[Qemu-devel] [PATCH] linux-user: correctly align types in thunking code

[Laurent Vivier <laurent@vivier.eu>]

This is a follow up
of patch:

        commit c2e3dee6e03527baf8698698cce76b1a3174969a
        Author: Laurent Vivier <laurent@vivier.eu>
        Date:   Sun Feb 13 23:37:34 2011 +0100

            linux-user: Define target alignment size

In my case m68k aligns "int" on 2 not 4. You can check this with the
following program:

int main(void)
{
        struct rtentry rt;
        printf("rt_pad1 %ld %zd\n", offsetof(struct rtentry, rt_pad1),
                sizeof(rt.rt_pad1));
        printf("rt_dst %ld %zd\n", offsetof(struct rtentry, rt_dst),
                sizeof(rt.rt_dst));
        printf("rt_gateway %ld %zd\n", offsetof(struct rtentry, rt_gateway),
                sizeof(rt.rt_gateway));
        printf("rt_genmask %ld %zd\n", offsetof(struct rtentry, rt_genmask),
                sizeof(rt.rt_genmask));
        printf("rt_flags %ld %zd\n", offsetof(struct rtentry, rt_flags),
                sizeof(rt.rt_flags));
        printf("rt_pad2 %ld %zd\n", offsetof(struct rtentry, rt_pad2),
                sizeof(rt.rt_pad2));
        printf("rt_pad3 %ld %zd\n", offsetof(struct rtentry, rt_pad3),
                sizeof(rt.rt_pad3));
        printf("rt_pad4 %ld %zd\n", offsetof(struct rtentry, rt_pad4),
                sizeof(rt.rt_pad4));
        printf("rt_metric %ld %zd\n", offsetof(struct rtentry, rt_metric),
                sizeof(rt.rt_metric));
        printf("rt_dev %ld %zd\n", offsetof(struct rtentry, rt_dev),
                sizeof(rt.rt_dev));
        printf("rt_mtu %ld %zd\n", offsetof(struct rtentry, rt_mtu),
                sizeof(rt.rt_mtu));
        printf("rt_window %ld %zd\n", offsetof(struct rtentry, rt_window),
                sizeof(rt.rt_window));
        printf("rt_irtt %ld %zd\n", offsetof(struct rtentry, rt_irtt),
                sizeof(rt.rt_irtt));
}

And result is :

i386

rt_pad1 0 4
rt_dst 4 16
rt_gateway 20 16
rt_genmask 36 16
rt_flags 52 2
rt_pad2 54 2
rt_pad3 56 4
rt_pad4 62 2
rt_metric 64 2
rt_dev 68 4
rt_mtu 72 4
rt_window 76 4
rt_irtt 80 2

m68k

rt_pad1 0 4
rt_dst 4 16
rt_gateway 20 16
rt_genmask 36 16
rt_flags 52 2
rt_pad2 54 2
rt_pad3 56 4
rt_pad4 62 2
rt_metric 64 2
rt_dev 66 4
rt_mtu 70 4
rt_window 74 4
rt_irtt 78 2

This affects the "route" command :

WITHOUT this patch:

$ sudo route add -net default gw 10.0.3.1 window 1024 irtt 2 eth0
$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.3.1        0.0.0.0         UG        0 67108866  32768 eth0
10.0.3.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0

WITH this patch:

$ sudo route add -net default gw 10.0.3.1 window 1024 irtt 2 eth0
$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.3.1        0.0.0.0         UG        0 1024       2 eth0
10.0.3.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 include/exec/user/thunk.h |   22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/exec/user/thunk.h b/include/exec/user/thunk.h
index 87025c3..d3e9f3d 100644
--- a/include/exec/user/thunk.h
+++ b/include/exec/user/thunk.h
@@ -151,20 +151,32 @@ static inline int thunk_type_align(const argtype *type_ptr, int is_host)
     case TYPE_CHAR:
         return 1;
     case TYPE_SHORT:
-        return 2;
+        if (is_host) {
+            return __alignof__(short);
+        } else {
+            return TARGET_SHORT_ALIGNMENT;
+        }
     case TYPE_INT:
-        return 4;
+        if (is_host) {
+            return __alignof__(int);
+        } else {
+            return TARGET_INT_ALIGNMENT;
+        }
     case TYPE_LONGLONG:
     case TYPE_ULONGLONG:
-        return 8;
+        if (is_host) {
+            return __alignof__(long long);
+        } else {
+            return TARGET_LLONG_ALIGNMENT;
+        }
     case TYPE_LONG:
     case TYPE_ULONG:
     case TYPE_PTRVOID:
     case TYPE_PTR:
         if (is_host) {
-            return sizeof(void *);
+            return __alignof__(long);
         } else {
-            return TARGET_ABI_BITS / 8;
+            return TARGET_LONG_ALIGNMENT;
         }
         break;
     case TYPE_OLDDEVT:
-- 
1.7.10.4