[PATCH] Fix link error in 32bit arch because of 64bit division

Subsystems: netfilter, networking [general], the rest

STALE3678d

3 messages, 3 authors, 2016-09-27 · open the first message on its own page

[PATCH] Fix link error in 32bit arch because of 64bit division

From: Vishwanath Pai <hidden>
Date: 2016-09-27 07:42:03

Fix link error in 32bit arch because of 64bit division

Division of 64bit integers will cause linker error undefined reference
to `__udivdi3'. Fix this by replacing divisions with div64_64

Signed-off-by: Vishwanath Pai <redacted>

---
 net/netfilter/xt_hashlimit.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 44a095e..7fc694e 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c

@@ -465,19 +465,20 @@ static u64 user2credits(u64 user, int revision)
 {
 	if (revision == 1) {
 		/* If multiplying would overflow... */
-		if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1))
+		if (user > div64_u64(0xFFFFFFFF, (HZ*CREDITS_PER_JIFFY_v1)))
 			/* Divide first. */
-			return (user / XT_HASHLIMIT_SCALE) *\
+			return div64_u64(user, XT_HASHLIMIT_SCALE) *\
 						HZ * CREDITS_PER_JIFFY_v1;
 
-		return (user * HZ * CREDITS_PER_JIFFY_v1) \
-						/ XT_HASHLIMIT_SCALE;
+		return div64_u64((user * HZ * CREDITS_PER_JIFFY_v1),
+				  XT_HASHLIMIT_SCALE);
 	} else {
-		if (user > 0xFFFFFFFFFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
-			return (user / XT_HASHLIMIT_SCALE_v2) *\
+		if (user > div64_u64(0xFFFFFFFFFFFFFFFF, (HZ*CREDITS_PER_JIFFY)))
+			return div64_u64(user, XT_HASHLIMIT_SCALE_v2) *\
 						HZ * CREDITS_PER_JIFFY;
 
-		return (user * HZ * CREDITS_PER_JIFFY) / XT_HASHLIMIT_SCALE_v2;
+		return div64_u64((user * HZ * CREDITS_PER_JIFFY),
+				 XT_HASHLIMIT_SCALE_v2);
 	}
 }

-- 
1.9.1

Re: [PATCH] Fix link error in 32bit arch because of 64bit division

From: Liping Zhang <hidden>
Date: 2016-09-27 10:23:50

Hi  Vishwanath Pai,

2016-09-27 15:42 GMT+08:00 Vishwanath Pai [off-list ref]:

Fix link error in 32bit arch because of 64bit division

This should be "netfilter: xt_hashlimit: fix ... "

quoted hunk

--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c

@@ -465,19 +465,20 @@ static u64 user2credits(u64 user, int revision)
 {
        if (revision == 1) {
                /* If multiplying would overflow... */
-               if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1))
+               if (user > div64_u64(0xFFFFFFFF, (HZ*CREDITS_PER_JIFFY_v1)))

Here divisor and dividend are all 32-bit integer, so covert "/" to div64_u64
seems unnecessary.

quoted hunk

                        /* Divide first. */
-                       return (user / XT_HASHLIMIT_SCALE) *\
+                       return div64_u64(user, XT_HASHLIMIT_SCALE) *\
                                                HZ * CREDITS_PER_JIFFY_v1;

-               return (user * HZ * CREDITS_PER_JIFFY_v1) \
-                                               / XT_HASHLIMIT_SCALE;
+               return div64_u64((user * HZ * CREDITS_PER_JIFFY_v1),
+                                 XT_HASHLIMIT_SCALE);
        } else {
-               if (user > 0xFFFFFFFFFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
-                       return (user / XT_HASHLIMIT_SCALE_v2) *\
+               if (user > div64_u64(0xFFFFFFFFFFFFFFFF, (HZ*CREDITS_PER_JIFFY)))

0xFFFFFFFFFFFFFFFF and "HZ*CREDITS_PER_JIFFY" are both
constant, and GCC will do constant folding optimization, so I think
convert "/" to div64_u64 here is also unnecessary.

quoted hunk

+                       return div64_u64(user, XT_HASHLIMIT_SCALE_v2) *\
                                                HZ * CREDITS_PER_JIFFY;

-               return (user * HZ * CREDITS_PER_JIFFY) / XT_HASHLIMIT_SCALE_v2;
+               return div64_u64((user * HZ * CREDITS_PER_JIFFY),
+                                XT_HASHLIMIT_SCALE_v2);
        }
 }

Re: [PATCH] Fix link error in 32bit arch because of 64bit division

From: Eric Dumazet <hidden>
Date: 2016-09-27 13:32:21

On Tue, 2016-09-27 at 03:42 -0400, Vishwanath Pai wrote:

quoted hunk

Fix link error in 32bit arch because of 64bit division

Division of 64bit integers will cause linker error undefined reference
to `__udivdi3'. Fix this by replacing divisions with div64_64

Signed-off-by: Vishwanath Pai <redacted>

---
 net/netfilter/xt_hashlimit.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index 44a095e..7fc694e 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c

@@ -465,19 +465,20 @@ static u64 user2credits(u64 user, int revision)
 {
 	if (revision == 1) {
 		/* If multiplying would overflow... */
-		if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1))
+		if (user > div64_u64(0xFFFFFFFF, (HZ*CREDITS_PER_JIFFY_v1)))

How can this be needed ? 0xFFFFFFFF is 32bits, compiler knows how to
compute 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1) itself, without using a
64 bit divide !

Please be selective.

quoted hunk

 			/* Divide first. */
-			return (user / XT_HASHLIMIT_SCALE) *\
+			return div64_u64(user, XT_HASHLIMIT_SCALE) *\
 						HZ * CREDITS_PER_JIFFY_v1;
 
-		return (user * HZ * CREDITS_PER_JIFFY_v1) \
-						/ XT_HASHLIMIT_SCALE;
+		return div64_u64((user * HZ * CREDITS_PER_JIFFY_v1),
+				  XT_HASHLIMIT_SCALE);
 	} else {
-		if (user > 0xFFFFFFFFFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
-			return (user / XT_HASHLIMIT_SCALE_v2) *\

Probably same remark here.

quoted hunk

+		if (user > div64_u64(0xFFFFFFFFFFFFFFFF, (HZ*CREDITS_PER_JIFFY)))
+			return div64_u64(user, XT_HASHLIMIT_SCALE_v2) *\
 						HZ * CREDITS_PER_JIFFY;
 
-		return (user * HZ * CREDITS_PER_JIFFY) / XT_HASHLIMIT_SCALE_v2;
+		return div64_u64((user * HZ * CREDITS_PER_JIFFY),
+				 XT_HASHLIMIT_SCALE_v2);
 	}
 }
 

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