Patchwork linux-user: correctly align types in thunking code

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Submitter Laurent Vivier
Date Dec. 8, 2012, 3:18 p.m.
Message ID <1354979928-19000-1-git-send-email-laurent@vivier.eu>
Download mbox | patch
Permalink /patch/204669/
State New
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Comments

Laurent Vivier - Dec. 8, 2012, 3:18 p.m.
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 thunk.h |   22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)
Peter Maydell - Dec. 8, 2012, 4:40 p.m.
On 8 December 2012 15:18, Laurent Vivier <laurent@vivier.eu> wrote:
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>

This kind of patch really needs an explanation (and ideally
test case) of what the bug is that it is attempting to fix...

thanks
-- PMM
Andreas Färber - Dec. 8, 2012, 4:55 p.m.
Am 08.12.2012 16:18, schrieb Laurent Vivier:
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  thunk.h |   22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/thunk.h b/thunk.h
> index 87025c3..d3e9f3d 100644
> --- a/thunk.h
> +++ b/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);

Might __alignof__() depend on a certain GCC version? Is it supported by
clang?

Andreas
Laurent Vivier - Dec. 8, 2012, 5:10 p.m.
Le samedi 08 décembre 2012 à 16:40 +0000, Peter Maydell a écrit :
> On 8 December 2012 15:18, Laurent Vivier <laurent@vivier.eu> wrote:
> > Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> 
> This kind of patch really needs an explanation (and ideally
> test case) of what the bug is that it is attempting to fix...

Yes... of course, but sometime no one reads my patches, so I was
lazy ;-)

The 3 first patches I sent today allow to run netstat and route in a
linux container with qemu linux-user (qemu-m68k in my case).

The first one, obviously, allows to have IP addresses in correct order
in the case of "netstat -nr".

The second one, allows to use the command "route". 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:

#include <stdio.h>
#include <net/route.h>
#include <stddef.h>

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));
}

On x86_64:

        rt_pad1 0 8
        rt_dst 8 16
        rt_gateway 24 16
        rt_genmask 40 16
        rt_flags 56 2
        rt_pad2 58 2
        rt_pad3 64 8
        rt_pad4 74 6
        rt_metric 80 2
        rt_dev 88 8

on 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


The third one, allows to set the interface for the command "route", for
instance : route add -net default gw 10.0.3.1 eth0

Obviously, If patches seem correct for everyone, I can resend them with
comments and in a serie.

Bonus: To test this, find attached a little script that will compile
qemu-m68k, install debian etch-m68k in a linux container. Then you will
be able to run debian m68k system with "sudo lxc-start -n virtm68k".
(tested on an ubuntu 12.10, you should check that lxc creates a lxcbr0
bridge with IP address 10.0.3.1). Check variable at the beginning for
the paths used.

Regards,
Laurent
--
"Just play. Have fun. Enjoy the game."
Laurent Vivier - Dec. 8, 2012, 5:13 p.m.
Le samedi 08 décembre 2012 à 17:55 +0100, Andreas Färber a écrit :
> Am 08.12.2012 16:18, schrieb Laurent Vivier:
> > Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> > ---
> >  thunk.h |   22 +++++++++++++++++-----
> >  1 file changed, 17 insertions(+), 5 deletions(-)
> > 
> > diff --git a/thunk.h b/thunk.h
> > index 87025c3..d3e9f3d 100644
> > --- a/thunk.h
> > +++ b/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);
> 
> Might __alignof__() depend on a certain GCC version? Is it supported by
> clang?

I'm a big fan of copy&paste: I took them from linux-user/syscall.c :

static const StructEntry struct_termios_def = {
    .convert = { host_to_target_termios, target_to_host_termios },
    .size = { sizeof(struct target_termios), sizeof(struct host_termios) },
    .align = { __alignof__(struct target_termios), __alignof__(struct host_termios) },
};

Regards,
Laurent

Patch

diff --git a/thunk.h b/thunk.h
index 87025c3..d3e9f3d 100644
--- a/thunk.h
+++ b/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: