[143/192] mm: define default MAX_PTRS_PER_* in include/pgtable.h

Commit Message

Andrew Morton June 29, 2021, 2:40 a.m. UTC

From: Daniel Axtens <[e-mail]>
Subject: mm: define default MAX_PTRS_PER_* in include/pgtable.h

Commit c65e774fb3f6 ("x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable")
made PTRS_PER_P4D variable on x86 and introduced MAX_PTRS_PER_P4D as a
constant for cases which need a compile-time constant (e.g.  fixed-size
arrays).

powerpc likewise has boot-time selectable MMU features which can cause
other mm "constants" to vary.  For KASAN, we have some static
PTE/PMD/PUD/P4D arrays so we need compile-time maximums for all these
constants.  Extend the MAX_PTRS_PER_ idiom, and place default definitions
in include/pgtable.h.  These define MAX_PTRS_PER_x to be PTRS_PER_x unless
an architecture has defined MAX_PTRS_PER_x in its arch headers.

Clean up pgtable-nop4d.h and s390's MAX_PTRS_PER_P4D definitions while
we're at it: both can just pick up the default now.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Daniel Axtens <[e-mail]>
Acked-by: Andrey Konovalov <[e-mail]>
Reviewed-by: Christophe Leroy <[e-mail]>
Reviewed-by: Marco Elver <[e-mail]>
Cc: Aneesh Kumar K.V <[e-mail]>
Cc: Balbir Singh <[e-mail]>
Cc: Alexander Potapenko <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 arch/s390/include/asm/pgtable.h     |    2 --
 include/asm-generic/pgtable-nop4d.h |    1 -
 include/linux/pgtable.h             |   22 ++++++++++++++++++++++
 3 files changed, 22 insertions(+), 3 deletions(-)

Patch

--- a/arch/s390/include/asm/pgtable.h~mm-define-default-max_ptrs_per_-in-include-pgtableh
+++ a/arch/s390/include/asm/pgtable.h
@@ -344,8 +344,6 @@  static inline int is_module_addr(void *a
 #define PTRS_PER_P4D	_CRST_ENTRIES
 #define PTRS_PER_PGD	_CRST_ENTRIES
 
-#define MAX_PTRS_PER_P4D	PTRS_PER_P4D
-
 /*
  * Segment table and region3 table entry encoding
  * (R = read-only, I = invalid, y = young bit):
--- a/include/asm-generic/pgtable-nop4d.h~mm-define-default-max_ptrs_per_-in-include-pgtableh
+++ a/include/asm-generic/pgtable-nop4d.h
@@ -9,7 +9,6 @@ 
 typedef struct { pgd_t pgd; } p4d_t;
 
 #define P4D_SHIFT		PGDIR_SHIFT
-#define MAX_PTRS_PER_P4D	1
 #define PTRS_PER_P4D		1
 #define P4D_SIZE		(1UL << P4D_SHIFT)
 #define P4D_MASK		(~(P4D_SIZE-1))
--- a/include/linux/pgtable.h~mm-define-default-max_ptrs_per_-in-include-pgtableh
+++ a/include/linux/pgtable.h
@@ -1592,4 +1592,26 @@  typedef unsigned int pgtbl_mod_mask;
 #define pte_leaf_size(x) PAGE_SIZE
 #endif
 
+/*
+ * Some architectures have MMUs that are configurable or selectable at boot
+ * time. These lead to variable PTRS_PER_x. For statically allocated arrays it
+ * helps to have a static maximum value.
+ */
+
+#ifndef MAX_PTRS_PER_PTE
+#define MAX_PTRS_PER_PTE PTRS_PER_PTE
+#endif
+
+#ifndef MAX_PTRS_PER_PMD
+#define MAX_PTRS_PER_PMD PTRS_PER_PMD
+#endif
+
+#ifndef MAX_PTRS_PER_PUD
+#define MAX_PTRS_PER_PUD PTRS_PER_PUD
+#endif
+
+#ifndef MAX_PTRS_PER_P4D
+#define MAX_PTRS_PER_P4D PTRS_PER_P4D
+#endif
+
 #endif /* _LINUX_PGTABLE_H */