The code multiplying the # of cylinders/heads/sectors in ata_id_n_sectors()
to get a disk capacity implicitly uses the *int* type for that calculation
and casting the result to 'u64' before returning ensues a sign extension.
Explicitly casting the 'u16' typed multipliers to 'u32' results in avoiding
a sign extension instruction and so in a more compact code...
Found by Linux Verification Center (linuxtesting.org) with the SVACE static
analysis tool.
Signed-off-by: Sergey Shtylyov <s.shtylyov@xxxxxx>
---
This patch is against the 'for-next' branch of Damien's 'libata.git' repo.
drivers/ata/libata-core.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
Index: libata/drivers/ata/libata-core.c
===================================================================
--- libata.orig/drivers/ata/libata-core.c
+++ libata/drivers/ata/libata-core.c
@@ -1107,11 +1107,13 @@ static u64 ata_id_n_sectors(const u16 *i
return ata_id_u32(id, ATA_ID_LBA_CAPACITY);
} else {
if (ata_id_current_chs_valid(id))
- return id[ATA_ID_CUR_CYLS] * id[ATA_ID_CUR_HEADS] *
- id[ATA_ID_CUR_SECTORS];
+ return (u32)id[ATA_ID_CUR_CYLS] *
+ (u32)id[ATA_ID_CUR_HEADS] *
+ (u32)id[ATA_ID_CUR_SECTORS];
else
- return id[ATA_ID_CYLS] * id[ATA_ID_HEADS] *
- id[ATA_ID_SECTORS];
+ return (u32)id[ATA_ID_CYLS] *
+ (u32)id[ATA_ID_HEADS] *
+ (u32)id[ATA_ID_SECTORS];
}
}
