Avoid possible uninitialized variables on machines where
division by zero does not trap. Add __divmoddi4, and
use it in __moddi3 and __divdi3.
Reported-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
lib/ldiv32.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)
diff --git a/lib/ldiv32.c b/lib/ldiv32.c
index 96f4b35..897a4b9 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. */
@@ -35,31 +39,35 @@ uint64_t __udivmoddi4(uint64_t num, uint64_t den, uint64_t *p_rem)
return quot;
}
-int64_t __moddi3(int64_t num, int64_t den)
+int64_t __divmoddi4(int64_t num, int64_t den, int64_t *p_rem)
{
- uint64_t mask = num < 0 ? -1 : 0;
+ 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 + mask) ^ mask;
+ num = (num + nmask) ^ nmask;
if (den < 0)
den = -den;
- /* Copy sign of num into result. */
- return (__umoddi3(num, den) + mask) ^ mask;
+ /* Copy sign of num^den into quotient, sign of num into remainder. */
+ quot = (__udivmoddi4(num, den, (uint64_t *)p_rem) + qmask) ^ qmask;
+ if (p_rem)
+ *p_rem = (*p_rem + nmask) ^ nmask;
+ return quot;
}
-int64_t __divdi3(int64_t num, int64_t den)
+int64_t __moddi3(int64_t num, int64_t den)
{
- uint64_t mask = (num ^ den) < 0 ? -1 : 0;
-
- /* Compute absolute values and do an unsigned division. */
- if (num < 0)
- num = -num;
- if (den < 0)
- den = -den;
+ int64_t rem;
+ __divmoddi4(num, den, &rem);
+ return rem;
+}
- /* Copy sign of num^den into result. */
- return (__udivdi3(num, den) + mask) ^ mask;
+int64_t __divdi3(int64_t num, int64_t den)
+{
+ int64_t rem;
+ return __divmoddi4(num, den, &rem);
}
uint64_t __udivdi3(uint64_t num, uint64_t den)
--
2.31.1
