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

[Laurent Vivier <Laurent@vivier.eu>]

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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."

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