The patch titled
Subject: random: simplify API for random address requests
has been added to the -mm tree. Its filename is
random-simplify-api-for-random-address-requests.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/random-simplify-api-for-random-address-requests.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/random-simplify-api-for-random-address-requests.patch
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------------------------------------------------------
From: Jason Cooper <jason@xxxxxxxxxxxxxx>
Subject: random: simplify API for random address requests
To date, all callers of randomize_range() have set the length to 0, and
check for a zero return value. For the current callers, the only way to
get zero returned is if end <= start. Since they are all adding a
constant to the start address, this is unnecessary.
We can remove a bunch of needless checks by simplifying the API to do just
what everyone wants, return an address between [start, start + range).
While we're here, s/get_random_int/get_random_long/. No current call site
is adversely affected by get_random_int(), since all current range
requests are < UINT_MAX. However, we should match caller expectations to
avoid coming up short (ha!) in the future.
All current callers to randomize_range() chose to use the start address if
randomize_range() failed. Therefore, we simplify things by just returning
the start address on error.
randomize_range() will be removed once all callers have been converted
over to randomize_addr().
Link: http://lkml.kernel.org/r/20160803233913.32511-2-jason@xxxxxxxxxxxxxx
Signed-off-by: Jason Cooper <jason@xxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: "Roberts, William C" <william.c.roberts@xxxxxxxxx>
Cc: Yann Droneaud <ydroneaud@xxxxxxxxxx>
Cc: "Russell King - ARM Linux" <linux@xxxxxxxxxxxxxxxx>
Cc: "Theodore Ts'o" <tytso@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>
Cc: Nick Kralevich <nnk@xxxxxxxxxx>
Cc: Jeffrey Vander Stoep <jeffv@xxxxxxxxxx>
Cc: Daniel Cashman <dcashman@xxxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Guan Xuetao <gxt@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 33 +++++++++++++++++++++++++++++++++
include/linux/random.h | 1 +
2 files changed, 34 insertions(+)
diff -puN drivers/char/random.c~random-simplify-api-for-random-address-requests drivers/char/random.c
--- a/drivers/char/random.c~random-simplify-api-for-random-address-requests
+++ a/drivers/char/random.c
@@ -2119,6 +2119,39 @@ randomize_range(unsigned long start, uns
return PAGE_ALIGN(get_random_int() % range + start);
}
+/**
+ * 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);
+}
+
/* Interface for in-kernel drivers of true hardware RNGs.
* Those devices may produce endless random bits and will be throttled
* when our pool is full.
diff -puN include/linux/random.h~random-simplify-api-for-random-address-requests include/linux/random.h
--- a/include/linux/random.h~random-simplify-api-for-random-address-requests
+++ a/include/linux/random.h
@@ -35,6 +35,7 @@ extern const struct file_operations rand
unsigned int get_random_int(void);
unsigned long get_random_long(void);
unsigned long randomize_range(unsigned long start, unsigned long end, unsigned long len);
+unsigned long randomize_page(unsigned long start, unsigned long range);
u32 prandom_u32(void);
void prandom_bytes(void *buf, size_t nbytes);
_
Patches currently in -mm which might be from jason@xxxxxxxxxxxxxx are
random-simplify-api-for-random-address-requests.patch
x86-use-simpler-api-for-random-address-requests.patch
arm-use-simpler-api-for-random-address-requests.patch
arm64-use-simpler-api-for-random-address-requests.patch
tile-use-simpler-api-for-random-address-requests.patch
unicore32-use-simpler-api-for-random-address-requests.patch
random-remove-unused-randomize_range.patch
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