ARM_DELAY_H
 #define __ASM_ARM_DELAY_H
 
-#include <asm/memory.h>
+#include <asm/page.h>
 #include <asm/param.h>	/* HZ */
 
 /*

arch/arm/include/asm/io.h

@@ -23,7 +23,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <asm/byteorder.h>
-#include <asm/memory.h>
+#include <asm/page.h>
 #include <asm-generic/pci_iomap.h>
 
 /*

arch/arm/include/asm/memory.h

@@ -5,11 +5,16 @@
  *  Copyright (C) 2000-2002 Russell King
  *  modification for nommu, Hyok S. Choi, 2004
  *
- *  Note: this file should not be included by non-asm/.h files
+ *  Note: this file should not be included explicitly, include <asm/page.h>
+ *  to get access to these definitions.
  */
 #ifndef __ASM_ARM_MEMORY_H
 #define __ASM_ARM_MEMORY_H
 
+#ifndef _ASMARM_PAGE_H
+#error "Do not include <asm/memory.h> directly"
+#endif
+
 #include <linux/compiler.h>
 #include <linux/const.h>
 #include <linux/types.h>
@@ -288,10 +293,12 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
 
 #endif
 
-#define virt_to_pfn(kaddr) \
-	((((unsigned long)(kaddr) - PAGE_OFFSET) >> PAGE_SHIFT) + \
-	 PHYS_PFN_OFFSET)
-
+static inline unsigned long virt_to_pfn(const void *p)
+{
+	unsigned long kaddr = (unsigned long)p;
+	return (((kaddr - PAGE_OFFSET) >> PAGE_SHIFT) +
+		PHYS_PFN_OFFSET);
+}
 #define __pa_symbol_nodebug(x)	__virt_to_phys_nodebug((x))
 
 #ifdef CONFIG_DEBUG_VIRTUAL

arch/arm/include/asm/page.h

@@ -161,10 +161,10 @@ extern int pfn_valid(unsigned long);
 #define pfn_valid pfn_valid
 #endif
 
-#include <asm/memory.h>
-
 #endif /* !__ASSEMBLY__ */
 
+#include <asm/memory.h>
+
 #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
 
 #include <asm-generic/getorder.h>

arch/arm/include/asm/pgtable.h

@@ -27,7 +27,7 @@ extern struct page *empty_zero_page;
 #else
 
 #include <asm-generic/pgtable-nopud.h>
-#include <asm/memory.h>
+#include <asm/page.h>
 #include <asm/pgtable-hwdef.h>
 
 

arch/arm/include/asm/proc-fns.h

@@ -147,8 +147,6 @@ static inline void init_proc_vtable(const struct processor *p)
 
 extern void cpu_resume(void);
 
-#include <asm/memory.h>
-
 #ifdef CONFIG_MMU
 
 #define cpu_switch_mm(pgd,mm) cpu_do_switch_mm(virt_to_phys(pgd),mm)

arch/arm/include/asm/sparsemem.h

@@ -2,7 +2,7 @@
 #ifndef ASMARM_SPARSEMEM_H
 #define ASMARM_SPARSEMEM_H
 
-#include <asm/memory.h>
+#include <asm/page.h>
 
 /*
  * Two definitions are required for sparsemem:

arch/arm/include/asm/uaccess-asm.h

@@ -5,7 +5,7 @@
 
 #include <asm/asm-offsets.h>
 #include <asm/domain.h>
-#include <asm/memory.h>
+#include <asm/page.h>
 #include <asm/thread_info.h>
 
 	.macro	csdb

arch/arm/include/asm/uaccess.h

@@ -9,7 +9,7 @@
  * User space memory access functions
  */
 #include <linux/string.h>
-#include <asm/memory.h>
+#include <asm/page.h>
 #include <asm/domain.h>
 #include <asm/unaligned.h>
 #include <asm/unified.h>