random: move randomize_page() into mm where it belongs

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.

Jason A. Donenfeld committed 4 years ago

Commit 5ad7dd81 parent 6701de64 files · +33 −34Browse files

Unified · Split

4 files

drivers/char/random.c +0 −32
include/linux/mm.h +1 −0
include/linux/random.h +0 −2
mm/util.c +32 −0

drivers/char/random.c+0−32

@@ -573,38 +573,6 @@ int __cold random_prepare_cpu(unsigned int cpu) · 572 unmodified lines
573	573	}
574	574	#endif
575	575
576		−/**
577		− * randomize_page - Generate a random, page aligned address
578		− * @start: The smallest acceptable address the caller will take.
579		− * @range: The size of the area, starting at @start, within which the
580		− * random address must fall.
581		− *
582		− * If @start + @range would overflow, @range is capped.
583		− *
584		− * NOTE: Historical use of randomize_range, which this replaces, presumed that
585		− * @start was already page aligned. We now align it regardless.
586		− *
587		− * Return: A page aligned address within [start, start + range). On error,
588		− * @start is returned.
589		− */
590		−unsigned long randomize_page(unsigned long start, unsigned long range)
591		−{
592		− if (!PAGE_ALIGNED(start)) {
593		− range -= PAGE_ALIGN(start) - start;
594		− start = PAGE_ALIGN(start);
595		− }
596		−
597		− if (start > ULONG_MAX - range)
598		− range = ULONG_MAX - start;
599		−
600		− range >>= PAGE_SHIFT;
601		−
602		− if (range == 0)
603		− return start;
604		−
605		− return start + (get_random_long() % range << PAGE_SHIFT);
606		−}
607		−
608	576
609	577	/**********************************************************************
610	578	*

include/linux/mm.h+1−0

@@ -2677,6 +2677,7 @@ extern int install_special_mapping(struct mm_struct *mm, · 2676 unmodified lines
2677	2677	unsigned long flags, struct page **pages);
2678	2678
2679	2679	unsigned long randomize_stack_top(unsigned long stack_top);
	2680	+unsigned long randomize_page(unsigned long start, unsigned long range);
2680	2681
2681	2682	extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
2682	2683

include/linux/random.h+0−2

@@ -72,8 +72,6 @@ static inline unsigned long get_random_canary(void) · 71 unmodified lines
72	72	return get_random_long() & CANARY_MASK;
73	73	}
74	74
75		−unsigned long randomize_page(unsigned long start, unsigned long range);
76		−
77	75	int __init random_init(const char *command_line);
78	76	bool rng_is_initialized(void);
79	77	bool rng_has_arch_random(void);

mm/util.c+32−0

@@ -343,6 +343,38 @@ unsigned long randomize_stack_top(unsigned long stack_top) · 342 unmodified lines
343	343	#endif
344	344	}
345	345
	346	+/**
	347	+ * randomize_page - Generate a random, page aligned address
	348	+ * @start: The smallest acceptable address the caller will take.
	349	+ * @range: The size of the area, starting at @start, within which the
	350	+ * random address must fall.
	351	+ *
	352	+ * If @start + @range would overflow, @range is capped.
	353	+ *
	354	+ * NOTE: Historical use of randomize_range, which this replaces, presumed that
	355	+ * @start was already page aligned. We now align it regardless.
	356	+ *
	357	+ * Return: A page aligned address within [start, start + range). On error,
	358	+ * @start is returned.
	359	+ */
	360	+unsigned long randomize_page(unsigned long start, unsigned long range)
	361	+{
	362	+ if (!PAGE_ALIGNED(start)) {
	363	+ range -= PAGE_ALIGN(start) - start;
	364	+ start = PAGE_ALIGN(start);
	365	+ }
	366	+
	367	+ if (start > ULONG_MAX - range)
	368	+ range = ULONG_MAX - start;
	369	+
	370	+ range >>= PAGE_SHIFT;
	371	+
	372	+ if (range == 0)
	373	+ return start;
	374	+
	375	+ return start + (get_random_long() % range << PAGE_SHIFT);
	376	+}
	377	+
346	378	#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
347	379	unsigned long arch_randomize_brk(struct mm_struct *mm)
348	380	{