mm: consolidate pte_index() and pte_offset_*() definitions

All architectures define pte_index() as

	(address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)

and all architectures define pte_offset_kernel() as an entry in the array
of PTEs indexed by the pte_index().

For the most architectures the pte_offset_kernel() implementation relies
on the availability of pmd_page_vaddr() that converts a PMD entry value to
the virtual address of the page containing PTEs array.

Let's move x86 definitions of the PTE accessors to the generic place in
<linux/pgtable.h> and then simply drop the respective definitions from the
other architectures.

The architectures that didn't provide pmd_page_vaddr() are updated to have
that defined.

The generic implementation of pte_offset_kernel() can be overridden by an
architecture and alpha makes use of this because it has special ordering
requirements for its version of pte_offset_kernel().

[rppt@linux.ibm.com: v2]
  Link: http://lkml.kernel.org/r/20200514170327.31389-11-rppt@kernel.org
[rppt@linux.ibm.com: update]
  Link: http://lkml.kernel.org/r/20200514170327.31389-12-rppt@kernel.org
[rppt@linux.ibm.com: update]
  Link: http://lkml.kernel.org/r/20200514170327.31389-13-rppt@kernel.org
[akpm@linux-foundation.org: fix x86 warning]
[sfr@canb.auug.org.au: fix powerpc build]
  Link: http://lkml.kernel.org/r/20200607153443.GB738695@linux.ibm.com

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Guo Ren <guoren@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stafford Horne <shorne@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vincent Chen <deanbo422@gmail.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Link: http://lkml.kernel.org/r/20200514170327.31389-10-rppt@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 93 insertions, 0 deletions

diff --git a/include/asm-generic/pgtable-nopmd.h b/include/asm-generic/pgtable-nopmd.h
index 0d9b28cba16d..3e13acd019ae 100644
--- a/include/asm-generic/pgtable-nopmd.h
+++ b/include/asm-generic/pgtable-nopmd.h
@@ -45,6 +45,7 @@ static inline pmd_t * pmd_offset(pud_t * pud, unsigned long address)
 {
 	return (pmd_t *)pud;
 }
+#define pmd_offset pmd_offset
 
 #define pmd_val(x)				(pud_val((x).pud))
 #define __pmd(x)				((pmd_t) { __pud(x) } )
diff --git a/include/asm-generic/pgtable-nopud.h b/include/asm-generic/pgtable-nopud.h
index ad05c1684bfc..a9d751fbda9e 100644
--- a/include/asm-generic/pgtable-nopud.h
+++ b/include/asm-generic/pgtable-nopud.h
@@ -43,6 +43,7 @@ static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
 {
 	return (pud_t *)p4d;
 }
+#define pud_offset pud_offset
 
 #define pud_val(x)				(p4d_val((x).p4d))
 #define __pud(x)				((pud_t) { __p4d(x) })
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index ee85b222d098..90a5d0c78fca 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -29,6 +29,97 @@
 #endif
 
 /*
+ * A page table page can be thought of an array like this: pXd_t[PTRS_PER_PxD]
+ *
+ * The pXx_index() functions return the index of the entry in the page
+ * table page which would control the given virtual address
+ *
+ * As these functions may be used by the same code for different levels of
+ * the page table folding, they are always available, regardless of
+ * CONFIG_PGTABLE_LEVELS value. For the folded levels they simply return 0
+ * because in such cases PTRS_PER_PxD equals 1.
+ */
+
+static inline unsigned long pte_index(unsigned long address)
+{
+	return (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
+}
+
+#ifndef pmd_index
+static inline unsigned long pmd_index(unsigned long address)
+{
+	return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
+}
+#define pmd_index pmd_index
+#endif
+
+#ifndef pud_index
+static inline unsigned long pud_index(unsigned long address)
+{
+	return (address >> PUD_SHIFT) & (PTRS_PER_PUD - 1);
+}
+#define pud_index pud_index
+#endif
+
+#ifndef pgd_index
+/* Must be a compile-time constant, so implement it as a macro */
+#define pgd_index(a)  (((a) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
+#endif
+
+#ifndef pte_offset_kernel
+static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
+{
+	return (pte_t *)pmd_page_vaddr(*pmd) + pte_index(address);
+}
+#define pte_offset_kernel pte_offset_kernel
+#endif
+
+#if defined(CONFIG_HIGHPTE)
+#define pte_offset_map(dir, address)				\
+	((pte_t *)kmap_atomic(pmd_page(*(dir))) +		\
+	 pte_index((address)))
+#define pte_unmap(pte) kunmap_atomic((pte))
+#else
+#define pte_offset_map(dir, address)	pte_offset_kernel((dir), (address))
+#define pte_unmap(pte) ((void)(pte))	/* NOP */
+#endif
+
+/* Find an entry in the second-level page table.. */
+#ifndef pmd_offset
+static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address)
+{
+	return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address);
+}
+#define pmd_offset pmd_offset
+#endif
+
+#ifndef pud_offset
+static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
+{
+	return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address);
+}
+#define pud_offset pud_offset
+#endif
+
+static inline pgd_t *pgd_offset_pgd(pgd_t *pgd, unsigned long address)
+{
+	return (pgd + pgd_index(address));
+};
+
+/*
+ * a shortcut to get a pgd_t in a given mm
+ */
+#ifndef pgd_offset
+#define pgd_offset(mm, address)		pgd_offset_pgd((mm)->pgd, (address))
+#endif
+
+/*
+ * a shortcut which implies the use of the kernel's pgd, instead
+ * of a process's
+ */
+#define pgd_offset_k(address)		pgd_offset(&init_mm, (address))
+
+/*
  * In many cases it is known that a virtual address is mapped at PMD or PTE
  * level, so instead of traversing all the page table levels, we can get a
  * pointer to the PMD entry in user or kernel page table or translate a virtual