mm: constify arch_pick_mmap_layout() for improved const-correctness

This function only reads from the rlimit pointer (but writes to the
mm_struct pointer which is kept without `const`).

All callees are already const-ified or (internal functions) are being
constified by this patch.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Max Kellermann <[e-mail]>
Reviewed-by: Vishal Moola (Oracle) <[e-mail]>
Reviewed-by: Lorenzo Stoakes <[e-mail]>
Acked-by: David Hildenbrand <[e-mail]>
Acked-by: Vlastimil Babka <[e-mail]>
Acked-by: Mike Rapoport (Microsoft) <[e-mail]>
Acked-by: Shakeel Butt <[e-mail]>
Cc: Alexander Gordeev <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Andreas Larsson <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Axel Rasmussen <[e-mail]>
Cc: Baolin Wang <[e-mail]>
Cc: Borislav Betkov <[e-mail]>
Cc: Christian Borntraeger <[e-mail]>
Cc: Christian Brauner <[e-mail]>
Cc: Christian Zankel <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: David S. Miller <[e-mail]>
Cc: Gerald Schaefer <[e-mail]>
Cc: Heiko Carstens <[e-mail]>
Cc: Helge Deller <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Bottomley <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Jocelyn Falempe <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Matthew Wilcox (Oracle) <[e-mail]>
Cc: Max Filippov <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: "Nysal Jan K.A" <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Russel King <[e-mail]>
Cc: Suren Baghdasaryan <[e-mail]>
Cc: Sven Schnelle <[e-mail]>
Cc: Thomas Gleinxer <[e-mail]>
Cc: Thomas Huth <[e-mail]>
Cc: Vasily Gorbik <[e-mail]>
Cc: Wei Xu <[e-mail]>
Cc: Yuanchu Xie <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

arch/s390/mm/mmap.c

···
 }
 
 static inline unsigned long mmap_base(unsigned long rnd,
-				      struct rlimit *rlim_stack)
+				      const struct rlimit *rlim_stack)
 {
 	unsigned long gap = rlim_stack->rlim_cur;
 	unsigned long pad = stack_maxrandom_size() + stack_guard_gap;
···
  * This function, called very early during the creation of a new
  * process VM image, sets up which VM layout function to use:
  */
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 {
 	unsigned long random_factor = 0UL;
 

arch/sparc/kernel/sys_sparc_64.c

···
 	return rnd << PAGE_SHIFT;
 }
 
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 {
 	unsigned long random_factor = mmap_rnd();
 	unsigned long gap;

arch/x86/mm/mmap.c

···
 }
 
 static unsigned long mmap_base(unsigned long rnd, unsigned long task_size,
-			       struct rlimit *rlim_stack)
+			       const struct rlimit *rlim_stack)
 {
 	unsigned long gap = rlim_stack->rlim_cur;
 	unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
···
  */
 static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
 		unsigned long random_factor, unsigned long task_size,
-		struct rlimit *rlim_stack)
+		const struct rlimit *rlim_stack)
 {
 	*legacy_base = mmap_legacy_base(random_factor, task_size);
 	if (mmap_is_legacy())
···
 		*base = mmap_base(random_factor, task_size, rlim_stack);
 }
 
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 {
 	if (mmap_is_legacy())
 		mm_flags_clear(MMF_TOPDOWN, mm);

include/linux/sched/mm.h

···
 #endif
 
 extern void arch_pick_mmap_layout(struct mm_struct *mm,
-				  struct rlimit *rlim_stack);
+				  const struct rlimit *rlim_stack);
 
 unsigned long
 arch_get_unmapped_area(struct file *filp, unsigned long addr,
···
 				  unsigned long flags, vm_flags_t vm_flags);
 #else
 static inline void arch_pick_mmap_layout(struct mm_struct *mm,
-					 struct rlimit *rlim_stack) {}
+					 const struct rlimit *rlim_stack) {}
 #endif
 
 static inline bool in_vfork(struct task_struct *tsk)

mm/util.c

···
 #define MIN_GAP		(SZ_128M)
 #define MAX_GAP		(STACK_TOP / 6 * 5)
 
-static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
+static unsigned long mmap_base(const unsigned long rnd, const struct rlimit *rlim_stack)
 {
 #ifdef CONFIG_STACK_GROWSUP
 	/*
···
 #endif
 }
 
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 {
 	unsigned long random_factor = 0UL;
 
···
 	}
 }
 #elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+void arch_pick_mmap_layout(struct mm_struct *mm, const struct rlimit *rlim_stack)
 {
 	mm->mmap_base = TASK_UNMAPPED_BASE;
 	mm_flags_clear(MMF_TOPDOWN, mm);