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authorYury Norov <yury.norov@gmail.com>2023-02-27 22:24:36 +0300
committerYury Norov <yury.norov@gmail.com>2023-06-22 23:57:41 +0300
commitc1d2ba10f594046831d14b03f194e8d05e78abad (patch)
tree6d6ad141cd6405d9620287e868a6b4770578fca8
parentc4c14c290682e080da5cee81f4998062e1be274a (diff)
downloadlinux-c1d2ba10f594046831d14b03f194e8d05e78abad.tar.xz
lib/bitmap: drop optimization of bitmap_{from,to}_arr64
bitmap_{from,to}_arr64() optimization is overly optimistic on 32-bit LE architectures when it's wired to bitmap_copy_clear_tail(). bitmap_copy_clear_tail() takes care of unused bits in the bitmap up to the next word boundary. But on 32-bit machines when copying bits from bitmap to array of 64-bit words, it's expected that the unused part of a recipient array must be cleared up to 64-bit boundary, so the last 4 bytes may stay untouched when nbits % 64 <= 32. While the copying part of the optimization works correct, that clear-tail trick makes corresponding tests reasonably fail: test_bitmap: bitmap_to_arr64(nbits == 1): tail is not safely cleared: 0xa5a5a5a500000001 (must be 0x0000000000000001) Fix it by removing bitmap_{from,to}_arr64() optimization for 32-bit LE arches. Reported-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/lkml/20230225184702.GA3587246@roeck-us.net/ Fixes: 0a97953fd221 ("lib: add bitmap_{from,to}_arr64") Signed-off-by: Yury Norov <yury.norov@gmail.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
-rw-r--r--include/linux/bitmap.h8
-rw-r--r--lib/bitmap.c2
2 files changed, 4 insertions, 6 deletions
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 7d6d73b78147..03644237e1ef 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -302,12 +302,10 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap,
#endif
/*
- * On 64-bit systems bitmaps are represented as u64 arrays internally. On LE32
- * machines the order of hi and lo parts of numbers match the bitmap structure.
- * In both cases conversion is not needed when copying data from/to arrays of
- * u64.
+ * On 64-bit systems bitmaps are represented as u64 arrays internally. So,
+ * the conversion is not needed when copying data from/to arrays of u64.
*/
-#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN)
+#if BITS_PER_LONG == 32
void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits);
void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits);
#else
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 1c81413c51f8..ddb31015e38a 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -1495,7 +1495,7 @@ void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits)
EXPORT_SYMBOL(bitmap_to_arr32);
#endif
-#if (BITS_PER_LONG == 32) && defined(__BIG_ENDIAN)
+#if BITS_PER_LONG == 32
/**
* bitmap_from_arr64 - copy the contents of u64 array of bits to bitmap
* @bitmap: array of unsigned longs, the destination bitmap