random: move randomize_page() into mm where it belongs

commit 5ad7dd882e45d7fe432c32e896e2aaa0b21746ea upstream.

randomize_page is an mm function. It is documented like one. It contains
the history of one. It has the naming convention of one. It looks
just like another very similar function in mm, randomize_stack_top().
And it has always been maintained and updated by mm people. There is no
need for it to be in random.c. In the "which shape does not look like
the other ones" test, pointing to randomize_page() is correct.

So move randomize_page() into mm/util.c, right next to the similar
randomize_stack_top() function.

This commit contains no actual code changes.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 83055a60877101fd92cc69a0b5c455c1388af1bd..f00360536c114b3654a0bceba9622d63912fcea5 100644 (file)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -622,38 +622,6 @@ int __cold random_prepare_cpu(unsigned int cpu)
 }
 #endif
 
-/**
- * randomize_page - Generate a random, page aligned address
- * @start:     The smallest acceptable address the caller will take.
- * @range:     The size of the area, starting at @start, within which the
- *             random address must fall.
- *
- * If @start + @range would overflow, @range is capped.
- *
- * NOTE: Historical use of randomize_range, which this replaces, presumed that
- * @start was already page aligned.  We now align it regardless.
- *
- * Return: A page aligned address within [start, start + range).  On error,
- * @start is returned.
- */
-unsigned long randomize_page(unsigned long start, unsigned long range)
-{
-       if (!PAGE_ALIGNED(start)) {
-               range -= PAGE_ALIGN(start) - start;
-               start = PAGE_ALIGN(start);
-       }
-
-       if (start > ULONG_MAX - range)
-               range = ULONG_MAX - start;
-
-       range >>= PAGE_SHIFT;
-
-       if (range == 0)
-               return start;
-
-       return start + (get_random_long() % range << PAGE_SHIFT);
-}
-
 /*
  * This function will use the architecture-specific hardware random
  * number generator if it is available. It is not recommended for

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5744a3fc47169a512880561aa2ea91ebad8772fd..9cb0ff065e8b18f20d92df222b3739e1605a253f 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2678,6 +2678,7 @@ extern int install_special_mapping(struct mm_struct *mm,
                                   unsigned long flags, struct page **pages);
 
 unsigned long randomize_stack_top(unsigned long stack_top);
+unsigned long randomize_page(unsigned long start, unsigned long range);
 
 extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
 

diff --git a/include/linux/random.h b/include/linux/random.h
index d6ef6cf4346aafc849c1d984372c6ac97083a4e7..917470c4490ac9015421d5bccc717ca6f0366e3d 100644 (file)
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -64,8 +64,6 @@ static inline unsigned long get_random_canary(void)
        return get_random_long() & CANARY_MASK;
 }
 
-unsigned long randomize_page(unsigned long start, unsigned long range);
-
 int __init random_init(const char *command_line);
 bool rng_is_initialized(void);
 int wait_for_random_bytes(void);

diff --git a/mm/util.c b/mm/util.c
index d3102081add001d4986f15b6e7dc539ce769e583..5223d7e2f65ec48b71651ec3d1afc85f2aa08202 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -343,6 +343,38 @@ unsigned long randomize_stack_top(unsigned long stack_top)
 #endif
 }
 
+/**
+ * randomize_page - Generate a random, page aligned address
+ * @start:     The smallest acceptable address the caller will take.
+ * @range:     The size of the area, starting at @start, within which the
+ *             random address must fall.
+ *
+ * If @start + @range would overflow, @range is capped.
+ *
+ * NOTE: Historical use of randomize_range, which this replaces, presumed that
+ * @start was already page aligned.  We now align it regardless.
+ *
+ * Return: A page aligned address within [start, start + range).  On error,
+ * @start is returned.
+ */
+unsigned long randomize_page(unsigned long start, unsigned long range)
+{
+       if (!PAGE_ALIGNED(start)) {
+               range -= PAGE_ALIGN(start) - start;
+               start = PAGE_ALIGN(start);
+       }
+
+       if (start > ULONG_MAX - range)
+               range = ULONG_MAX - start;
+
+       range >>= PAGE_SHIFT;
+
+       if (range == 0)
+               return start;
+
+       return start + (get_random_long() % range << PAGE_SHIFT);
+}
+
 #ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
 unsigned long arch_randomize_brk(struct mm_struct *mm)
 {