Avoid possible uninitialized variables on machines where
division by zero does not trap. Add __divmoddi4, and
do not use 64-bit math unnecessarily in __moddi3 and __divdi3.
Reported-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
lib/ldiv32.c | 28 +++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/lib/ldiv32.c b/lib/ldiv32.c
index 96f4b35..c39fccd 100644
--- a/lib/ldiv32.c
+++ b/lib/ldiv32.c
@@ -1,6 +1,7 @@
#include <stdint.h>
extern uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem);
+extern int64_t __divmoddi4(int64_t num, int64_t den, int64_t *p_rem);
extern int64_t __moddi3(int64_t num, int64_t den);
extern int64_t __divdi3(int64_t num, int64_t den);
extern uint64_t __udivdi3(uint64_t num, uint64_t den);
@@ -11,8 +12,11 @@ uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem)
uint64_t quot = 0;
/* Trigger a division by zero at run time (trick taken from iPXE). */
- if (den == 0)
+ if (den == 0) {
+ if (p_rem)
+ *p_rem = 0;
return 1/((unsigned)den);
+ }
if (num >= den) {
/* Align den to num to avoid wasting time on leftmost zero bits. */
@@ -35,9 +39,27 @@ uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem)
return quot;
}
+int64_t __divmoddi4(int64_t num, int64_t den, int64_t *p_rem)
+{
+ int32_t nmask = num < 0 ? -1 : 0;
+ int32_t qmask = (num ^ den) < 0 ? -1 : 0;
+ uint64_t quot;
+
+ /* Compute absolute values and do an unsigned division. */
+ num = (num + nmask) ^ nmask;
+ if (den < 0)
+ den = -den;
+
+ /* Copy sign of num^den into quotient, sign of num into remainder. */
+ quot = (__divmoddi4(num, den, p_rem) + qmask) ^ qmask;
+ if (p_rem)
+ *p_rem = (*p_rem + nmask) ^ nmask;
+ return quot;
+}
+
int64_t __moddi3(int64_t num, int64_t den)
{
- uint64_t mask = num < 0 ? -1 : 0;
+ int32_t mask = num < 0 ? -1 : 0;
/* Compute absolute values and do an unsigned division. */
num = (num + mask) ^ mask;
@@ -50,7 +72,7 @@ int64_t __moddi3(int64_t num, int64_t den)
int64_t __divdi3(int64_t num, int64_t den)
{
- uint64_t mask = (num ^ den) < 0 ? -1 : 0;
+ int32_t mask = (num ^ den) < 0 ? -1 : 0;
/* Compute absolute values and do an unsigned division. */
if (num < 0)
--
2.31.1
