Enabling CONFIG_UBSAN_SANITIZE_ALL on ARM caused a link error:
last_lba.part.0':
:(.text+0xc3440): undefined reference to `____ilog2_NaN'
:(.text+0xc3538): undefined reference to `__aeabi_uldivmod'
:(.text+0xc38e8): undefined reference to `__aeabi_uldivmod'
This is caused by gcc not behaving in the expected ways with __builtin_constant_p(),
but it also points to somewhat inefficient code: As we know that the
block size is a power-of-two value, we can turn the expensive 64-bit
division into a simpler variable bit shift.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
block/partitions/efi.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index bcd86e5cd546..7d83cf069574 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -147,10 +147,13 @@ efi_crc32(const void *buf, unsigned long len)
*/
static u64 last_lba(struct block_device *bdev)
{
+ unsigned int blocksize;
+
if (!bdev || !bdev->bd_inode)
return 0;
- return div_u64(bdev->bd_inode->i_size,
- bdev_logical_block_size(bdev)) - 1ULL;
+
+ blocksize = bdev_logical_block_size(bdev);
+ return (bdev->bd_inode->i_size >> ilog2(blocksize)) - 1ULL;
}
static inline int pmbr_part_valid(gpt_mbr_record *part)
--
2.9.0
--
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